text
stringlengths 286
572k
| score
float64 0.8
0.98
| model_output
float64 3
4.39
|
|---|---|---|
Pluto’s atmosphere is hard to observe from Earth. It can only be studied when Pluto passes in front of a distant star, allowing astronomers to see the effect the atmosphere has on starlight. When this happened in 2016, it confirmed that Pluto’s atmosphere was growing, a trend that astronomers had observed since 1988, when they noticed it for the first time.
Now, all that has changed — Pluto’s atmosphere appears to have collapsed. The most recent occultation in July last year was observed by Ko Arimatsu at Kyoto University in Japan and colleagues. They say the atmospheric pressure seems to have dropped by over 20 percent since 2016.
First, some background. Astronomers have long known that Pluto’s atmosphere expands as it approaches the sun and contracts as it recedes. When the sun heats its icy surface, it sublimates, releasing nitrogen, methane and carbon dioxide into the atmosphere. When it moves away, the atmosphere is thought to freeze and fall out of the sky in what must be one of the most spectacular ice storms in the solar system.
Pluto reached its point of closest approach to the sun in 1989, and has since been moving away. But its atmosphere has continued to increase to a level that is about 1/100,000 of Earth’s.
Astronomers think they know why, thanks to the images sent back by the New Horizons spacecraft that flew past Pluto in 2015. These images revealed an unexpectedly complex surface with widely varying colors. A mysterious reddish cap at the north pole turned out to be colored by organic molecules. And a large, white, ice-covered basin called Sputnik Planitia stretched across a large part of one hemisphere.
Planetary geologists think Sputnik Planitia plays an important role in regulating Pluto’s atmosphere. That’s because, when it faces the sun, it releases gas into the atmosphere. Simulations suggest that this is why Pluto’s atmosphere has continued to grow, even as it has begun to move away from the sun.
The simulations are complicated by Sputnik Planitia’s color, which determines the amount of light it absorbs, and this in turn is influenced by ice formation in ways that are hard to predict.
Nevertheless, these same simulations suggest that, since 2015, Sputnik Planitia should have begun to cool, causing the atmosphere to condense into ice. Arimatsu and colleagues say that’s probably what’s behind their new observation.
There is a problem, however. The models suggest that Pluto’s atmosphere ought to have shrunk by less than 1 percent since 2016, not the 20 percent observed by the Japanese team. So there may be some other factor at work that is accelerating Pluto’s atmospheric collapse.
The result must also be treated with caution. The effect of Pluto’s atmosphere on distant starlight is small and hard to observe with the 60-centimeter reflecting telescope that the team used. They say the various sources of error in their measurement make it only marginally significant.
Better observations from larger telescopes are desperately needed. But this is unlikely to happen anytime soon. As well as moving away from the sun, Pluto is moving out of the galactic plane, making stellar occultations much rarer and with less bright stars.
That means the chances to make better observations in the future will be few and far between. The team concludes with a plea for astronomers to observe Pluto with bigger, more sensitive telescopes, preferably those with diameters measured in meters.
Until then, Pluto’s vanishing atmosphere will remain something of a mystery.
Ref: Evidence For a Rapid Decrease of Pluto’s Atmospheric Pressure Revealed by a Stellar Occultation In 2019. arxiv.org/abs/2005.09189 | 0.91462 | 3.977587 |
RECENT observations with the Spacewatch telescope indicate that the flux of Earth-crossing objects with diameters below about 50 m is some 10-100 times higher than predicted by simple extrapolation from the known main-belt asteroid population1,2. This might seem to imply3 a significantly greater terrestrial hazard from atmospheric explosions such as those that occurred over Revelstoke or Tunguska4,5. Here I show that explosions due to Spacewatch objects with diameters less than 50 m (having kinetic energies below about 10 megatonnes high-explosive equivalent) typically occur too high in the atmosphere to cause substantial surface damage. Exclusive of relatively rare iron objects, no comet or asteroid with an energy below ∼2 megatonnes threatens the Earth's surface. The high flux of small Earth-crossing objects identified by Spacewatch therefore does not imply a greater terrestrial hazard.
All Science Journal Classification (ASJC) codes | 0.822532 | 3.403891 |
If you enjoy chemistry, physics and math, it’s difficult not to love astronomy. Where else can you find an extraterrestrial interplay of this trio of intellectual endeavours?
Uncompounded, neutral hydrogen ( H2 ) occupies an extremely small part of the earth’s atmosphere. It is continuously produced naturally by tectonic and microbiological processes, thanks to iron-rich mafic rocks and iron-hydrogenase enzymes, respectively. Hydrogen gas is less dense than any other so it rises above the rest of the atmosphere’s components. Since hydrogen molecules have the same kinetic energy as air molecules, due to their lower molar mass, H2 ‘s molecules move 3.7 times faster than nitrogen and four times faster than oxygen. Although their molecules’ average speed of 1.8 km/s¹ at 10 °C is still inferior to Earth’s escape velocity of 11.2 km/s, the low mass of hydrogen’s charged products helps them accelerate to higher speeds by mechanisms in the ionosphere. Thus most of the lightweight gas leaves our planet.
Once hydrogen atoms join their own kind in space, they find plenty of company. In the universe hydrogen is by far the most common element. It is the fuel of main sequence-stars; half of the galaxy’s hydrogen is in suns. The rest is found elsewhere in far lower densities in three forms:
(1) In molecular clouds the simplest element can be found bonded to its own kind as H2. For these clouds to exist, dust must shield them from ultraviolet rays, which are otherwise capable of breaking the single bond between atoms. But H2 is difficult to detect. Due to the perfectly symmetrical nature of the molecule, it cannot absorb infrared(IR) and change vibrational states. But luckily, H2 is usually associated with the detectable and asymmetric carbon monoxide.
If a molecular cloud becomes large enough, thanks to gravity, the cloud can become astronomically fertile and lead to the birth of a star. This is what’s happening in the so-called “Pillars of Creation”, part of Messier Object 16, commonly known as the Eagle Nebula.
(2) In so-called HI regions, hydrogen can exist in free, atomic form (H). The spin of its lone proton (really a measurement of quantum angular momentum) is normally opposite that of its only electron. In a rare event, a collision between atoms can excite the hydrogen atom from the described spin state to one where the spin of the electron flips. When this state revert to its more common and stable one, energy in the ” twilight-zone” between microwaves and radio is emitted. Since there are so many free hydrogen atoms over large areas of space, despite the rarity of the events, there are enough of them to be observable with a radio telescope. Apparently small radio telescopes (1-3m) for observations of the 21 cm hydrogen
line can be built for about $300.
(3) An HII region is a thin plasma of charged hydrogen atoms and unbound electrons. It forms in the vicinity of certain stars whose radiation is capable of ionizing hydrogen gas. The star’s surface temperature and size will determine the size of the spherical HII region around it—the so-called Strömgren sphere. Some of the most beautiful sights of astronomy include HII regions. When the excited electron in each atom temporarily returns to a previously charged one, electromagnetic energy of select wavelengths is released. We don’t see the ultraviolet, but a transition from the third(n=3) to second(n=2) energy level leads to a prominent red emission at 656 nanometres, while n=4 to 2 and n=5 to 2 transitions create blue (486 nm) and blue-violet (486 nm), respectively. Each of the following familiar nebulae includes HII regions: Messier objects M8 (Lagoon Nebula), M16 (Eagle Nebula), M17 (Omega Nebula), M42 (Orion Nebula), and M20 (Trifid Nebula), presented below in clockwise order.
One more : Heart and Soul Nebulas in Cassiopeia
The International Encyclopedia of Astronomy. Patrick Moore, editor
¹hydrogen’s average molecular speed can be calculated by equating 0.5 mv2 (kinetic energy) to 1.5 RT, where m is the molar mass in kg/mole while R = 8.31 J/mole K. Earth’s escape velocity in the absence of friction is obtained by equating kinetic energy to potential energy GMm/r, where G = gravitational constant and M and r are the mass and radius of the earth. | 0.858258 | 3.918043 |
(CNN) — The Orionid meteor shower will peak on Monday and Tuesday, sprinkling remnants of Halley’s Comet in Earth’s atmosphere to create a dazzling display.
This meteor shower may not be the most spectacular of the year, but it delights in other ways. The Orionids appear each year between October 2 and November 7, according to the American Meteor Society.
The peak occurs when the Earth passes through a debris stream left by the Comet Halley as we intersect its orbit each year at this time. Halley’s comet itself was last seen in our sky in 1986 and will reappear in 2061. The comet makes an appearance every 76 years on its journey around the sun, according to NASA.
The meteors radiate from the well-known Orion constellation, but you don’t have to look in the direction of the constellation to see them. In fact, you probably shouldn’t because those meteors will have short trails and be harder to see.
The best time to see this meteor shower, which could produce 10 to 20 meteors per hour during the peak window, is when the moon isn’t dominating the night sky. That’s because these meteors are more faint than the Perseid meteor shower.
While the meteor shower will peak in the overnight hours of early morning on October 21 and 22, the best view will be during a brief window between the setting of the moon and the beginning of morning twilight. Allow yourself an hour or two to observe. You can check timeanddate.com to see when the shower peaks in your area.
Orionids are also hard to see because they’re so fast. They zip into our atmosphere at 41 miles per second, vaporizing in our upper atmosphere about 60 miles above the Earth’s surface. Some have been clocked at 148,000 miles per hour. But there’s no danger of these bright meteors colliding with Earth. Some of the meteoroids are only the size of a grain of sand.
But they leave beautiful gas trails that can stretch out for seconds after the meteor itself is gone. Or they can break up into bright fragments.
Find an open area away from the city that will afford you a wide view of the sky, and don’t forget to bring a blanket or chair and dress for the weather. Allow yourself time for your eyes to adjust to the dark. And you won’t need binoculars or telescopes to enjoy the show.
(Copyright (c) 2020 CNN. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.) | 0.807378 | 3.259435 |
Mar 25, 2013
The Sun is not a fusion reactor.
In a recent Picture of the Day, it was noted that sunspots are not well understood by astronomers. Furthermore, their bizarre electromagnetic displays are not readily explainable by models of solar activity that rely on radiant emissions from thermonuclear energy. The Sun demonstrates that electrical and magnetic properties dominate its behavior.
Almost 70 years ago, Dr. C. E. R. Bruce offered a new hypothesis about the Sun. Being an electrical researcher, as well as an astronomer, Bruce proposed that the Sun was a discharge phenomenon:
“It is not coincidence that the photosphere has the appearance, the temperature and spectrum of an electric arc; it has arc characteristics because it is an electric arc, or a large number of arcs in parallel. These arcs quickly result in the neutralization of the accumulated space charge in their neighbourhood and go out. They are not therefore stable discharges, but may rather be looked upon as transient sparks. Arcs thus continually appear and disappear. It is this coming and going which accounts for the observed granulation of the solar surface.” (A New Approach in Astrophysics and Cosmogony By C. E. R. Bruce)
Years later, in 1972, the late Ralph Juergens wrote a series of articles suggesting that the Sun is not an isolated body, but is the most electrically active object in the solar system—the focus of a radial electric field extending outward almost to the next star system. Juergens was the first one to link electricity in the Solar System to the galactic circuit and to theorize that the Sun might have an external power source.
In the electric Sun hypothesis, the Sun is an anode, or positively charged terminal. As previously mentioned, the cathode is an invisible “virtual cathode,” called the heliopause, at the farthest limit of the Sun’s coronal discharge, millions of kilometers from its surface. This is the double layer that isolates the Sun’s plasma cell from the galactic plasma that surrounds it.
In the Electric Universe model, the voltage difference between the Sun and the galaxy occurs across the heliopause boundary sheath. Inside the heliopause the weak, constant electric field centered on the Sun is enough to power the solar discharge. The visible component of the glow discharge occurs above the solar surface in layers.
In the chromosphere, at 500 kilometers above the surface, the coldest temperature exists: 4400 Kelvin. At the top of the chromosphere, 2200 kilometers up, the temperature rises to about 20,000 Kelvin. It then jumps by hundreds of thousands of Kelvin, slowly continuing to rise, eventually reaching 2 million Kelvin in the corona. The Sun’s reverse temperature gradient agrees with the glow discharge model, but contradicts the idea of nuclear fusion.
The discovery that a “solar wind” escapes the Sun at between 400 and 700 kilometers per second was a surprise for the nuclear theory. In a gravity-driven Universe, the Sun’s heat and radiation pressure are insufficient to explain how the particles of the solar wind accelerate past Venus, Earth and the rest of the planets. Since they are not rocket-powered particles, no one expected such acceleration.
According to the Electric Sun theory, an electric field focused on the Sun causes the radial movement of charged particles: the greater their acceleration, the stronger the field. A positive space-charge sheath nearest the anode (Sun) accelerates positive ions, principally protons, to form the solar wind. But as noted, the interplanetary electric field is extremely weak. No spacecraft has been designed to measure the voltage differential across 100 meters, but the solar wind does confirm the Sun’s e-field, sufficient to sustain a drift current across the Solar System. Within the heliospheric volume, the implied current is sufficient to power the Sun. | 0.826652 | 3.952277 |
Should we beam messages into deep space, announcing our presence to any extraterrestrial civilizations that might be out there? Or, should we just listen? Since the beginnings of the modern Search for Extraterrestrial Intelligence (SETI), radio astronomers have, for the most part, followed the listening strategy.
In 1999, that consensus was shattered. Without consulting with other members of the community of scientists involved in SETI, a team of radio astronomers at the Evpatoria Radar Telescope in Crimea, led by Alexander Zaitsev, beamed an interstellar message called ‘Cosmic Call’ to four nearby sun-like stars. The project was funded by an American company called Team Encounter and used proceeds obtained by allowing members of the general public to submit text and images for the message in exchange for a fee.
Similar additional transmissions were made from Evpatoria in 2001, 2003, and 2008. In all, transmissions were sent towards twenty stars within less than 100 light years of the sun. The new strategy was called Messaging to Extraterrestrial Intelligence (METI). Although Zaitsev was not the first to transmit an interstellar message, he and his associates where the first to systematically broadcast to nearby stars. The 70 meter radar telescope at Evpatoria is the second largest radar telescope in the world.
In the wake of the Evpatoria transmissions a number of smaller former NASA tracking and research stations collected revenue by making METI transmissions as commercially funded publicity stunts. These included a transmission in the fictional Klingon language from Star Trek to promote the premier of an opera, a Dorito’s commercial, and the entirety of the 2008 remake of the classic science fiction movie “The Day the Earth Stood Still”. The specifications of these commercial signals have not been made public, but they were most likely much too faint to be detectable at interstellar distances with instruments comparable to those possessed by humans.
Zaitsev’s actions stirred divisive controversy among the community of scientists and scholars concerned with the field. The two sides of the debate faced off in a recent special issue of the Journal of the British Interplanetary Society, resulting from a live debate sponsored in 2010 by the Royal Society at Buckinghamshire, north of London, England.
Modern SETI got its start in 1959, when astrophysicists Giuseppe Cocconi and Phillip Morrison published a paper in the prestigious scientific journal Nature, in which they showed that the radio telescopes of the time were capable of receiving signals transmitted by similar counterparts at the distances of nearby stars. Just months later, radio astronomer Frank Drake turned an 85 foot radio telescope dish towards two nearby sun-like stars and conducted Project Ozma, the first SETI listening experiment. Morrison, Drake, and the young Carl Sagan supposed that extraterrestrial civilizations would “do the heavy lifting” of establishing powerful and expensive radio beacons announcing their presence. Humans, as cosmic newcomers that had just invented radio telescopes, should search and listen. There was no need to take the risk, however small, of revealing our presence to potentially hostile aliens.
Drake and Sagan did indulge in one seeming exception to their own moratorium. In 1974, the pair devised a brief 1679 bit message that was transmitted from the giant Arecibo Radar Telescope in Puerto Rico. But the transmission was not a serious attempt at interstellar messaging. By intent, it was aimed at a vastly distant star cluster 25,000 light years away. It merely served to demonstrate the new capabilities of the telescope at a rededication ceremony after a major upgrade.
In the 1980’s and 90’s SETI researchers and scholars sought to formulate a set of informal rules for the conduct of their research. The First SETI Protocol specified that any reply to a confirmed alien message must be preceded by international consultations, and an agreement on the content of the reply. It was silent on the issue of transmissions sent prior to the discovery of an extraterrestrial signal.
A Second SETI Protocol was to have addressed the issue, but, somewhere along the way, critics charge, something went wrong. David Brin, a space scientist, futurist consultant, and science fiction writer was a participant in the protocol discussion. He charged that “collegial discussion started falling apart” and “drastic alterations of earlier consensus agreements were rubber-stamped, with the blatant goal of removing all obstacles from the path of those pursuing METI”.
Brin accuses “the core community that clusters around the SETI Institute in Silicon Valley, California”, including astronomers Jill Tartar and Seth Shostak of “running interference for and enabling others around the world- such as Russian radio astronomer Dr. Alexander Zaitsev” to engage in METI efforts. Shostak denies this, and claims he simply sees no clear criteria for regulating such transmissions.
Brin, along with Michael A. G. Michaud, a former U.S. Foreign Service Officer and diplomat who chaired the committee that formulated the first and second protocol, and John Billingham, the former head of NASA’s short lived SETI effort, resigned their memberships in SETI related committees to protest the alterations to the second protocol.
The founders of SETI felt that extraterrestrial intelligence was likely to be benign. Carl Sagan speculated that extraterrestrial civilizations (ETCs) older than ours would, under the pressure of necessity, become peaceful and environmentally responsible, because those that didn’t would self-destruct. Extraterrestrials, they supposed, would engage in interstellar messaging because of a wish to share their knowledge and learn from others. They supposed that ETCs would establish powerful omnidirectional beacons in order to assist others in finding them and joining a communications network that might span the galaxy. Most SETI searches have been optimized for detecting such steady constantly transmitting beacons.
Over the fifty years since the beginnings of SETI, searches have been sporadic and plagued with constant funding problems. The space of possible directions, frequencies, and coding strategies has only barely been sampled so far. Still, David Brin contends that whole swaths of possibilities have been eliminated “including gaudy tutorial beacons that advanced ETCs would supposedly erect, blaring helpful insights to aid all newcomers along the rocky paths”. The absence of obvious, easily detectable evidence of extraterrestrial intelligence has led some to speak of the “Great Silence”. Something, Brin notes, “has kept the prevalence and visibility of ETCs below our threshold of observation”. If alien civilizations are being quiet, could it be that they know something that we don’t know about some danger?
Alexander Zaitsev thinks that such fears are unfounded, but that other civilizations might suffer from the same reluctance to transmit that he sees as plaguing humanity. Humanity, he thinks, should break the silence by beaming messages to its possible neighbors. He compares the current state of humanity to that of a man trapped in a one-man prison cell. “We”, he writes “do not want to live in a cocoon, in a ‘one –man cell’, without any rights to send a message outside, because such a life is not INTERESTING! Civilizations forced to hide and tremble because of farfetched fears are doomed to extinction”. He notes that in the ‘60’s astronomer Sebastian von Hoerner speculated that civilizations that don’t engage in interstellar communication eventually decline through “loss of interest”.
METI critics maintain that questions of whether or not to send powerful, targeted, narrowly beamed interstellar transmissions, and of what the content of those transmissions should be needs to be the subject of broad international and public discussion. Until such discussion has taken place, they want a temporary moratorium on such transmissions.
On the other hand, SETI Institute radio astronomer Seth Shostak thinks that such deliberations would be pointless. Signals already leak into space from radio and television broadcasting, and from civilian and military radar. Although these signals are too faint to be detected at interstellar distances with current human technology, Shostak contends that with the rapid growth in radio telescope technology, ETCs with technology even a few centuries in advance of ours could detect this radio leakage. Billingham and Benford counter that to collect enough energy to tune in on such leakage; an antenna with a surface area of more than 20,000 square kilometers would be needed. This is larger than the city of Chicago. If humans tried to construct such a telescope with current technology it would cost 60 trillion dollars.
Shostak argues that exotic possibilities might be available to a very technologically advanced society. If a telescope were placed at a distance of 550 times the Earth’s distance from the sun, it would be in a position to use the sun’s gravitational field as a gigantic lens. This would give it an effective collecting area vastly larger than the city of Chicago, for free. If advanced extraterrestrials made use of their star’s gravitational field in this way, Shostak maintains “that would give them the capacity to observe many varieties of terrestrial transmissions, and in the optical they would have adequate sensitivity to pick up the glow of street lamps”. Even Brin conceded that this idea was “intriguing”.
Civilizations in a position to do us potential harm through interstellar travel, Shostak contends, would necessarily be technologically advanced enough to have such capabilities. “We cannot pretend that our present level of activity with respect to broadcasting or radar usage is ‘safe’. If danger exists, we’re already vulnerable” he concludes. With no clear means to say what extraterrestrials can or can’t detect, Shostak feels the SETI community has nothing concrete to contribute to the regulation of radio transmissions.
Could extraterrestrials harm us? In 1897 H. G. Wells published his science fiction classic “The War of the Worlds” in which Earth was invaded by Martians fleeing their arid, dying world. Besides being scientifically plausible in terms of its times, Wells’ novel had a political message. An opponent of British colonialism, he wanted his countrymen to imagine what imperialism was like from the other side. Tales of alien invasion have been a staple of science fiction ever since. Some still regard European colonialism as a possible model for how extraterrestrials might treat humanity. The eminent physicist Steven Hawking thinks very advanced civilizations might have mastered interstellar travel. Hawking warned that “If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans”.
Though dismissing Hawking’s fears of alien invasion as an “unlikely speculation”, David Brin notes that interstellar travel by small automated probes is quite feasible, and that such a probe could potentially do harm to us in many ways. It might, for example, steer an asteroid onto a collision course with Earth. A relatively small projectile traveling at one tenth the speed of light could wreak terrible damage by simply colliding with our planet. “The list of unlikely, but physically quite possible scenarios is very long” he warns.
Diplomat Michael Michaud warns that “We can all understand the frustration of not finding any signals after fifty years of intermittent searching” but “Impatience with the search is not a sufficient justification for introducing a new level of potential risk for our entire species”.
METI critics David Brin, James Benford, and James Billingham think that the current lack of results from SETI warrants a different sort of response than METI. They call for a reassessment of the search strategy. From the outset, SETI researchers have assumed that extraterrestrials will use steady beacons transmitting constantly in all directions to attract our attention. Recent studies of interstellar radio propagation and the economics of signaling show that such a beacon, which would need to operate on a vast timescale, is not an efficient way to signal.
Instead, an alien civilization might compile a list of potentially habitable worlds in its neighborhood and train a narrowly beamed signal on each member of the list in succession. Such brief “ping” messages might be repeated, in sequence, once a year, once a decade, or once a millennium. Benford and Billingham note that most SETI searches would miss this sort of signal.
The SETI Institute’s Allen telescope array, for example, is designed to target narrow patches of sky (such as the space around a sun-like star) and search those patches in sequence, for the presence of continuously transmitting beacons. It would miss a transient “ping” signal, because it would be unlikely to be looking in the right place at the right time. Ironically, the Evpatoria messages, transmitted for less than a day, are examples of such transient signals.
Benford and Billingham propose the construction of a new radio telescope array designed to constantly monitor the galactic plane (where stars are most abundant) for transient signals. Such a telescope array, they estimate, would cost about 12 million dollars, whereas a serious, sustained METI program would cost billions.
The METI controversy continues. On February 13, the two camps debated each other at the American Association for the Advancement of Science conference in San Jose, California. At that conference David Brin commented “It’s an area where opinion rules, and everyone has a fierce opinion”. In the wake of the meeting a group of 28 scientists, scholars, and business leaders issued a statement that “We feel the decision whether or not to transmit must be based on a worldwide consensus, and not a decision based on the wishes of a few individuals with access to powerful communications equipment”.
References and Further Reading:
J. Benford, J. Billingham, D. Brin, S. Dumas, M. Michaud, S. Shostak, A. Zaitsev, (2014) Messaging to Extraterrestrial Intelligence special section, Journal of the British Interplanetary Society, 67, p. 5-43.
F. Cain (2013) How could we find aliens? The search for extraterrestrial intelligence (SETI), Universe Today.
E. Hand (2015), Researchers call for interstellar messages to alien civilizations, Science Insider, Science Magazine.
P. Patton (2014) Communicating across the cosmos, Part 1: Shouting into the darkness, Part 2: Petabytes from the Stars, Part 3: Bridging the Vast Gulf, Part 4: Quest for a Rosetta Stone, Universe Today. | 0.923601 | 3.208877 |
A telescope is an optical instrument utilized for stargazing, but not only. There are terrestrial models that are widely utilized for surveillance purposes. Such a device makes a great present for someone interested in finding out more about space, in general, but also about phenomena dealing with astrophysics.
This article will tell you about some of the essential factors that you ought to have in mind if you’ve ever thought of purchasing a telescope. There are a wide variety of units available out there, and doing a bit more research before making up your mind is a great idea so as to make sure that you don’t end up spending your precious pennies on something that isn’t worth it.
What do you need it for?
First off, the simplest categorization when it comes to telescopes is that they are either terrestrial or astronomical. Land-viewing units rarely excel if what you want the device for is stargazing. Start by estimating your own needs and preferences and only then move on to the actual features that the product needs to come equipped with.
The aperture is crucial
The main optical component of such an optical device, whether it’s a lens or a mirror has a diameter. This diameter is known as the aperture of the telescope. The bigger the size of the lens or mirror, the greater the amount of light that the telescope is capable of capturing. But why is that important?
More light is synonymous with more clarity, so the bigger the aperture, the better you’re going to see the celestial objects you are interested in visualizing.
Keep in mind that the device will end up being hefty if you want to get a model with the biggest aperture you can afford. Bigger isn’t necessarily better, especially in those situations when what you actually need is a portable telescope.
The magnification shouldn’t be your sole decision-making factor
The clarity of the images you’re going to look at is far more important compared to the magnification. Here’s an analogy, if it might make you better understand the point that we are trying to make.
If you’ve ever used a digital camera before, you probably know that it comes with optical and digital zoom. The optical one is way better than the digital one, which means that the image is fuzzy and grainy once you start using the second.
With telescopes, the magnification is determined by the eyepiece you will utilize. Thus, if you want to make sure that you can use the same device for looking at closer and more distant celestial objects, it might be better to purchase an extra eyepiece than to choose a telescope that comes with powerful magnification right from the beginning.
Refractors, reflectors, catadioptric telescopes, and computerized variants
Each of these comes with advantages and cons, so you’re going to have to assess your requirements. The pros of refractors range from the fact that they have a simple design and as such, they’re easy to use. They can be employed for lunar stargazing, and they’re somewhat rugged.
Reflectors are typically unsuitable for terrestrial applications, but they’re great if what you want to look at distant nebulae and galaxies. Cassegrain telescopes are compact, durable, and versatile. Many of the models available out there are computerized, and telescopes like these ones can be used conveniently and efficiently and without too much effort on the part of the user.
So, which telescope do you need? | 0.826917 | 3.557845 |
Star of Bethlehem
The Star of Bethlehem, or Christmas Star, appears only in the nativity story of the Gospel of Matthew where "wise men from the East" (Magi) are inspired by the star to travel to Jerusalem. There, they met King Herod of Judea, and asked him:
Herod calls his scribes and priests who quote to him that a verse from the Book of Micah interpreted as a prophecy, states that the Jewish Messiah would be born in Bethlehem to the south of Jerusalem. Secretly intending to find and kill the Messiah in order to preserve his own kingship, Herod invites the wise men to return to him on their way home.
The star leads them to Jesus' home in the town, where they worship him and give him gifts. The wise men are then given a divine warning not to return to Herod, so they return home by a different route.
Many Christians believe the star was a miraculous sign. Some theologians claimed that the star fulfilled a prophecy, known as the Star Prophecy. Astronomers have made several attempts to link the star to unusual celestial events, such as a conjunction of Jupiter and Venus, a comet, or a supernova.
The subject is a favorite at planetarium shows during the Christmas season. However, most ancient sources and Church tradition generally indicate that the wise men visited Bethlehem sometime after Jesus’ birth. The visit is traditionally celebrated on Epiphany (January 6) in western Christianity.
Matthew's account describes Jesus with a broader Greek word παιδίον (paidion), which can mean either "infant" or "child", rather than the more specific word for infant βρέφος (bréphos), possibly implying that some time has passed since the birth. However, the word παιδίον (paidíon) is also used in Luke’s Gospel specifically concerning Jesus’ birth and his presentation at the temple. Herod I has all male Hebrew babies up to age two in the area killed in the Massacre of the Innocents.
In the Gospel of Matthew account, the Magi (often translated as "wise men", but more accurately astrologers) arrive at the court of Herod in Jerusalem and tell the king of a star which signifies the birth of the King of the Jews:
Now after Jesus was born in Bethlehem of Judea in the days of Herod the king, behold, wise men from the East came to Jerusalem, saying, Where is He who has been born King of the Jews? For we have seen His star in the East [or at its rising] and have come to worship Him. When Herod the king heard this, he was troubled, and all Jerusalem with him. And when he had gathered all the chief priests and scribes of the people together, he inquired of them where the King of the Jews was to be born.
Herod is "troubled", not because of the appearance of the star, but because the Magi have told him that a "king of the Jews" had been born, which he understands to refer to the Messiah, a leader of the Jewish people whose coming was believed to be foretold in scripture. So he asks his advisors where the Messiah would be born. They answer Bethlehem, birthplace of King David, and quote the prophet Micah.[nb 1] The king passes this information along to the Magi.
Then Herod, when he had secretly called the wise men, determined from them what day the star appeared. And he sent them to Bethlehem and said, Go and search carefully for the young Child, and when you have found Him, bring back word to me, that I may come and worship Him also. When they heard the king, they departed; and behold, the star which they had seen in the East went before them, till it came and stood over where the young Child was. When they saw the star, they rejoiced with exceedingly great joy. And when they had come into the house, they saw the young Child with Mary His mother, and fell down and worshiped Him. And when they had opened their treasures, they presented gifts to Him: gold, frankincense, and myrrh.
Matthew's account suggests that the Magi knew from the star that the "king of the Jews" had been born before they arrived in Jerusalem. They present Jesus with gifts of gold, frankincense, and myrrh, and as verse 11 describes: "they saw the child with his mother Mary, and they bowed down and worshipped him". In a dream, they are warned not to return to Jerusalem, so they leave for their own country by another route.
When Herod realizes he has been tricked, he orders the execution of all male children in Bethlehem "two years old and younger," based on the age the child could be in regard to the information the magi had given him concerning the time the star first appeared.[nb 2]
Joseph, warned in a dream, takes his family to Egypt for their safety. The Gospel links the escape to a verse from scripture, which it interprets as a prophecy: "Out of Egypt I called my son." This was a reference to the departure of the Hebrews from Egypt under Moses, so the quote suggests that Matthew saw the life of Jesus as recapitulating the story of the Jewish people, with Judea representing Egypt and Herod standing in for pharaoh.
After Herod dies, Joseph and his family return from Egypt, and settle in Nazareth in Galilee. This is also said to be a fulfillment of a prophecy ("He will be called a Nazorean," (NRSV) which could be attributed to Judges 13:5 regarding the birth of Samson and the Narazite vow. The word "Nazareth" is related to the word "netzer" which means "sprout", and which some Bible commentators think refers to Isaiah 11:1, "And there shall come forth a shoot out of the stock of Jesse, and a branch out of his roots shall bear fruit." (ESV).[nb 3]
Many scholars who see the gospel nativity stories as later apologetic accounts created to establish the messianic status of Jesus regard the Star of Bethlehem as a pious fiction. Aspects of Matthew's account which have raised questions of the historical event include: Matthew is the only one of the four gospels which mentions either the Star of Bethlehem or the Magi. Scholars suggest that Jesus was born in Nazareth and that the Bethlehem nativity narratives reflect a desire by the Gospel writers to present his birth as the fulfillment of prophecy.
The Matthew account conflicts with that given in the Gospel of Luke, in which the family of Jesus already lives in Nazareth, travel to Bethlehem for the census, and return home almost immediately.
Matthew's description of the miracles and portents attending the birth of Jesus can be compared to stories concerning the birth of Augustus (63 BC).[nb 4] Linking a birth to the first appearance of a star was consistent with a popular belief that each person's life was linked to a particular star. Magi and astronomical events were linked in the public mind by the visit to Rome of a delegation of magi at the time of a spectacular appearance of Halley's Comet in AD 66, about the time the Gospel of Matthew was being composed. This delegation was led by King Tiridates of Armenia, who came seeking confirmation of his title from Emperor Nero. Ancient historian Dio Cassius wrote that, "The King did not return by the route he had followed in coming," a line similar to the text of Matthew's account, but written some time after the completion of Matthew's gospel.
Fulfillment of prophecy
The ancients believed that astronomical phenomena were connected to terrestrial events - As Above, So Below. Miracles were routinely associated with the birth of important people, including the Hebrew patriarchs, as well as Greek and Roman heroes.
I see him, but not now;
I behold him, but not near;
A Star shall come out of Jacob;
A Scepter shall rise out of Israel,
And batter the brow of Moab,
And destroy all the sons of tumult.
Although possibly intended to refer to a time that was long past, since the kingdom of Moab had long ceased to exist by the time the Gospels were being written, this passage had become widely seen as a reference to the coming of a Messiah. It was, for example, cited by Josephus, who believed it referred to Emperor Vespasian. Origen, one of the most influential early Christian theologians, connected this prophecy with the Star of Bethlehem:
If, then, at the commencement of new dynasties, or on the occasion of other important events, there arises a comet so called, or any similar celestial body, why should it be matter of wonder that at the birth of Him who was to introduce a new doctrine to the human race, and to make known His teaching not only to Jews, but also to Greeks, and to many of the barbarous nations besides, a star should have arisen? Now I would say, that with respect to comets there is no prophecy in circulation to the effect that such and such a comet was to arise in connection with a particular kingdom or a particular time; but with respect to the appearance of a star at the birth of Jesus there is a prophecy of Balaam recorded by Moses to this effect: There shall arise a star out of Jacob, and a man shall rise up out of Israel.
Origen suggested that the Magi may have decided to travel to Jerusalem when they "conjectured that the man whose appearance had been foretold along with that of the star, had actually come into the world".
The Magi are sometimes called "kings" because of the belief that they fulfill prophecies in Isaiah and Psalms concerning a journey to Jerusalem by gentile kings. Isaiah mentions gifts of gold and incense. In the Septuagint, the Greek translation of the Old Testament probably used by Matthew, these gifts are given as gold and frankincense, similar to Matthew's "gold, frankincense, and myrrh." The gift of myrrh symbolizes mortality, according to Origen.
While Origen argued for a naturalistic explanation, John Chrysostom viewed the star as purely miraculous: "How then, tell me, did the star point out a spot so confined, just the space of a manger and shed, unless it left that height and came down, and stood over the very head of the young child? And at this the evangelist was hinting when he said, "Lo, the star went before them, till it came and stood over where the young Child was."
Although magi (Greek μαγοι) is usually translated as "wise men," in this context it probably means 'astronomer'/'astrologer'. The involvement of astrologers in the story of the birth of Jesus was problematic for the early Church, because they condemned astrology as demonic; a widely cited explanation was that of Tertullian, who suggested that astrology was allowed 'only until the time of the Gospel'.
In 1614, German astronomer Johannes Kepler determined that a series of three conjunctions of the planets Jupiter and Saturn occurred in the year 7 BC. He argued (incorrectly) that a planetary conjunction could create a nova, which he linked to the Star of Bethlehem. Modern calculations show that there was a gap of nearly a degree (approximately twice a diameter of the moon) between the planets, so these conjunctions were not visually impressive. An ancient almanac has been found in Babylon which covers the events of this period, but does not indicate that the conjunctions were of any special interest. In the 20th century, Professor Karlis Kaufmanis, an astronomer, argued that this was an astronomical event where Jupiter and Saturn were in a triple conjunction in the constellation Pisces. Archaeologist and Assyriologist Simo Parpola has also suggested this explanation.
In 6 BC, there were conjunctions/occultations (eclipses) of Jupiter by the Moon in Aries. "Jupiter was the regal 'star' that conferred kingships - a power that was amplified when Jupiter was in close conjunctions with the Moon. The second occultation on April 17 coincided precisely when Jupiter was 'in the east', a condition mentioned twice in the biblical account about the Star of Bethlehem."
In 3–2 BC, there was a series of seven conjunctions, including three between Jupiter and Regulus and a strikingly close conjunction between Jupiter and Venus near Regulus on June 17, 2 BC. "The fusion of two planets would have been a rare and awe-inspiring event", according to Roger Sinnott. Another Venus–Jupiter conjunction occurred earlier in August, 3 BC. These events however occurred after the generally accepted date of 4 BC for the death of Herod. Since the conjunction would have been seen in the west at sunset it could not have led the magi south from Jerusalem to Bethlehem.
Other writers highly suggest that the star was a comet. Halley's Comet was visible in 12 BC and another object, possibly a comet or nova, was seen by Chinese and Korean stargazers in about 5 BC. This object was observed for over seventy days, possibly with no movement recorded. Ancient writers described comets as "hanging over" specific cities, just as the Star of Bethlehem was said to have "stood over" the "place" where Jesus was (the town of Bethlehem). However, this is generally thought unlikely as in ancient times comets were generally seen as bad omens. The comet explanation has been recently promoted by Colin Nicholl. His theory involves a hypothetical comet which could have appeared in 6 BC.
A recent (2005) hypothesis advanced by Frank Tipler is that the star of Bethlehem was a supernova or hypernova occurring in the nearby Andromeda Galaxy. Although it is difficult to detect a supernova remnant in another galaxy, or obtain an accurate date of when it occurred, supernova remnants have been detected in Andromeda.
The Christmas Star As A Supernova In Aquila
Another theory is the more likely supernova of February 23 4 BC, which is now known as PSR 1913+16 or the Hulse-Taylor Pulsar. It is said to have appeared in the constellation of Aquila, near the intersection of the winter colour and the equator of date. The nova was recorded in China, Korea, and Palestine.
The Sparkling Star in Aquila in 4 BC
A nova or comet was recorded in China in 4 BC. " In the reign of Ai-ti, in the third year of the Chien-p'ing period. In the third month, day chi-yu, there was a rising po at Hoku" (Han Shu, The History of the Former Han Dynasty). The date is equivalent to April 24, 4 BC. This identifies the date when it was first observed in China. It was also recorded in Korea. "In the fifty-fourth year of Hyokkose Wang, in the spring, second month, day chi-yu, a po-hsing appeared at Hoku" (Samguk Sagi, The Historical Record of the Three Kingdoms). The Korean is particularly corrupt because Ho (1962) points out that " the chi-yu day did not fall in the second month that year but on the first month" (February 23) and on the third month (April 24). The original must have read "day chi-yu, first month" (February 23) or "day chi-yu, third month" (April 24). The latter would coincide with the date in the Chinese records although professor Ho suggests the date was "probably February 23, 4 BC."....
The Magi told Herod that they saw the star "in the East," or according to some translations, "at its rising", which may imply the routine appearance of a constellation, or an asterism. One theory interprets the phrase in Matthew 2:2, "in the east," as an astrological term concerning a "heliacal rising." This translation was proposed by Edersheim and Heinrich Voigt, among others. The view was rejected by the philologist Franz Boll (1867–1924). Two modern translators of ancient astrological texts insist that the text does not use the technical terms for either a heliacal or an acronycal rising of a star. However, one concedes that Matthew may have used layman's terms for a rising.
Double occultation on Saturday (Sabbath) April 17, 6 BC
Astronomer Michael R. Molnar argues that the "star in the east" refers to an astronomical event with astrological significance in the context of ancient Greek astrology. He suggests a link between the Star of Bethlehem and a double occultation of Jupiter by the moon on March 20 and April 17 of 6 BC in Aries, particularly the second occultation on April 17. Occultations of planets by the moon are quite common, but Firmicus Maternus, an astrologer to Roman Emperor Constantine, wrote that an occultation of Jupiter in Aries was a sign of the birth of a divine king. He argues that Aries rather than Pisces was the zodiac symbol for Judea, a fact that would affect previous interpretations of astrological material. Molnar’s theory was debated by scientists, theologians, and historians during a colloquium on the Star of Bethlehem at the Netherlands’ University of Groningen in October 2014. Harvard astronomer Owen Gingerich supports Molnar’s explanation but noted technical questions. "The gospel story is one in which King Herod was taken by surprise," said Gingerich. "So it wasn’t that there was suddenly a brilliant new star sitting there that anybody could have seen [but] something more subtle." Astronomer David A. Weintraub says, "If Matthew’s wise men actually undertook a journey to search for a newborn king, the bright star didn’t guide them; it only told them when to set out."
There is an explanation given that the events were quite close to the sun and would not have been visible to the naked eye.
Royal celestial signs centered on the cycle of MUL.BABBAR/Jupiter
Another theory connects the star to a series of highly symbolic, but generally unspectacular celestial events involving the planet Jupiter. Babylonian astronomers usually referred to the planet as MUL.BABBAR, meaning the "White Star." A series of symbolically royal celestial events, which were centered on the planet's annual cycle, could have been associated with Judaism and the Messiah. D. Hutchison has made a thorough analysis of the symbolically royal astronomical events visible from Babylonia.
According to the theory, the star was not a guiding light. Matthew’s wise men never visually followed anything, anywhere, at any moment. The star was given to inform, not to guide. The Magi were not present with the shepherds at the time of Jesus’s birth. They arrived in Judea about a year and a half after the first celestial signs.
After an initial series of celestial signs involving the star, the wise men journeyed from the East to Judea and Bethlehem in the daytime. However, after their arrival in Bethlehem, the wise men made a new, unexpected association with the star. The star “preceded” the men from the East in a manner similar to how Jesus preceded his disciples to Galilee after his resurrection, not visually, but chronologically (Matthew 26:32, 28:7). The star did not indicate a specific house, but after a careful search, the Magi discovered the child who was about one year old. This conception of the star has been referred to as “a serious study of what could have been a messianic Jewish perspective concerning the heavens two millennia ago.”
Regulus, Jupiter, and Venus
Attorney Frederick Larson examined the biblical account in the Gospel of Matthew, chapter 2 and found the following nine qualities of Bethlehem's Star: It signified birth, it signified kingship, it was related to the Jewish nation, and it rose "in the East"; King Herod had not been aware of it; it appeared at an exact time; it endured over time; and, according to Matthew, it was in front of the Magi when they traveled south from Jerusalem to Bethlehem, and then it stopped over Bethlehem.
Using astronomy software, and an article written by astronomer Craig Chester based on the work of Ernest Martin, Larson thinks all nine characteristics of the Star of Bethlehem are found in events that took place in the skies of 3-2 BC. Highlights include a triple conjunction of Jupiter, called the king planet, with the fixed star Regulus, called the king star, starting in September 3 BC. Larson believes that may be the time of Jesus' conception.
By June of 2 BC, nine months later, the human gestation period, Jupiter had continued moving in its orbit around the sun and appeared in close conjunction with Venus in June of 2 BC. In Hebrew Jupiter is called "Sedeq", meaning "righteousness", a term also used for the Messiah, and suggested that because the planet Venus represents love and fertility, so Chester had suggested astrologers would have viewed the close conjunction of Jupiter and Venus as indicating a coming new king of Israel, and Herod would have taken them seriously. Astronomer Dave Reneke independently found the June 2 BC planetary conjunction, and noted it would have appeared as a "bright beacon of light".
Jupiter next continued to move and then it stopped in its apparent retrograde motion on December 25 of 2 BC over the town of Bethlehem. Since planets in their orbits have a "stationary point", a planet moves eastward through the stars but "After it passes the opposite point in the sky from the sun, it appears to slow, come to a full stop, and move backward (westward) for some weeks. Again it slows, stops, and resumes its eastward course," said Chester. The date of December 25 that Jupiter appeared to stop while in retrograde took place in the season of Hanukkah, and is the date later chosen to celebrate Christmas.
Relating the star historically to Jesus' birth
If the story of the Star of Bethlehem described an actual event, it might identify the year Jesus was born. The Gospel of Matthew describes the birth of Jesus as taking place when Herod was king. According to Josephus, Herod died after a lunar eclipse and before a Passover Feast. The eclipse is usually identified as the eclipse of March 13, 4 BC. Other scholars suggested dates in 5 BC, because it allows seven months for the events Josephus documented between the lunar eclipse and the Passover rather than the 29 days allowed by lunar eclipse in 4 BC. Others suggest it was an eclipse in 1 BC. The narrative implies that Jesus was born sometime between the first appearance of the star and the appearance of the Magi at Herod's court. That the king is said to have ordered the execution of boys two years of age and younger implies that the Star of Bethlehem appeared within the preceding two years. Some scholars date the birth of Jesus as 6–4 BC, while others suggest Jesus' birth was in 3/2 BC.
The Gospel of Luke says the census from Caesar Augustus took place when Quirinius was governor of Syria. Tipler suggests this took place in AD 6, nine years after the death of Herod, and that the family of Jesus left Bethlehem shortly after the birth. Some scholars explain the apparent disparity as an error on the part of the author of the Gospel of Luke, concluding that he was more concerned with creating a symbolic narrative than a historical account, and was either unaware of, or indifferent to, the chronological difficulty.
However, there is some debate among Bible translators about the correct reading of Luke 2:2. Instead of translating the registration as taking place "when" Quirinius was governor of Syria, some versions translate it as "before" or use "before" as an alternative, which Harold Hoehner, F.F. Bruce, Ben Witherington and others have suggested may be the correct translation. While not in agreement, Emil Schürer also acknowledged that such a translation can be justified grammatically. According to Josephus, the tax census conducted by the Roman senator Quirinius particularly irritated the Jews, and was one of the causes of the Zealot movement of armed resistance to Rome. From this perspective, Luke may have been trying to differentiate the census at the time of Jesus’ birth from the tax census mentioned in Acts 5:37 that took place under Quirinius at a later time. One ancient writer identified the census at Jesus’ birth, not with taxes, but with a universal pledge of allegiance to the emperor.
Jack Finegan noted some early writers' reckoning of the regnal years of Augustus are the equivalent to 3/2 BC, or 2 BC or later for the birth of Jesus, including Irenaeus (3/2 BC), Clement of Alexandria (3/2 BC), Tertullian (3/2 BC), Julius Africanus (3/2 BC), Hippolytus of Rome (3/2 BC), Hippolytus of Thebes (3/2 BC), Origen (3/2 BC), Eusebius of Caesarea (3/2 BC), Epiphanius of Salamis (3/2 BC), Cassiodorus Senator (3 BC), Paulus Orosius (2 BC), Dionysus Exiguus (1 BC), and Chronographer of the Year 354 (AD 1). Finegan places the death of Herod in 1 BC, and says if Jesus was born two years or less before Herod the Great died, the birth of Jesus would have been in 3 or 2 BC. Finegan also notes the Alogi reckoned Christ's birth with the equivalent of 4 BC or AD 9.
In the Orthodox Church, the Star of Bethlehem is interpreted as a miraculous event of symbolic and pedagogical significance, regardless of whether it coincides with a natural phenomenon; a sign sent by God to lead the Magi to the Christ Child. This is illustrated in the Troparion of the Nativity:
In Orthodox Christian iconography, the Star of Bethlehem is often depicted not as golden, but as a dark aureola, a semicircle at the top of the icon, indicating the Uncreated Light of Divine grace, with a ray pointing to "the place where the young child lay" (Matt 2:9). Sometimes the faint image of an angel is drawn inside the aureola.
The Church of Jesus Christ of Latter-day Saints
LDS members believe that the Star of Bethlehem was an actual astronomical event visible the world over. In the Book of Mormon, which they believe contains writings of ancient prophets, Samuel the Lamanite prophesies that a new star will appear as a sign that Jesus has been born, and Nephi later writes about the fulfillment of this prophecy.
Members of Jehovah's Witnesses believe that the "star" was a vision or sign created by Satan, rather than a sign from God. This is because it led the pagan astrologers first to Jerusalem where King Herod consequently found out about the birth of the "king of the Jews", with the result that he attempted to have Jesus killed.
Depiction in art
Paintings and other pictures of the Adoration of the Magi may include a depiction of the star in some form. In the fresco by Giotto di Bondone, it is depicted as a comet. In the tapestry of the subject designed by Edward Burne-Jones (and in the related watercolour), the star is held by an angel.
The colourful star lantern known as a paról is a cherished and ubiquitous symbol of Christmas for Filipinos, its design and light recalling the star. In its basic form, the paról has five points and two "tails" that evoke rays of light pointing the way to the Christ Child, and candles inside the lanterns have been superseded by electric illumination.
In the Church of the Nativity in Bethlehem, a silver star with 14 undulating rays marks the location traditionally claimed to be that of Jesus' birth.
In quilting, a common eight-pointed star design is known as the Star of Bethlehem.
- Caesar's Comet
- Star of David - The Jewish symbol of King David, which the Star of Bethlehem is often associated with having been a miraculous appearance of.
- Matthew 2:5–6. Matthew's version is a conflation of Micah 5:2 and 2 Samuel 5:2.
- Matthew 2:16 This is presented as a fulfillment of a prophecy and echoes the killing of firstborn by pharaoh in Exodus 11:1–12:36.
- Judges 13:5–7 is sometimes identified as the source for Matthew 2:23 because Septuagint ναζιραιον (Nazirite) resembles Matthew's Ναζωραῖος (Nazorean). But few scholars accept the view that Jesus was a Nazirite.
- Augustus' mother was said to have become pregnant by the god Apollo and there was a "public portent" indicating that a king of Rome would soon be born. (Suetonius, C. Tranquillus, "The Divine Augustus", The Lives of the Twelve Caesars chapter 94, archived from the original on 2006-09-20).
- A Christmas Star for SOHO, NASA, archived from the original on December 24, 2004, retrieved 2008-07-04.
- Matthew 2:1–2
- Matthew 2:11–12
- Freed, Edwin D. (2001), The Stories of Jesus' Birth: A Critical Introduction, Continuum International, p. 93, ISBN 0-567-08046-3
- Telegraph (2008-12-09), "Jesus was born in June", The Daily Telegraph, London, retrieved 2011-12-14.
- "Star of Bethlehem." Cross, F. L., ed. The Oxford dictionary of the Christian church. New York: Oxford University Press. 2005.
- For example, Paul L. Maier, "Herod and the Infants of Bethlehem", in Chronos, Kairos, Christos II, Mercer University Press (1998), 171; Geza Vermes, The Nativity: History and Legend, London, Penguin, 2006, p22; E. P. Sanders, The Historical Figure of Jesus, 1993, p.85; Aaron Michael Adair, "Science, Scholarship and Bethlehem's Starry Night", Sky and Telescope, Dec. 2007, pp. 26–29 (reviewing astronomical theories).
- John, Mosley. "Common Errors in 'Star of Bethlehem' Planetarium Shows". Archived from the original on 2008-05-16. Retrieved 2008-06-05..
- Andrews, Samuel James (2020). "When did the Magi visit?". Salem Web Network. Retrieved 3 February 2020.
- Ratti, John, First Sunday after the Epiphany, archived from the original on 2008-06-13, retrieved 2008-06-05.
- Luke chapter 2, verses 17 and 27. Retrieved on December 15, 2019.
- Brown, Raymond Edward (1988). An Adult Christ at Christmas: Essays on the Three Biblical Christmas Stories, Liturgical Press, p. 11 ISBN 0-8028-3931-2; Eerdmans Dictionary of the Bible, Eerdmans (2000), p. 844.
- Matthew 2:2. New Revised Standard Version.
- Matthew 2:1–4 New King James Version (1982).
- Thomas G. Long, Matthew (Westminster John Knox Press, 1997), page 18.
- Matthew 2:4.
- Matthew 2:8.
- Matthew 2:7–11.
- Matthew 2:11
- Matthew 2:12.
- Matthew 2:13–14
- Matthew 2:15 The original is from Hosea 11:1.
- "An Exodus motif prevails in the entire chapter." (Kennedy, Joel (2008), Recapitulation of Israel, Mohr Siebeck, p. 132, ISBN 978-3-16-149825-1, retrieved 2009-07-04).
- Matthew 2:10–21
- Matthew 2:23
- Concordances on the meaning of the word "netzer" on Bible Hub. Retrieved December 29, 2015.
- Commentaries for Matthew 2:23 on Bible Hub. Retrieved on December 29, 2005.
- Isaiah chapter 11, verse 1 on Bible Hub with commentaries. Retrieved on December 29, 2015.
- Brown, Raymond E. (1993), The Birth of the Messiah, Anchor Bible Reference Library, p. 188.
- Markus Bockmuehl, This Jesus (Continuum International, 2004), page 28; Vermes, Géza (2006-11-02), The Nativity: History and Legend, Penguin Books Ltd, p. 22., ISBN 0-14-102446-1; Sanders, Ed Parish (1993), The Historical Figure of Jesus, London: Allen Lane, p. 85., ISBN 0-7139-9059-7; Believable Christianity: A lecture in the annual October series on Radical Christian Faith at Carrs Lane URC Church, Birmingham, October 5, 2006.
- Nikkos Kokkinos, "The Relative Chronology of the Nativity in Tertullian", in Ray Summers, Jerry Vardaman and others, eds., Chronos, Kairos, Christos II, Mercer University Press (1998), page 125–6.
Funk, Robert W. and the Jesus Seminar, The Acts of Jesus: The Search for the Authentic Deeds of Jesus, HarperSanFrancisco, 1999, ISBN 0-06-062979-7. pp. 499, 521, 533.
Paul L. Maier, "Herod and the Infants of Bethlehem", in Chronos, Kairos, Christos II, Mercer University Press (1998), 171.
For Micah's prophecy, see Micah 5:2.
- Bart D. Ehrman, Jesus: apocalyptic prophet of the new millennium, Oxford University Press 1999, page 38.
- Nolland, p. 110.
Pliny the Elder, Natural History, II vi 28.
- Jenkins, R.M. (June 2004). "The Star of Bethlehem and the Comet of AD 66" (PDF). Journal of the British Astronomy Association (114). pp. 336–43. Retrieved 2016-12-23.
- Matthew 2:12
- Vermes, Geza (December 2006), "The First Christmas", History Today, 56 (12), pp. 23–29, archived from the original on 2007-12-14, retrieved 2009-07-04.
- Numbers 24:17
- Josephus, Flavius, The Wars of the Jews, retrieved 2008-06-07 Translated by: William Whiston.
Lendering, Jona, Messianic claimants, retrieved 2008-06-05.
- Adamantius, Origen. "Contra Celsum". Retrieved 2008-06-05., Book I, Chapter LIX.
- Adamantius, Origen. "Contra Celsum".. Book I, Chapter LX.
- France, R.T., The Gospel according to Matthew: an introduction and commentary, p. 84. See Isaiah 60:1–7 and Psalms 72:10.
- Isaiah 60:6
- Isaiah 60:6 (Septuagint).
- Schaff, Philip (1886), St. Chrysostom: Homilies on the Gospel of Saint Matthew, New York: Christian Literature Publishing Co., p. 36, archived from the original on 2009-02-07, retrieved 2009-07-04.
- Raymond Edward Brown, An Adult Christ at Christmas: Essays on the Three Biblical Christmas Stories, Liturgical Press (1988), p. 11.
- S. J. Tester, A History of Western Astrology, (Boydell & Brewer, 1987), page 111–112.
- Mark, Kidger. "Chinese and Babylonian Observations". Retrieved 2008-06-05.
- Minnesota Astronomy Review Volume 18 – Fall 2003/2004 "The Star of Bethlehem by Karlis Kaufmanis" (PDF).
- Audio Version of Star of Bethlehem by Karlis Kaufmanis "The Star of Bethlehem by Karlis Kaufmanis".
- Simo Parpola, "The Magi and the Star," Bible Review, December 2001, pp. 16-23, 52, and 54.
- Molnar, Michael. "Revealing the Star of Bethlehem". Retrieved 3 February 2020.
- Sinnott, Roger, "Thoughts on the Star of Bethlehem", Sky and Telescope, December 1968, pp. 384–386.
- Greg Garrison (7 March 2019). "Is this what the Star of Bethlehem looked like? Venus, Jupiter put on a show". Alabama Media Group. Retrieved 3 February 2020.
- Kidger, Mark (2005), Astronomical Enigmas: Life on Mars, the Star of Bethlehem, and Other Milky Way Mysteries, Baltimore: Johns Hopkins University Press, p. 63, ISBN 0-8018-8026-2
- Colin Humphreys, 'The Star of Bethlehem', in Science and Christian Belief 5 (1995), 83–101.
- Mark Kidger, Astronomical Enigmas: Life on Mars, the Star of Bethlehem, and Other Milky Way Mysteries, (Johns Hopkins University Press, 2005), page 61.
- Colin R. Nicholl. 2015. The Great Christ Comet: Revealing the True Star of Bethlehem. Crossway.
- Interview Greg Cootsona. "What Kind of Astronomical Marvel was the Star of ... - Christianity Today". ChristianityToday.com.
- Guillermo Gonzalez. "The Great Christ Comet: Revealing the True Star of Bethlehem". TGC - The Gospel Coalition.
- Frank J. Tipler (2005). "The Star of Bethlehem: A Type Ia/Ic Supernova in the Andromeda Galaxy?" (PDF). The Observatory. 125: 168–74. Bibcode:2005Obs...125..168T.
- Eugene A. Magnier; Francis A. Primini; Saskia Prins; Jan van Paradijs; Walter H. G. Lewin (1997). "ROSAT HRI Observations of M31 Supernova Remnants" (PDF). The Astrophysical Journal. 490 (2): 649–652. Bibcode:1997ApJ...490..649M. doi:10.1086/304917.
- Matthew 2:2
- Edersheim, Alfred. The Life and times of Jesus the Messiah. Peabody, (MA: Hendrickson, 1993), several references, chapter 8.
- Adair, Aaron (2013), The Star of Bethlehem: A Skeptical View (Kindle Edition - location 1304), Onus Books, ISBN 0956694861
- Roberts, Courtney (2007), The Star of the Magi, Career Press, pp. 120–121, ISBN 1564149625
- Weintraub, David A., "Amazingly, astronomy can explain the biblical Star of Bethlehem", Washington Post, December 26, 2014
- Molnar, Michael R. (1999), The Star of Bethlehem: The Legacy of the Magi, Rutgers University Press, pp. 86, 89, 106–107, ISBN 0-8135-2701-5, archived from the original on 1999-10-12, retrieved 2009-07-04.
- For a similar interpretation, see Minnesota Astronomy Review Volume 18 – Fall 2003/2004 "The Star of Bethlehem by Karlis Kaufmanis" (PDF).
- Stenger, Richard (December 27, 2001), "Was Christmas star a double eclipse of Jupiter?", CNN, retrieved 2009-07-04.
- Govier, Gordon. "O Subtle Star of Bethlehem", Christianity Today, Vol. 58, No. 10, Pg 19, December 22, 2014
- Kidger, Mark (December 5, 2001), "The Star of Bethlehem", Cambridge Conference Correspondence, retrieved 2007-07-04.
- Barthel, Peter and Van Kooten, George, eds. The Star of Bethlehem and the Magi: Interdisciplinary Perspectives from Experts on the Ancient Near East, the Greco-Roman World, and Modern Astronomy, (Leiden: Brill, 2015), p. 4.
- Hutchison, Dwight, “Matthew’s Magi Never Visually Followed a Star Anywhere, But …” Perspectives on Science and Christian Faith, Volume 71 Number 3, September 2019, pp. 162-175.
- Sachs, Abraham, and Hunger, Hermann Astronomical Diaries and Related Texts from Babylonia, (Vienna: Verlag Der OÌsterreichischen Akademie Der Wissenschaften, 1988-2014), MUL.BABBAR is used throughout the series, Vol. I-VII (see examples in Vol. III pages: 12, 26, 30, 34, 40, 42).
- Evans, James The History & Practice of Ancient Astronomy. (New York: Oxford University Press, 1998), 321.
- Jupiter's synodic cycle is composed of the following: heliacal rising, the first station, the acronycal rising, second station, and heliacal setting. See Swerdlow, N. M. The Babylonian Theory of the Planets, (Princeton, NJ: Princeton UP, 1998),24.
- Elchert, Ken, “Prophecy, Jupiter, and the Dead Sea Scrolls,” Griffith (Observatory) Observer, Vol. 82, N° 6, June 2018, pp. 10-11.
- Hutchison, pp. 167-172.
- Hutchison, pp. 164-165.
- Barthel and Van Kooten, p. 4.
- Hutchison, pp. 172-173.
- See Hutchison in Barthel and Van Kooten, p. 4 and p. 115.
- Matthew chapter 2 on Bible Gateway, Amplified Version with footnotes. Retrieved on December 22, 2015.
- Lawton, Kim. "Christmas star debate gets its due on Epiphany". USA Today. January 5, 2008. Retrieved on December 19, 2015.
- Herzog, Travis. "Did the Star of Bethlehem exist?" abc13 Eyewitness News. December 20, 2007. Retrieved on December 19, 2015.
- Matthew chapter 2, verse 2. Bible Hub with commentaries. Retrieved on December 19, 2015.
- Matthew chapter 2, verse 3. Bible Hub with commentaries. Retrieved on December 19, 2015.
- Matthew chapter 2 verse 7. Bible Hub with commentaries. Retrieved on December 19, 2015.
- Matthew chapter 2, verses 2-10. Bible Hub with whole chapter and commentaries. Retrieved on December 19, 2015.
- Gospel of Matthew chapter 2 verse 9. Bible Hub with commentaries. Retrieved on December 19, 2015.
- Ireland, Michael. "Evidence emerges for Star of Bethlehem’s reality". Assist News Service. Christian Headlines. October 18, 2007. Retrieved on December 19, 2015.
- Chester, Craig. "The Star of Bethlehem". Imprimis. December 1993, 22(12). Originally presented at Hillsdale College during fall 1992. Retrieved on December 19, 2015.
- Vaughn, Cliff. "The Star of Bethlehem". Ethics Daily. November 26, 2009. Retrieved on January 2, 2016.
- Scripps Howard News Service. "Astronomer Analyzes The Star Of Bethlehem". The Chicago Tribune. December 24, 1993. Retrieved on December 19, 2015.
- Martin, Ernest. 1991 The Star that Astonished the World. ASK Publications. Can be read for free online, for personal study only. Other uses prohibited. Retrieved on February 12, 2016. ISBN 9780945657880
- Lawton, Kim. "Star of Bethlehem". Interview with Rick Larson. PBS, Religion & Ethics Newsweekly. December 21, 2007. Retrieved on December 19, 2015.
- Rao, Joe. "Was the Star of Bethlehem a star, comet … or miracle?" NBC News. Updated December 12, 2011. Includes a brief interactive at the bottom, “What’s the story behind the Star?” showing retrograde motion and the 3-2 BC planetary conjunctions. Retrieved on January 2, 2016.
- Larson, Frederick. "A coronation" Description of Jupiter as king planet. Retrieved December 22, 2015.
- Foust, Michael. Baptist Press. December 14, 2007. Retrieved on December 19, 2015.
- The Free Dictionary by Farlex; Medical Dictionary. Retrieved on February 12, 2016.
- Larson, Frederick. "Westward leading" Description of when Jupiter and Venus aligned. Retrieved December 22, 2015.
- Telegraph. "'Jesus was born in June", astronomers claim". The Telegraph. December 9, 2008. Retrieved on December 22, 2015.
- "History of Christmas". History. Retrieved on December 22, 2015.
- Matthew 2:1
- Josephus, Antiquities XVII:7:4.
- Josephus, Flavius. ~AD 93. Antiquities of the Jews. Book 17, chapter 9, paragraph 3 (17.9.3) Bible Study Tools website. First sentence of paragraph 3 reads: "Now, upon the approach of that feast ..." Retrieved on March 16, 2016.
- Josephus, Flavius. ~93 AD. The War of the Jews. Book 2, chapter 1, paragraph 3 (2.1.3) Bible Study Tools website. About one-third through paragraph three it reads: "And indeed, at the feast ...". Retrieved on March 16, 2016.
- Timothy David Barnes, "The Date of Herod’s Death," Journal of Theological Studies ns 19 (1968), 204–19.
P. M. Bernegger, "Affirmation of Herod’s Death in 4 B.C.," Journal of Theological Studies ns 34 (1983), 526–31.
- Finegan, Jack. Handbook of Biblical Chronology: Principles of Time Reckoning in the Ancient World and Problems of Chronology in the Bible. Peabody, MA: Hendrickson, 1998. p 300. ISBN 1565631439
- Andrew Steinmann, From Abraham to Paul: A Biblical Chronology. (St. Louis, MO: Concordia Pub. House, 2011), Print. pp. 219-256.
- W.E. Filmer, "The Chronology of the Reign of Herod the Great". The Journal of Theological Studies, 1966. 17(2): p. 283-298.
- Finegan, Jack. Handbook of Biblical Chronology: Principles of Time Reckoning in the Ancient World and Problems of Chronology in the Bible. Peabody, MA: Hendrickson, 1998, 2015. pp. 238-279.
- Jesus Christ. Chicago: Encyclopædia Britannica. 2010.
- Luke 2:2 Luke chapter 2 verse in parallel translations on Bible Hub. Retrieved on March 3, 2016.
- Ralph Martin Novak, Christianity and the Roman Empire: background texts (Continuum International, 2001), page 293.
- Raymond E. Brown, Christ in the Gospels of the Liturgical Year, (Liturgical Press, 2008), page 114. See, for example, James Douglas Grant Dunn, Jesus Remembered, (Eerdmans, 2003) p. 344. Similarly, Erich S. Gruen, 'The expansion of the empire under Augustus', in The Cambridge ancient history Volume 10, p. 157, Geza Vermes, The Nativity, Penguin 2006, p. 96, W. D. Davies and E. P. Sanders, 'Jesus from the Jewish point of view', in The Cambridge History of Judaism ed William Horbury, vol 3: the Early Roman Period, 1984, Anthony Harvey, A Companion to the New Testament (Cambridge University Press 2004), p221, Meier, John P., A Marginal Jew: Rethinking the Historical Jesus. Doubleday, 1991, v. 1, p. 213, Brown, Raymond E. The Birth of the Messiah: A Commentary on the Infancy Narratives in Matthew and Luke. London: G. Chapman, 1977, p. 554, A. N. Sherwin-White, pp. 166, 167, Millar, Fergus (1990). "Reflections on the trials of Jesus". A Tribute to Geza Vermes: Essays on Jewish and Christian Literature and History (JSOT Suppl. 100) [eds. P.R. Davies and R.T. White]. Sheffield: JSOT Press. pp. 355–81. repr. in Millar, Fergus (2006). "The Greek World, the Jews, and the East". Rome, the Greek World and the East. University of North Carolina Press. 3: 139–163.
- Marcus J. Borg, Meeting Jesus Again for the First Time: The Historical Jesus and the Heart of Contemporary Faith, (HarperCollins, 1993), page 24.
- Elias Joseph Bickerman, Studies in Jewish and Christian History, Page 104.
- Luke 2:2 commentaries on Bible Hub. Retrieved on March 3, 2016.
- Wright, N. T. 2011. The Kingdom New Testament: A Contemporary Translation. Luke 2:2. New York, HarperOne. ISBN 9780062064912
- Luke 2:2 in the Orthodox Jewish Bible (OJB)on BibleGateway. Retrieved on March 3, 2016.
- Luke 2:2 in the New International Version NIV) Bible on BibleGateway. Retrieved on March 3, 2016.
- Luke 2:2 in the English Standard Version (ESV) Bible on BibleGateway. Retrieved on March 3, 2016.
- Luke 2:2 in Holman Christian Standard Bible (HSCB) on BibleGateway. Retrieved on March 3, 2016.
- Brindle, Wayne. "The Census And Quirinius: Luke 2:2." JETS 27/1 (March1984) 43-52. Other scholars cited in Brindle's article include A. Higgins, N. Turner, P. Barnett, I. H. Marshall and C. Evan.
- Emil Schürer, Géza Vermès, and Fergus Millar, The History of the Jewish People in the Age of Jesus Christ (175 B.C.-A.D. 135), (Edinburgh: Clark, 1973 and 1987), 421.
- Josephus, Flavius. ~93 AD. Antiquities of the Jews. Book 18, chapter 1, paragraph 1 (hereafter noted as 18.1.1) Entire book free to read online. Bible Study Tools website. Scroll down from 18.1.1 to find Jewish revolt also mentioned in 18.1.6. Retrieved on March 3, 2016.
- Acts of the Apostles, chapter 5, verse 2 with commentaries. Bible Hub. Retrieved on March 16, 2016.
- Vincent, Marvin R. Vincent's Word Studies. Luke chapter 2, verse 2. Bible Hub. Retrieved on March 16, 2016.
- Paulus Orosius, Historiae Adversus Paganos, VI.22.7 and VII.2.16.
- Finegan, Jack. Handbook of Biblical Chronology: Principles of Time Reckoning in the Ancient World and Problems of Chronology in the Bible. Peabody, MA: Hendrickson, 1998. pp. 279-292.
- Finegan, Jack. Handbook of Biblical Chronology: Principles of Time Reckoning in the Ancient World and Problems of Chronology in the Bible. Peabody, MA: Hendrickson, 1998. p. 301.
- Finegan, Jack. Handbook of Biblical Chronology: Principles of Time Reckoning in the Ancient World and Problems of Chronology in the Bible. Peabody, MA: Hendrickson, 1998. pp. 289-290.
- "Hymns of the Feast". Feast of the Nativity of our Lord and Savior Jesus Christ. Greek Orthodox Archdiocese of America. 2009.
- Venerable Simon the Myrrh-gusher of Mt Athos at oca.org, accessed 31 October 2017.
- Smith, Paul Thomas (December 1997), "Birth of the Messiah", Ensign
- Jesus—The Way, the Truth, the Life, ch. 7: Astrologers Visit Jesus
- The Desire of Ages, pp. 60.
- Pliny the Elder, Naturalis Historia, 2.93-94.
|Wikimedia Commons has media related to Star of Bethlehem.|
- Case, Shirley Jackson (2006). Jesus: A New Biography, Gorgias Press LLC: New Ed. ISBN 1-59333-475-3.
- Coates, Richard (2008) 'A linguist's angle on the Star of Bethlehem', Astronomy and Geophysics, 49, pp.27-49
- Consolmagno S.J., Guy (2010) Looking for a star or Coming to Adore?
- Gill, Victoria: Star of Bethlehem: the astronomical explanations and Reading the Stars by Helen Jacobus with link to, Jacobus, Helen, Ancient astrology: how sages read the heavens/ Did the heavens predict a king?, BBC
- Griffith Observatory, a video on the star presented on MSNBC's Mysteries of the Universe.
- Hutchison, Dwight, “Matthew’s Magi Never Visually Followed a Star Anywhere, But …” Perspectives on Science and Christian Faith, Volume 71 Number 3, September 2019, pp. 162-175.
- Jenkins, R.M., "The Star of Bethlehem and the Comet of 66AD", Journal of the British Astronomy Association, June 2004, 114, pp. 336–43. This article argues that the Star of Bethlehem is a historical fiction influenced by the appearance of Halley's Comet in AD 66.
- Larson, Frederick A. What Was the Star?
- Nicholl, Colin R., The Great Christ Comet: Revealing the True Star of Bethlehem. Crossway, 2015. ISBN 978-1-4335-4213-8
- Star of Bethlehem Bibliography. Provides an extensive bibliography with Web links to online sources.
- Helmut W. Diedrichs: "The Star of Bethlehem: Possibilities and Facts" Had the wise men an order of King Phraates IV.? Perhaps for destabilizing Rom? https://www.academia.edu/39212400/The_wise_men_from_the_East_and_the_Star_of_Bethlehem_--_Ecbatana_versus_Babylon -- | 0.928889 | 3.044732 |
I spoke about the video not the zipped files...
For good reasons, Celestia offers to get rid of the clouds with a click (I-key), in order to have an unobstructed view of the surface! For curious people who have no idea what the surface of Venus looks like, this info is definitely instructive.
And so why do it ?
I find this NASA PhotoJournal image for example very worthwhile:
[Three-dimensional perspective views of Venusian Terrains composed of reduced resolution left-looking synthetic-aperture radar images merged with altimetry data from the Magellan spacecraft.]
My personal reservations are rather due to the fact that radar mapping has possibly a quite different interpretation from photographic surface imaging! More precisely: Radar images are black
-- where the surface is smooth
, and reflects the radar signal away from the spacecraft,
-- where the surface is rough
(on the radar scale of 12.5 cm), and backscatters the radar signal;
Furthermore, your quoted cloud image,
is NOT what the eye would see! It has been taken in UV light
by Pioneer Venus Orbiter, at wavelengths strongly absorbed by sulfur compounds in the atmosphere. This technique strongly enhances patterns in the clouds caused by upper atmospheric winds.
The view of Venus in visible light looks MUCH more dull and far less colored:
That's also how Venus looks in my (fairly big) telescope...
More 12 Go, it's so waste of space
for most of celestia users...
I am quite sure that you are simply wrong here. A principal strategy of the Celestia Devs has always been to visualize the Universe as closely as possible to reality (i.e. with unaided vision). Whether YOU like that or not. Since its start in 2002, Celestia has been downloaded from SourceForge more than 10 million times
..This great success may well be viewed as a confirmation of our basic philosophy | 0.848672 | 3.02555 |
For being one of the most loyal presences in our lives, we likely don’t think about Earth’s Moon. It’s just always there, a daily friend and a pleasant night light.
Well, in this post, we’re going to change all that with some fascinating facts about the Moon to impress your friends, win that crucial bar trivia question, or just keep in mind for the next time you peer up at the big white orb in the night sky.
Here are the most interesting Moon facts to know:
1. The Moon Goes by Several Names
When we capitalize the word “moon” (Moon), we are referring to Earth’s moon, or our Moon. All other moons start with a lowercase “m.”
However, the Moon also goes by other names, as well. There’s Luna, of course, which comes from Latin lūna and Middle English luna or lune. There’s also Selene, which comes from the Ancient Greek, as well as Cynthia
2. It’s a Satellite
The moon is a satellite, but not the kind you saw on rooftops to get cable television before Netflix came along. A satellite is simply something that revolves around a planet or minor planet in space, and a our Moon is Earth’s only natural satellite.
As such, our Moon orbits the Earth, just as our Earth orbits the Sun. Every 27.3 days, the Moon makes one complete rotation around the Earth. Back in the day, many people used a lunar calendar, such as the Julian calendar, to mark the days of the year.
To power our modern technology, from espionage systems to GPS, we’ve launched some human-made satellites up there to orbit Earth, so the Moon has some company.
3. Australia is Wider Than the Moon
Australia, being about 2,511 mi (4,042 km) long at its widest point, is about 352 mi (567 km) wider than the moon, which has a diameter of 2,159 mi (3,475 km). This means that if you were to set the moon down in the middle of Australia, the edges of Australia at its easternmost and westernmost points would stick out further than the moon!
Definitely one of the most interesting moon facts, right?
4. It’s Actually Pretty Big
Despite being smaller in diameter than Australia, the Moon is pretty large in size. In fact, out of all the planetary satellites in the entire Solar System, Earth’s Moon is the biggest when it comes to moon-planet size ratio. Out of all Solar System satellites, it is the fifth largest.
It’s average, or mean, radius is 1,079.4 mi (1737 km). It has a total circumference of 6,786 mi (10,921 km).
5. The Moon Causes Earth’s Tides
Because the Moon has significant gravity, actually causes the rising and falling of sea levels each day. When a part of Earth with oceans, seas, and even lakes is closest to Earth, there will be high tides, due to the gravitational pull of the Moon. However, the farthest part of the Earth from the Moon also gets high tides, due to inertia. Low tides form in the places in between these two distances.
Well, that’s all our Moon facts for now, but we’ll be adding more regularly. We hope you’ve found them easy to understand and informative! Got any questions, feedback, or other facts about the Moon to add to our list? Let us know below in the comments, and thanks for reading! | 0.830656 | 3.105695 |
The way we think of flying saucers is about to get a pretty serious makeover.
Instead of transporting aliens across the universe (as portrayed in sci-fi films), rocket-powered flying saucers could send the first humans to the surface of Mars.
At least, if everything goes according to NASA's plans.
Right now, NASA's Jet Propulsion Laboratory in California is testing its low-density supersonic decelerator (LDSD) project, which includes the test model of an actual flying saucer that will carry heavier loads — including astronauts — to Mars in the not-too-distant future.
The technology NASA used to land its Curiosity rover on the red planet in 2012 won't cut it when it comes to heavier payloads like manned missions. So, NASA is pushing the boundaries of spacecraft technology with their LDSD project to design the safest, most cost-effective way of slowing a spacecraft down once it has entered the Red Planet's atmosphere.
The most cost-effective way to slow down larger loads as they approach Mars is to take advantage of the natural drag, or friction, in the atmosphere. The LDSD's large, flat, saucer-like surface will maximize this potential, generating a lot of drag to help slow it down as it falls to Mars.
Still, the craft could benefit from even more drag. That's why scientists created the Supersonic Inflatable Aerodynamic Decelerator (SIAD). It slows it down even more by making the object larger.
Here, the SIAD is shown the center with the LDSD vehicle on the right. True to its name, SIAD is an inflatable tube that expands the overall size of the LDSD vehicle from 15 feet in diameter to up to 26 feet wide.
The SIAD does its job by wrapping around the body of the LDSD and then inflating with pressurized gas. NASA has two different versions of the SIAD: One that expands to make a circle 20-feet wide that could be used on future robotic missions and another that is 26-feet-wide for eventual manned missions.
The SIAD is designed to slow down a vehicle from speeds of 2,600 miles per hour or higher to 1,500 miles per hour or lower. To test the sturdiness of the LDSD vehicle and the SIAD material at those breakneck speeds, NASA engineers attach the LDSD vehicle to a rocket sled and then inflate the device once the vehicle reaches supersonic speeds.
The flight tests are used to show how well the SIAD and its parachute can slow down the LDSD vehicle. Although they're testing it on Earth, they want the conditions to resemble the supersonic speeds it would reach on Mars. So, they send the vehicle to 180,000 feet above Earth's surface. Here's a schematic of how the test worked. | 0.812474 | 3.472766 |
Journal of the Franklin Institute, Vol. 268, No. 6, December, 1959
* Based on a series of Reports of the Electrical Research Association, Leatherhead, England.
Applications of the writer's electrical discharge theory of some astrophysical phenomena are discussed, and interesting interrelationships are adduced between corresponding physical processes in the laboratory and in the terrestrial, stellar and galactic atmospheres. The building-up of electrostatic fields in these atmospheres is discussed, and the breakdown of these fields in electrical discharges is shown to account for the light emission from, and gas movements in, the atmospheres of the long-period variable and combination-spectra stars. The theory has a bearing on the evolutionary process in, and chemical composition of, late-type stars. It will explain the gas movements observed in extra-galactic radio sources, and accounts for the magnetic fields and "relativistic" electrons required by the synchrotron theory of the radio noise itself, for which no other explanation has so far been offered. The theory likewise suggests an explanation for the existence in some galaxies of two stellar populations, which is in agreement with observations of some of their major features. A new theory of propagation of these cosmical electrical discharges is put forward which offers a way out of the difficulty hitherto met in explaining the short time lags of some magnetic storms on the causative solar outbursts, and the correspondingly high average velocities of the particles responsible for these storms. These are much greater than any velocities so far observed at or near the sun's surface. It is shown that in these large cosmic electrical discharges thermonuclear reactions become important when the discharge temperature reaches about 400,000,000 K.
Some years ago the writer (1a) attempted to out-Franklin Franklin in the extension of the field of electrical discharges in gases, by suggesting a series of steps, the greatest of which may be as great as the universe itself. However, the present survey will be limited to the presentation of the evidence for some applications of the theory on the stellar and galactic scales. The manifestations of a series of physical processes will be studied in the laboratory, as well as in the terrestrial, stellar and galactic atmospheres, in the hope that the consideration of electric field-building and discharge phenomena on such a wide variety of magnitudes may prove suggestive for meteorological and nuclear physicists, as well as for astrophysicists and those interested in the study of electrical discharges themselves. For, in the course of these investigations an estimate has been obtained for the temperature required for the engendering of thermonuclear reactions to quite a marked degree in these extensive electrical discharges in cosmic atmospheres. This is found to occur at a temperature of about 400 million degrees absolute.
In a letter to Dr. Lining of Charles Town, South Carolina, addressed and dated "Philadelphia, March 18, 1755," Franklin wrote: "I wish I could give you any satisfaction in the article of clouds. I am still at a loss about the manner in which they become charged with electricity; no hypothesis I have yet formed perfectly satisfying me." After over 200 years that last sentence might, and indeed can still be found in any exhaustive discussion of the subject. For example a paper presented to last year's U. S. Air Force Conference on Atmospheric Electricity and entitled "'The Lightning Mechanism and its Relation to Natural and Artificial Freezing Nuclei" opens with the sentence, "There is as yet no generally accepted theory for the electric charge generation in thunderstorms", while another paper refers to "the unsolved problem of thunderstorm electricity."
Not surprisingly it is still more difficult to deal adequately with the problem of charge separation and field-building in cosmic atmospheres, in which the air, water and ice of the terrestrial atmosphere are replaced mainly by hydrogen and helium and the oxides, hydrides etc. of a variety of metals, such as titanium, zirconium, vanadium, etc. Indeed the writer has often been told authoritatively, as at the Liège astrophysical symposium in 1957, that it is "impossible" for electrostatic fields to be built up, even in the relatively cold atmospheres of the long-period variable stars. However he hopes to show that far from it being "impossible," it would be quite surprising if electrical effects were not observed in the conditions existing in these stellar atmospheres.
Terrestrial Atmospheric Electric Fields
Two names which should be better known to students of electricity than they appear to be are those of Stephen Gray and the late Professor P. E. Shaw of Nottingham University. The former first showed that electricity could be conducted, and thus greatly extended the science of electricity as it was known in 1729 (2), while the latter (3a) fundamentally changed the subject of electrostatics by showing that in order to cause the separation of electric charges by the rubbing together of two bodies it is not necessary to start with two different materials, an experimental fact which still causes surprise to most physics students when they are informed of it. Two sticks of the same material will become oppositely charged provided the rubbing is asymmetrical; for example, if a limited section, say 1 cm. in length, of one rod, is rubbed along the whole length of a similar rod, then the two rods will have opposite charges.
Such asymmetrical reactions obviously occur in wind-blown dusts and powders, and Shaw showed (3b) that these also become charged, even though the reactions are limited to those between particles of the same material. Furthermore, he showed that the charging effect is of the same order of magnitude with cold dry ice particles as it is with sand.
In view of the chief cause of asymmetry of the effects in these conditions we may suppose that on an average larger and smaller particles will become oppositely charged, and there is some experimental evidence to support this conclusion. Their separation in wind-blown clouds of dust in a gravitational field will then load to the generation of electric fields in such clouds. It is well known that electric fields are set up in such circumstances, and in terrestrial sand and dust storms and in the ejectamenta from volcanoes the fields so generated can lead to the electrical breakdown of air at atmospheric pressure.
It seems to the writer significant that during a discussion of thunderstorm problems at the Royal Meteorological Society (4), two of the most active observers both averred that no electrical effects are to be anticipated in thunderclouds until the anvil-shaped cap of cirrus cloud is formed at the top of the thundercloud. This forms at about -30 C. and at a height of 30,000 to 40,000 ft., and is composed of dry ice crystals. This view of the critical requirement for the occurrence of electrification in thunderclouds is supported by the recent mass attack on this problem in the U. S. (5). It was found that lightning only occurs when the top of the thundercloud reaches heights of the order of 30,000 to 40,000 ft. and temperatures below - 20 C. Though the actual physical processes involved in thundercloud charge separation are still the subject of considerable discussion, it seems to the writer that these observations in the laboratory, in sand and dust storms, and in volcanic eruptions point to the adequacy of static electrification to explain the phenomena (3b).
This is supported by other papers in the aforementioned volume of the proceedings of the second U. S. Air Force on Atmospheric Electricity where Chalmers (6) writes "... there seems to be support for the idea that the charge separation is concerned with ice particles colliding with one another," as Simpson and Scrase had earlier suggested. In an investigation of charge generation on a mountain top it was noted that "All strong charging rates are connected with ice crystals in the air (7)."
But perhaps the strongest evidence on the origin of thunderstorm electricity afforded by that Symposium is the observation of the quite remarkable intensity of the electrical effects in the electric storms associated with tornadoes and at heights where ice particles alone exist (8).
Electric Fields in Stellar Atmospheres
The most obvious extension of these ideas is to the atmospheres of the long-period variable stars, the outstanding characteristics of which, apart from their great cyclical variation in optical magnitude, are their size and their extensive atmospheres, and their very low temperatures; some of them hardly shine at all, and the highest of their "surface" temperatures is under 4000 K. These cold "surfaces" -- if they can be said to have a surface at all -- have radii approximating in some cases to that of the Earth's orbit, and outside these "surfaces" extend tenuous atmospheres which could in some cases envelop the whole solar system.
These atmospheres would be, and are, relatively cold, apart from the periodical outbursts, during which the nature of the light emitted shows that some of it must originate in gas whose temperature has somehow been raised to 5000 or 10,000 K., and in a few cases even to 500,000 K. or a million degrees absolute. The vexed question has been, whence come these high temperatures? To which the writer's reply is, from lightning flashes in stellar thunderstorms (1a, c). For at minimum light the temperatures of these extensive atmospheres fall far below their "surface" temperatures of 1500 or 2000 K., and there would appear to be nothing to prevent them reaching values at which the electrical conductivity is sufficiently low to allow of the generation of electrostatic fields.
At these low temperatures a number of materials, such as metallic oxides, hydrides, and carbides will solidify out of the atmosphere. The existence at minimum phase of these solid or liquid particles had indeed already been deduced, as they offer the likeliest explanation of a large proportion of the diminution of the star's light at minimum brightness. To a large extent the nature of the light remains the same -- there is just less of it. It is veiled by the cloud of particles.
It is also known from a spectroscopic analysis of the light that great winds blow in these atmospheres, with velocities up to more than 10 km. per second, so that the solid particles in these atmospheres will be subject to the violent impacts required for the generation of static.
The conclusion would appear to be inevitable that there will be considerable generation of static and of electric fields in these stellar atmospheres. These fields will go on building up at an increasing rate as the temperature falls towards minimum, so that, unless some other, and hitherto quite unforeseen, cause of the outburst becomes effective, electrical breakdown in discharges is bound to occur sooner or later.
Temporal Characteristics of Stellar Outbursts
One can compare very roughly the time which will be required for the build-up to breakdown by comparing the gas densities and velocities and the gravitational forces in these stellar atmospheres with those observed in thunderstorms. Whereas the build-up time in the thundercloud is of the order of 100 seconds, the estimated time under these stellar atmospheric conditions is of the order of 106 to 109 seconds, according as the process of charge separation depends on the first or second power of the relative velocity of the particles (1c). This agrees as well as can be expected with the observed periods of these stars, which range from about 100 to 600 days, or 107 to 108 seconds. The writer has therefore suggested (1d) that meteorological physicists may be able to elucidate the process of charge separation in thunderclouds, by a more precise comparison of the conditions therein, with those existing in the different types of long-period variable and combination-spectra stars, to which more reference will be made later.
Another check on the times involved in these stellar outbursts is obtained from a consideration of the duration of the period during which bright emission lines are observed in the stars, spectra, indicating the occurrence of the discharges. Apart from an effect to be discussed later, which does not affect the present argument, the velocity of propagation of electrical discharges will be independent of the gas density, and equal to the velocity of propagation of the lightning leader stroke at atmospheric pressure -- that is, 107 to 108 cm. per second, the velocity of propagation of electrical breakdown in a hydrogen atmosphere being probably slightly greater than in air (9). Since the distances involved are of the order of 1014 to 1015 cm., the duration of the discharge process will be of the order of 107 seconds, again in good agreement with the observed periods of variation, during about half of each of which the bright lines are observed in these stellar spectra. Thus the temporal characteristics of this type of star agree reasonably well with those to be expected on the "thunderstorm" theory of their periodical outbursts.
The general nature of the light itself during each increase in magnitude of these stars -- which at maximum may reach 10,000 times their brightness at light minimum, the average increase being by a factor of about 100 -- and its regular "programme," is also quite in accord with the electrical discharge theory (1c). Indeed it has so far proved impossible to account for it in any other way. For in this low temperature atmosphere, mainly hydrogen, there suddenly appear emission lines of hydrogen, helium, including ionized helium, and ionized metals. As we shall see later, in the closely associated combination-spectra stars, the level of excitation reaches that of six times, and even possibly nine or thirteen times, ionized iron atoms, representing an excitation equivalent to temperatures of between five hundred thousand and a million degrees, or more. Indeed so varied is the light emitted by this last type of star at different phases of its cycle, that they have been assumed to comprise a pair of stars, one very cold and one very hot, and an associated nebula.
However, we shall consider simply one large cold star surrounded by an extensive atmosphere. The rate of build-up of the electric field increases with the square of the density, with the gravitational force, and with the velocity; while the breakdown voltage is inversely proportional to the gas density. It follows (1c) that the conditions requisite for electrical breakdown will be reached first low down in the star's atmosphere and the discharges will be propagated outwards towards the star's peripheral layers.
The writer has emphasized (1b, e) that these long electrical discharges will serve as "energy pumps," so to speak, just as does the lightning leader stroke, causing energy generated in one place to be liberated at another. In the lightning discharge, for example, whereas the electrical energy generator is in the thundercloud, the highest current in the discharge actually flows just at the Earth's surface (1f), several kilometers away from the generator. The leader stroke acts as almost a complete short-circuit of the space between the cloud and the ground (1g, h), so that very high field concentrations occur around its advancing tip. This effect is likely to be enhanced in an atmosphere in which the discharge is propagated outwards through a decreasing gas density.
There are thus two effects to be looked for as the discharge proceeds. In the early stages, since it starts low down in the star's atmosphere, the light will be subject to considerable general and selective absorption by the dust particles and molecules of the vapors which abound, such as the oxides of titanium, zirconium, vanadium, etc., as well as C2, CN, and other radicals. It is not to be expected, therefore, that such series of emission lines as the Balmer series of hydrogen, or the various multiplets in say the iron spectrum, will have the relative intensities observed in the laboratory, or anything like them. These relationships will be considerably mutilated by differential absorption in the upper regions of the atmosphere. However, as the discharge is propagated outwards, and as the energy liberated in it causes dissociation of the molecules already referred to, then the relative intensities of these series and multiplets will approach more and more those observed in the laboratory.
This sequence of events has been observed repeatedly by Merrill and other investigators. It is well illustrated, for example, by the variation of the individual lines of multiplet (2) of Fe of which Merrill writes(10a) :
"In the last column, phase + 162 days (i.e. 162 days after maximum light) the relative intensities are the same as in the laboratory. At earlier phases, the intensities are modified, probably by TiO band absorption, as in R Leonis. The behaviour of this multiplet presents another example of the general tendency of bright lines to escape from the effects of the reversing layer as the phase advances."
The same explanation will account for the wide variation in the relative intensities of Hg: Hd at different phases of the brightness cycle (10b). It is only some considerable time after maximum light that this ratio approaches the value observed in the laboratory.
As a result of the intensification of the field at the head of the advancing discharge, and its projection outwards into regions of lower gas pressure, referred to above, the excitation of the gas will be increased. The spectrum of the gas will, therefore, change during the outburst from one of high temperature at relatively high gas pressure, to one of higher excitation at lower gas density, with forbidden lines entering as the very low pressures of the outer regions of the star's atmosphere are reached. The former of these two phases accounts for the spectrum to account for which it was earlier assumed that the large cold star was accompanied by a small hot "companion" star; while the later stages of the discharge account for the '"nebular" contribution to the spectrum. It was therefore suggested (1c) that the theory will account for the combination spectra in such stars as R Aquarii, Z Andromedae, BF Cygni and AX Persei. In these the initial bright line spectrum, that usually attributed to the postulated "companion" star, comprising lines of H, HeI, Fe II, Ti II, and Si II, gives place, after 100 or 200 days, to a spectrum of higher excitation, containing lines of He II, N III, C III, [O III], [Ne III] and [Fe III]. The nature of this last nebular spectrum is in accord with the suggestion that it originates in regions of very low pressure, far out in the star's atmosphere, towards the completion of electrical neutralization.
The two spectra follow one another fairly regularly after periods of the order of 100 to 200 days in different stars. One observer (11) summed up his description of the sequence of the two different types of spectra by concluding that it is just "... as though they occurred as a consequence of the propagation of running waves over an extended medium." This will be seen to be in accord with the electrical discharge theory, the "running waves" being waves of electrical excitation.
Though the period of variability and brightness at maximum of the long-period variable stars are fairly well defined, they are subject to considerable variation in any one star. This may amount to about 10 days in a period of say 200 days, and to one or two magnitudes in maximum brightness. This variability may have an interesting analogy in the variability of the current in different lightning flashes in the same thunderstorm.
Some years ago (1g), when putting forward a new theory of the initiation and propagation of lightning leader strokes, the writer showed that the theory would explain the very wide variation in lightning currents. For a lightning flash to occur two things are necessary: first, an average electric field between the two charges in the cloud, or between one of these charges and its image in the Earth, sufficient to maintain the process of arc conduction in the leader stroke, when once it is initiated, that is, an average field of 10 to 100 V/cm ; second, in that relatively low average field there must exist a field concentration, such as is caused by a tall grounded building on the Earth, or an elongated volume of space charge in the cloud, sufficient to cause the transition from the field-maintained corona discharge in the St. Elmo's fire at its tip, to a thermally-ionized column of arc discharge. When this transition occurs it was shown that the discharge will become self-propagating, so to speak, and bridge the gap. The smaller the initiating field concentration, the greater must be the average field before the leader stroke is initiated, and the greater will be the current in the discharge when it does occur.
It may be noted in passing that this new conception had an important bearing on the theory of the operation of a lightning conductor (1g), probably the first major change since its introduction by Franklin nearly two hundred years earlier. For the field concentration at the advancing tip of the leader stroke will also vary with the average predischarge field, so that upward streamers will be initiated from grounded buildings earlier in the leader stroke's descent for high average predischarge fields. Thus, heavy flashes will be attracted to the conductor from much greater lateral distances than will light or low current flashes. Previously it had been considered that the protective range of a lightning conductor depended only on its height, and not at all on the nature of the lightning flash.
Fortuitous variation in the distribution of space charge may be expected to cause a similar variability in the conditions required for discharge initiation in all long and purely atmospheric discharges. The longer the initiation of the discharge is delayed in the stellar atmosphere, the greater will be the cooling of the atmosphere after the previous outburst, and the greater also will be the amount of dust solidified out of the atmosphere during the minimum phase. This will have two results. It will cause a greater dimming of the star's light, and hence a lower light minimum, and there will also be a greater increase in the average pre-discharge field, and hence a greater outburst and increase in luminosity when the discharges do occur.
Thus, besides accounting for the irregularity of the periods and the amplitudes of the variations of brightness observed in these stars generally, the theory would also explain some observations made by Merrill (10c) on the combination-spectra star R Aquarii. He has pointed out that in a series of pulsations of this star in the early 1930's very marked dimming of the main "cold" red star was associated with extra bright outbursts of the "companion" star or discharge spectra. The idea of a "companion" star was introduced, as we have seen, to account for the early stages of the electrical discharge. Merrill is the leading observer of and authority on this type of variable star, and it should be recorded that, though the belief is generally held that in all cases two stars and a nebula are required to account for the phenomena, Merrill himself in his Monograph (10c) and papers has been careful to emphasize that in many cases, including R Aquarii itself, there is no positive evidence for the existence of the '"companion" star as he has usually so written it, and that all might in fact come from one large "'cold" star and its atmosphere. Summing up the discussion of this type of star in his Monograph, Merrill wrote (10d) that "... it would be inadvisable at the moment to accept without reserve the hypothesis of actual duplicity for all combination spectra."
The application of the discharge theory to the long-period variable stars has a bearing on two questions of major interest in astronomy, namely, stellar evolution, and the uniformity of the chemical composition of matter throughout the universe, since the atmospheres of these late-type stars are one of the few places where there is generally considered to be a departure from this uniformity. The theory suggests that the observations can be explained by differences in the physical state of matter of the same general chemical composition.
Stars can be arranged in a series having decreasing "surface" temperatures until temperatures of the order of 3500 to 4000 K. are arrived at, that is, temperatures at which the freezing out of hydrides and carbides and carbon itself from their atmospheres begins. Below these temperatures the series apparently trifurcates, the three branches being differentiated by the different absorbing molecules in their atmospheres. The spectra of one group, the carbon stars of Classes R and N, show the bands produced by the C2 and CN molecules; another, group, the titanium stars of Class M, shows mainly bands of titanium oxide; while in the third group, the zirconium stars of Class S, the titanium oxide bands are replaced by those of zirconium oxide. These differences are usually attributed to actual differences in the chemical constitution of the stars, atmospheres. The writer, however, has suggested (1j) that the difference is mainly one of average physical state of the atmospheric material external to the star's "surfaces" or photospheres.
Let us assume that during the evolutionary process the average temperature of this outer atmosphere is falling. The arguments adduced can be reversed if in fact this average temperature rises as the stars age. The first molecules to form will be those of C2 and CN. At still lower temperatures particles of carbon, carbides and hydrides will be formed so that the molecules of C2 will disappear, and with them the C2 bands will disappear from the spectrum. They will be replaced by the bands of molecules which associate at lower temperatures, such as zirconium oxide, which will begin to appear at temperatures of the order of 3000 K. However, in its turn zirconium oxide will freeze out and become solid particles at temperatures of around 2500 K., its place being taken by titanium oxide and others which associate at around these temperatures. Titanium oxide will remain in the vapor state, and give rise to bands in the star's spectrum, until it too solidifies at temperatures of around 1600 K.
At any one point in the evolution of the outer atmosphere of a star, therefore, the oscillations in temperature of that atmosphere, due to the occurrence of the discharges followed by a period of cooling and electric field-generation, will occur within a given range. This range will be appropriate for the appearance in its spectrum of each of the three main sets of bands in turn as the average temperature falls. First, the carbon molecules will disappear, having become particles of carbon which will no longer be vaporized to any appreciable extent by the discharges when they occur. The carbon bands will be replaced by zirconium bands, until they too in turn disappear when the average temperature falls so low that the solid particles of zirconium oxide are no longer vaporized, and finally only titanium oxide bands will appear in the star's spectrum throughout its cycle..
There is one piece of evidence which strongly supports the new theory, and which would appear entirely to negative the possibility that the explanation lies in differing chemical constitutions. It is quite possible on the view now proposed that stellar atmospheres will exist in which at minimum only titanium oxide bands appear in their spectra, but in which the rise in temperature caused by the discharges is so great that, at maximum, all the titanium oxide molecules are dissociated, and sufficient zirconium oxide particles are vaporized, to lead to the replacement of the titanium oxide bands by those of zirconium oxide at maximum brightness. In other words, the star will change from type M, at minimum, to type S, at maximum, a change which would be quite impossible if the difference between these two stellar types is one of chemical composition.
In fact, however, stars do exist in which this change occurs as the result of a specially great outburst -- that is, when they reach what is for them an exceptionally bright maximum, and consequently an unusually high average temperature. One such star is c Cygni. It has been observed to change from type M to type S at unusually bright maxima.
It would thus seem that these three types of late stars -- carbon stars, zirconium stars and titanium stars of types N, R, S and M, respectively -- are not necessarily in conflict with the uniformity of chemical constitution of matter observed fairly generally throughout the universe, as they are generally believed to be, nor do they necessarily indicate a trifurcation of the stellar evolutionary sequence in the way they are generally regarded as doing.
Perhaps the most intriguing inter-relationship so far brought to light between the characteristics of these electrical discharges in the laboratory, the atmosphere, and in stellar and galactic atmospheres, is that existing between the gas movements engendered by the discharges. We are not here concerned with movements analogous to the explosive movement of the surrounding gas, which results in the thunder of the lightning discharge. It is, in contrast, a continuous axial flow of the hottest gas along the central regions of the discharge channel. The latter acts like a hose-pipe squirting gas from regions of high current and high current density towards regions where the product of these two quantities is reduced.
The Arc and Lightning Discharges
R. C. Mason (12) showed that because the charged particles of the electric discharge flow along the channel in its own magnetic field, they will be constrained by the field to move inwards towards the axis of the discharge. He showed that this would result in an axial increase in gas pressure, which is proportional to the product of the current and the current density.
Maecker (13) later drew the "obvious" conclusion that constrictions in the discharge channel, such as exist at the anode and cathode spots of the arc discharge, will give rise to high pressures, and therefore to gas movement down the resulting pressure gradient. And so the anode and cathode jets of the electric arc were explained satisfactorily for the first time. King (14) has shown in these laboratories that these jets account in large part for the transfer of metal in the arc welding process, and explain why it is independent of gravity. (He has also shown that the temperature of the welding arc is several times greater than the 6000 or 7000 K. usually quoted for it. It is usually in the range 15,000 to 20,000 K.)
The pressure will increase with the product of the current and the current density, but the velocity of the gas flow cannot go on increasing indefinitely. It is limited by the velocity of sound in the gas at the temperature of the discharge. For example (1h), in the lightning discharge the temperature will vary with the current in different flashes, but will almost certainly lie between 50,000 and 100,000 K., for periods of hundreds of microseconds or a millisecond. With these ranges of temperatures and times, the distance moved up the lightning channel by the gas and vaporized material at the Earth's surface will lie between 70 and 1000 cm. This agrees with, and indeed explains, the observations of Israel and Wurm (15) that metal lines are observed in the spectrum of a lightning flash up to a height of about 2 meters above the ground.
The Long-Period Variable Stars
The first extra-terrestrial application of these ideas is again to the discharges in the atmospheres of the long-period variable stars (1k). When the bright emission lines appear amid the molecular absorption bands in the spectra of these stars, they are those of ionized and neutral metal atoms, hydrogen, and helium, denoting gas temperatures of between 5000 and 10,000 K. Since the gas is largely ionized hydrogen the velocity of sound in it at these temperatures will lie between 8.5 and 12 km. per second. This is an extremely narrow range of velocities when one considers that, apart from the theory now being put forward, the gas velocities might have been measured in miles per hour, miles per minute, miles, tens, hundreds or thousands or more of miles per second. However, extremely narrow though this theoretical range of gas velocities is, relative to the whole gamut of possible cosmic velocities, it contains both the average values obtained for these gas velocities by the two leading authorities on this type of star at Mount Wilson. In these stars the light absorption is so great that only that from the discharges on the near side of the star's atmosphere is photographed, so that the spectra show broadened emission lines displaced towards the violet relative to the absorption lines produced by the relatively stationary atmosphere. From the displacement of the emission lines towards the violet in the spectra of 72 long-period variable stars, Merrill (10e) obtained an average value for the velocity of the gas of 11km. per second, while from similar measurements in the spectra of seventeen closely similar irregular variable stars Joy (16) obtained an average velocity of 9 km. per second.
The Combination-Spectra Stars
As has already been seen the combination-spectra stars are similar in many respects to the long-period variable stars. It was therefore somewhat disconcerting (11) from the point of view of this theory of these gas movements, to find that in one of these stars, AX Persei, Merrill (10f) had observed displacements of the emission lines relative to the absorption lines which were equivalent to velocities of approach of 110 km. per second. Since the velocity of sound in a gas only increases as the square root of the absolute temperature, this meant that in the very extensive cold atmosphere of this star the gas temperature in the discharges must have reached 500,000 to 1,000,000 K., if the theory were to be saved. The theory was saved, however, by an equally surprising observation in another paper, by Swings and Struve (17), in which they showed that some of the emission lines in the spectra of AX Persei derived from Fe VI, Fe VII, and even possibly from Fe X, that is, from five, six, or even possibly nine times ionized iron atoms, which also require for their production the buffeting to be expected in a gas at the temperature of about a million degrees absolute, required to account for the high gas velocity.
Galactic Electrical Discharges
This upward trend of the axial temperatures with increase in the scale of these cosmic electrical discharges cannot go on indefinitely. There will come a time when those temperatures are reached, which are being eagerly pursued in the world's physical laboratories at the moment, namely those at which thermonuclear reactions will occur. When the latter are produced in sufficient degree then the increase in gas pressure which they produce will balance the inward pressure of the magnetic pinch effect, and further increase in temperature will be prevented.
Instead of taking place in deuterium, as in the laboratory discharges aimed at producing thermonuclear reactions, the cosmic discharges occur in a gas which is probably about 80 per cent hydrogen, with two parts in 10,000 deuterium, and with about 20 per cent helium and fractional percentages of the other atoms. The experts will probably agree that in the conditions of these large cosmic discharges temperatures of 108 to 109 K. will be required to cause nuclear reactions on a large scale. On the gas velocity thermometer, so to describe it, maximum velocities of 1750 to 5400 km. per second, the velocity of sound in ionized hydrogen at these temperatures, will therefore be observed in these larger electrical discharges when these temperatures are reached. These galactic discharges have indeed been investigated by Seyfert (18) at Mount Wilson, for he has examined the spectra emitted by bright emission patches in some extra-galactic nebulae. In these discharges velocities of recession are observed, as well as velocities of approach, so that the emission lines are ,broadened, rather than displaced. The velocities which Seyfert has recorded are in the range 1800 to 4250 km. per second, in good agreement with the above "theoretical" range of velocities.
An interesting observation from the new point of view is Baade and Minkowski's (19) determination of the gas velocities in the well-known radio source, NGC 1275, illustrated in Fig. 1. They find that the gas in the well-defined arms is moving at a velocity of about 5250 km. per second, while that in the less well-defined patches of the back-ground gas is moving at about 8250 km. per second. They have therefore suggested that the source is a collision between two nebulae or galaxies, moving with these two velocities. The writer has suggested (1m) that at least some of these extra-galactic radio sources are galaxies in which the galactic radial electric field is breaking down and being. neutralized in electrical discharges, which ultimately result in the formation of the spiral arms, for which last there is still no satisfactory theory. On this view the channels in NGC 1275 are these discharge channels, and the gas in them has been accelerated to a velocity of about 3000 km. per second in the line of sight by the pressure gradient caused by the magnetic pinch effect in the galactic discharge.
Fig. 1. Photograph of the radio source NGC 1275 taken with the 200-in. telescope at Mount Palomar Observatory.(ll3600-5000 Å.)
Fig. 2. Photograph of the radio source NGC 4486 taken with the 200-in. telescope at Mount Palomar Observatory. (ll3600-5000 Å)
The light from the discharges on the other side of the galaxy may well be lost in the nebula's dusty atmosphere. The difficulty of photographing these discharge channels, even on the near side of a galaxy is illustrated in Figs. 2 and 3. The length of the discharge channel in that radio source, NGC 4486, is 300 parsecs and its diameter about 30 parsecs -- a parsec being about 19 million million miles (19).
As regards the actual mechanism producing the radio waves, Shklovsky (20) showed that this could be explained in terms of synchrotron radiation emitted by extremely high speed electrons moving in a magnetic field. However, the world's astrophysicists recently assembled in the U.S.A. (21) had no clue to offer as to the origin of either the magnetic field or the "relativistic" electrons, so that, as it stood, the "'explanation" left something to be desired. This something would appear to be supplied by the electrical discharge theory of the phenomena. The current in the discharge obviously produces the required magnetic field. As regards the high speed electrons, the gas velocities being 1800 to 5400 km. per second, the corresponding electronic velocities will be over 40 times these values or over 7.2 x 109 to 2.16 x 1011 cm. per second. The theoretical values are therefore in the range required by Shklovsky's theory.
Fig. 3. Photograph of the central regions of NGC 4486 taken with the 100-in. telescope at Mount Wilson Observatory. (l < 4000Å)
At an earlier Symposium of the I.A.U. (22) prominence was given to the prediction made by Shklovsky that the radiation from NGC 4486 should be polarized on the synchrotron radiation theory, and to Baade's observations confirming this prediction. However, many years ago (1p) the writer pointed out that the radiation from these large single electrical discharges should be polarized, and that this could be looked for in the initial stages of novae, for example. As a result of this suggestion this observation was put on the observing program of Mount Wilson Observatory for the next bright nova outburst.
In the galactic radio source, the Crab Nebula, from which the radiation, both optical and radio, is similar to that from NGC 4486, the phenomena can be subjected to more detailed investigation. As a result of such an examination Woltjer (23) has recently deduced that the varying directions of the polarization can be accounted for if electric currents flow along the gaseous filaments. The conclusion that these filaments are electrical discharge channels would appear to be inevitable, and the observed gas velocity of over 1,000 km. per second enables their temperature to be determined as about 3 x 107 K.
Shklovsky (20) has estimated that if all metagalactic radio noise is to be accounted for as originating in such "jets" or discharge channels as that in NGC 4486, then at present about one per cent of all galaxies must be passing through this phase. From this the velocity of propagation of these discharges can be calculated, since, on the discharge theory, the time scale of these phenomena is determined by this velocity. The age of the nebulae is 109 to 1010. years, so that if at any one time one per cent are passing through a particular phase of their life, this phase must last for 107 to 108 years in any one nebula. As the length of the discharges is of the order of 104 to 105 light years, it follows that the velocity of propagation is of the order of 10-3 times the velocity of light, or of the same order as the velocity of propagation of electrical discharges in the terrestrial and stellar atmospheres. This is a result to be expected a priori on theory (1n), since the expression for the velocity of propagation of electrical breakdown depends on the product of the mean free path and the breakdown potential gradient. One is directly and the other inversely proportional to the gas density, so the velocity of propagation may be expected to be independent of the gas density, even over the range of about 1020 to 1 in density, embraced by the range of atmospheres considered.
Actually another factor enters in these galactic nebulae, which changes the nature of the discharge propagation process; however, it does not materially alter the above argument, as will be seen later.
Another major question on which the discharge theory would appear to have an important bearing is that of the origin of the two stellar Populations in the galaxies (1q). Globular and elliptical nebulae, which are those in which the main galactic discharge has still to occur (1a), contain stars of Population II. These, on the view now proposed, are the oldest stars which have been formed contemporaneously with the development of the rotational form of the nebula, and with the building up of the generally radial electric field in the nebula's gaseous atmosphere, which envelops the stars of Population II. The electrical breakdown of this atmospheric electric field results in the development of either an irregular nebula, from a globular nebula, or a more or less well defined spiral nebula, from a more or less markedly elliptical nebula. The older Population II stars in the nebula will be little affected by the occurrence of the discharges. The latter will, however, have a considerable effect on the disposition of gas and dust in the nebula. This will be collected into the discharge channels -- the spiral arms -- by the magnetic pinch effect, a deduction which has been in fact amply confirmed by various observations, optical and radio. There, in gas of greatly increased density, a second population of younger smaller stars will be formed relatively quickly.
On this view, therefore, this second population of stars, which corresponds to Baade's Population I, should be formed along discharge channels, superposed on, or threading through, the general aggregate of Population II stars, which had been formed earlier in the original globular or elliptical phase of the nebula.
That this conclusion agrees well with observation will be seen from the following description (24) of what is actually observed, in which the italics are the writer's:
"A spiral galaxy combines the properties of irregular and elliptical nebulae. The flattened spiral arms are populated by the same objects that characterize irregular systems -- dust, gas and blue super giants. The spiral structure is imbedded in, and rotates within, a structureless sub-stratum that resembles an elliptical galaxy in general features and, in particular, in the objects that populate it."
A main idea behind the present account, as expressed in the introductory section, has been the study of various phenomena -- atmospheric electrostatic field-building, electrical discharge characteristics, etc. -- on a wide variety of scales. The new theory of discharge propagation now to be considered applies, however, only to the breakdown of electrostatic fields in cosmical atmospheres, and does not apply at all in normal long sparks or terrestrial lightning discharges. For the latter the theory that breakdown to a thermally ionized column of arc discharge is complete during the leader stroke still applies (lg, h). The theory now proposed is merely a development of that conception which becomes applicable when the temperature in the leader stroke reaches a sufficiently high value -- of the order of 8 million degrees.
The writer has emphasized above, and in a recent note (1n), that, so far as the normal process of voltage breakdown is concerned, there is no reason to expect that the velocity of propagation of the breakdown process will vary with gas density. However, in these long cosmical electrical discharges a point will be reached at which a radical change will occur in the whole propagation process. In the discharge channel already formed a jet of gas will be generated, which will flow along the axis of the channel towards its advancing head. As the temperature of the channel rises, so also will the velocity of this jet. When this velocity reaches about 5 x 10, cm. per second, that is, when the axial gas temperature reaches about 8 million degrees absolute, then the velocity of the jet of hot gas will exceed that of the normal process of voltage breakdown in a hydrogen atmosphere, which is probably less than 5 x 107 cm. per second. Thereafter the propagation will depend on the jet of hot gas, and the velocity of propagation will depend upon its temperature. Velocities of propagation of up to about 4000 km. per second will thus become a possibility.
The last remark in the previous section may help to solve an outstanding difficulty which confronts even the electrical discharge theory of those magnetic storms which are observed to follow events at the sun's surface by periods of 1 to 4 days. Whereas no gas velocities greater than 600 or 700 km. per second have been observed at or near the sun's surface, the shorter of these two periods, 1 day, represents an average velocity of the jet of particles causing the magnetic storm of over 2000 km. per second. This situation has been rendered even more perplexing by Meinel's recent observation (25), that during aurorae and the accompanying magnetic storms protons enter the Earth's upper atmosphere at velocities of over 3,500 km. per second, or about five times the maximum velocity so far observed in outbursts near the sun's surface.
It will be seen that, applied to the theory (1a) that the time interval represents the time required for the propagation of an electrical discharge through a tenuous solar atmosphere, the new developments on discharge propagation offer a possible solution. For, as has already been shown, electrical discharges can accelerate particles up to just about the maximum velocities so far observed in these particles comprising magnetic storms.
Indeed the existence of this upper limit of about 3000 or 4000 km. per second to these relative velocities in a wide variety of discharge conditions in cosmical atmospheres suggests that the corresponding discharge temperature, namely about 400 million degrees absolute, is that at which thermonuclear processes become of paramount importance in these cosmical electrical discharges.
An attempt has been made to show that a great extension of the field of electrical discharges in gases may result from a reassessment of many astrophysical phenomena from the point of view outlined in the preceding pages.
In the letter referred to earlier in this paper, Benjamin Franklin quoted a passage from the "Minutes" he kept of his experiments, in which he had enumerated twelve particulars in which the "electrical fluid agrees with lightning." He continued:
"The electric fluid is attracted by points. We do not know whether this property is in lightning. But since they agree in all the particulars wherein we can already compare them, is it not probable that they agree likewise in this? Let the experiment be made"
The last sentence is surely one of the most pregnant in the history of electricity, and one wonders if perchance it was known to Marconi! In suggesting a step of still greater ratio in the study of this same field of electricity in gases, the writer cannot unfortunately end this note on the intercomparison of the various fields with a similar suggestion. He can only suggest that the observations made in some branches of the wider field of astrophysics should be studied from the new point of view, and hopes he has demonstrated that the first fruits of so doing are at least promising. | 0.911186 | 3.850085 |
Milton Humason: The Man Behind the Hubble Law
Too frequently in science, people who make huge contributions are lost to history for various reasons. Some people assist important scientists in their work, providing critical ideas, while others may even have their work stolen from them. In this article, we will examine the case of the former, with Milton Humason. Here we will find an incredible example of a man who started with little and ended up shaping how we view the universe.
Working Up The Ladder
Humason’s astronomy career really began in 1902, when he moved to Los Angeles at the age of 12. Near there is Mt. Wilson, the location of the observatory that he would eventually work at for over 60 years. At 14, he decided to quit school and work at the mountain observatory, with the goal of living there. Clearly, the location was a fixation for the young man, and he started to help the staff build the telescopes that were built for them (Voller 52).
In fall of 1917 he got a job as a janitor there, mostly by virtue of his personality. The staff loved him and began to instruct him on some of the techniques of astrophotography. George Ellery Hale, the director and founder of the observatory, noticed that Humason had great potential and promoted him from janitor to night assistant. By 1922, 20 years after Humason first moved to LA, he was further promoted to the stellar spectroscopy department. This would forever shape his career, for it was at this time that Edwin Hubble was collecting data which would lead to the famous result of universal expansion (52, 54).
You see, in 1915 Einstein’s relativity was published. In it, one of the implications was a universe existing in 4 dimensions we call space-time. Friedmann was able to expound on this and in 1924 came up with an amazing result: the universe should be expanding. But theory is one thing, and evidence is another. Hubble came up with the evidence for the claim through his redshift study, which measured the stretching of light from the motion of an object. Hubble used Cepheid variables, which have a known period-luminosity relation that makes computing their distance easy. He had previously made use of them in his famous 1929 discovery of M31 aka the Andromeda galaxy, which he was able to show using the Cepheid variable star that the galaxy was outside the confines of our Milky Way. This then led to the “island universe” theory, which we know of as the concept of galaxies. But now, with more at his disposal, he was able to find compelling evidence for universal expansion (54).
Or so the story goes.
When Humason was promoted to the stellar spectroscopy department, he would take spectrum measurements of stars, breaking down the light they shined into wavelength components. Humason would verbally dictate the location of the object they were analyzing while assistant Allan Sardage would write it down. Now, supposedly around the time of this promotion of Humason, Shapely asked him to look at the photographic plates of M31 for any signs of a supernova or any new stars. Humason did just this and found some oddballs he suspected were Cepheid. Humason presented this to Shapely, who erased those marks because he felt they were clouds of gas with no stars in them. Imagine, if that incident actually did happen (for no evidence exists for the event) then Humason was potentially robbed of the chance to uncover the universe’s true nature. Hubble didn’t even start the work that would lead to that conclusion until 1923. We would be talking about the Humason Law instead of the Hubble Law! (Ibid)
So, the question begs: why didn’t Humason defend his findings? After all, he was gifted enough to be a member of the staff without a formal education, but this may have been considered a hindrance to some. Humason also looked up to Shapely as a mentor figure, so maybe out of respect Humason did nothing. Whatever the reason, Humason missed the opportunity. But that doesn’t mean the story with Hubble has ended (55).
Hubble and Humason at Mt. Wilson
At an IAU meeting in 1928, Hubble begins to think about Friedmann’s prediction of an expanding universe and specifically what those conditions would result in. Hubble wanted to find evidence for the expansion, and so his thoughts turned to what he had been studying for years: his “island universes.” He figured out that fainter objects would imply a faster receding velocity because of the Doppler effect stretching out the light. To prove this, Hubble needed data, which translated to lots of spectrums. Through word of mouth, Hubble heard about Humason and his work at Mt. Wilson as well as his reputation of being one of the best of the field. Hubble went to the observatory and began to work with Humason in an effort to collect more spectrums (Ibid).
And boy, did they not mesh. Humason was what many considered to be “an everyman” who just wanted to do his work but have fun with others. Hubble, a graduate of Oxford and not a dropout like Humason, was a former member of the army during World War I. Even though he saw no combat action, he still took his service with pride and preferred to be called Major Hubble. This hints at his possible feelings of superiority and at minimum is a demonstration of his ability to polarize people. He even had a British accent despite being born in Missouri! Many of his colleagues also describe him as desiring to be the center of attention. Despite all of these differences, the spectroscopy was needed and both men began to work (56).
At the time, the largest radial velocity (or movement along the line of sight, aka towards or away) known was recorded in the elliptical galaxy known as NGC 584 by astronomer M. Slipher in Flagstaff, Arizona, with a value of about 1,000 miles per second. But Humason was able to do better when he looked at elliptical galaxy NGC 7619 in the Pegasus Constellation. After a 33 hour exposure on a 100 inch telescope he was able to find a radial velocity of about 2,400 miles per second, After comparing the distance of this object and its radial velocity to NGC 584, they saw a direct proportion between distance and velocity. They found evidence of an expanding universe! (Voller 56, Humason)
Even though they had a small data set, they still published their results in Proceedings of the National Academy of Science in 1929. Hubble knew that if the universe was expanding that possible evidence for the cosmological constant, a numerical construct in many field equations that predicts the expansion (or contraction) factor of the universe. Humason, however, was not enthused about taking another run at the telescope. The reasons were not personal but more about working conditions. The prisms of the time used in spectroscopy were yellow in nature and not good at collecting light from portions of the spectrum. To ensure a good exposure for objects that were hundreds of times fainter than most imaged at that time, long exposures requiring days would be needed. For Humason, it meant a long time in cold, cramped conditions as he worked the equipment (Voller 56-7).
Hubble, perhaps more out of a desire to get great data rather than care for Humason, appeals to Hale to somehow make the working conditions better for Humason. Hale always had liked Humason and thus made the arrangements as fast as possible for improvements to the tech that was being utilized. John Anderson was able to create a new camera that had a decreased necessary exposure time by a significant factor. In fact, the time needed to image a galaxy like NGC 7619 was brought down to 4-6 hours instead of the 33 normally needed. Humason was definitely onboard with these improvements and rejoins Hubble. Over a 2 year period they record even more data and were able to confirm the Hubble Law as fact (57).
Humason, Milton L. “The Large Radial Velocity of NGC 7619. From the Proceedings of the National Academy of Sciences Vol. 15, No. 3, 15 Mar. 1929. Print.
Voller, Ron L. “The Man Who Measured the Cosmos.” Astronomy Jan. 2012: 52, 54-7. Print.
Questions & Answers
© 2016 Leonard Kelley | 0.868846 | 3.292021 |
Today, the Moon has a very weak magnetic field, but researchers from the Massachusetts Institute of Technology (MIT) recently released a paper in Nature showing that the Moon used to have a much stronger magnetic field.
In fact, they believe the Moon’s magnetic field was even stronger than the Earth’s. Planetary geologists have been trying to figure out what lies underneath the surface of the Moon for decades, but solid conclusions have eluded them. The Earth’s magnetic field is generated by the rotation of molten metal in the core creating a dynamo, but scientists had not established the mechanism of the Moon’s magnetic field. It was unknown whether or not the Moon had Earthlike composition: with a crust, quasi-mantle and metallic core or if the Moon retained a partially un-melted and undifferentiated interior.
This recent study supports the idea that the Moon’s magnetic field was also generated by a rotating metal core as opposed to other forces. In the past, researchers speculated the Moon’s magnetic field could have been caused by the wobble of the Moon’s spin axis which could have mobilized the core to produce more magnetism. Others have speculated that the magnetic fields could have formed from large basin-forming impacts.
It has been established that a strong magnetic field existed on the Moon from 4.5 billion to 3.56 billion years ago, but suddenly declined by an order of magnitude about 3.3 billion years ago. The long-lived magnetism was surprising to researchers given how small the lunar core is and how quickly it should have cooled off. The MIT researchers deduced that the intense and long-lived magnetic field required an exceptional energy source. Currently, scientists are still stumped as to why the Moon’s magnetic field was so strong. Another puzzling result from this research is how quickly the Moon’s magnetic field diminished, but the solidification of a previously molten core could be a valid explanation. But other researchers do not believe that the Moon’s core has fully cooled. They believe the Moon’s interior is still molten due to the Earth’s gravitational pull. Although this recent study sheds light on our Moon, much remains unknown about the interior and magnetic field of our closest planetary body. | 0.879655 | 3.530344 |
Scientists discover 10,000 black holes hiding at centre of Milky Way.
Scientists have found thousands of huge black holes lurking at the centre of our galaxy.
A new study reveals that about 10,000 of the giant black holes have been hiding in our own neighbourhood, and we haven’t previously been able to see them.
Scientists have long suspected that there might be a host of smaller black holes surrounding the supermassive one that sits at the centre of our Milky Way. But they are by their nature difficult to see, and so the theory hasn’t been proven.
Now scientists have been able to spot the traces sent out by the smaller black holes.
They searched for X-rays emitted by a subgroup of low-mass black holes that have captured a passing star in their gravitational grip, creating a “black hole binary”.
The hunt came up with evidence of 300 to 500 of the binaries, from which it was possible to infer how many “isolated” black holes there must be at the galactic core. The answer was about 10,000.
US astrophysicist Dr Chuck Hailey, from Columbia University in New York City, said: “This finding confirms a major theory and the implications are many.
“It is going to significantly advance gravitational wave research because knowing the number of black holes in the centre of a typical galaxy can help in better predicting how many gravitational wave events may be associated with them.
“All the information astrophysicists need is at the centre of the galaxy.”
The supermassive black hole at the heart of the Milky Way known as Sagittarius A (Sgr A) contains about four million times the mass of the sun and is 26,000 light years from Earth.
The halo of gas and dust around Sgr A is thought to provide the perfect breeding ground for massive stars that collapse into black holes when they die. These black holes, and others from outside the halo, are pulled towards Sgr A and held captive around it, scientists believe.
However, detecting them is a major a challenge. “Isolated, unmated black holes are just black – they don’t do anything,” said Dr Hailey. “So looking for isolated black holes is not a smart way to find them.”
Instead, his team scoured through archived data from the Chandra X-ray space telescope to identify the X-ray signatures of black hole binaries. The search turned up 12 of the objects within three light years of Sgr A. Further analysis of their properties indicated that there must be up to 500 black hole binaries in total.
The findings are reported in the latest issue of Nature journal.
In the Beatles’ 1967 song Day In The Life, from the Sergeant Pepper album, John Lennon sings: “I read the news today, oh boy: 4,000 holes in Blackburn, Lancashire”. He adds: “Now they know how many holes it takes to fill the Albert Hall.” | 0.829792 | 3.769725 |
A new project called Exoplanets in Transits and their Atmospheres (ExTrA) has been set in motion at the European Southern Observatory’s site at La Silla (Chile). Funded by the European Research Council and the French Agence National de la Recherche, ExTrA’s three 0.6-metre telescopes will be operated remotely from Grenoble, France. This is an exoplanet transit effort centered around finding and characterizing Earth-sized planets orbiting M-dwarf stars.
Not an easy task from the ground, as lead researcher Xavier Bonfils makes clear, though if you’re going to attempt it, northern Chile offers optimum conditions:
“La Silla was selected as the home of the telescopes because of the site’s excellent atmospheric conditions. The kind of light we are observing — near-infrared — is very easily absorbed by Earth’s atmosphere, so we required the driest and darkest conditions possible. La Silla is a perfect match to our specifications.”
To do its work, ExTrA weds spectroscopic information to traditional photometry. The collected light from the target star is fed through optical fibres into a multi-object spectrograph. Known as differential photometry, the method involves collecting light not only from the target but also from four comparison stars. The comparison helps the technology filter out atmospheric distortions and effects produced by the instruments and detectors themselves.
Image: A new national facility at ESO’s La Silla Observatory has successfully made its first observations. The ExTrA telescopes will search for and study Earth-sized planets orbiting nearby red dwarf stars. ExTrA’s novel design allows for much improved sensitivity compared to previous searches. Astronomers now have a powerful new tool to help in the search for potentially habitable worlds. Credit: ESO.
“With the next generation of telescopes, such as ESO’s Extremely Large Telescope, we may be able to study the atmospheres of exoplanets found by ExTra to try to assess the viability of these worlds to support life as we know it. The study of exoplanets is bringing what was once science fiction into the world of science fact.”
Thus ground-based observation continues to increase in precision, soon to be supplemented by space missions like the Transiting Exoplanet Survey Satellite (TESS), the James Webb Space Telescope (JWST) and the European CHaracterising ExOPlanet Satellite (CHEOPS).
Close Look at TRAPPIST-1
And while we’re talking about M-dwarfs, a new paper is out looking at one of the most interesting systems yet discovered, comprising the seven planets around TRAPPIST-1. Lead author Amy Barr (Planetary Science Institute) and colleagues go to work on the interior structures of these planets as well as their tidal heating and convection given what we know about their mass and radius. The balance between tidal heating and convective transport has implications for the mantles of each planet.
Image: A size comparison of the planets of the TRAPPIST-1 system, lined up in order of increasing distance from their host star. The planetary surfaces are portrayed with an artist’s impression of their potential surface features, including water, ice, and atmospheres. The paper from Amy Barr, Vera Dobos and László L. Kiss shows that planets d and e are the most likely to be habitable due to their moderate surface temperatures, modest amounts of tidal heating, and because their heat fluxes are low enough to avoid entering a runaway greenhouse state. Planet d is likely covered by a global water ocean. Credit: NASA/R. Hurt/T. Pyle.
Given that their orbits are slightly eccentric, there is the possibility of tidal heating, which in the Galilean moons has intrigued us for its possibilities at providing an energy source for life beneath an icy crust, and indeed, the paper notes that “…on planets b, e, f, g and h, life might appear in the tidally heated (subsurface) ocean close to hydrothermal vents.“
In the TRAPPIST-1 system, though, we have much to learn about the composition of the respective worlds. The Barr paper examines the limits of present knowledge:
Assuming the planets are composed of water ice, rock, and iron, we determine how much of each might be present, and how thick the different layers would be. Because the masses and radii of the planets are not very well-constrained, we show the full range of possible interior structures and interior compositions.
The paper is a thoroughgoing examination of the TRAPPIST-1 planets, with planets d and e flagged as the most likely to produce habitable conditions. Here tidal heating would be modest and heat flux low enough to avoid runaway greenhouse conditions:
Planet d is likely to be covered by a global water ocean, and can be habitable if its albedo is ≳ 0.3. Planetary albedos may be estimated from photometric measurements during occultations (see e.g. Rowe et al., 2008) which may give an additional constraint on the habitability of TRAPPIST-1d. As discussed in Section 5, planet e is likely to have liquid water on its surface, too, according to climate models (Turbet et al., 2017; Wolf, 2017).
Planets f, g, and h, the authors believe, are rich in H2O, possibly containing liquid water oceans beneath a thick ice mantle. Planets b and c likely harbor magma oceans in their interiors. Planet b in particular demands further work, given its proximity to the central star and its “seemingly water-rich composition,” while c may experience eruptions from its magma ocean, a phenomenon that may eventually become detectable.
But note how far we have to go:
Our knowledge of the compositions of the four interior planets, chiefly, their water content, can significantly be improved if their masses can be determined to within ∼ 0.1 to 0.5M⊕, which will require further observations of the TRAPPIST-1 system.
The paper is Barr et al., “Interior Structures and Tidal Heating in the TRAPPIST-1 Planets,” accepted at Astronomy & Astrophysics (preprint). | 0.86401 | 3.908701 |
It takes a lot of detective work to figure out the nature of a type Ia supernova. Celestial Pig Pens and new tricks from old telescopes are contributing to the effort. That’s what we learned at the most recent meeting of Astronomy on Tap Seattle.
Messy Siblings: Supernovae in Binary Systems
Dr. Melissa Graham is a project science analyst for the Large Synoptic Survey Telescope, working out of the Astronomy Department at the University of Washington. Her main research focus is supernovae. In particular, she’s doing a lot of work on type Ia supernovae, which occur in binary star systems. One of the stars involved will be a carbon-oxygen white dwarf star.
“It’s a star that wasn’t massive enough to fuse anything else inside the carbon layers,” Graham explained. Outer layers of hydrogen and helium are thrown off in a planetary nebula phase, so the carbon and oxygen are what’s left.
“Carbon-oxygen white dwarf stars are very compact, very dense, about the size of the Earth but they can be up to about 1.4 times the mass of the Sun,” Graham said. These stars are pretty stable as stars go, so they don’t blow up under normal circumstances.
“When we do see these kind of supernovae that are clearly the explosion of carbon-oxygen white dwarf stars we have to wonder why,” she said. It turns out there are two possible scenarios. The binary can be a pair of carbon-oxygen white dwarf stars that spiral in on each other, merge, and then explode. Or the binary can include one white dwarf and a more typical hydrogen-rich companion star.
“In this case the companion star can feed material onto this carbon-oxygen white dwarf star, might make it go over 1.4 solar masses, become unstable, and then explode,” Graham said.
Which is which?
The key to figuring out which of these scenarios actually occurred is to take a look at the area around the supernova. If the companion is a more hydrogen-rich companion star, the neighborhood can get a little messy.
“It’s sort of like a celestial Pig Pen star that leaves a lot of material lying around,” Graham said. A blast from a supernova can interact with this material and cause it to brighten. The trouble is that astronomers typically only observe type Ia supernovae for a couple of months; they fade quickly. So if this extra material is far away from the event, they might not see the interaction. The answer is patience, to look at the supernova sites for up to 2-3 years after.
Graham did exactly that, using the Hubble Space Telescope to keep an eye on the locations of 65 type Ia supernovae.
“Out of these 65, I very luckily found one” in which there was brightening much later. They checked the spectrum of the light and found hydrogen, a sure sign that the companion in this particular type Ia supernova was a Pig Pen. Graham suspects that up to five percent of such explosions involve messy sibling stars.
Graham looks forward to having the Large Synoptic Survey Telescope (LSST) come on line. She expects it will find some 10 million supernovae in a decade.
“This marks a massive increase in our ability to both find and characterize supernovae,” she said.
Old scope, new tricks
While we wait for LSST an old workhorse telescope is doing interesting work in a similar vein. Professor Eric Bellm of the UW works with the Zwicky Transient Facility (ZTF), which uses the 48-inch telescope at Palomar observatory in California. The scope is a Schmidt, completed in 1948, and for years it was the largest Schmidt telescope in the world. It’s main function at first was to use its wide-field view of the sky to create maps that helped astronomers point Palomar Mountain’s 200-inch Hale Telescope.
The 48-inch was used to do numerous sky surveys over the years. It discovered many asteroids, and Mike Brown used it to find the dwarf planets he used to kill Pluto. The old photographic plates gave way to modern CCDs, and Bellm became the project scientist for the Zwicky Transient Facility—named for astronomer Fritz Zwicky, a prolific discoverer of supernovae—in 2011.
They outfitted the scope with a new camera with 16 CCDs that are four inches per side. They got some big filters for it and put in a robotic arm that could change the filters without getting in the way of the camera. They started surveying in March of last year and can photograph much of the sky on any given night.
“That’s letting us look for things that are rare, things that are changing quickly, things that are unusual,” Bellm said.
Examples of what the ZTF has found include a pair of white dwarfs that are spinning rapidly around each other, with a period of just seven minutes. They can see the orbits decay because of gravitational wave radiation. It has discovered more than 100 young type 1a supernovae. And it found an asteroid with the shortest “year” of any yet discovered; its orbit is entirely within that of Venus.
It’s doing the same sort of work that the LSST will do when it comes online.
“It’s super cool that we’ve got this more than 70 year old telescope that we’re doing cutting-edge science with thanks to the advances of technology,” Bellm said.
Astronomy on Tap Seattle is organized by graduate students in astronomy at the University of Washington, and typically meets on the fourth Wednesday of each month at Peddler Brewing Company in Ballard. The next event is set for September 25. | 0.925036 | 3.895633 |
Measurements made by Rosetta and Philae during the probe’s multiple landings on Comet 67P/Churyumov-Gerasimenko show that the comet’s nucleus is not magnetised.
Studying the properties of a comet can provide clues to the role that magnetic fields played in the formation of Solar System bodies almost 4.6 billion years ago. The infant Solar System was once nothing more than a swirling disc of gas and dust but, within a few million years, the Sun burst into life in the centre of this turbulent disc, with the leftover material going into forming the asteroids, comets, moons and planets.
The dust contained an appreciable fraction of iron, some of it in the form of magnetite. Indeed, millimetre-sized grains of magnetic materials have been found in meteorites, indicating their presence in the early Solar System.
This leads scientists to believe that magnetic fields threading through the proto-planetary disc could have played an important role in moving material around as it started to clump together to form larger bodies.
But it remains unclear as to how crucial magnetic fields were later on in this accretion process, as the building blocks grew to centimetres, metres and then tens of metres across, before gravity started to dominate when they grew to hundreds of metres and kilometres in scale.
Some theories concerning the aggregation of magnetic and non-magnetic dust particles show that the resulting bigger objects could also remain magnetised, allowing them to also be influenced by the magnetic fields of the proto-planetary disc.
Because comets contain some of the most pristine materials in the Solar System, they offer a natural laboratory for investigating whether or not these larger chunks could have remained magnetised. However, detecting the magnetic field of comets has proven difficult in previous missions, which have typically made rapid flybys, relatively far from comet nuclei.
It has taken the proximity of ESA’s Rosetta orbiter to Comet 67P/Churyumov-Gerasimenko, and the measurements made much closer to and at the surface by its lander Philae, to provide the first detailed investigation of the magnetic properties of a comet nucleus.
Philae’s magnetic field measuring instrument is the Rosetta Lander Magnetometer and Plasma Monitor (ROMAP), while Rosetta carries a magnetometer as part of the Rosetta Plasma Consortium suite of sensors (RPC-MAG).
Changes in the magnetic field surrounding Rosetta allowed RPC-MAG to detect the moment when Philae was deployed in the morning of 12 November 2014.
Then, by sensing periodic variations in the measured external magnetic field and motions in its boom arm, ROMAP was able to detect the touchdown events and determine the orientation of Philae over the following hours. Combined with information from the CONSERT experiment that provided an estimate of the final landing site location, timing information, images from Rosetta’s OSIRIS camera, assumptions about the gravity of the comet, and measurements of its shape, it was possible to determine Philae’s trajectory.
The mission teams soon discovered that Philae not only touched down once at Agilkia, but also came into contact with the comet’s surface four times in fact – including a grazing collision with a surface feature that sent it tumbling towards the final touchdown point at Abydos. This complex trajectory turned out to be scientifically beneficial to the ROMAP team.
“The unplanned flight across the surface actually meant we could collect precise magnetic field measurements with Philae at the four points we made contact with, and at a range of heights above the surface,” says Hans-Ulrich Auster, co-principal investigator of ROMAP and lead author of the results published in the journal Science and presented at the European Geosciences Union General Assembly in Vienna, Austria, today.
ROMAP measured a magnetic field during these sequences, but found that its strength did not depend on the height or location of Philae above the surface. This is not consistent with the nucleus itself being responsible for that field.
“If the surface was magnetised, we would have expected to see a clear increase in the magnetic field readings as we got closer and closer to the surface,” explains Hans-Ulrich. “But this was not the case at any of the locations we visited, so we conclude that Comet 67P/Churyumov-Gerasimenko is a remarkably non-magnetic object.”
Instead, the magnetic field that was measured was consistent with an external one, namely the influence of the solar wind interplanetary magnetic field near the comet nucleus. This conclusion is confirmed by the fact that variations in the field that were measured by Philae closely agree with those seen at the same time by Rosetta.
“During Philae’s landing, Rosetta was about 17 km above the surface, and we could provide complementary magnetic field readings that rule out any local magnetic anomalies in the comet’s surface materials,” says Karl-Heinz Glassmeier, principal investigator of RPC-MAG on board the orbiter and a co-author of the Science paper.
If large chunks of material on the surface of 67P/Churyumov-Gerasimenko were magnetised, ROMAP would have recorded additional variations in its signal as Philae flew over them.
“If any material is magnetised, it must be on a scale of less than one metre, below the spatial resolution of our measurements. And if Comet 67P/Churyumov-Gerasimenko is representative of all cometary nuclei, then we suggest that magnetic forces are unlikely to have played a role in the accumulation of planetary building blocks greater than one metre in size,” concludes Hans-Ulrich.
“It’s great to see the complementary nature of Rosetta and Philae’s measurements, working together to answer this simple, but important ‘yes-no’ question as to whether the comet is magnetised,” says Matt Taylor, ESA’s Rosetta project scientist.
“The non-magnetic nucleus of Comet 67P/Churyumov-Gerasimenko,” by H.-U. Auster et al. is published in Science Express on 14 April. (https://www.sciencemag.org/lookup/doi/10.1126/science.aaa5102)
Overall, the data show that the comet has an upper magnetic field magnitude of less than 2 nT at the cometary surface at multiple locations, with a specific magnetic moment of < 3.1 x 10^–5 Am^2/kg, less than known values for lunar material and meteorites measured on Earth.
About ROMAP: ROMAP is the Rosetta Lander Magnetometer and Plasma Monitor. The contributing institutions to ROMAP are: Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig, Germany; Max-Planck Institut für Sonnensystemforschung, Göttingen, Germany; Hungarian Academy of Sciences Centre for Energy Research, Hungary; and Space Research Institute Graz, Austria. The co-principal investigators are Hans-Ulrich Auster (Technische Universität, Braunschweig) and István Apáthy, KFKI, Budapest, Hungary.
About RPC-MAG: RPC-MAG one of six instruments comprising the Rosetta Plasma Consortium. The fluxgate magnetometer (RPC-MAG) is led by Karl-Heinz Glassmeier, Technische Universität, Braunschweig, Germany. | 0.850617 | 4.099297 |
Organohalogens, a class of molecules that contain at least one halogen atom bonded to carbon, are abundant on the Earth where they are mainly produced through industrial and biological processes1. Consequently, they have been proposed as biomarkers in the search for life on exoplanets2. Simple halogen hydrides have been detected in interstellar sources and in comets, but the presence and possible incorporation of more complex halogen-containing molecules such as organohalogens into planet-forming regions is uncertain3,4. Here we report the interstellar detection of two isotopologues of the organohalogen CH3Cl and put some constraints on CH3F in the gas surrounding the low-mass protostar IRAS 16293–2422, using the Atacama Large Millimeter/submillimeter Array (ALMA). We also find CH3Cl in the coma of comet 67P/Churyumov–Gerasimenko (67P/C-G) by using the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument. The detections reveal an efficient pre-planetary formation pathway of organohalogens. Cometary impacts may deliver these species to young planets and should thus be included as a potential abiotical production source when interpreting future organohalogen detections in atmospheres of rocky planets.
Organohalogens are well known for their use in industry and for their detrimental effect on the ozone layer1. Some organohalogens are also produced naturally5, through different geological and biological processes. Because of their relationship to biology and industry on Earth, organohalogens have been proposed as biomarkers on other planets2,6,7. Methyl chloride (CH3Cl), the most abundant organohalogen in the Earth’s atmosphere, has both natural and synthetic production pathways. Its total production rate approaches 3 megatonnes per year, with most originating from biological processes8. Recent observations of Cl-bearing organic molecules, including methyl chloride, on Mars by the rover Curiosity, has challenged a straightforward connection between organohalides and biology; one proposed source of Cl-bearing organic molecules on Mars is meteoritic impacts9,10. This naturally raises the question of whether circumstellar and interstellar environments can produce organohalogens abiotically, and, if so, in what amounts
ieit turns out that these co,pounds are fairly common in space and so probably don’t mean they come from alein beings, as previously thought. | 0.803779 | 3.894943 |
It was just back in July that NASA’s New Horizons spacecraft flew past Pluto with the mission of grabbing as detailed of photographs as possible before continuing into interstellar space, and it managed to do just that and grab some very high-detail close-up images of Pluto.
But it wasn’t just that single color photograph that the New Horizons spacecraft captured; instead, the spacecraft went into a high sensitivity mode, in which it got into position to snap several photographs during the fly-by process.
NASA has been receiving those photographs slowly over time, and has been releasing them over time to the public for viewing. It takes time because New Horizons is very far away from Earth – more than 3 billion miles away – and transmitting those radio waves back to Earth isn’t exactly as fast as the fiber optic or cable broadband connections you may have at home.
On Thursday, September 17th, NASA has released additional photographs that it received from the New Horizons spacecraft. These photographs show the surface of Pluto in high detail, illustrating the mountainous terrains of Pluto, and getting a good look at the icy ‘heart’-shaped plain on Pluto’s surface.
NASA says they got the images on September 14th from New Horizons’ wide-angle Multispectral Visual Imaging Camera (MVIC). At New Horizons’ height, the wide-angle lens was able to capture what NASA says is 780 miles of Pluto’s surface in a single shot.
“This image really makes you feel you are there, at Pluto, surveying the landscape for yourself,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute, Boulder, Colorado. “But this image is also a scientific bonanza, revealing new details about Pluto’s atmosphere, mountains, glaciers and plains.”
The images also show off the mysterious-looking haze that floats over the planet’s surface due to the frozen nitrogen that encapsulates the surfaces of Pluto’s plains, such as the famous ‘heart’-shaped area on the surface that appears in the first image of Pluto that NASA released.
"In addition to being visually stunning, these low-lying hazes hint at the weather changing from day to day on Pluto, just like it does here on Earth," said Will Grundy, lead of the New Horizons Composition team from Lowell Observatory, Flagstaff, Arizona.
To see more of the photos, check out the video below:
Since Pluto is now entering interstellar space, NASA wants to send the probe to a Kuiper Belt Object (KBO) known as 2014 MU69. It's an icy body that lies out in the middle of the Kuiper Belt. Scientists expect that studying it, as far out in space as it is, could help us better understand the formation of our solar system. | 0.864899 | 3.228615 |
Titan’s mountains of ice may have been built following a violent impact that cracked the crust of Saturn’s giant moon. The moon’s tallest known mountains were revealed in the latest images from the Cassini spacecraft on Tuesday.
The mountains appear in images from the probe’s VIMS instrument (Visual Infrared Mapping Spectrometer). The features have been seen before but this time, crucially, the instrument also spotted a hazy shadow stretching away from the range. The length of the shadow reveals that the mountains are about 1500 metres high (nearly a mile).
The range is about 150 kilometres (93 miles) long, but makes up just part of a larger mountainous area. “There are a whole bunch of these features, probably also mountain ranges,” says Robert Brown at the University of Arizona, leader of the VIMS team.
They are all clustered close to a huge semicircular feature that Cassini scientists suspect to be an ancient impact basin, the scar left behind when something heavy hit Titan.
Brown suggests that the impact might have broken the thick ice crust, and that could have created the mountains: “We think it works like Earth’s mid-ocean ridges, with plates pulling apart and magma welling up in the middle.” And another odd feature, shaped like a vast letter H, might be a rift valley created by the same event.
The material that welled up to build Titan’s mountains was not molten rock, but something much chillier – probably a mixture of water and ammonia. This “cryomagma” would be at subzero temperatures, though still hot compared with the surface temperature of -180°C.
Some of the mountains appear to be snowcapped, with bright deposits lying along the ridge. It could be methane snow, or some other organic material.
The mountains also seem to be the source of a band of clouds that sometimes stretche almost all the way around Titan. These clouds had puzzled planetary scientists because they are fixed at a precise latitude – about 40° south.
One suggestion was that the cloud-band might be puffed out of an ice volcano, but now it seems more likely to be generated simply by the height of the mountain range. A steady wind blows from west to east around Titan, and as it rises up over the mountains it should cool down, forcing methane droplets to condense out of the nitrogen atmosphere, forming clouds.
More on these topics: | 0.8059 | 3.835899 |
From the highest volcano to the deepest canyon: Amazing video uses space probe's 12,500 orbits to reveal the beauty of Mars
- Video was put together using images taken over ten years by Mars Express
- Nine detectors sweeped the surface in sequence from nine different angles
- This data was then processed into three dimensional images by scientists
- Most of Mars' surface has been imaged at resolution better than 100 metres
Trenches 23,000 feet deep, psychedelic spirals of lava and the highest known mountain in the solar system - these are just some of the highlights see by the Mars Express spacecraft over the past decade.
Mars Express, launched in 2003, has now orbited the planet nearly 12,500 times, providing scientists with unprecedented images and data collected by its range of scientific instruments.
The data have been used to create an almost global digital topographic model of Mars' surface, providing a unique flyby video.
Scroll down for video...
Mars Express (pictured) was launched in 2003 and has now orbited the planet nearly 12,500 times
The images in this video were taken by the High Resolution Stereo Camera (HSRC) and were put together by the DLR German Aerospace Center as part of the ten years of Mars Express celebrations.
‘For the first time, we can see Mars spatially – in three dimensions,’ said Ralf Jaumann, project manager for the mission at the German Aerospace Center (DLR).
Mars Express reached its destination on 25 December 2003 – and caused an initial shock.
The HRSC took its first close look down towards Mars and sent back an almost plain white image.
This was the first of many images of a crater taken from the spacecraft's camera at an altitude of 277 km
MARS ROVER BEGINS ITS ASCENT
As well as images from the Mars' Express, Nasa's Mars Exploration Rover Opportunity has been capturing images from the ground.
The above southward uphill view was taken when the rover began to ascend the northwestern slope of 'Solander Point' on the western rim of Mars' Endeavour Crater.
The view combines five frames taken by Opportunity's navigation camera on the 3,463rd Martian day, or sol, of the rover's work on Mars.
Opportunity had begun climbing the hill on Sol 3451 and completed three additional uphill drives before reaching this point.
The rover team is using the rover to investigate outcrops on the slope. The northward-facing slope will tilt the rover's solar panels toward the sun in the southern-hemisphere winter sky, providing an important energy advantage for continuing mobile operations through the upcoming winter.
‘Everyone just swallowed,’ recalled Mr Jaumann.
Scientists were worried that the camera had failed. But one of the nine different channels of the camera – the infrared channel – was still showing weak contours of the surface of Mars.
The solution to the problem was quickly found; the sensitivity of the camera close to Mars was much greater than that expected by the researchers, meaning that the first image was overexposed.
Two Mars orbits later, on 10 January 2004, and with the correct exposure time, the first of many successful images was acquired from an altitude of 277 kilometres.
Since then an almost complete 3D global view of the Red Planet has been created from the numerous images.
The scientists put the camera images together piece by piece like a jigsaw puzzle, creating a global map of Mars.
Of the 145 million square kilometres of the surface of Mars, 97 million have already been covered at very high resolution, where one pixel corresponds to less than 20 metres on the surface.
Almost the entire surface of Mars has now been imaged at a resolution of better than 100 metres.
The 3D view of the valleys, canyons and lava flows is possible because of the unusual imaging principle used by the camera.
Valles Marineris pictured here is a system of canyons that runs along the Martian surface east of the Tharsis region. At more than 4,000 km long and 200 km wide, the Valles Marineris rift system is one of the larger canyons of the solar system
Nine light-sensitive detectors sweep the surface in sequence from nine different observation angles.
This data is then processed into three-dimensional images by the DLR planetary researchers.
‘We can see the entire topography almost as well as if we were standing on Mars ourselves,’ said Mrs Jaumann.
Although the conditions on Mars are no longer suitable for the existence of liquid water, at some time in its past water must have flowed over its surface, scouring out deep valleys in the highlands and creating huge outflow valleys three to four billion years ago.
Using the camera's super resolution channel, images can be acquired that are so rich in detail that geological processes in which water was involved can be seen.
It is likely that there were periods of flowing and standing water during the history of this planet, which is so dry and dusty today.
Of the 145 million square kilometres of the surface of Mars, 97 million have already been covered at very high resolution, where one pixel corresponds to less than 20 metres on the surface
This means that different climatic conditions must have been predominant in the planet’s early history.
This is also clearly visible in the three-dimensional camera images showing structures near the equator that have been caused by glaciation.
‘The Mars Express mission was due to end after one Mars year – or about two Earth years,’ said Mr Jaumann.
But during the past 10 years the European Space Agency (ESA) has kept extending the mission. The spacecraft is now due to continue orbiting Mars until the end of 2014.
Mr Jaumann added: ‘That is actually the bottom line on the past 10 years; everything is still functioning perfectly and we are still acquiring new data that is important for Mars research.’
Most watched News videos
- Woman in China left with frown after failed plastic surgery
- PM shuts down Politico's journalist question who is then cut short
- Pakistan: Baby pulled alive from rubble after plane crash
- Clip purports to show aftermath of plane crash in Pakistan
- Last moments of Pakistan plane heard in audio clip
- Clip purportedly shows Pakistan plane before crash
- Bizarre clip sees 'drunk' man in Poland attempt to drown a bear
- Enraged jogger kicks cars parked at busy beach in Cornwall
- North Londoners make the most of bank holiday sun
- Aerial footage shows mass graves in Brazil's Sao Paulo
- Dominic Cummings confronts media saying public are 'angry at him'
- Clip purports to show moment of Pakistan plane crash | 0.84912 | 3.250466 |
If you want to feel just how small you really are, you need only to look up and observe the grandeur of space. Considering the vastness and seeming endlessness of the universe, you will realize that we are just tiny specks of dust in this cosmos.
We live in a fascinatingly mysterious universe. These fantastic photos will literally take you out of this world!
1. Eagle Nebula
The Eagle Nebula is a column-like formation of interstellar dust and hydrogen gas and incubates new stars.
2. Tarantula Nebula
The Tarantula Nebula was found by the Hubble Space Telescope during Earth’s 100,000th orbit. Possibly triggered by a nearby supernova, this stellar nursery is a firestorm of raw celestial creation.
3. Wolf-Rayet Star
This massive bright blue star is lying on the center of a nebula. It almost has over 20 times the mass of our Sun.
4. Needle Galaxy
The magnificent Needle Galaxy is possibly similar to the spiral Milkyway Galaxy, but only viewed sideways from far away.
5. Thin Section of a Supernova
Taken by NASA’s Hubble Space Telescope, this thin section of a supernova is likely formed by a stellar explosion that happened thousands of years ago.
6. Saturn’s Moon Dione
This icy moon is a fascinating heavenly body. The picture was created through the combination of green, ultraviolet, and infrared images.
7. Earth’s Curvature
This image of Earth was captured above the northwestern African continent. Observable in the image is Earth’s curvature and atmosphere.
8. Spiral Galaxy M81
Located in the center of this amazing galaxy is a supermassive black hole that is around 70 million times larger than the Sun.
9. Helix Nebula
This cosmic starlet is notable for its eerie-looking resemblance to an eye. The vivid colors also add to the fascination.
10. Rho Ophiuchi Cloud Complex
Taken by the Wide-field Infrared Survey Explorer (WIDE), this photo of the Rho Ophiuchi Cloud Complex is such a magnificent view.
11. Glowing Stellar Nursery
The Glowing Stellar Nursery was discovered by the Spitzer Space Telescope, named after one of the most notable scientists of the 20th century, Dr. Lyman Spitzer, Jr.
12. Comet McNaught
Discovered in September 2009, this comet is only one of the 54 comets discovered by Robert McNaught.
13. “Martian Forest”
Looking like forests from afar, the “Martian Forest” is really just sand particles stuck together during a Martian Winter with frozen Carbon Dioxide covering them.
14. Saturn’s Rings
One of the most notable planets in our Solar System is Saturn because of its magnificent ring system.
15. Gas Sphere
The Gas Sphere is a giant gas bubble formed by a supernova.
These beautiful interstellar pictures show how mysterious and mystical our universe really is.
7 Strange Facts About The Planets In Our Solar System
Our solar system is really weird.
Earth truly is beautiful and strange but our home seems relatively harmless compared to the other planets in our solar system. After all, Uranus reportedly smells like rotten eggs due to the hydrogen sulfide in its atmosphere. However, this isn't the strangest thing you will find about our nearest neighbors.
We should be happy with how stable Earth is compared to other planets. Case in point, the dwarf planet Pluto is constantly losing tons of nitrogen from its atmosphere. This is because Pluto is too small to have enough gravity to keep its atmosphere and yet the tiny planet never runs out of nitrogen. Is there a hidden nitrogen factory under Pluto's surface? Scientists are hoping to find out soon.
In the meantime, here are seven strange facts about the other planets in our solar system....
Scientists Discover A New Shape Called The ‘Scutoid’
This newly-discovered form is hiding inside your body and it is called a scutoid.
Scientists have discovered an entirely new geometric shape that was previously unknown to humankind. In fact, this newly-discovered form is hiding inside your body, and it is called a scutoid.
The discovery occurred while they were studying epithelial cells, the building blocks of embryos that eventually form the linings of many organs including the skin. The researchers at The University of Seville and Seville Institute of Biomedicine (IBiS) explained that the new shape is like a “twisted prism.”
A brand new shape has been discovered beneath our skin cells, and it's called the scutoid
NASA Spots Earth-like Aurora Crown in Newly Discovered Planet
The first of its kind, this free-floating astronomical object was originally believed to be a failed star during it’s discovery.
NASA's explorations have always been a quest for planets other than Earth that can support life. In the course of many years, the agency uncovered many of the secrets held by the universe. One of which is the discovery of a rouge planet, about 20 light years away from Earth.
The first of its kind, this free-floating astronomical object was originally believed to be a failed star during it's discovery. Recent studies revealed that it is not a star, but a planet. This discovered planet is found to be 12 times bigger than Jupiter. It features an aurora crown and a magnetic field 200 times more than that of Jupiter.
The discovery inspires research about magnetic processes for stars and planets. | 0.933797 | 3.044122 |
Venus is a dazzling beacon in the western sky, setting 3 to 4 hours after the sun. Fainter Mars follows closely behind Venus early in the month, then the two gradually separate as the month wears on. Jupiter, accompanied by the bluish star Spica, is slowly rising during the more convenient evening hours in February. You still have to wait until well after midnight to see Saturn, while Mercury, initially visible low near the east-southeast horizon in the dawn twilight at the start of the month, ultimately succumbs to the fiery glow of the rising sun by the second week of February.
In our skywatching schedule below, remember that when measuring the angular separation between two celestial objects, your clenched fist held at arm’s length measures roughly 10 degrees. Here, we present a schedule that provides some of the best planet-viewing times as well as directions on how to see them.
Mercury moves eastward in the sky and closer to the sun every day. It can be spotted near the east-southeast horizon in the middle of twilight — about 45 minutes before sunrise — for the first week of February. In the southern United States, it may remain visible for another week before sinking into the sun’s glare. On March 6, Mercury will be at superior conjunction, meaning it
Venus dominates the western sky soon after sunset. The resplendent planet attains a stunning maximum brilliance of magnitude -4.8 in the latter half of February. At a really dark site, can you see your shadow cast by Venus on snow-covered ground (or even on a white sheet). Viewed from midnorthern latitudes, the lamp-like world appears about 40 degrees above the horizon at sundown — almost its highest possible altitude in the sky. But the time between sunset and Venus-set decreases from 4 hours at the beginning of February to 3 hours at the end of the month. Venus’ crescent thins to less than one-quarter lit during February, but lengthens to about 0.75 arcminutes tall — big enough to discern in steadily supported binoculars. As always, your best telescopic views will be before the sky darkens and Venus starts glaring. On Feb. 28, a slender crescent moon passes far to the lower left of Venus.
Mars remains 5.5 degrees to the upper left of Venus during the first four days of February. That will be as close as they come to each other before Mars pulls away from Venus to the east. The two planets present some interesting contrasts. The colors of Venus and Mars are sparkling white and ochre-orange, respectively. Mars remains visible against the faint stars of Pisces all month long, setting around 9:25 p.m. local time, and dims from magnitude +1.1 to magnitude +1.3 as it continues to recede from Earth, kicking off this month at a distance of 172 million miles (277 million kilometers) from Earth and moving out to 189 million miles (304 million km) by Feb. 28. You can use Mars to locate Uranus on Feb. 26 using a pair of binoculars. Uranus will appear as a tiny, greenish-blue star 0.6 degrees to the left of Mars. At magnitude +5.9, Uranus glows with only one-seventieth the radiance of Mars.
Jupiter rises brilliantly in the east around 11 p.m. local time in early February and will gradually rise earlier each day, coming up at 9 p.m. by month’s end. Once it lifts above the horizon, Jupiter easily outshines Sirius, the brightest star in the night sky, and will brighten from a magnitude of -2.1 to a magnitude of -2.3 during the month. On Monday, Feb. 6, the planet will appear to halt as it begins retrograde (westward) motion relative to the background stars of Virgo. Feb. 23 marks the second of three conjunctions in 2017 of Jupiter with Virgo’s brightest star, Spica; Jupiter will pass 4 degrees to the north of the star. The third and final conjunction in the series will come on Sept. 5. Jupiter doesn’t come to opposition until April, so this means that skywatchers need to stay up late for “Big Jupe” to rise high enough to show a clear image in a telescope. Telescopes can show a bounty of cloud features on Jupiter as well as its four bright moons. This month, the planet’s apparent diameter grows by more than 7 percent as the distance between Jupiter and Earth shrinks. Look toward the east-southeast at 11 p.m. local time on Feb. 14 to see a waning gibbous moon standing high above Jupiter. On the following night, the moon will have moved well to the lower left of Jupiter.
Saturn appears as a yellowish “star” of magnitude +0.6, rising in the early-morning hours around 4 a.m. local time on Feb. 1 and 2:30 a.m. on Feb. 28. The ringed planet starts February in the nonzodiacal constellation of Ophiuchus, but will cross over into Sagittarius on Feb. 24. The waning crescent moon will slide north of Saturn during Feb. 20 to Feb. 21. Facing southeast at 4 a.m. local time on Feb. 20, Saturn can be found to the lower left of the moon. On the following morning, the moon will have shifted to Saturn’s left. | 0.842887 | 3.688899 |
The first test images from NASA’s Mars Reconnaissance Orbiter have been difficult to appreciate, since they don’t show any familiar landmarks or give a sense of scale. But today the spacecraft delivered the goods, with a photograph from orbit of NASA’s Opportunity Mars rover, perched at the edge of Victoria Crater. It’s possible to make out the shape of the silver rover, and see its tracks in the Martian soil. By using both the aerial and ground level views, planetary scientists will be able to plot out the rover’s next moves in search of evidence of past water.
NASA’s long-lived robotic rover Opportunity is beginning to explore layered rocks in cliffs ringing the massive Victoria crater on Mars.
While Opportunity spent its first week at the crater, NASA’s newest eye in the Martian sky photographed the rover and its surroundings from above. The level of detail in the photo from the high-resolution camera on the Mars Reconnaissance Orbiter will help guide the rover’s exploration of Victoria.
“This is a tremendous example of how our Mars missions in orbit and on the surface are designed to reinforce each other and expand our ability to explore and discover,” said Doug McCuistion, director of NASA’s Mars Exploration Program in Washington. “You can only achieve this compelling level of exploration capability with the sustained exploration approach we are conducting at Mars through integrated orbiters and landers.”
“The combination of the ground-level and aerial view is much more powerful than either alone,” said Steve Squyres of Cornell University, Ithaca, N.Y. Squyres is principal investigator for Opportunity and its twin, Spirit. “If you were a geologist driving up to the edge of a crater in your jeep, the first thing you would do would be to pick up the aerial photo you brought with you and use it to understand what you’re seeing from ground level. That’s exactly what we’re doing here.”
Images from NASA’s Mars Global Surveyor, orbiting the red planet since 1997, prompted the rover team to choose Victoria two years ago as the long-term destination for Opportunity. The images show the one-half-mile-wide crater has scalloped edges of alternating cliff-like high, jutting ledges and gentler alcoves. The new image by the Mars Reconnaissance Orbiter adds significantly more detail.
Exposed geological layers in the cliff-like portions of Victoria’s inner wall appear to record a longer span of Mars’ environmental history than the rover has studied in smaller craters. Victoria is five times larger than any crater Opportunity has visited during its Martian trek.
High-resolution color images taken by Opportunity’s panoramic camera since Sept. 28 reveal previously unseen patterns in the layers. “There are distinct variations in the sedimentary layering as you look farther down in the stack,” Squyres said. “That tells us environmental conditions were not constant.”
Within two months after landing on Mars in early 2004, Opportunity found geological evidence for a long-ago environment that was wet. Scientists hope the layers in Victoria will provide new clues about whether that wet environment was persistent, fleeting or cyclical.
The rovers have worked on Mars for more than 10 times their originally planned three-month missions. “Opportunity shows a few signs of aging but is in good shape for undertaking exploration of Victoria crater,” said John Callas, project manager for the rovers at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
“What we see so far just adds to the excitement. The team has worked heroically for nearly 21 months driving the rover here, and now we’re all rewarded with views of a spectacular landscape of nearly 50-foot-thick exposures of layered rock,” said Jim Bell of Cornell. Bell is lead scientist for the rovers’ panoramic cameras. NASA plans to drive Opportunity from crater ridge to ridge, studying nearby cliffs across the intervening alcoves and looking for safe ways to drive the rover down. “It’s like going to the Grand Canyon and seeing what you can from several different overlooks before you walk down,” Bell said.
The orbiter images will help the team choose which way to send Opportunity around the rim, and where to stop for the best views. Conversely, the rover’s ground-level observations of some of the same features will provide useful information for interpreting orbital images.
“The ground-truth we get from the rover images and measurements enables us to better interpret features we see elsewhere on Mars, including very rugged and dramatic terrains that we can’t currently study on the ground,” said Alfred McEwen of the University of Arizona, Tucson. He is principal investigator for the orbiter’s High Resolution Imaging Science Experiment camera.
JPL manages the rovers and orbiter for NASA’s Science Mission Directorate. JPL is a division of the California Institute of Technology in Pasadena.
For images and information about the rovers, visit: http://www.nasa.gov/rovers
For images and information about the Mars Reconnaissance Orbiter, visit: http://www.nasa.gov/mro
Original Source: NASA/JPL News Release | 0.836815 | 3.600438 |
If you’ve read the “about me” page you’ll know that I’m a fan of variable stars. Most of my astronomy colleagues think it’s a bit weird, but I love to test the ability of my eyes to judge brightness and follow the changes in the 30 stars on my regular programme. I now use my naked eye, binoculars and a telescope to observe variables, but I didn’t start that way…## Astronomy with no equipment
It began by following the American Association of Variable Star Observers (AAVSO) 10-Star Tutorial comprised of variables you can see through their entire range of magnitude with the naked eye under reasonable skies.
If you’d like a go I’d recommend following the antics of Delta Cephei on every clear night with nothing more than a dim torch (nearly no equipment then) and a comparison chart like this one from the AAVSO tutorial.
Delta Cephei is a historically important star that helped us understand the truly staggering distances between objects in space. For the observer it has the distinction of being very active over a wide range of magnitude, all of which is visible to the naked eye.
This comparison chart not only helps you find the star that’s the variable one, but it also provides several other stars with known magnitudes. You can see those with the numbers next to them. The number is the magnitude with the decimal point removed (they look too much like stars). So the star with 42 next to it is 4.2 magnitude.
How to use a comparison chart
Let’s assume you’ve found the right part of the night sky. It’s possible, and acceptable to decide that delta Cephei is the same magnitude as one of the other stars. If that’s the case your work is done and you have your estimate. If it’s the same as star 42 for example, you write =42 in you notes.
If it doesn’t match any of the comparison stars, it often won’t, you need to use the chart to look for a star that’s just brighter than delta Cephei. Make a note of its number. Next look for one just fainter and note that number down too.
Then you need to decide which of the two comparison stars is closest in brightness to delta Cephei and call that difference 1. The tricky part is to decide how many times larger the magnitude difference is between delta Cephei and the other comparison star. An example might help.
You can see that in my logbook above I have an observation of delta Cephei near the top of the left-hand page on the night of 11 September 2016 at 21:26 UT (always use Universal Time). I decided that delta Cephei was between stars 34 and 38, but closest to 38, and that it was 3 times fainter than star 34: 34(3)V(1)38. This worked out to a magnitude of 3.7 as follows: (38 – 34) / 4 = 1, so 38 – 1 = 37 which adding the decimal point is magnitude 3.7. You can see the results weren’t the same on every night.
What to do with your observations
Once you have your estimate you might want to submit it to the AAVSO via their website so that researchers can use your data. You don’t need to be a member (I wasn’t at the beginning) just create an account and get busy. However submitting them isn’t essential, it’s fine to note them down for your own record and the enjoyment of tracking your chosen star.
Moving on to fainter variable stars
From the naked eye beginnings I moved on mostly binocular variables (those requiring binoculars and nothing more). The tool of choice was a Pentax 10×50 binocular which allows me to reach for magnitude 9 stars. I’ve since added some telescopic variables to my observing list which can be pursued down to magnitude 12.5 in my Skywatcher 130P newtonian. The process given in this article remains the same, and note that none of this is complex or expensive equipment.
That’s the beauty of visual variable star observation and what drew me to it in the first place. With this basic kit I’ve made visual estimates of several different types of variable star including a Nova explosion and even a Supernova in another galaxy! | 0.858186 | 3.726712 |
Atmospheric refraction should not be confused with Atmospheric diffraction.
Atmospheric refraction is the deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of height. This refraction is due to the velocity of light through air, decreasing (the refractive index increases) with increased density. Atmospheric refraction near the ground produces mirages. Such refraction can also raise or lower, or stretch or shorten, the images of distant objects without involving mirages. Turbulent air can make distant objects appear to twinkle or shimmer. The term also applies to the refraction of sound. Atmospheric refraction is considered in measuring the position of both celestial and terrestrial objects.
Astronomical or celestial refraction causes astronomical objects to appear higher above the horizon than they actually are. Terrestrial refraction usually causes terrestrial objects to appear higher than they actually are, although in the afternoon when the air near the ground is heated, the rays can curve upward making objects appear lower than they actually are.
Refraction not only affects visible light rays, but all electromagnetic radiation, although in varying degrees. For example, in the visible spectrum, blue is more affected than red. This may cause astronomical objects to appear dispersed into a spectrum in high-resolution images.
Whenever possible, astronomers will schedule their observations around the times of culmination, when celestial objects are highest in the sky. Likewise, sailors will not shoot a star below 20° above the horizon. If observations of objects near the horizon cannot be avoided, it is possible to equip an optical telescope with control systems to compensate for the shift caused by the refraction. If the dispersion is also a problem (in case of broadband high-resolution observations), atmospheric refraction correctors (made from pairs of rotating glass prisms) can be employed as well.
Since the amount of atmospheric refraction is a function of the temperature gradient, temperature, pressure, and humidity (the amount of water vapor, which is especially important at mid-infrared wavelengths), the amount of effort needed for a successful compensation can be prohibitive. Surveyors, on the other hand, will often schedule their observations in the afternoon, when the magnitude of refraction is minimum.
Atmospheric refraction becomes more severe when temperature gradients are strong, and refraction is not uniform when the atmosphere is heterogeneous, as when turbulence occurs in the air. This causes suboptimal seeing conditions, such as the twinkling of stars and various deformations of the Sun's apparent shape soon before sunset or after sunrise.
Astronomical refraction deals with the angular position of celestial bodies, their appearance as a point source, and through differential refraction, the shape of extended bodies such as the Sun and Moon.
Atmospheric refraction of the light from a star is zero in the zenith, less than 1′ (one arc-minute) at 45° apparent altitude, and still only 5.3′ at 10° altitude; it quickly increases as altitude decreases, reaching 9.9′ at 5° altitude, 18.4′ at 2° altitude, and 35.4′ at the horizon; all values are for 10 °C and 1013.25 hPain the visible part of the spectrum.
On the horizon refraction is slightly greater than the apparent diameter of the Sun, so when the bottom of the sun's disc appears to touch the horizon, the sun's true altitude is negative. If the atmosphere suddenly vanished at this moment, one couldn't see the sun, as it would be entirely below the horizon. By convention, sunrise and sunset refer to times at which the Sun's upper limb appears on or disappears from the horizon and the standard value for the Sun's true altitude is -50′: -34′ for the refraction and -16′ for the Sun's semi-diameter. The altitude of a celestial body is normally given for the center of the body's disc. In the case of the Moon, additional corrections are needed for the Moon's horizontal parallax and its apparent semi-diameter; both vary with the Earth–Moon distance.
Refraction near the horizon is highly variable, principally because of the variability of the temperature gradient near the Earth's surface and the geometric sensitivity of the nearly horizontal rays to this variability. As early as 1830, Friedrich Bessel had found that even after applying all corrections for temperature and pressure (but not for the temperature gradient) at the observer, highly precise measurements of refraction varied by ±0.19′ at two degrees above the horizon and by ±0.50′ at a half degree above the horizon. At and below the horizon, values of refraction significantly higher than the nominal value of 35.4′ have been observed in a wide range of climates. Georg Constantin Bouris measured refraction of as much of 4° for stars on the horizon at the Athens Observatory and, during his ill-fated Endurance expedition, Sir Ernest Shackleton recorded refraction of 2°37′:
“The sun which had made ‘positively his last appearance’ seven days earlier surprised us by lifting more than half its disk above the horizon on May 8. A glow on the northern horizon resolved itself into the sun at 11 am that day. A quarter of an hour later the unreasonable visitor disappeared again, only to rise again at 11:40 am, set at 1 pm, rise at 1:10 pm and set lingeringly at 1:20 pm. These curious phenomena were due to refraction which amounted to 2° 37′ at 1:20 pm. The temperature was 15° below 0° Fahr., and we calculated that the refraction was 2° above normal.”
Day-to-day variations in the weather will affect the exact times of sunrise and sunset as well as moon-rise and moon-set, and for that reason it generally is not meaningful to give rise and set times to greater precision than the nearest minute. More precise calculations can be useful for determining day-to-day changes in rise and set times that would occur with the standard value for refraction if it is understood that actual changes may differ because of unpredictable variations in refraction.
Because atmospheric refraction is nominally 34′ on the horizon, but only 29′ at 0.5° above it, the setting or rising sun seems to be flattened by about 5′ (about 1/6 of its apparent diameter).
Young distinguished several regions where different methods for calculating astronomical refraction were applicable. In the upper portion of the sky, with a zenith distance of less than 70° (or an altitude over 20°), various simple refraction formulas based on the index of refraction (and hence on the temperature, pressure, and humidity) at the observer are adequate. Between 20° and 5° of the horizon the temperature gradient becomes the dominant factor and numerical integration, using a method such as that of Auer and Standish and employing the temperature gradient of the standard atmosphere and the measured conditions at the observer, is required. Closer to the horizon, actual measurements of the changes with height of the local temperature gradient need to be employed in the numerical integration. Below the astronomical horizon, refraction is so variable that only crude estimates of astronomical refraction can be made; for example, the observed time of sunrise or sunset can vary by several minutes from day to day. As The Nautical Almanac notes, "the actual values of …the refraction at low altitudes may, in extreme atmospheric conditions, differ considerably from the mean values used in the tables."
Many different formulas have been developed for calculating astronomical refraction; they are reasonably consistent, differing among themselves by a few minutes of arc at the horizon and becoming increasingly consistent as they approach the zenith. The simpler formulations involved nothing more than the temperature and pressure at the observer, powers of the cotangent of the apparent altitude of the astronomical body and in the higher order terms, the height of a fictional homogeneous atmosphere. The simplest version of this formula, which Smart held to be only accurate within 45° of the zenith, is:
An early simple approximation of this form, which directly incorporated the temperature and pressure at the observer, was developed by George Comstock:
where R is the refraction in seconds of arc, b is the barometric pressure in millimeters of mercury, and t is the Celsius temperature. Comstock considered that this formula gave results within one arcsecond of Bessel's values for refraction from 15° above the horizon to the zenith.
A further expansion in terms of the third power of the cotangent of the apparent altitude incorporates H0, the height of the homogeneous atmosphere, in addition to the usual conditions at the observer:
A version of this formula is used in the International Astronomical Union's Standards of Fundamental Astronomy; a comparison of the IAU's algorithm with more rigorous ray-tracing procedures indicated an agreement within 60 milliarcseconds at altitudes above 15°.
Bennett developed another simple empirical formula for calculating refraction from the apparent altitude which gives the refraction R in arcminutes:
This formula is used in the U. S. Naval Observatory's Vector Astrometry Software, and is reported to be consistent with Garfinkel's more complex algorithm within 0.07′ over the entire range from the zenith to the horizon. Sæmundsson developed an inverse formula for determining refraction from true altitude; if h is the true altitude in degrees, refraction R in arcminutes is given by
the formula is consistent with Bennett's to within 0.1′. The formulas of Bennet and Sæmundsson assume an atmospheric pressure of 101.0 kPa and a temperature of 10 °C; for different pressure P and temperature T, refraction calculated from these formulas is multiplied by
Refraction increases approximately 1% for every 0.9 kPa increase in pressure, and decreases approximately 1% for every 0.9 kPa decrease in pressure. Similarly, refraction increases approximately 1% for every 3 °C decrease in temperature, and decreases approximately 1% for every 3 °C increase in temperature.
Turbulence in Earth's atmosphere scatters the light from stars, making them appear brighter and fainter on a time-scale of milliseconds. The slowest components of these fluctuations are visible as twinkling (also called scintillation).
Turbulence also causes small, sporadic motions of the star image, and produces rapid distortions in its structure. These effects are not visible to the naked eye, but can be easily seen even in small telescopes. They perturb astronomical seeing conditions. Some telescopes employ adaptive optics to reduce this effect.
Terrestrial refraction, sometimes called geodetic refraction, deals with the apparent angular position and measured distance of terrestrial bodies. It is of special concern for the production of precise maps and surveys. Since the line of sight in terrestrial refraction passes near the earth's surface, the magnitude of refraction depends chiefly on the temperature gradient near the ground, which varies widely at different times of day, seasons of the year, the nature of the terrain, the state of the weather, and other factors.
As a common approximation, terrestrial refraction is considered as a constant bending of the ray of light or line of sight, in which the ray can be considered as describing a circular path. A common measure of refraction is the coefficient of refraction. Unfortunately there are two different definitions of this coefficient. One is the ratio of the radius of the Earth to the radius of the line of sight, the other is the ratio of the angle that the line of sight subtends at the center of the Earth to the angle of refraction measured at the observer. Since the latter definition only measures the bending of the ray at one end of the line of sight, it is one half the value of the former definition.
The coefficient of refraction is directly related to the local vertical temperature gradient and the atmospheric temperature and pressure. The larger version of the coefficient k, measuring the ratio of the radius of the Earth to the radius of the line of sight, is given by:
where temperature T is given in kelvins, pressure P in millibars, and height h in meters. The angle of refraction increases with the coefficient of refraction and with the length of the line of sight.
Although the straight line from your eye to a distant mountain might be blocked by a closer hill, the ray may curve enough to make the distant peak visible. A convenient method to analyze the effect of refraction on visibility is to consider an increased effective radius of the Earth Reff, given by
where R is the radius of the Earth and k is the coefficient of refraction. Under this model the ray can be considered a straight line on an Earth of increased radius.
The curvature of the refracted ray in arc seconds per meter can be computed using the relationship
where 1/σ is the curvature of the ray in arcsec per meter, P is the pressure in millibars, T is the temperature in kelvins, and β is the angle of the ray to the horizontal. Multiplying half the curvature by the length of the ray path gives the angle of refraction at the observer. For a line of sight near the horizon cos β differs little from unity and can be ignored. This yields
where L is the length of the line of sight in meters and Ω is the refraction at the observer measured in arc seconds.
A simple approximation is to consider that a mountain's apparent altitude at your eye (in degrees) will exceed its true altitude by its distance in kilometers divided by 1500. This assumes a fairly horizontal line of sight and ordinary air density; if the mountain is very high (so much of the sightline is in thinner air) divide by 1600 instead. | 0.827468 | 4.080119 |
Crescent ♒ Aquarius
Moon phase on 9 February 2002 Saturday is Waning Crescent, 26 days old Moon is in Capricorn.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 4 days on 4 February 2002 at 13:33.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Moon is passing about ∠19° of ♑ Capricorn tropical zodiac sector.
Lunar disc appears visually 6.7% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1818" and ∠1945".
Next Full Moon is the Snow Moon of February 2002 after 17 days on 27 February 2002 at 09:17.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 26 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 25 of Meeus index or 978 from Brown series.
Length of current 25 lunation is 29 days, 18 hours and 12 minutes. It is 10 minutes shorter than next lunation 26 length.
Length of current synodic month is 5 hours and 28 minutes longer than the mean length of synodic month, but it is still 1 hour and 35 minutes shorter, compared to 21st century longest.
This New Moon true anomaly is ∠123.9°. At beginning of next synodic month true anomaly will be ∠155.3°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
10 days after point of perigee on 30 January 2002 at 09:02 in ♍ Virgo. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 5 days, until it get to the point of next apogee on 14 February 2002 at 22:22 in ♓ Pisces.
Moon is 394 245 km (244 972 mi) away from Earth on this date. Moon moves farther next 5 days until apogee, when Earth-Moon distance will reach 406 361 km (252 501 mi).
1 day after its descending node on 7 February 2002 at 15:33 in ♐ Sagittarius, the Moon is following the southern part of its orbit for the next 12 days, until it will cross the ecliptic from South to North in ascending node on 22 February 2002 at 06:26 in ♊ Gemini.
14 days after beginning of current draconic month in ♋ Cancer, the Moon is moving from the second to the final part of it.
1 day after previous South standstill on 8 February 2002 at 20:59 in ♑ Capricorn, when Moon has reached southern declination of ∠-24.309°. Next 13 days the lunar orbit moves northward to face North declination of ∠24.418° in the next northern standstill on 23 February 2002 at 11:48 in ♋ Cancer.
After 2 days on 12 February 2002 at 07:41 in ♒ Aquarius, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.107525 |
Transcript of a lecture given by Cynthia Chung at ‘The Universe, Creativity and You’ Symposium August 3, 2019.
We live in a strange time.
Many have forgotten the power of imagination and are instead bogged down with the reality of ‘practicality’. The reality of ‘the budget’, and the reality of ‘what is deemed useful and what is deemed useless’. Many have come to the conclusion that the study and exploration of space is a useless endeavour and that we cannot afford to waste our time on something that is more akin to a child’s fantasy, our immature dreams from our ancient past.
This is not only false but disregards the minds of scientists throughout the centuries who always placed the power of imagination at the helm of their navigation. Imagination allows us a glimpse of the unknown before we can confirm it to be known. It is with our ability to first imagine new possibilities that major discoveries can then be born.
This class will discuss ancient as well as modern Chinese astronomy, which like ancient Egyptian and Greek astronomy, would not have made their revolutionary discoveries if they had not first dared to imagine there existed a purpose and therefore a knowable explanation for how the universe works. This will serve as a reminder to those of us who have forgotten or are in the process of forgetting, that the study of astronomy has always been at the core of human kind’s exploration for meaning and purpose. And if we accept such a challenge, the opening up of the most impressive kind of potential and responsibility for the future of human kind lies before us.
The ‘Guest Star’
Let us start our voyage in 1054 AD. Chinese astronomers at this time observed the sudden appearance of a new star in the sky, which was incredibly bright, much more so than any other star in the sky.
This was not the first time that the Chinese had observed such a phenomena. In 185 AD, the Chinese were the first in history to ever reliably record the observation of a suddenly appearing star in the sky. This very rare phenomena was nicknamed kèxīng which means ‘guest star’, since it would only remain visible in the sky for a short amount of time, around several months. The picture shown here is obviously not a real picture but a digital recreation of what it probably looked like, although it could have been even brighter than this.
There have only been five reliable recordings of a such a phenomena in history. In 185 AD, 1006, 1054, 1572 and 1604.
Though it was widely reported in China, other than Japan’s note of the 1054 AD ‘guest star’, only one other record exists from outside East Asia; an Arabic work which cites its observation, probably originating from Constantinople but not confirmed.
However, it was the Chinese who would most accurately map and describe the ‘guest star’. In fact, the 1054 AD observation by chinese astronomers was the first description of a ‘guest star’ that met a standard suitable for modern astronomy, such that astronomers today rely on much of the data recorded from this 1054 AD documentation in their studies.
So what was it that the ancient chinese astronomers actually observed and what is its significance?
Before this mystery is named let us first go over what we now know about how light travels through space and what it consists of, since this was afterall what the ancient astronomers were entirely working with since they had no other tool at the time but the direct observation of light in the sky.
What is Light?
Light is emitted in the form of electromagnetic waves. The below picture shows the different electromagnetic waves that are known so far, which consist of periodic variations of electric and magnetic field intensity. As you can see from the diagram the spectrum of light visible to the human eye is very small (and by the way, these are all considered forms of radiation).
The reason why space often looks black to us is several fold, for visible light to travel through space it not only takes time and is not an instantaneous thing, but it also depends on how light is being bent in space, if the source of light is moving towards us or away from us and whether an object is actually emitting visible light and not some other form of light, like gamma rays or radio waves. With the naked eye we are actually extremely limited in seeing most of the forms of light which actually fill all of space. That is, “space” or better called “the Universe”, is filled with light- our eyes just can’t see most of it. With aid of modern telescopes that can view various spectrums of light, we are much better able to appreciate the majestic beauty of what truly fills what we first thought to be just dark space.
In addition, not all visible light is qualitatively the same. For instance sunlight appears as white light to the human eye, but is actually made up of all the colors of the rainbow, it is in fact why we see the phenomena of rainbows in the sky, the effect of sunlight being refracted by rain droplets. Trillions of rain droplets are all refracting the sunlight at the same angle such that you get the effect of an arch of rainbow.
Think about how odd this phenomena would sound to you if you didn’t have the ability to see it yourself! If you couldn’t see the visible light spectrum the sky would look like an entirely different thing. The sky wouldn’t even be blue!
Not all visible light sources in space generate ‘white light’, but can generate light consisting mostly of ‘red’, ‘blue’ or other spectrums of visible light. Our eyes do not see all forms of light equally and therefore even amongst the small spectrum of light that is deemed visible to the human eye, we do not have the capability to view certain parts of the visible spectrum as well as others.
Our eyes alone are thus extremely limited in their ability to observe the night sky, even on the clearest of nights.
But that is not the whole of it. How we see our surroundings on earth in clear daylight is actually something we are also very limited in!
Here is a comparison between human vision vs that of bees, birds and fish which all can see parts of the ultraviolet spectrum, while humans cannot.
Hopefully with just these few but quite dramatic examples, we can form an idea of how much of ‘reality’ our naked eye actually misses out on. In fact, even our very concept of ‘physical reality’ as something that could exist through sense alone is challenged! That is, for just sight, there exists no form of vision that encapsulates all forms of light, therefore there is no complete ‘reality’ through vision.
In addition, there is the concept of how light travels. Presently, it is thought that all wavelengths of light travel at the same speed, and that this speed differs depending on what medium it is traversing through. For instance, light travels faster through air than through water.
One light year is measured as having traversed approximately 6 trillion miles. That is, in one earth year, light travels about 10^12 km. This is probably not entirely accurate since it assumes that light will not change its speed throughout the ‘medium’ of space but it gives us the most reliable estimate thus far of what our distance is to other objects in space.
So now keeping this all in mind, what did the ancient chinese astronomers observe as a phenomena in 1054 AD?
It was probably the death of a star, though it is still not completely certain. This process is known as a supernova and is recorded as a powerful and luminous stellar explosion. At its peak of brightness, its optical luminosity is comparable to that of a galaxy. The particular supernova of 1054 AD is now called the Crab Nebula, which I will talk further about throughout this class.
Keep in mind that the only five reliable recordings of such an event, that is the observation of a supernova, occurred in 185 AD, 1006, 1054 and later in 1572 and 1604. Therefore the last supernova event to have been observed was over 400 years ago!
In addition, with the use of telescopes, we can now calculate the distance between the Crab Nebula and Earth, and therefore calculate that what ancient Chinese astronomers observed in 1054 AD as this bright light, actually occurred about 6500 years before their actual observation of it!
We should take a step back at this moment and reflect upon the magnitude of what we are dealing with. What we observe in so called space, which is all based on multiple wavelengths of light, are all reaching earth from various points in time!
With further advancement in modern telescopes, we are able to see further into the so called dark abyss of space through the lens of multiple spectrums of light and observe phenomena that have occurred within multiple points in time!
Oldest Astronomical Observatory Ever Found
In 2001, Chinese archaeologists launched a project to seek the origins of their over 5,000-year-old civilization. Taosi, in Shangxi Province, is one of the most important sites in this project. The ancient city of Taosi dates back to 4300 to 4000 BC, and is thought to be the capital of the legendary Yao period.
Yao ( 2333 BCE–2234 BCE) was a famous sage king who ruled before the Xia dynasty, the first dynasty in chinese history. Many Confucian histories praised Yao as a model of morality and benevolence.
According to some Chinese classic documents, King Yao assigned astronomy officers to observe celestial phenomena such as the sunrise, sunset, and the rising of the evening stars. This was done in order to make a solar and lunar calendar with 366 days for a year, also providing for the leap month.
In 2003, while searching for evidence of the undocumented era at Taosi, Chinese archaeologists found the ruins of a mysterious semi-circular building. After excavations, indications that 13 stone pillars were originally erected at the site were found, forming 12 gaps between them.
Chinese archeo-astronomers have reconstructed the site to test the accuracy of the positioning of the stone pillars that cast the shadows to mark the seasons and was confirmed as a functional observatory to observe the sunrise in order to determine the start of the seasons. This recent find has proven to now be the oldest astronomy observatory in the world, constructed and used during the Middle Taosi Period (21st century BC).
The Chinese have thus been observing and cataloguing the heavens for over 4000 years!
FAST (five hundred meter aperture spherical radio telescope), nicknamed Tianyan (天眼, lit. “Sky Eye” or “The Eye of Heaven” was completed in 2016, and is located in Guizhou Province in China. It is the world’s largest filled-aperture radio telescope.
The telescope made its first discovery of two new pulsars in August 2017 and are 16,000 and 4,100 light years away.
With FAST, we can observe more distant celestial bodies with fainter brightnesses. It is thus a powerful tool for detecting pulsars at great distances. FAST is equipped with multi beam receivers which can detect thousands of pulsars in the Milky Way.
It is theorised that a pulsar is a highly magnetized rotating neutron star that emits a beam of electromagnetic radiation. This radiation can be observed only when the beam of emission is pointing toward Earth (much like the way a lighthouse can be seen only when the light is pointed in the direction of an observer). Neutron stars are very dense, and have short, regular rotational periods. This produces a very precise interval between pulses that ranges from milliseconds to seconds for an individual pulsar. Pulsars are one of the candidates for the source of ultra-high-energy cosmic rays.
This picture is thought to be a pulsating dead star that appears to be burning with the energy of 10 million suns, making it the brightest pulsar ever to be detected. The pulsar was found in the galaxy Messier 82 (M82), a relatively close galactic neighbor 12 million light-years from Earth.
What is the significance of the Crab Nebula?
The Crab Nebula is thought to be a supernova remnant in the constellation of Taurus. At the center of the nebula lies the Crab pulsar, a neutron star 28-30 kilometres wide with a spin rate of 30.2 times per second which emits pulses of radiation from gamma rays to radio waves.
It is still generally the brightest persistent source in the sky.
Recently, as in this past month, the Crab Nebula hit Earth with the highest energy gamma rays ever detected.
What does this tell us about the Crab Nebula? By our increased ability to detect more clearly the range of energies the Crab Nebula is producing, we will be better able to understand what is organising the dense star at its center. Detecting more of these types of events will also help to explain the origins of these superpowered cosmic rays.
The process of light generation and propagation through the universe is still surrounded by many mysteries. Stars like human beings have a life cycle; they are born, they grow older and they die. It is thought that the trigger of a star’s life is gravity, the gravitational force pulls together the original nebula, a cloud of hydrogen, because of the increasing density, the temperature increases and a nuclear fusion process starts. Once this chain reaction is stable a star is born.
The Book of Changes (the oldest of the ancient chinese texts) says, “Heaven displays its signs of fortune, and the sage arrives at his interpretations”. This means that the Universe is governed by its own rules. If you obey those rules, you will win favour; if not, you may suffer from disasters. Wise people know the rules of the Universe, and they act accordingly.
The purpose of astronomy has always been to study the correlation between man and the Universe, instead of the Universe by itself. The chinese thought and still think of the Universe as the relationship among the heavens, the earth and humans. The three parts are unified as a harmonious whole and can communicate with each other.
Recently, Ye Peijian Head of the Chinese Lunar Exploration Program said
The universe is an ocean, the moon is the Diaoyu Islands, Mars is Huangyan Island. If we don’t go there now even though we’re capable of doing so, then we will have failed our descendants.
In a very real way, space is our new unexplored ocean, with the planets and moons as forms of land. And the space station as our international port, with individual space ships, as well, ships on the sea. However, there is an immense qualitative difference between ocean navigation and space navigation. Unlike the news blips that sell on fabricating drama. Our ability to function in space has always been based on cooperation. And despite it being the common thing, that your crew members in space all speak a different native language than you, there is an undeniable union shared which may have appeared on earth as a giant gulf of difference. This is a joint mission of human kind, and it will only flourish as a joint mission.
Let us dare to imagine the potential behind the unknown!
Or make a one time assist of $10
We only exist through the support of people like you | 0.936111 | 3.059086 |
Copyright © Astronomy Roadshow Planetarium All rights Reserved
Monday - Friday: 9am-5.00pm
A Typical Star- may exist for billions of years converting hydrogen into helium. In around 4.5 billion years, the sun’s core would have used up most of the hydrogen. Hydrogen-Helium fusion will cease. The outward pressure generated by the heat is now largely lost. The core’s gravity takes over, and compresses the helium into a much smaller volume. At a critical moment, if the temperature reaches 100 millionºC, the Helium will begin to fuse into Carbon (known as the Helium Flash). So much heat is now leaking out toward the surface, that the upper atmospheric gases (still mostly hydrogen) will overcome the force of gravity, and will expand. The heat will be more spread out within this new upper layer, so the surface temperature will cool from around 6000ºC to 3000ºC. The colour will now change from Yellow, to Orange then to Red. The sun has now become a Red-Giant star. Its diameter is now so great that Mercury, Venus, and the Earth have met their doom inside the sun’s upper layers. Most stars will undergo the same life story, but the star’s mass will determine the final outcome.
Birth of a Star... The key factor in a star’s life span is its Mass. No other factor is as important as this. A star is formed under the gravitational force within a cloud of hydrogen gas-Nebula. The hydrogen reduces in volume, the pressure within itself increases. The greater the mass of the whole cloud, the greater its gravitational pull, and the faster the whole process takes place. Temperatures will rise as the contraction continues. If the temperature at the core reaches a minimum 9millionºC, hydrogen gas (single Protons) will fuse together. One of the protons will emit a Positron & a Neutrino; it will convert into a neutron to form Deuterium, then another proton may fuse to produce Helium-3. During this reaction, a Gamma Ray is released. As the core is so dense, the Gamma radiation will ‘bump into’ other atoms at the speed of light. During each collision, the gamma ray looses a little energy. It will drop in frequency. A million years later, the radiation will reach the surface as ultra-violet, light, infrared etc, and radiate outwards across the universe. (Neutrinos will shoot out of the sun and into space at the speed of light as if the matter in the sun didn’t exist – we still don’t know how). A star is born.
Stars of differing masses will suffer different fates.
Massive stars - large cores - short lifespan - more violent ending. | 0.844813 | 3.539478 |
Planets without suns float around orphaned in interstellar space. We’ve always assumed they couldn’t support life. Find out why that view is changing.
Everything on Earth revolves around the sun. Our planet orbits the sun, of course, but the sun is also central to everything life does in our world.
All of the energy on Earth is solar energy. Even fossil fuels were created by the sun, having formed from the remains of dead plants and animals millions of years ago.
Plants rely on the sun for their energy and animals eat plants for theirs. Our seasons result from the shifts in Earth’s angle toward the sun. We use the hours of daylight we have during the day to mark them.
PLANTS GET ENERGY FROM THE SUN AND ANIMALS EAT PLANTS
Daylight arrives when our part of the world is facing the sun and nighttime comes when we rotate away from the sun. Our circadian rhythms align with the timing of the sunrise, noon and sunset where we live. When we don’t get enough sunshine, we don’t feel well.
The sun warms our oceans and determines their currents. It also warms our atmosphere, causing the weather we experience.
It’s no wonder humans have traditionally worshipped the sun. We all intuitively sense our close connection and dependence on the star we all orbit together.
ALWAYS IMAGINED LIFE ON PLANETS ORBITING OWN SUN
Naturally, we’ve always imagined that we would discover life on other planets orbiting their own sun. Since the sun is so central to our lives, surely life can only be found in star systems like our own.
That’s always been the assumption and the basis for our search for life outside our solar system. Our search for exoplanets is based almost entirely on observing other stars in the galaxy.
We know that there are planets without suns in our galaxy. For example, astronomers detected the free-floating planet PSO J318.5-22 in interstellar space. They used the Pan-STARRS 1 wide-field survey telescope on Mount Haleakala, on the island of Maui in 2013. (Science is a tough life sometimes!)
OPPHAN GAS PLANET SIX TIMES MORE MASSIVE THAN JUPITER
It’s a gas giant planet about six times more massive than Jupiter and about 80 light-years from Earth. Instead of orbiting a star, it revolves around the centre of the galaxy itself.
Not everyone defines planets the same way. Some scientists define planets as having to be in a planetary system.
They prefer to call bodies like PSO J318.5-22 “planetary-mass objects” or “planemos.” Other names for them include “orphan planets” or “rogue planets.”
MAY HAVE BEEN A BIAS BASED ON OUR DEPENDENCE ON THE SUN
However, we name them, the consensus has always been that they couldn’t possibly support life. This may have been a bias based on our own experience living lives that are wholly dependent on our sun.
A new study in Astrophysical Journal Letters proposes that earth-sized planets without suns could sustain surface water and other liquids. This could happen due to radioactive decay.
As we know, there are radioactive isotopes, or radionuclides, in the Earth’s crust. These include uranium-238, thorium-232, and potassium-40, among others.
RADIONUCLIDES GENERATE POWER IN THE FORM OF HEAT
These isotopes generate power in the form of heat as they decay. Mind you, the sun produces 30,000 times more power, but the energy is there.
A planet that had enough radionuclides and that was close to the centre of the Milky Way Galaxy might have enough heat to prevent freezing on its surface, according to the study. If true, this could change our approach to the search for life on other planets.
Harvard astrophysicist and study co-author Avi Loeb told the journal Science, “That gives you the freedom to be anywhere. You don’t need to be close to a star.”
“YOU DON’T NEED TO BE CLOSE TO A STAR”
The researchers thought about what heat sources planets without suns could rely on instead of stars. The came up with three, the heat left from when they formed, radioactive isotopes that decay quickly and radioactive isotopes that decay slowly.
Then they build computer models to simulate the energy needed to keep water, ammonia and ethane in liquid form on the planet surface. Life would need some sort of liquid solvent to form, and these are the three primary solvents we find in our solar system.
They found that an earth-like planet with about 1,000 times more of both kinds of radioactive isotopes could maintain liquid water over hundreds of millions of years. For liquid ethane, it would only need 100 times more of these isotopes than we have on Earth.
RADIATION LEVELS HUNDREDS OF TIMES HIGHER THAN CHERNOBYL
These planets without suns would still be nasty places to live. The radiation levels would be hundreds of times higher than those seen in the 1986 Chernobyl nuclear disaster.
You probably wouldn’t find any multicellular life such as plants or animals there. If the cells were anything like the ones we know about here on Earth, most of them couldn’t survive there.
Even so, there are some unusually tough, resilient microbes on Earth that might be able to cope with the radiation there. There’s a bacterium called Deinococcus radiodurans that can put up with extreme radiation levels.
UNUSUALLY TOUGH, RESILIENT MICROBES MIGHT BE ABLE TO COPE
Co-author Manasvi Lingam, an astrobiologist at the Florida Institute of Technology, put it this way, “Deinococcus radiodurans is a really crazy organism.” Assuming resistant microbes could evolve, where would these radioactive planets without suns come from.
They wouldn’t be able to form in our galactic neighbourhood. However, since the heavy elements like uranium and others seem to form from neutron star collisions, it could happen near a group of these collapsed stars.
The centre of the Milky Way Galaxy is much more crowded, so there would be more neutron stars there, and they would be more likely to collide. Even if planets without suns with enough radionuclides exist, they would be harder to find than a needle in a haystack.
THEY WOULD BE HARDER TO FIND THAN A NEEDLE IN A HAYSTACK
For one thing, it would be hard to tell these planets from the failed stars that astronomers called brown dwarfs.
One possibility would be to use the new James Webb Space Telescope, which launches in 2021. It could detect a target planet based on its high radiation levels. Still, it would take about ten days, which is a lot of telescope time to divert from other, more promising projects.
If this sounds pretty hypothetical, it is. It’s easier and more efficient to keep concentrating on stars with solar systems in our quest for life.
AN INTRIGUING POSSIBILITY IN THE PRELIMINARY STAGES
Despite this, it’s an intriguing possibility, even though it’s in the preliminary stages. Whether it pans out or not, learning more about this hypothesis would help us to fill in some blanks in the story of how our own planet formed, and our relationships with it and with nature which are both a bit of a mystery.
As Professor Lingam explained, “There are so many unknowns. We haven’t said the last word.”
We always have more to learn if we dare to know.
Science Magazine (AAAS)
On the Habitable Lifetime of Terrestrial Worlds with High Radionuclide Abundances
Newborn Stars Bringing Forth Solar Systems
NASA Discovery Program – 4 Bids to Explore Solar System
Origin of Life Before the Origin of Species – 4 Theories | 0.899749 | 3.324956 |
New Hubble mosaic of the Orion Nebula
In the search for rogue planets and failed stars astronomers using the NASA/ESA Hubble Space Telescope have created a new mosaic image of the Orion Nebula. During their survey of the famous star formation region, they found what may be the missing piece of a cosmic puzzle; the third, long-lost member of a star system that had broken apart.
The Orion Nebula is the closest star formation region to Earth, only 1400 light-years away. It is a turbulent place—stars are being born, planetary systems are forming and the radiation unleashed by young massive stars is carving cavities in the nebula and disrupting the growth of smaller, nearby stars.
Because of this ongoing turmoil, Hubble has observed the nebula many times to study the various intriguing processes going on there. This large composite image of the nebula's central region, combining visual and near-infrared data, is the latest addition to this collection.
Astronomers used these new infrared data to hunt for rogue planets—free-floating in space without a parent star—and brown dwarfs in the Orion Nebula. The infrared capabilities of Hubble also allow it to peer through the swirling clouds of dust and gas and make the stars hidden within clearly visible; the unveiled stars appear with bright red colours in the final image. Among these, astronomers stumbled across a star moving at an unusually high speed—about 200 000 kilometres per hour. This star could be the missing piece of the puzzle of a star system that had been broken apart 540 years ago.
Astronomers already knew about two other runaway stars in the Orion Nebula which were most likely once part of a now-defunct multiple-star system. For years it was suspected that the original system contained more than just these two stars. Now, by virtue of accident and curiosity, Hubble may have found the missing third piece of this cosmic puzzle.
Whether the new star is indeed the missing—and the last—piece of the puzzle will require further observations. So will the answer to the question of why the original star system broke apart in the first place. While there are several theories—interactions with other, nearby stellar groups, or two of the stars getting too close to each other—none can be ruled out or confirmed yet.
And while the astronomers are looking for the answers to these questions, who knows what mystery they will find next? | 0.863447 | 3.69518 |
The team that took the first ever image of a black hole has announced plans to capture “razor sharp” full colour video of the one at the centre of our galaxy.
Satellites would be launched to supplement the existing network of eight telescopes to make this movie.
The researchers say the upgraded network will be able to see the supermassive black hole consuming the material around it.
The team has been awarded the Breakthrough Award for Physics.
Prof Heino Falcke, of Radboud University in the Netherlands, who proposed the idea of the so-called Event Horizon Telescope (EHT), told BBC News that the next step was to see a black hole in action.
“Just like planets, a black hole rotates. And because of its incredibly strong gravity, it distorts space and time around it. And so seeing this very weird effect of space itself being rotated is one of the holy grails of astrophysics.”
Even more puzzling is the prospect of taking a colour picture of an object whose gravity is so intense that not even light can escape.
Earlier this year, the EHT team published a photograph of a supermassive black hole at the heart of a distant galaxy measuring 40 billion km across – three million times the size of Earth. The image shows superheated gas falling into it in different shades of orange.
A black hole has no colour of course. But what astronomers can see is the material pouring into it that becomes superheated gas. This gas is thought to change colour as it gets closer to the black hole. Like the Sun when it sets behind clouds in the evening, light from the superheated material will have to travel through more gas on its way to instruments on Earth. So the effect will be to change the colour and appearance of the material around the black hole.
The international consortium expects to add ground-based telescopes in Greenland, France and parts of Africa and has applied for funding from the US National Science Foundation (NSF) to send three small satellites into orbit to supplement the ground-based survey.
According to Prof Falcke, this will create a super telescope, effectively larger than the Earth, capable of taking razor sharp images of the black hole at the centre of our galaxy.
Prof Shep Doleman of Harvard University, US, who is the EHT’s project director, said the images and video would enable the team to test Einstein’s theories to new limits and unravel how black holes generate light-speed jets that can pierce entire galaxies.
“(We plan to) create huge virtual telescopes, and new radio facilities will be built around the globe. The EHT team is just getting started,” he said.
Prof Falcke told BBC News about the EHT consortium’s plans as the international team of 347 scientists received a $ 3m (£2.48m) cash award from the Breakthrough Prize Foundation.
Although he first proposed the idea and battled with the help of colleagues to get it funded, he said that the award was a recognition of a global effort by the entire team.
“There have been scientists in Europe, China, South Africa, Japan and Taiwan involved. For me, what was a much larger reward was the overwhelming response across the world from ordinary people who were touched by seeing the image,” he said.
“It was not just scientific; it was emotional. One person told me that she was in tears. It was so pleasing to know that everyone was able to appreciate it and celebrate it.” | 0.863004 | 3.661006 |
Anybody who has been up early in the past month and looked at the eastern sky will have noticed a brilliant white object – the planet Venus, sometimes called the Morning Star. It is much brighter than any other planet and is the third brightest object in the sky after the Sun and the Moon.
Image from NASA. Venus in the pre-dawn morning sky. The less bright object near to Venus is the planet Jupiter. Venus appears as a disc in the image because it is so bright that it has flooded the camera with light. To the naked eye Venus appears as a point of light.
The orbit of Venus
Venus is the planet which passes closest to Earth. At its closest approach it is only 40 million km from Earth, roughly 100 times the distance from the Earth to the Moon (Williams 2015). A year on Venus is the equivalent of 225 Earth days, because not only is it nearer to the Sun but it also moves faster in its orbit.
The orbit of Venus in shown in the diagram above. As you can see, because Venus orbits the Sun inside the Earth’s orbit, to an observer on Earth it always stays close to the Sun. This means that for most of the time Venus is only above the horizon in the daytime when it is difficult to see.. The points marked as A in the diagram are known as the greatest elongations and are the points where, to an observer on Earth, Venus appears to be the greatest distance from the Sun in the sky. At these times, although Venus is still visible mainly in the daytime, it is also visible for a few hours at night before sunrise or after sunset. This effect is greater at higher latitudes, because the path of Venus through the sky has a shallower angle.
This is also true for Mercury. The other planets orbit outside the Earth’s orbit and therefore can be seen in the middle of the night at certain times.
Venus over the next two years
Venus has just passed one of the greatest elongation points and currently rises 3-4 hours before the Sun It is clearly visible as a brilliant white object in the eastern sky before sunrise. As the Sun rises then Venus becomes difficult to see against the brightness of the daytime sky. However, it doesn’t disappear altogether. Venus can be seen in the day, if you know exactly where to look, appearing to the naked eye as a faint white dot. There are actually very few astronomical objects visible during the day – only the Sun, the Moon, Venus, Jupiter and Mars.
As Venus continues in its orbit, over the next few months it will appear to an observer on the Earth to get gradually closer to the sun. This will cause it to rise later and later in the morning, so it will be clearly visible as a bright shining object for a shorter and shorter time before it becomes too light. By early March 2016 it will be only visible for about 30 minutes before sunrise. On 6 June Venus will be in a direct line behind the Sun. This is called superior conjunction (Espenak 2014) and, for a few weeks or so either side of this date, Venus will be very difficult to see because it will only be visible in daytime and will appear close to the Sun. As it continues in its orbit it will continue to rise and set later and later. By late July 2016 it will be visible as the bright Evening Star in the West for an hour after sunset. It will reach the other greatest elongation point on 12 January 2017, when it will be a brilliant object in the western sky, visible for about 4 hours after sunset.
After the greatest elongation the apparent distance from the sun will start to get smaller again. Venus will therefore be visible for a shorter time after sunset. On 25 March 2017 it will pass between the Earth and the Sun, a phenomenon called inferior conjunction, and again for a few weeks or so either side of this date Venus will be very difficult to see because it will only be visible in daytime close to the Sun.
After inferior conjunction, it will continue to rise earlier and will be visible again in the morning as the Morning Star in the East. It will be at the other greatest elongation point once again, when it visible for the greatest time before sunrise, on 3 June 2017.
Transit of Venus
Because the orbit of Venus is tilted with respect to the orbit of the Earth, at inferior conjunction Venus normally passes just below or just above the Sun. Occasionally things line up so that Venus passes directly in front of the Sun as seen from the Earth. This is called a transit of Venus and the planet appears as a small dark dot against the bright disc of the Sun. This is a rare occurrence. It happened a few years ago in 2012, and it won’t happen again until 2117 (McClure 2012).
Image from Wikimedia Commons
As seen from the Earth, Venus goes through a full set of phases in a similar way to the Moon, although, because Venus appears so small, these are only visible through a telescope.
Starting with with a “new Venus”, shown as A in the diagram above, when Venus is between the Earth to the Sun and the sunlit part of Venus faces away from us making the planet almost invisible, over a 584 day cycle the sunlit part of the Venus gets larger or waxes through to a crescent phase (B), to a half Venus (C) at the greatest elongation, to a full Venus at superior conjunction (D), when the whole Earth-facing side is illuminated. It then gets smaller or wanes back to a half Venus (E) at greatest elongation, then to a crescent (F) and then finally back to a new Venus.
The first person to discover the phases of Venus was the Italian astronomer Galileo Galilei (1564-1642).
Image from Wikimedia Commons
In 1543, just before his death, Nicolas Copernicus (1473-1543) had published the theory of heliocentrism which was completely revolutionary in its day – that the planets orbit the Sun. However, in Gallileo’s time, the teaching of the Catholic church favoured geocentrism, the widely held view that the Earth was the centre of the Universe and the stars, planets, the Sun and the Moon were in orbit around it. Indeed certain verses of the bible could be interpreted as supporting that viewpoint, such as Psalm 104:5 “the Lord set the earth on its foundations; it can never be moved.”
However, the phases of Venus and the way that it appears smaller when it is a full Venus can only be fully explained by Venus orbiting the Sun, not the Earth. Therefore, Galileo concluded that the geocentric theory was incorrect. Unfortunately for Galileo, in 1616 the Catholic church declared heliocentrism to be heresy. Heliocentric books were banned and Galileo was ordered to refrain from holding, teaching or defending heliocentric ideas.
However Galileo continued to defend heliocentrism, so in 1633 The Roman Inquisition tried Galileo in 1633 and found him “vehemently suspect of heresy”, sentencing him to indefinite imprisonment. Galileo was kept under house arrest until his death in 1642.
However the facts cannot be disputed. When viewed through a telescope Venus does show changes in size and shape, which can only be satisfactorily explained in a heliocentric model. Eventually, in 1758, the the Catholic Church dropped the general prohibition of books advocating heliocentrism.
The properties of Venus
Through a telescope Venus appears to be a featureless object. This is in contrast to Mars where surface detail can be clearly seen.
Venus through a telescope -Image from NASA
Mars through a telescope_image from NASA
This reason why we can’t see any details on Venus is because the planet is completely covered in thick clouds which reflect most of the sunlight back into space and prevent us from seeing details underneath. So despite it being the closest astronomical object to the Earth other than the Moon, little was known about Venus until the 1960s. Without any surface markings to follow as the planet spins on its axis it was difficult to estimate how long a day on Venus is. This wasn’t discovered until 1961 when astronomers bounced radar signals of the planet and studied their echos.
It wasn’t until the planet was visited by spacecraft in the 1960s that we knew how hot the surface and how thick the atmosphere were. Indeed, before then many scientists thought that conditions on Venus underneath the clouds were similar to Earth and there are many science fiction stories written before the 1960s where Venus is inhabited by alien life forms. However, it turns out that the surface temperature is an incredibly hot 460 degrees Celsius on average, which is hot enough to melt lead, and the atmospheric pressure at the surface is a crushing 92 times the surface pressure of the Earth. The bright clouds turns out to be made out of highly toxic and corrosive sulfuric acid.
In my next post I shall talk about current, past and future missions to explore Venus.
Mariner 2 was the first successful interplanetary spacecraft. Launched on 27 August 1962, Mariner 2 passed within about 34,000 kilometers (21,000 miles) of Venus.
Espenak, F (2014) 2016 calendar of astronomical events, Available at:http://www.astropixels.com/ephemeris/astrocal/astrocal2016gmt.html (Accessed: 10 November 2015).
McClure, B (2012) Everything you need to know: Venus transit on June 5-6, Available at: http://earthsky.org/astronomy-essentials/last-transit-of-venus-in-21st-century-will-happen-in-june-2012 (Accessed: 10 November 2015).
Williams, D (2015) Venus Fact Sheet, Available at:http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html (Accessed: 10 November 2015). | 0.843374 | 3.765385 |
A launch loop or Lofstrom loop is a proposed system for launching objects into orbit using a moving cable-like system situated inside a sheath attached to the Earth at two ends and suspended above the atmosphere in the middle. The design concept was published by Keith Lofstrom and describes an active structure maglev cable transport system that would be around 2,000 km (1,240 mi) long and maintained at an altitude of up to 80 km (50 mi). A launch loop would be held up at this altitude by the momentum of a belt that circulates around the structure. This circulation, in effect, transfers the weight of the structure onto a pair of magnetic bearings, one at each end, which support it.
Launch loops are intended to achieve non-rocket spacelaunch of vehicles weighing 5 metric tons by electromagnetically accelerating them so that they are projected into Earth orbit or even beyond. This would be achieved by the flat part of the cable which forms an acceleration track above the atmosphere.
In 1982, Paul Birch published a series of papers in Journal of the British Interplanetary Society which described orbital rings and described a form which he called Partial Orbital Ring System (PORS). The launch loop idea was worked on in more detail around 1983-1985 by Lofstrom. It is a fleshed-out version of PORS specifically arranged to form a mag-lev acceleration track suitable for launching humans into space; but whereas the orbital ring used superconducting magnetic levitation, launch loops use electromagnetic suspension (EMS).
A launch loop is proposed to be a structure 2,000 km long and 80 km high. The loop runs along at 80 km above the earth for 2000 km then descends to earth before looping back on itself rising back to 80 km above the earth to follow the reverse path then looping back to the starting point. The loop would be in the form of a tube, known as the sheath. Floating within the sheath is another continuous tube, known as the rotor which is a sort of belt or chain. The rotor is an iron tube approximately 5 cm (2 inches) in diameter, moving around the loop at 14 km/s (31,000 miles per hour).
When at rest, the loop is at ground level. The rotor is then accelerated up to speed. As the rotor speed increases, it curves to form an arc. The structure is held up by the force from the rotor, which attempts to follow a parabolic trajectory. The ground anchors force it to go parallel to the earth upon reaching the height of 80 kilometers. Once raised, the structure requires continuous power to overcome the energy dissipated. Additional energy would be needed to power any vehicles that are launched.
To launch, vehicles are raised up on an 'elevator' cable that hangs down from the West station loading dock at 80 km, and placed on the track. The payload applies a magnetic field which generates eddy currents in the fast-moving rotor. This both lifts the payload away from the cable, as well as pulls the payload along with 3g (30 m/s²) acceleration. The payload then rides the rotor until it reaches the required orbital velocity, and leaves the track.
If a stable or circular orbit is needed, once the payload reaches the highest part of its trajectory then an on-board rocket engine ("kick motor") or other means is needed to circularize the trajectory to the appropriate Earth orbit.
The eddy current technique is compact, lightweight and powerful, but inefficient. With each launch the rotor temperature increases by 80 kelvins due to power dissipation. If launches are spaced too close together, the rotor temperature can approach 770 °C (1043 K), at which point the iron rotor loses its ferromagnetic properties and rotor containment is lost.
Closed orbits with a perigee of 80 km quite quickly decay and re-enter, but in addition to such orbits, a launch loop by itself would also be capable of directly injecting payloads into escape orbits, gravity assist trajectories past the Moon, and other non closed orbits such as close to the Trojan points.
To access circular orbits using a launch loop a relatively small 'kick motor' would need to be launched with the payload which would fire at apogee and would circularise the orbit. For GEO insertion this would need to provide a delta-v of about 1.6 km/s, for LEO to circularise at 500 km would require a delta-v of just 120 m/s. Conventional rockets require delta-vs of roughly 14 and 10 km/s to reach GEO and LEO respectively.
Launch loops in Lofstrom's design are placed close to the equator and can only directly access equatorial orbits. However other orbital planes might be reached via high altitude plane changes, lunar perturbations or aerodynamic techniques.
Launch rate capacity of a launch loop is ultimately limited by the temperature and cooling rate of the rotor to 80 per hour, but that would require a 17 GW power station; a more modest 500 MW power station is sufficient for 35 launches per day.
For a launch loop to be economically viable it would require customers with sufficiently large payload launch requirements.
Lofstrom estimates that an initial loop costing roughly $10 billion with a one-year payback could launch 40,000 metric tons per year, and cut launch costs to $300/kg. For $30 billion, with a larger power generation capacity, the loop would be capable of launching 6 million metric tons per year, and given a five-year payback period, the costs for accessing space with a launch loop could be as low as $3/kg.
Compared to space elevators, no new high-tensile strength materials have to be developed, since the structure resists Earth's gravity by supporting its own weight with the kinetic energy of the moving loop, and not by tensile strength.
Lofstrom's launch loops are expected to launch at high rates (many launches per hour, independent of weather), and are not inherently polluting. Rockets create pollution such as nitrates in their exhausts due to high exhaust temperature, and can create greenhouse gases depending on propellant choices. Launch loops as a form of electric propulsion can be clean, and can be run on geothermal, nuclear, wind, solar or any other power source, even intermittent ones, as the system has huge built-in power storage capacity.
Unlike space elevators which would have to travel through the Van Allen belts over several days, launch loop passengers can be launched to low earth orbit, which is below the belts, or through them in a few hours. This would be a similar situation to that faced by the Apollo astronauts, who had radiation doses about 0.5% of what the space elevator would give.
Unlike space elevators which are subjected to the risks of space debris and meteorites along their whole length, launch loops are to be situated at an altitude where orbits are unstable due to air drag. Since debris does not persist, it only has one chance to impact the structure. Whereas the collapse period of space elevators is expected to be of the order of years, damage or collapse of loops in this way is expected to be rare. In addition, launch loops themselves are not a significant source of space debris, even in an accident. All debris generated has a perigee that intersects the atmosphere or is at escape velocity.
Launch loops are intended for human transportation, to give a safe 3g acceleration which the vast majority of people would be capable of tolerating well, and would be a much faster way of reaching space than space elevators.
Launch loops would be quiet in operation, and would not cause any sound pollution, unlike rockets.
A running loop would have an extremely large amount of energy in its linear momentum. While the magnetic suspension system would be highly redundant, with failures of small sections having essentially no effect, if a major failure did occur the energy in the loop (1.5×1015joules or 1.5 petajoules) would approach the same total energy release as a nuclear bomb explosion (350 kilotons of TNT equivalent), although not emitting nuclear radiation.
While this is a large amount of energy, it is unlikely that this would destroy much of the structure due to its very large size, and because most of the energy would be deliberately dumped at preselected places when the failure is detected. Steps might need to be taken to lower the cable down from 80 km altitude with minimal damage, such as by the use of parachutes.
Therefore, for safety and astrodynamic reasons, launch loops are intended to be installed over an ocean near the equator, well away from habitation.
The published design of a launch loop requires electronic control of the magnetic levitation to minimize power dissipation and to stabilize the otherwise under-damped cable.
The two main points of instability are the turnaround sections and the cable.
The turnaround sections are potentially unstable, since movement of the rotor away from the magnets gives reduced magnetic attraction, whereas movements closer gives increased attraction. In either case, instability occurs. This problem is routinely solved with existing servo control systems that vary the strength of the magnets. Although servo reliability is a potential issue, at the high speed of the rotor, very many consecutive sections would need to fail for the rotor containment to be lost.
The cable sections also share this potential issue, although the forces are much lower. However, an additional instability is present in that the cable/sheath/rotor may undergo meandering modes (similar to a Lariat chain) that grow in amplitude without limit. Lofstrom believes that this instability also can be controlled in real time by servo mechanisms, although this has never been attempted.
In works by Alexander Bolonkin it is suggested that Lofstrom's project has many non-solved problems and that it is very far from a current technology. For example, the Lofstrom project has expansion joints between 1.5 meter iron plates. Their speeds (under gravitation, friction) can be different and Bolonkin claims that they could wedge in the tube; and the force and friction in the ground 28 km diameter turnaround sections are gigantic. In 2008, Bolonkin proposed a simple rotated close-loop cable to launch the space apparatus in a way suitable for current technology.
Another project, the space cable, is a smaller design by John Knapman that is intended for launch assist for conventional rockets and suborbital tourism. The space cable design uses discrete bolts rather than a continuous rotor, as with the launch loop architecture. John Knapman has also mathematically shown that the meander instability can be tamed.
The skyhook is another launch system concept. Skyhook could be either rotating or non-rotating. The non-rotating skyhook hangs from a low Earth orbit down to just above the Earth's atmosphere (skyhook cable is not attached to Earth). The rotating skyhook changes this design to decrease the speed of the lower end; the entire cable rotates around its center of gravity. The advantage of this is an even greater velocity reduction for the launch vehicle flying to the bottom end of the rotating skyhook which makes for an even larger payload and a lower launch cost. The two disadvantages of this are: the greatly reduced time available for the arriving launch vehicle to hook up at the lower end of the rotating skyhook (approximately 3 to 5 seconds), and the lack of choice regarding the destination orbit. | 0.80821 | 3.625447 |
Jupiter to begin its reign in the Arizona night sky
Jupiter is the true king of the planets.
Of all the major planets in our solar system, Jupiter is by far the most amazing in terms of its size and composition.
Jupiter is a very bright planet and will now become an easy late evening planet in our Arizona skies.
More specifically, Jupiter is the fifth-largest planet in the solar system, with a mass of one-thousandth the mass of the Sun and two-and-a-half times the mass of all the other planets in the solar system.
Jupiter is so large, you could pack some 1,321 Earths into the volume of this gas giant!
In a size comparison, you could line up nearly 12 Earths along Jupiter’s equator. Jupiter is primarily made up of mostly hydrogen and helium.
The great astronomer Galileo looked at the planet Jupiter with his crude telescope and noticed that there appeared to be small moons next to the planet.
Galileo observed these on Jan. 7, 1610.
They are named Io, Europa, Ganymede and Callisto. Jupiter now has some 79 known moons and there may be many more to be discovered.
We have an amazing opportunity to view Jupiter in our Arizona skies, as the next great opposition will take place in early June.
Begin by looking to the southeast sky as early as 10:30 p.m. local time, as Jupiter will be the brightest object in that region of the sky.
Now would be a great opportunity to have a pair of binoculars and a small telescope to begin more detailed observations of Jupiter.
A small telescope with at least a magnification of 100 times the human eye will help you to get a good view of the moons and some detail on the cloud tops of the planet.
Here is an image of Jupiter to help you identify the band and belts on the planet, as well as the famous “Red Spot” Jovian storm.
Many space probes have passed the mighty Jupiter and much has been learned about the structure of the clouds and the great Red Spot.
The latest space probe to be conducting research and imaging of Jupiter, is the Juno space probe. This is a solar powered craft that is now in orbit around Jupiter.
Here is a recent image taken by Juno.
Jupiter will reach opposition on the night of June 10 at 8:17 p.m. Mountain Time. At that time, Jupiter will rise at sunset and be in the sky all night. This is the best time to plan your observations of the planet, but a few weeks on either side of this date, is also a good time to view the planet.
Jupiter will be some 398,000,000 miles from Earth at that time, with Jupiter being well placed in the constellation of Ophiuchus.
Get set for some great views of Jupiter, the might Zeus!
To print your own monthly star chart, click here.
To view satellites/dates/times of passage, click here.
Listen to the Dr. Sky Show on KTAR News 92.3 FM every Saturday morning at 3 a.m.
- Memorial Day weekend DUI arrests in Arizona decreased from 2019
- Live updates: Latest on coronavirus in Arizona, which has 17,763 cases
- Swoon over Full Strawberry Moon and other June sights in Arizona skies
- ‘Bummed out’: SpaceX launch scrubbed because of bad weather
- Arizona professor says Elon Musk’s SpaceX launch may change the future | 0.85576 | 3.272624 |
Bakersfield Night Sky – November 15, 2014
by Nick Strobel
The Philae Lander has landed successfully on Comet 67P/Churyumov-Gerasimenko. This was an insanely difficult landing as I'll describe further below. Part of the landing sequence did not work as planned, so Philae bounced off its original intended target location, traveled about two hours in a kilometer-long arc in the very weak gravity field of the comet to its current location on the side of a cliff or crater wall. As I write this on Thursday afternoon, the precise location had not been determined but it looks like Philae is positioned vertically with two feet resting on a surface and the third foot "dangling" out in space. Unfortunately, it is not placed well for the solar panels on the lander to capture enough sunlight to recharge its battery, so the scientists are scrambling to get as much data from Philae's science instruments and cameras as they can before the battery runs down.
Even though the landing was partially successful, this "double-landing" was a far more successful venture than anyone had a right to expect. Let me explain. This is the FIRST landing on a comet. Both the Rosetta orbiter and Philae lander were launched ten years ago without any knowledge of what the comet looked like up close and before any of our other major comet missions had reached their targets such as StarDust in 2004 or Deep Impact in 2005.
The Rosetta/Philae technology took years to develop, so it was in the finishing stages of development when the Deep Space 1 spacecraft whizzed by Comet Borrelly in 2001. The only other close-up investigation of a comet was the fleet of craft that visited Comet Halley in 1986 with only the European Space Agency's Giotto spacecraft getting close enough to image the comet nucleus while it flew past the nucleus at 68 kilometers/second (152,000 mph).
All of the previous comet missions were flybys. In its November 3rd ScienceCast, NASA classifies space missions in three tiers of challenge: "difficult", "more difficult", and "ridiculously difficult". Flybys are "difficult". Orbiter missions are "more difficult" because the craft not only has to arrive at the object's position, it has to brake in just the right way to go into orbit around the object (and not burn up in its upper atmosphere or get slingshotted out into deep space). Lander missions are "ridiculously difficult" as witnessed by all the stages of descent of the Curiosity rover on Mars two years ago (the "seven minutes of terror").
Not to take away from the accomplishments of the Curiosity rover landing team but the Philae lander probably had an even more difficult task. Comet 67P/CG is not the oblong, rounded, lazily spinning object scientists and engineers envisioned when Rosetta and Philae were built and like the other comets visited by spacecraft. No, that would be too easy. Comet 67P/CG is a contact binary that wobbles about every 12.4 hours. It looks like two big chunks, each less than 2 miles across, that hit each other at a slow enough speed to stick to each other. The two chunks are connected by a neck of smoother material. It turns out that the neck looks smooth because there are jets of gas and dust shooting out of it that would erase any irregularities such as craters.
Those jets were not expected this far out from the Sun (almost 300 million miles). If Philae flew through a jet on its way down to the nucleus, it could have been deflected out to space. Jets also can change the rotation direction and speed of a comet just like firing a rocket thruster. Philae was essentially "dropped" from Rosetta at a distance of 14 miles and coasted for 7.5 hours to its original landing spot at the "front end" of the smaller chunk. Philae has only one small thruster and that was supposed to fire only as Philae made contact with the ground. If the Rosetta teams didn't time the release from the Rosetta orbiter just right or if the comet changed its wobble in the wrong way, Philae would have missed the comet. The comet is much too low in mass to have enough gravity to pull Philae in.
The comet has approximately 100,000 times less gravity than Earth does, so Philae was to use two harpoons and drills on each of its three feet to anchor itself to the comet's surface. A rocket thruster at the top of the lander was supposed to fire, pushing Philae downward as it made contact with the surface to prevent the lander from rebounding off the surface. The Rosetta team found out before Philae was released from the Rosetta orbiter that there was a problem with the rocket thruster but they gave the go-ahead with the hope that the harpoons would still be able to find a solid enough patch to which to attach.
The lander had to take care of all of the landing steps by itself without help from mission control because it did the landing while over 316 million miles away from Earth, so radio waves take over 28 minutes to travel between the comet and Earth. It turns out that the harpoons did not fire upon landing which may have been good luck in one sense. Firing the harpoons would cause a recoil that the defective rocket thruster was supposed to counter. However, without the harpoons anchoring Philae onto the surface, it did have a gentle bounce off the original landing location and floated for two hours over to another location.
The science instruments and cameras on Philae are working properly. That is a testament to quality engineering. They've been traveling for hundreds of millions of miles for over ten years of harsh radiation and temperature swings of outer space. The landing, however successful, was definitely, "ridiculously difficult"!
The Rosetta orbiter has plenty of science instruments to study the comet through its various stages of activity as it approaches its closest distance to the Sun in August 2015. At closest approach to the Sun (perihelion), the comet will still be outside the orbit of the Earth at a distance of 1.2 AU. The mission is designed to follow the comet for the few months following perihelion to track the waning of activity as the comet heads back out to its farthest distance, slightly greater than Jupiter's distance from the Sun. For more about Rosetta, see either the JPL site at http://rosetta.jpl.nasa.gov or the primary mission site at http://rosetta.esa.int .
Another comet-related event is the Leonid meteor shower that peaks on the mornings of November 17th and 18th. Meteor showers are the result of the Earth plowing through the dust trail left behind a comet as the comet sheds material when it nears the Sun. The dust trail spreads out along the comet's orbit so the few nights before and after a shower's peak will still bring comet bits hurtling through the upper atmosphere at speeds far faster than a bullet. The Leonids are from Comet 55P/Tempel-Tuttle and its dust particles hit our atmosphere at 71 km/sec (almost 160,000 mph). Good thing there's several tens of miles of atmosphere between us and them!
The dust trail is densest near the comet's nucleus. Comet 55P/Tempel-Tuttle has an orbital period of 33 years so every 33 years we get an especially impressive display for the Leonids. However, the last perihelion passage of the Comet Tempel-Tuttle was in 1998, so we'll need to wait until 2031 for another meteor storm. For this year's shower you'll see about 6 to 10 meteors per hour.
The Moon will be in a Waning Crescent phase so its light won't wash out the meteors and it won't rise until 2 AM on the 17th and 3 AM on the 18th. Jupiter will be well up in the eastern sky by then, just to the right of the Sickle (backward question mark) part of Leo (see the attached star chart below). When you trace the Leonid meteor streaks backward, you'll see that they appear to intercept under the crook of Leo's sickle (at the head of the lion), hence the name of the shower. Jupiter is at a 90-degree angle with respect to the Sun, so a view through a telescope will show the biggest distance between the large moons and their shadows on the cloud tops of Jupiter. The Moon will be at New Phase next Saturday, but, alas, no solar eclipse this time.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning Astronomy Notes website at www.astronomynotes.com | 0.826342 | 3.531319 |
Aldebaran (Alpha Tauri) is the brightest star in the constellation Taurus, and the 14th most luminous star in the entire night sky. Although it is relatively close to Earth, the Pioneer 10 space probe currently moving in the general direction of Aldebaran will only make its closest approach to the star in about 2 million years from now.
• Constellation: Taurus
• Star Type: Orange-Red giant (K5 III)
• Age: 7 billion years
• Distance: 65.3 light years
• Apparent magnitude (V): 0.75 to 0.95
• Apparent magnitude (J): -2.10
• Radius: 44.2 sol
• Mass: 1.7 sol
• Luminosity: 425 sol
• Surface Temperature: 3,910K
• Radial velocity: 54.26 km/s
• Rotation: 643 days
• Coordinates: RA: 4h 35m 55s, dec: 16°30’35”
• Other Designations: 87 Tauri, Alpha Tauri, BD+16°629, GJ 171.1, GJ 9159
Around 5000 years ago in ancient Persia, Aldebaran was one of the Four Royal Stars considered to be guardians of the heavens, and represented the ‘Watcher of the East’, with the others being Regulus (South), Antares (West), and Fomalhaut (North). The star was likewise worshiped by the Babylonians, who called the constellation Gud.Anna (“Bull of Heaven“), while to the ancient Egyptians it represented the bull-god Orissi. In Ancient Greece, Aldebaran marked the southern eye of the Bull, with the star’s name derived from the Arabic word ‘Al Dabaran’, meaning the ‘Follower’, in reference to its apparent tracking motion of the Pleiades star cluster. Interestingly, for the Seris people of north-western Mexico, Aldebaran is “[the] star that goes ahead” and provides light for the Pleiades, which is known as “[the] seven women giving birth”.
Even novice observers should not find it difficult to spot Aldebaran in the Taurus constellation, the star being located, by pure chance, exactly in the line of sight between Earth and the Hyades open cluster. This gives it the appearance of being the most luminous star in the V-shaped asterism that marks out the “head” of the Bull, but recent measurements have shown that the five brightest stars which make up the Hyades asterism lie 151 light years away compared to the 65 light years distant Aldebaran. Therefore, Aldebaran in no way interact with the Hyades, is not considered to be part of the asterism, and its exact origins remain unknown, since it cannot be linked to any structure, cloud, or group of stars.
One way of finding Aldebaran in the northern hemisphere is to follow the line formed by the three stars in Orion’s Belt from left to right to the first bright red star that you come across. Southern observers need to follow the stars in Orion’s Belt from right to left, though.
Taurus is a northern hemisphere constellation that can be seen by observers located between +90° and -65° of latitude, with the best time to view Aldebaran, the constellation’s brightest star, being autumn/winter in the northern hemisphere, and spring/summer from southern locations. Although Aldebaran is too far south of the ecliptic to be occulted by the planets, due to precession, in the distant past both Mercury and Venus had occulted the star, with the next occultation of Aldebaran by a planet, in this case Venus, set to happen on August 27th of 5366 AD. Aldebaran can be occulted by the Moon, though, but this phenomena cannot be observed from the southern hemisphere.
Aldebarans’ K5 III classification denotes it as an orange-red giant that has evolved off the main sequence, having consumed its hydrogen fuel. The resulting collapse of the core has ignited a remaining shell of hydrogen surrounding it, which has subsequently overcome the inward pushing force of the gravity of the star’s outer layers, thereby causing it to swell up to around 44.2 solar masses. A further consequence is that the expanded bulk of the star now shines at a visual luminosity 153 times brighter than the Sun, and an absolute luminosity about 425 times brighter. In terms of infrared (IR) radiation in the J-band, Aldebaran shines at magnitude -2.1, making it the fifth brightest star in this frequency, with only Betelgeuse (-2.9), Antares (-2.7), R Doradus (-2.6), and Arcturus (-2.2) being more luminous.
The stars’ photosphere displays carbon, oxygen, and nitrogen abundances, which suggests the first dredge-up stage in the life cycle of Aldebaran, a normal step in the evolutionary process of red giant stars that involves “dredging” up material from the star’s deep interior by means of convection currents, which then gets mixed into the star’s outer layers. Being a very slow rotator the processes that create a corona do not occur on Aldebaran, which means that the star does not emit hard X-ray radiation. Although a fierce dynamo effect is lacking, weak magnetic fields and together with a strong solar wind is causing the star to lose mass, and in a few million years it will become a planet-sized, white dwarf star.
Stretching out from the star to a distance of between 1.2 and 2.8 times the radius of the star, is a MOLsphere (molecular outer atmosphere) in which temperatures are low enough (1,000K – 2,000K) for various gaseous molecules to form. Spectra of this region have revealed the presence of carbon monoxide, water, and titanium oxide, however, past this region, and out to a distance of about 1 AU, the temperature of the slow solar wind declines to only about 7,500K. Nonetheless, the stars’ solar wind continues outward up to the termination shock boundary, which is where it collides with the (hot) ionized interstellar medium that predominates in the Local Bubble, a roughly spherical astrosphere that stretches outward from Aldebaran to a distance of about 1,000 AU. | 0.824801 | 3.722011 |
HomeSkyWas Venus Once Habitable? A Case for Further Exploration of Earth’s Twin Charles April 14, 2017 Sky Owing to its infernal environment, Earth’s twin has been largely ignored in recent years, but further exploration might reveal if Venus was once habitable. On March 5, 1982, the Soviet Union’s Venera 4 landed on the surface of Venus after parachuting through its dense atmosphere. It recorded a surface temperature of 465°C and air pressures 94 times higher than those on Earth at sea level. After just under an hour of running soil analysis tests, the lander succumbed to the immense pressures and temperatures. No mission has ever landed on our nearest planetary neighbour since. Although there have been several successful missions sent to explore Venus from orbit in the past 35 years, interest in our sister planet seems to have almost evaporated in recent years. With Mars getting all the attention, Venus has been all but forgotten, despite the fact it actually has much more in common with Earth than the Red Planet likely ever did. Indeed, the Venusian surface might be the proverbial hell, but it probably wasn’t always this way. Searching for Earth 2.0 Wikimedia Commons Home to one of the most hostile environments in the solar system, Venus might sound like a pretty poor match for Earth 2.0, but there’s more to the planet than meets the eye. Firstly, its similar size, composition, mass and gravity are not replicated anywhere else in the solar system. We’re also having a hard time detecting planets of similar size around other stars, since they’re very difficult to detect. Even if when we do find them, we can’t possibly explore them as effectively as we can explore a planet right here on our doorstep. There’s little doubt that Venus started life in much the same way Earth did. 4.5 billion years ago, they were probably almost identical, forming in the same way at the same time. The only key difference and, indeed, a driving factor in Earth’s evolution, was that Venus never had a Moon. Unlike Earth, the planet wasn’t subject to an enormous impact event that practically ripped the planet in two. Although this has major evolutionary implications, Venus was likely once a much less hostile place than it is today. Present-day Venus might not exactly stack up as an Earth 2.0 candidate, but recent research suggests that it may have been the first habitable planet in our solar system. The simulations also demonstrate that Venus may have retained a potentially habitable climate until as recently as 715 million years ago, which was about the time when the first animal life started appearing on Earth. The simulations even take into account Venus’s bizarre retrograde rotation rate of 243 Earth days. What these results clearly demonstrate is that we can and should explore Venus to learn more about the evolution of Earth-like planets and even life itself as well as, perhaps, the catastrophic destruction of habitable environments. What Happened to Venus? NASA Venus might have once been Earth’s twin, but something happened during its troubled history that caused it to take an entirely different direction in its evolution. Today, the planet is home to a completely sterile environment; an endless rocky desert baking under crushing pressures and searing temperatures. Even in upper cloud levels, where temperatures and pressures are much more Earth-like, would-be visitors would still have to content with abrasive sulphuric acid rain. Venus underwent global resurfacing sometime between 300 and 600 million years ago, possibly due to a mantle overturn event. This cataclysmic event completely transformed the surface, burying almost any evidence of its past far beneath a layer of volcanic basalt that now covers 90% of the planet. In fact, Venus has more volcanoes than any other planet in the solar system yet, most mysteriously, almost all of them are long extinct, and there’s been no direct evidence of recent eruptions on the surface. The main problem with Venus is that is doesn’t have a magnetic field to protect it from the solar wind. Here on Earth, our magnetic field performs the critical function of protecting our atmosphere and oceans from getting swept away by the ‘electric’ wind of the Sun. Without it, the components that make up our oceans and atmosphere would be broken down and swept away into space. Only heavier materials, such as CO2 and sulphur, which are produced in abundance by volcanos, would remain. This appears to be precisely what happened to Venus. The loss of Venus’s magnetic field can be attributed to its extremely long rotational period. A day on Venus lasts almost 243 Earth days, making it longer than the Venusian year. Stranger still, the planet rotates backwards, so the sun rises in the west rather than the east. With this very slow rotation, Venus is incapable of maintaining a dynamo effect in its core, which is exactly what creates a magnetic field. Today, the strength of Venus’s magnetic field is 0.000015 of Earth’s. It’s unlikely that Venus always rotated in such a way, but no one is quite sure of what caused its current situation. Friction with the extremely dense atmosphere and tidal interactions with the sun have both been put forth as possible explanations. Delving into the Inferno Wikimedia Commons Because of its incredibly hostile environment, Venus is notoriously difficult to explore from the surface, and orbital missions can’t tell a great deal about the planet’s past habitability. Additionally, if Venus was ever habitable or was even home to some form of life, any fossil evidence would likely be buried deep beneath the surface or even destroyed entirely. There are, for example, some highland areas that are much older than the lava plains that cover about two thirds of the surface. Venus’s atmosphere gives few insights to the planet’s past habitability, so it would probably be necessary to send a lander there. This lander would need to be equipped with tools to drill into the surface and analyse the mineral composition of the oldest regions of the planet. As a result, we’d garner invaluable insights into the evolution of the planet’s atmosphere, past surface characteristics and, perhaps, even indications of past life. According to research conducted by NASA, Venus may have had water oceans and moderate surface temperatures for 2 billion years, which is more than enough time for microbial life to evolve. By contrast, microbial life has existed on Earth for at least 3.7 billion years, although multicellular life did not appear until much later. As such, we can’t reasonably expect to find a Venusian dinosaur fossil but, if life could thrive on Earth before there was even oxygen in the atmosphere, then it seems likely it could have arisen on an ocean-covered Venus as well. Unfortunately, the world’s space agencies continue to largely ignore Venus, which is understandable given their limited budgets and abundance of other promising opportunities. Last month, however, JPL’s James Cutts laid out a proposal as part of the Planetary Science Vision 2050 workshop that outlined a sample-return mission that would give us an unprecedented opportunity to study Venus’s past. However, if accepted, it’s not likely that such a mission would launch until the 2040s. Although NASA hasn’t sent a mission there in almost 30 years, Venus hasn’t been completely forgotten about. Scientists from both the US and Russia have recently been discussing the latter’s proposed Venera-D mission, which may launch as early as 2025. Should the mission go ahead, it will herald a new age of exploration of our neighbour, ultimately culminating in a lander that will be able to explore the surface up close. • It’s hard to imagine a more hellish world than Venus, and perhaps even harder still to imagine it as a habitable planet where life may have even taken a foothold before it did on Earth. How do you imagine our sister planet’s distant past? Share your thoughts and ideas in the comments below! Further Reading Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on Reddit (Opens in new window)Click to share on LinkedIn (Opens in new window)Click to share on Pinterest (Opens in new window)Click to share on WhatsApp (Opens in new window)Click to email this to a friend (Opens in new window) Leave a Reply Cancel ReplyYour email address will not be published.CommentName* Email* Website Please enter an answer in digits:twenty − 1 = Notify me of follow-up comments by email. Notify me of new posts by email. This site uses Akismet to reduce spam. Learn how your comment data is processed. | 0.823699 | 3.433978 |
NASA repurposed Kepler space telescope, now K2 mission, have proved a theory that white dwarfs are capable to destroy planets within its solar system. The telescope received data about a rocky object being torn apart as it spirals around a white dwarf star, Joinfo.ua reports with the reference to NASA.
“We are for the first time witnessing a miniature “planet” ripped apart by intense gravity, being vaporized by starlight and raining rocky material onto its star,” said Andrew Vanderburg, graduate student from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and lead author of the paper published in Nature.
As stars like our sun age, they puff up into red giants and then gradually lose about half their mass, shrinking down to 1/100th of their original size to roughly the size of Earth. This dead, dense star remnant is called a white dwarf.
The devastated planetesimal, or cosmic object formed from dust, rock, and other materials, is estimated to be the size of a large asteroid, and is the first planetary object to be confirmed transiting a white dwarf. It orbits its white dwarf, WD 1145+017, once every 4.5 hours. This orbital period places it extremely close to the white dwarf and its searing heat and shearing gravitational force.
Observing the universe K2 watched a 40% dip of brightness of the white dwarf, occurring every 4.5 hours. It meant that a small object periodically blocks the light from the dwarf. The white dwarfs have an intense gravity, so their surface is expected to have only light elements of helium and hydrogen. For years, researchers have found evidence that some white dwarf atmospheres are polluted with traces of heavier elements such as calcium, silicon, magnesium and iron. Scientists have long suspected that the source of this pollution was an asteroid or a small planet being torn apart by the white dwarf’s intense gravity.
“For the last decade we’ve suspected that white dwarf stars were feeding on the remains of rocky objects, and this result may be the smoking gun we’re looking for,” said Fergal Mullally, staff scientist of K2 at SETI and NASA’s Ames Research Center in Moffett Field, California. “However, there’s still a lot more work to be done figuring out the history of this system.” | 0.943457 | 3.708167 |
7 Earth-sized planets Orbit Dwarf star, NASA and European astronomers say These new Earth-sized planets orbit a dwarf star called Trappist-1 about 40 light years from Earth. Some of them could keep water on their surfaces. Crediteredit [NASA].
Not just one, but seven Earth-sized planets that could disturb life, orbiting a small star, not far away, the first realistic opportunity to discover signs of extraterrestrial life outside the solar system while providing.
The planets orbit about 40 light years or 235 billion miles from Earth, called the dwarf star called Trappist-1. It is quite close in cosmic terms, and by happy accident, the orientation of the seven planetary orbits allows them to study in great detail.
In this new system, one or more exoplanets may be at the right temperature to wake up in the water oceans, astronomers said, depending on the distance of the planets to the dwarf star.
“This is the first time that many of these planets have been found around a single star,” said Michael Gillon, an astronomer at the University of Liège, Belgium and leader of an international team observing Trappist-1. .
News conference call organized by Nature magazine, which published the findings on Wednesday. Scientists could also look for compelling evidence from aliens.
“I think we have taken an important step to discover if there is life there,” Amauri H.W. M. J. Said an astronomer from the University of Cambridge, Triad, England, and another member of the research team. “Here, if life were able to release and release gases corresponding to those on Earth, we would know.”
Cold red dwarfs are the most common type of star, so astronomers are likely to have more planetary systems around Trappist-1 in the coming years.
“You can imagine how much the world has to become a habitable ecosystem,” said Thomas Zurbuchen, associate administrator of the NASA Scientific Mission Directorate, during a NASA press conference.
“We’re alone?” We are taking a step forward with this, a leap forward, really, towards the answer to that question. ” Now the ground telescope and the Hubble space telescope in orbit will be able to detect certain molecules in the planet’s atmosphere.
A comparison will also appear between the seven different conditions.
“For the first time, we don’t have to guess. We just have to wait and then watch very carefully and see what’s in the atmosphere of the Trappist planets.”
Even if all the planets are lifeless, scientists have learned more about what happens when life flourishes. Astronomers always knew that other stars must have planets, but until a few decades ago.
They could not detect them. According to the Open Exoplanet catalog, they have now confirmed more than 3,400. (An exoplanet Catalog is the planet around a star that is not the Sun).
The authors of Nature’s article include Didier Queloz, one of the astronomers who discovered the first known exoplanet around the Sun star in 1995.
While the Trappist planets are about the size of the Earth, about 25 percent in diameter, the star is very different from our sun. Trappist-1, named for a robotic telescope in the Atacama desert of Chile.
Which astronomers initially used to study the star, is that astronomers consider the mass of the sun and the temperature of the mass as one.
With the twelfth part called “ultrafresque dwarf”. 4,150 degrees Fahrenheit, more than 10,000 degrees colder than the sun.
There is a shortage of Trappist planets in transit and small PlanetSimals telescopes. During the NASA press conference, Drs. Gillan gave a simple analogy: if our Sun were the size of a basketball, Trappist-1 would have been a golf ball.
In recent years, scientists seeking life in other parts of the galaxy have focused on finding planets the size of the Earth around stars like the Sun. But it is difficult to eliminate the light of a planet from the glow of the bright star. Small dwarfs are very easy to study.
Trappist-1 pointed out from time to time, indicating that a planet may be passing in front of the star, blocking part of the light. From the size of the dives, astronomers calculate the size of the planet.
The light of the Trapist-1 went down so often that astronomers concluded, last year, that research reported there were at least three planets around the star. Telescopes around the world observed TRAPPIST-1, as did NASA’s Spitzer space telescope.
Spitzer watched TRAPPIST-1 for approximately 20 days, capturing 34 entries. With terrestrial observations, he allowed scientists to count seven, not three planets. The planets are too small and too close to be photographed directly.
The seven dwarfs are very close to the star, orbiting faster than the planets of our solar system. The innermost one completes a class in just 1.5 days. The furthest person completes a ring road in about 20 days.
This makes the planet system more like the moons of Jupiter than a large planetary system like our solar system. “They make a very compact system,” Dr. “The planets are approaching each other and very close to the star,” Gillon said.
In addition, the orbital period of the six interiors suggests that the planets formed farther from the star and then all were slowly dragged in, Drs. Gillon said.
Since the planets are so close to a cold star, their surface may be at the right temperature for water to flow, which is considered one of the essential ingredients for life.
Fourth, the fifth and sixth planets revolve around the “habitable zone” of the stars, where the planets can play the oceans. So far, this is only speculation.
But by measuring how the wavelength of the planet’s light is blocked, scientists will be able to discover what gases float in the seven planetary atmospheres.
So far, it has confirmed for the two innermost planets that are not wrapped in hydrogen. This means that they are rocky like Earth, ruling out the possibility that they were mini-Neptune gas planets that prevail around many other stars.
Because the planets are so close to Trappist-1, they are always “gravitationally locked” toward the star, always facing the star with one side of the planet, it would always be the side of the Earth like Earth.
This would mean that one side would be hot, but an atmosphere would distribute heat, and scientists said that would not be an insurmountable obstacle to life.
For a person standing on a planet, it would be a dark environment, perhaps only about one hundredth of the light we see from the sun on Earth, Drs. The triad said. (It will still be brighter than the moon at night). The star will be much bigger.
On the fifth planet Trappist-1F, this star will be three times wider than the sun seen from Earth. As for the color of the star, “We had a debate about that,” Dr. La tríada said.
Some scientists expected a dark red color, but with most of the starlight emitted in the infrared wavelength and out of the human eye, perhaps a person “would see something more salmon,” Dr. The triad said.
If the observation reveals oxygen in the planet’s atmosphere, that may indicate photosynthesis of the plant, although not conclusively.
But oxygen with methane, ozone and carbon dioxide, especially in defined proportions, “will tell us that there is life with 99 percent confidence,” said Dr. Gillon.
Astronomers expect some decades of technological development to be needed before similar observations are made of the Earth’s planets around large bright, sun-like stars.
Dr. Triad said that if there is life around Trappist-1, then it is good that we have not expected too much. If there isn’t, then we have learned some depth from where life can arise,” he continued.
The discovery may also mean that scientists looking for radio signals from extraterrestrial civilizations will also search in the wrong places if most habitable planets are dwarfs, which last longer than larger stars like the Sun.
The SETI Institute in Mountain View, California, is using the Allen Telescope Array, a group of 42 radio antennas in California, to examine 20,000 red dwarfs. “This result is a kind of justification for that project,” said Seth Shostak, an institute astronomer.
“If you are looking for complex biology, intelligent aliens that can take a long time to develop from the scum of the pond, the elders can improve,” said Dr. Shostak. “
It seems like a good bet that most of the cunning beings that populate the universe see a faint red sun that hangs over their sky.” And at least they won’t have to worry about sunscreen. “
Astronomers discovered three compact planetary systems: the dispersed astronomers of the Planetary Matter Project (DMPP) discovered three new planetary systems: DMPP-1, 2 and 3, which houses six short-lived exopolites.
These planets are very close to their parent stars and have a surface temperature. These new discoveries are very promising for future studies, said Professor Carroll Havell, head of astronomy at the Open University and the principal investigator of the DMPP project.
We must allow the relationship between mass, size and composition of planets outside our solar system to be measured. Also known as HD 38677.
It maintains a compact planetary system with an orbital period of 2.9-19 days, comprising four large planets: DMPP-1B, C, D and E. DMPP-1C, D and E are super-terrestrial planets with a mass between 3 and 10 of the Earth. DMPP-1B is a planet similar to Neptune that has about 24 Earth masses.
DMPP-1 houses a truly important planet with three low mass exoplanets, whose structure we can measure, said Rutherford Appellate Laboratory, an astronomer at the Open University School of Physics.
DMPP-2, also known as HD 11231, is a type of F5V star from 2 billion years to about 452 light years from Earth. Its only known planet, DMPP-2B, is a massive planet in near orbit, about half of Jupiter in a 5.2-day orbit.
The DMPP-3, also known as HD 42936, is a binary stellar system of 6 billion years at a distance of approximately 153 light years. The primary star in the binary system, DMPP-3A, is a K0V type star that rotates slowly.
It is a super-Earth planet, DMPP-3Ab, and a star companion, DMPP-3B, in 6.7-day orbit. “DMPP-3B has a minimum mass at the boundary between brown dwarfs and low mass stars, and is probably dwarf with stable hydrogen combustion.
It is in the orbit of 507 days, “the astronomers explained. “DMPP-3 was a big surprise, we were looking for a small signal that indicated a planet in orbit around a low mass, but the first thing we found was due to a large signal we did not expect,” Dr. Said John Barnes, a free university researcher.
The astronomers used ESO’s high-precision radial velocity plane (HARPS) finder to observe these planetary systems. They discovered that the temperature of the planet’s surface is between 1,100 and 1,800 C.
At these temperatures, the rocky surface of the planet and even the rocky surface can be lost, and part of this material forms thin layers of gas, he said. This shroud filters the star’s light, providing clues that allow the team to discard small star trails with these unusual and very hot planets.
With more studies, you can measure the chemical composition of the roof, which reveals the type of rock on the surface of the hot planet.” “Now we can see how planets are formed in general, and if our own planets are specific,” said Professor Haswell.
For example, we still do not know if it is a coincidence that in the solar system, Earth and Venus are the largest rock objects and that the largest fraction of their mass is composed of iron.
Astronomers discovered three compact planetary systems and the Planetary Matter Project (DMPP) dispersed astronomers discovered three new planetary systems: DMPP-1, 2 and 3, with six short-lived exopartets.
These planets are very close to their parent stars and have a surface temperature between 1,100 and 1,800 ° C (2,012-3,272 ° F). These new discoveries are very promising for future studies, “said Professor Carroll Havell, head of astronomy at the Open Carroll University.
And the principal investigator of the DMPP project, which allows us to add the mass, size and structure of planets outside of our solar. The system, can be measured, can be measured DMPP-1 is a type of F8V star, 2,000 million years old.
Which is about 204 light years located Eur, also known as HD 38677, for example, maintains a Compact planetary system with an orbital period of 2.9-19 days, consisting of four large planets: DMPP-1B, C, D and E. DMPP-1C, D and E are 3 more than Earth.
There are super-terrestrial planets with a mass between 10. DMPP-1B is a planet similar to Neptune that has approximately 24 Earth masses. DMPP-1 is a truly important planet with three alphabet of low mass exoplanets.
Whose structure is Dr. Astronomist and Rutherford Appeal Laboratory is in the Faculty of Physics, “The Open University can measure. Daniel Stob said. DMPP-2, also known as HD 11231, is an F5V type star of 2 billion years about 452 light years from Earth.
Its only known planet, the DMPP-2B, is a massive planet, located in approximately half of Jupiter in a 5.2-day orbit. The DMPP-3, also known as HD 42936, is a binary stellar system of 6 billion years at a distance of approximately 153 light years.
The primary star in the binary system, DMPP-3A, is a K0V type star that rotates slowly. It is a 6.7-day super-orbiting planet, DMPP-3Ab, and a star companion, DMPP-3B. DMPP-3B has a minimum mass at the boundary between brown dwarfs and low mass stars, and is probably dwarf with stable hydrogen combustion.
It is in an orbit of 507 days, “the astronomers explained. DMPP-3 was a big surprise, we were looking for a small signal that indicated a low mass in orbit around a planet in orbit, but the first thing is What we got was a large signal that we did not expect. ” Dr. John said Barnes, a researcher at the Open University.
The astronomers used ESO’s high-speed radial plane finder (HARPS) to observe these planetary systems. It was discovered that the surface temperature of the planet was between 1,100 and 1,800 °.
At these temperatures, the atmosphere and even the rocky surface of the planet can be lost, and part of this material forms a thin layer of gas. “He said.
This cover produces wire light, providing clues that allow the team to exclude small star trails with these unusual and very hot stars. With more studies, the chemical structure of the roof can be measured.
For example, we still do not know that it is a coincidence that Earth and Venus are the highest in the solar system. Large rocks are objects and the largest fraction of their mass is made of iron. | 0.924891 | 3.266133 |
Mysterious, massive dark objects lurk at the centre of nearly all galaxies and can be observed with high enough sensitivity. Astronomers believe these to be black holes with masses that can exceed a billion Suns. Such supermassive black holes may power quasars, the most luminous sources in the Universe, and may halt the formation of stars by releasing copious amounts of energy which heats up and fragments the gas in their host galaxies.
One of their most astonishing properties is that, despite being tiny compared to their host galaxies – like a grape compared to the entire Earth – most observations suggest that the bigger the galaxy, the bigger the supermassive black hole it hosts. One does not expect the size of a grape to know about the size of the planet on which it grows! This suggests there must be an intimate link between supermassive black growth and galaxy evolution, but this has not yet been proven.
In this new study, published in Nature Astronomy, the international team led by Dr Francesco Shankar of the University of Southampton, in close collaboration with Dr Viola Allevato at the Normale di Pisa and University of Helsinki, set out to explain this link.
"Linking black hole and galaxy growth is the ultimate goal of the coevolution studies, and we are proud to put it on a robust footing", Dr. Allevato said.
Accurately measuring the masses of supermassive black holes is usually achieved by measuring the velocity of the surrounding stars or gas. This is incredibly challenging and requires extremely sensitive telescopes and complex observations. However, galaxies and their supermassive black holes are believed to reside in haloes made of dark matter. Numerical simulations show that more massive dark matter haloes deviate more from a spatial random spatial distribution – are more strongly clustered. Thus, their clustering strength can be used to weigh the halos.
We expect more massive black holes to be hosted by more massive halos, so the clustering of the black holes can be used to estimate the masses of their hosts. In turn, we can use this to constrain the masses of the black holes themselves. By comparing simulations with recent data on the spatial distribution of galaxies, the group found evidence that supermassive black holes are, on average, not as massive as previously thought.
Dr Shankar said: “These findings have significant implications for our understanding of the evolution and growth of supermassive black holes. What we have discovered suggests a greater ability to release energy, and less strength in powering gravitational waves as supermassive black holes merge.” | 0.810448 | 4.021682 |
Crescent ♓ Pisces
Moon phase on 10 May 2018 Thursday is Waning Crescent, 24 days old Moon is in Pisces.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 2 days on 8 May 2018 at 02:09.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Moon is passing about ∠17° of ♓ Pisces tropical zodiac sector.
Lunar disc appears visually 4.6% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1814" and ∠1900".
Next Full Moon is the Flower Moon of May 2018 after 19 days on 29 May 2018 at 14:20.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 24 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 226 of Meeus index or 1179 from Brown series.
Length of current 226 lunation is 29 days, 9 hours and 51 minutes. It is 1 hour and 56 minutes longer than next lunation 227 length.
Length of current synodic month is 2 hours and 53 minutes shorter than the mean length of synodic month, but it is still 3 hours and 16 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠296.5°. At the beginning of next synodic month true anomaly will be ∠321.7°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
4 days after point of apogee on 6 May 2018 at 00:35 in ♑ Capricorn. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 7 days, until it get to the point of next perigee on 17 May 2018 at 21:06 in ♊ Gemini.
Moon is 395 143 km (245 530 mi) away from Earth on this date. Moon moves closer next 7 days until perigee, when Earth-Moon distance will reach 363 777 km (226 041 mi).
3 days after its descending node on 7 May 2018 at 10:24 in ♒ Aquarius, the Moon is following the southern part of its orbit for the next 10 days, until it will cross the ecliptic from South to North in ascending node on 20 May 2018 at 13:13 in ♌ Leo.
16 days after beginning of current draconic month in ♌ Leo, the Moon is moving from the second to the final part of it.
5 days after previous South standstill on 4 May 2018 at 23:00 in ♑ Capricorn, when Moon has reached southern declination of ∠-20.562°. Next 8 days the lunar orbit moves northward to face North declination of ∠20.652° in the next northern standstill on 18 May 2018 at 15:02 in ♋ Cancer.
After 4 days on 15 May 2018 at 11:48 in ♉ Taurus, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.123946 |
Gravity waves are a hypothetical "ripple in the fabric of space-time" envisioned as a consequence of Einstein's general theory of relativity. They're hypothesized to result from highly energetic events such as black hole mergers, neutrons star mergers or wobbles, etc. (though whether black holes or neutron stars actually exist is perhaps a matter for mathemagicians and/or plasma physicists / EE's to battle to the death over).
So far, it seems LIGO has failed to turn up gravity waves.
To quote from a private exchange about LIGO,
So, in short, LIGO operated continuously in parallel for an entire year during the S5 data-gathering run but turned up no gravity wave signals, examined Gamma Ray Burst GRB070201 but found no gravity wave signal, and examined the Crab Pulsar but found no gravity wave signal. So, I'm wondering, is LIGO's sole ability that of turning out null results for gravity waves? (Probably too early to tell...)I wrote:I've managed to ferret out the original LIGO press releases from Caltech and document them on Digg. The relevant entries so far are here:
(LIGO and Virgo Join Forces In Search for Gravitational Waves)
http://digg.com/space/LIGO_and_Virgo_Jo ... onal_Waves
(LIGO Sheds Light on Cosmic Event - No Gravitational Waves...)
http://digg.com/space/LIGO_Sheds_Light_ ... onal_Waves
(NSF Funnels Additional $205M Toward Advanced LIGO Project.)
http://digg.com/space/NSF_Funnels_Addit ... GO_Project
(LIGO Observations Probe the Dynamics of the Crab Pulsar; additional null result for gravity waves, 0 for 2)
http://digg.com/space/LIGO_Observations ... rab_Pulsar
Not to mention this article from Virgo, the European counterpart to LIGO:
(h, The Gravitational Voice: LIGO Bids Farewell to S5 - Now onto Enhanced LIGO!)
http://www.ego-gw.it/public/hletter/doc ... RY2008.pdf
"Unlike its four predecessor science runs, S5 had a significantly more ambitious agenda. S5 was the first long duration data-taking run where all of the interferometers were operating with astrophysically interesting sensitivities. The main goal of S5 was to collect data in triple coincidence for one year ... The end of S5 occurred only after LIGO's three interferometers, the 4 km and 2 km interferometers at the Hanford Washington Observatory and the 4 km interferometer at the Livingston Louisiana Observatory had operated synchronously (all locked simultaneously) to acquire a total of one full year of science quality data.
We are still analyzing the S5 data and while no gravitational waves have been detected, S5 has already begun to yield interesting astrophysical results. One example - an intense gamma ray burst (GRB) occurring on February 1, 2007 was detected by gamma ray satellites originating from the direction of Andromeda (M31) galaxy, possibly due of the merger of a neutron star or black hole binary system or possibly, a soft gamma repeater."
So, [if I've understood correctly,] measurements were taken in triplicate for a period of an entire year (continuously, 24/7?), but no gravitational waves turned up!
Now the NSF (National Science Foundation) has dumped $250M into the project to upgrade the technology (which should have already been capable of detecting gravity waves, but has thus far failed to do so), chasing the ghost of gravity waves. The upgrade should "increase the sensitivity of the LIGO instruments by a factor of 10, giving a one thousand-fold increase in the number of astrophysical candidates for gravitational wave signals." However, if it still continues to return "null results" for gravity waves, what does that tell us about gravity waves? How long should we continue throwing good money after what may amount to a bad idea? If gravity waves are in effect falsified, what does that do to Einstein's relativity, and to the field of cosmology?
I might ask (as I have on Digg), how can we tell the difference between an INTERESTING null result (the LIGO team has called both null results "useful" or "interesting"), a null result that tells us NOTHING, and a null result which may INVALIDATE the notion of gravitational waves altogether?
Tough questions, all... But worth the asking, if we're to be brutally and scientifically honest with ourselves.
But, since one wouldn't want to jump the shark, I guess we'll have to adopt a "wait-and-see" approach for now. | 0.815383 | 3.408191 |
Published: November 6, 2107
Because stars are pinpoints of light, the camera does not capture them as our eyes see them. To our eyes, brighter stars stand out more noticeably than dimmer ones. At a workshop in Alabama Hills, one of the participants, Julian Köpke, was using a diffusion filter so the stars captured would look more like you see with the naked eye. Sometimes nature provides its own diffusion filter in the form of high, thin cirrus clouds as shown below. The large bright orb is the star Sirius in the constellation Canus Major (Big Dog). The orange star near the top of the frame is Betelgeuse in the constellation Orion. One nice thing about the blur that the clouds added is the star color is more noticeable. But the diffusion here is not uniform because the belt stars (Alnitak, Alnilam and Mintaka) and “corner” stars (Bellatrix, Rigel, Saiph) in Orion are all noticeably brighter than the surrounding stars while in this photo only Betelgeuse and Rigel stand out.
You can create a make-shift diffusion filter by shooting through a nylon stocking – or buy a diffusion filter. The disadvantages of using a filter are that everything is blurred – including the foreground and you reduce the amount of light collected. Most night sky photographers try to avoid clouds and you will get an image like this:
When what you had in mind is something like this:
How to Bring Out Star Color And Enhance The Apparent Star Size
Our Advanced Stacker Plus has two built-in ways to increase star brightness. We call those Bump Up and Pump Up the stars. Bump Up creates a small blur by literally duplicating the shot , nudging the duplicate(s) and recombining . Pump Up is more sophisticated and tries to find the stars so it can then apply enhancements to just the stars. But there is a new tool in the arsenal that I have begun using: Star Spikes Pro from ProDigital Software. Version 4 is the latest as of this writing.
NOTE: Star Spikes Pro and HLVG described later are currently only available on Windows machines.
You can use the Star Spikes Pro plugin to add diffraction spikes and diffusion. The most common diffraction spikes you see with stars are due to obstructions in the telescope used to photograph them and many people come to think of the spikes as evidence of astrophotography. You can create diffraction spikes easily on your own.- just stop down your aperture; however stopping down to make stars create those spikes will not work well.
The first time I tried to use Star Spikes Pro it did not quite work as I expected.
Indeed it took me a bit to realize what was going on. The good news is it was easy to work around. The huge moon looks like a huge star to Star Spikes Pro – and that makes perfect sense since the plugin is usually used with Astrophotography that does not involve landscapes.
Here is how I made it work as I wanted and limited the effect to just the desired stars.
Above left is the layer palette. Look carefully and you may spot the fix. After loading the image (1) I first duplicated the original and called the new layer Heal (2). I then did minor contrast adjustments, used the healing brush to remove hot pixels and other offenses (short satellite trail). Next I duplicated the Heal to another layer (3) and fed it into Hasta La Vista Green – a free plugin written by Rogelio Bernal Andreo of DeepSkyColors. HLVG removes green which is an unnatural sky color usually caused by RGB artifacts. HLVG operates on the entire layer and does not know the difference between land and sky. To leave the natural green in my landscape I used the quick selection tool, dragged it across the sky followed by Select -> Modify -> Expand 4 pixels. Then I created a Layer Mask using “Reveal Selection” (4). That made the foreground come back to its normal state. If you look carefully you will notice I also used a white brush to add some of that green removal back onto the mountain by painting on the HLVG layer mask (4).
The next operation was a finger twisting sequence that has no menu equivalent: Ctrl-Alt-Shift-E (on Mac that’s Command-Option-Shift-E). What that sequence does is “flatten” all the visible layers and create a NEW layer in the process (5). That layer I called Input to SSP. Since I had discovered that Star Spikes Pro was confused by the moon (and could be confused by the foreground), I used the quick selection tool again and brushed it across the foreground. By default using the quick select tool again ADDs to the current selection so I brushed it around inside the moon and its halo. At this point I did not need to create another layer (Ctrl-J/Command-J or Duplicate Layer) but I did so that it was easy to see what happens next. After creating the new layer I selected it and used the delete key. Delete removes the selection making it transparent – that is the foreground and moon were now gone (6).
Next up: let Star Spikes Pro loose on the image. First deselect (Ctrl-D / Command-D) or Select -> Deselect), and feed the sky layer to Star Spikes Pro via Filter -> ProDigital Software -> Star Spikes Pro. The defaults for SSP produced the image below (I’ve zoomed in on the teapot asterism)
I felt the color was a bit too strong, and I did not want the diffraction spikes. The next step was to select “Advanced” – just below Settings, set the Primary quantity to zero. Next was the Secondary tab where I reduced the quantity to 44, the intensity I bumped up to 23. Soft flare I set quantity to 12, bumped up the intensity, dialed down the size a little and dialed down the Hue to -21. These adjustments were all based on eyeballing the image and were made for aesthetic appeal. After all the adjustments looked about right, I saved the settings as a new adjustment I called “DiffusionOnly”. Finally I clicked OK and my layer was all nicely done by the SSP filter.
The filter processed a few more stars than I intended to augment. The simple solution was to create a “Reveal All Layer Mask”, select a brush, the color black and paint out all the effects I did not want on the layer mask (7).
The final operation was to use an Adjustment Layer (8) to increase the contrast and restrict that adjustment to the sky (where you see white) and tone the adjustment down a little with a low-flow back brush on one area that looked a little too dark.
The topmost layer in the layer palette is my watermark.
There Is An Easier Way!
With some experimentation, and some coaching from the plugin author I discovered that Star Spikes Pro has several features that make the process easier than I imagined. Instead of creating the transparency (deleting the moon and landscape) I only needed to select the area I wanted Star Spikes Pro to operate on.
Also, instead of masking off the stars I did not want affected after the fact, Star Spikes Pro has two tools to greatly simplify things the: “Hide” tool to turn off any effect that I did not want, and the “Show” tool to turn the effect on.
The net is that you can get that nice diffusion effect for your stars without having to compromise by shooting through a diffusion filter. However if you DO want to try a diffusion filter, I recommend you take two shots quickly. One with the filter off, one with the filter on. You can then place the diffused shot over the normal shot. Set the diffused shot to Lighten and mask in (or out) the areas where you want the diffusion to show through.
If you’re wondering whether there is a way to get the diffusion effect on a Mac or without purchasing Star Spikes Pro, there is, but it requires a lot of Photoshop twiddling and it is not anywhere near as pleasant as using ProDigital Software’s Star Spikes Pro.
Disclaimer and Book
I am not affiliated with ProDigital Sofware. I am a happy customer of Star Spikes Pro (and another product called Astronomy Tools). I was not paid, or encouraged to write about the product. I chose to because it is that good. Rogelio Bernal Andreo author of Hasta La Vista Green and purveyor of DeepSkyColors is a friend and a multi-multi award-winning astrophotographer. He has a Kickstarter Project that I recommend you look into called Notes From the Stars | 0.825213 | 3.555444 |
TESTS OF GRAVITY LAWS
Tests of Gravity Laws
Most gravity tests confirm the validity of general relativity, but windows remain open for deviations. One way to progress on these questions is to improve the precision, for example in the space tests of the equivalence principle by MICROSCOPE or of the redshift law by ACES.
Another way is to study ranges poorly tested today, that is short or long ranges. The first window, corresponding to distances below a fraction of a millimeter, is explored by Casimir tests of the gravity law. The second window, corresponding to distances beyond the size of planetary orbits in the solar system, is related to the puzzling questions of dark matter and dark energy observed in astrophysics and cosmology.
Space test of the equivalence principle : MICROSCOPE
The MICROSCOPE satellite was launched on April 25th 2016 from Kourou. It is a micro-satellite of the french space agency CNES with a payload provided by ONERA , in a collaboration with GeoAzur (CNRS / Observatoire de Côte d’Azur) and European partners.
All attempts to theoretical unification of general relativity and quantum physics lead to modifications of the theory. They introduce violations of the equivalence principle which is the basis of the theory of general relativity.
This principle, well tested in experiments on Earth, has seen its accuracy improved by a factor 10 by the recent preliminary results announced by the MICROSCOPE space experiment. Analyzing the full data at the end of the mission should lead to a further improvement by another factor 10.
- MICROSCOPE Mission: First Results of a Space Test of the Equivalence Principle, P. Touboul et al, Phys. Rev. Letters 119 231101 (2017)
Quantum tests of general relativity
Atomic clocks, high-performance time and frequency links and atomic interferometers are today able to measure frequency, time, and distances, and furthermore to track the motion of massive bodies, quantum particles, and light to accuracy levels never reached before. These instruments achieve their ultimate performance in space, where the clean environment and the free-fall conditions become essential for identifying tiny deformations in space–time that might bring the signature of new physics.
In collaboration with Christophe Salomon (LKB) and Peter Wolf (SYRTE), we have discussed the perspectives for new tests of general relativity with atomic clocks. In particular, we presented the scientific motivations of the space project ACES.
- Testing General Relativity with Atomic Clocks, S Reynaud, C Salomon, P Wolf, Space Science Review 148 233 (2009)
We have also proposed to perform clock comparisons between a ground clock and a remote spacecraft equipped with an ultra stable clock, rather than only ranging to an on-board transponder. Optimization of this technique would lead to significant improvements on present bounds on gravitational waves in interesting frequency ranges. The interest of this approach is illustrated by the SAGAS project which aims to fly an ultra stable optical clock in the outer solar system.
- Bounds on gravitational wave backgrounds from large distance clock comparisons, S. Reynaud, B. Lamine, L. Duchayne, P. Wolf, M.-T. Jaekel, Phys. Rev. D 77 122003 (2008)
- Quantum physics exploring gravity in the outer solar system: the SAGAS project, P Wolf, CJ Borde, A Clairon, L Duchayne, A Landragin, P Lemonde, G Santarelli, W Ertmer, E Rasel, FS Cataliotti, M Inguscio, GM Tino, P Gill, H Klein, S Reynaud, C Salomon, E Peik, O Bertolami, P Gil, J Paramos, C Jentsch, U Johann, A Rathke, P Bouyer, L Cacciapuoti, D Izzo, P De Natale, B Christophe, P Touboul, SG Turyshev, J Anderson, ME Tobar, F Schmidt-Kaler, J Vigue, AA Madej, L Marmet, MC Angonin, P Delva, P Tourrenc, G Metris, H Mueller, R Walsworth, ZH Lu, LJ Wang, K Bongs, A Toncelli, M Tonelli, H Dittus, C Laemmerzahl, G Galzerano, P Laporta, J Laskar, A Fienga, F Roques and K Sengstock, Exp. Astron. 23 651-687 (2009)
In collaboration with European colleagues involved in the space mission STE–QUEST, we have given a detailed analysis of different aspects of the Einstein Equivalence Principle, tested by using atomic clocks, matter wave interferometry and long distance time/frequency links. They correspond to fascinating science at the interface of quantum physics and gravitation that cannot be studied in ground experiments.
- Quantum tests of the Einstein Equivalence Principle with the STE-QUEST space mission, B Altschul, QG Bailey, L Blanchet, K Bongs, P Bouyer, L Cacciapuoti, S Capozziello, N Gaaloul, D Giulini, J Hartwig, L Iess, P Jetzer, A Landragin, E Rasel, S Reynaud, S Schiller, C Schubert, F Sorrentino, U Sterr, JD Tasson, GM Tino, P Tuckey, P Wolf, Advances in Space Research 55 501 (2015)
Extensions of general relativity
Metric extensions of general relativity preserve the equivalence principle, which is verified at a high accuracy level, but may correspond to a metric differing (slightly) from that predicted from the standard theory. They provide a natural framework for discussing the validity of general relativity.
Of course these extensions have to remain compatible with the number of observations which agree with the predictions of general relativity in the solar system. They may however suggest new effects to be looked for in existing observations or in new dedicated missions.
A general review with numerous references can be found in
- Tests of general relativity in the solar system, S. Reynaud, M. -T. Jaekel, International School of Physics Enrico Fermi (Varenna, 2007), in Atom Optics and Space Physics, p. 203-217 (Societa Italiana de Fisica & IOS Press, 2009) [in the arXiv]
This work is performed in close collaboration with Marc-Thierry Jaekel of the Laboratoire de Physique Théorique (LPT) de l’ENS.
In collaboration with other groups specialized in data analysis of space probes (Royal Observatory of Belgium, Bruxelles; Systèmes de Référence Temps Espace, Observatoire de Paris; Université Notre Dame de la Paix, Namur; Laboratoire de Physique Théorique de l’ENS, Paris; Institut de Mécanique Céleste et de Calcul des Ephémérides, Observatoire de Paris), we have also worked on the data analysis of already flown probes or forthcoming missions.
- Radioscience simulations in General Relativity and in alternative theories of gravity, A. Hees, B. Lamine, S. Reynaud, M. -T. Jaekel, C. Le Poncin-Lafitte, V. Lainey, A. Füzfa, J. -M. Courty, V. Dehant, P. Wolf, Classical and Quantum Gravity 29 235027 (2012)
Space probes and proposals for new missions
The Doppler tracking of Pioneer 10 & 11, during their travel to the outer solar system, did prove that the scientific analysis of navigation data of space probes could improve our knowledge of the gravity field at large distances, provided that the effect of non gravitational forces be properly controlled. An international collaboration investigated the Pioneer Anomaly to recover and analyse the data with the purpose of characterizing in the best manner the significance of the observations and also to define the relevant questions for future missions.
These discussions have led to proposals for new space missions which would be much more accurate than at the time of Pioneer 10 & 11. Using accelerometers for measuring the non gravitational forces acting on the probe would in particular lead to an unambiguous test of gravity laws at the solar system scale. Proposals have been submitted to the European Space Agency (ESA), with principal objectives dedicated to this test of gravity laws at the solar system scale.
- Odyssey: a solar system mission, B Christophe, PH Andersen, JD Anderson, S Asmar, P Berio, O Bertolami, R Bingham, F Bondu, P Bouyer, S Bremer, JM Courty, H Dittus, B Foulon, P Gil, U Johann, JF Jordan, B Kent, C Laemmerzahl, A Levy, G Metris, O Olsen, J Paramos, JD Prestage, SV Progrebenko, E Rasel, A Rathke, S Reynaud, B Rievers, E Samain, TJ Sumner, S Theil, P Touboul, S Turyshev, P Vrancken, P Wolf, N Yu, Experimental Astronomy 23 529 (2009)
- OSS (Outer Solar System): a fundamental and planetary physics mission to Neptune, Triton and the Kuiper Belt, B Christophe, LJ Spilker, JD Anderson, N Andre, SW Asmar, J Aurnou, D Banfield, A Barucci, O Bertolami, R Bingham, P Brown, B Cecconi, JM Courty, H Dittus, LN Fletcher, B Foulon, F Francisco, PJS Gil, KH Glassmeier, W Grundy, C Hansen, J Helbert, R Helled, H Hussmann, B Lamine, C Laemmerzahl, L Lamy, R Lehoucq, B Lenoir, A Levy, G Orton, J Paramos, J Poncy, F Postberg, SV Progrebenko, KR Reh, S Reynaud, C Robert, E Samain, J Saur, KM Sayanagi, N Schmitz, H Selig, F Sohl, TR Spilker, R Srama, K Stephan, P Touboul, P Wolf, Experimental Astronomy 34 203 (2012)
The addition of an ultra stable optical clock on board a probe going to the outer solar system would make possible a complete characterization of all aspects of the gravity field. This idea led to the ambitious SAGAS project based on atomic sensors.
- Quantum physics exploring gravity in the outer solar system: the SAGAS project, P Wolf, CJ Borde, A Clairon, L Duchayne, A Landragin, P Lemonde, G Santarelli, W Ertmer, E Rasel, FS Cataliotti, M Inguscio, GM Tino, P Gill, H Klein, S Reynaud, C Salomon, E Peik, O Bertolami, P Gil, J Paramos, C Jentsch, U Johann, A Rathke, P Bouyer, L Cacciapuoti, D Izzo, P De Natale, B Christophe, P Touboul, SG Turyshev, J Anderson, ME Tobar, F Schmidt-Kaler, J Vigue, AA Madej, L Marmet, MC Angonin, P Delva, P Tourrenc, G Metris, H Mueller, R Walsworth, ZH Lu, LJ Wang, K Bongs, A Toncelli, M Tonelli, H Dittus, C Laemmerzahl, G Galzerano, P Laporta, J Laskar, A Fienga, F Roques, K Sengstock, Experimental Astronomy 23 651 (2009)
More modest ideas have also been studied, consisting in embarking instruments such as electrostatic accelerometers on missions mainly devoted to the exploration of the outer solar system.
- The science case for an orbital mission to Uranus: Exploring the origins and evolution of ice giant planets, CS Arridge, N Achilleos, J Agarwal, CB Agnor, R Ambrosi, N Andre, SV Badman, K Baines, D Banfield, M Barthelemy, MM Bisi, J Blum, T Bocanegra-Bahamon, B Bonfond, C Bracken, P Brandt, C Briand, C Briois, S Brooks, J Castillo-Rogez, T Cavalie, B Christophe, AJ Coates, G Collinson, JF Cooper, M Costa-Sitja, R Courtin, IA Daglis, I De Pater, M Desai, D Dirkx, MK Dougherty, RW Ebert, G Filacchione, LN Fletcher, J Fortney, I Gerth, D Grassi, D Grodent, E Grun, J Gustin, M Hedman, R Helled, P Henri, S Hess, JK Hillier, MH Hofstadter, R Holme, M Horanyi, G Hospodarsky, S Hsu, P Irwin, CM Jackman, O Karatekin, S Kempf, E Khalisi, K Konstantinidis, H Kruger, WS Kurth, C Labrianidis, V Lainey, LL Lamy, M Laneuville, D Lucchesi, A Luntzer, J MacArthur, A Maier, A Masters, S McKenna-Lawlor, H Melin, A Milillo, G Moragas-Klostermeyer, A Morschhauser, JI Moses, O Mousis, N Nettelmann, FM Neubauer, T Nordheim, B Noyelles, GS Orton, M Owens, R Peron, C Plainaki, F Postberg, N Rambaux, K Retherford, S Reynaud, E Roussos, CT Russell, A Rymer, R Sallantin, A Sanchez-Lavega, O Santolik, J Saur, K Sayanagi, P Schenk, J Schubert, N Sergis, EC Sittler, A Smith, F Spahn, R Srama, T Stallard, V Sterken, Z Sternovsky, M Tiscareno, G Tobie, F Tosi, M Trieloff, D Turrini, EP Turtle, S Vinatier, R Wilson, P Zarkat, Planetary and Space Sciences 104 122 (2014)
- Neptune and Triton: Essential pieces of the Solar System puzzle, A Masters, N Achilleos, CB Agnor, S Campagnola, S Charnoz, B Christophe, AJ Coates, LN Fletcher, GH Jones, L Lamy, F Marzari, N Nettelmann, J Ruiz, R Ambrosi, N Andre, A Bhardwaj, J Fortney, CJ Hansen, R Helled, G Moragas-Klostermeyer, G Orton, L Ray, S Reynaud, N Sergis, R Srama, M Volwerk, Planetary and Space Sciences 104 108 (2014)
New instruments for new missions
When new space missions have been proposed, their scientific and technological content has been studied by the proposing collaborations and also by technical assessment at the european (ESA) or national (CNES) space agencies. During this process, it became clear that new instruments had to be developed in advance of missions with the aim of assessing the feasibility of new techniques of measurement before the selection process.
We have been involved in the development of bias correction for electrostatic accelerometers (derived from the ONERA expertise). This development has proven that these instruments were indeed suitable for outer space missions.
- Electrostatic accelerometer with bias rejection for gravitation and Solar System physics, B Lenoir, A Lévy, B Foulon, B Lamine, B Christophe, S Reynaud, Advances in Space Research 48 1248-1257 (2011)
- Unbiased acceleration measurements with an electrostatic accelerometer on a rotating platform, B Lenoir, B Christophe, S Reynaud, Advances in Space Research 51 188 (2013)
- Experimental demonstration of bias rejection from electrostatic accelerometer measurements, B Lenoir, B Christophe, S Reynaud, Measurement 46 1411 (2013) | 0.870953 | 3.812096 |
| ||Automatic translation|| ||Category: universe|
Updated June 01, 2013
Invisible Universe, which can be called "Universe X" refers to the universe that it is not, contrary to that usually seen in the visible frequency range, corresponding to the colors of the rainbow sky. Optical or visible light, only a small range of electromagnetic vibrations found in the electromagnetic spectrum. But the light is spread over a larger electromagnetic field. Maxwell determined that light is an electromagnetic wave and there is no reason to limit the wavelength of the latter to the interval corresponding to the visible light spectrum, the spectrum is light (image shown against). On both sides of the visible light there is light invisible infrared and ultraviolet, X-rays, invisible, too, is more energy and are beyond the ultraviolet.
X-rays are electromagnetic waves with high frequency whose wavelength ranges, roughly, between 5 picometers and 10 nanometers. X-rays are produced in the cosmos when matter is heated to millions of degrees. These temperatures occur where there is, extremely powerful magnetic fields, or extremely serious. X-rays, unlike optical rays, have the distinction of not being absorbed or deflected by interstellar dust clouds. X-rays, unlike optical rays, have the distinction of not being absorbed or deflected by interstellar dust clouds. These latter are the main obstacles limiting the observation of the universe. The "X-ray Universe", corresponds to the universe we can observe with telescopes designed to detect X-rays and for that we must get rid of the air filter of our planet.
These telescopes have been placed in space. The X-ray telescope can detect, the hot gases from the explosion of a star or X-rays from matter swirling on the edge of a black hole. The Chandra X-ray Observatory, launched by the Space Shuttle Columbia July 23, 1999 and allows a better definition of hot, turbulent regions of space. It was named "Chandra" in honor of Subrahmanyan Chandrasekhar. Radio astronomers can since capture images of the sky in the range of X-rays and see the amazing phenomena, objects falling into black holes, exploding stars, galaxies colliding, huge clusters of galaxies that cross.
The cosmos we now reveal, hidden secrets behind each end of the spectrum with the two observation satellites X: the European satellite XMM-Newton and Chandra the American satellite.
Image: Electromagnetic spectrum includes all the windows of the light. X-rays are ultraviolet rays between and gamma waves. Their wavelengths are approximately between 5 picometers and 10 nanometers. With Hubble, Spitzer, Wise, XMM-Newton, Chandra and other satellites, astronomers can see the universe by combining the visual, infrared, radio and X-radiation.
| || |
X-rays and gravity
| || || || |
What structures are large enough and hot to emit X-rays?
X-rays are produced when the material is heated to millions of degrees. The detection of X-rays will reveal regions where magnetic fields are extremely powerful, or places where gravity is extreme. This is the case of Stephan's Quintet, a cluster of galaxies located in the constellation of Pegasus. Galaxies attract each other because of their strong gravity, and they eventually merge. We see in this image, distorted by the shapes of filaments that extend far from the center of the galaxy. The blue spots in the spiral arm to the right of the bar, are groups of several thousand stars, seen in the range of X-ray In the center of the image, the galaxy appears to have two hearts, but they are actually two galaxies, NGC 7318A and NGC 7318B. A bright clusters of young blue stars, less than 10 million years, being born, encircles these galaxies.
This cluster is also seen in the range of X-ray This cluster was discovered in 1877 by the French astronomer Edouard Stephan, from the observatory of Marseille.
Image: The 3598 ESO galaxy clusters or clusters of galaxies Stephan's Quintet is located near the constellation of Pegasus, the winged horse. This beautiful blue trail in the heart of the Quintet of the cluster is seen by the Chandra X-ray telescope. The blue path is due to the extreme warming of the surrounding gas by shock waves caused by the passage of the galaxy NGC 7318b among his neighbors (NGC 7317, NGC 7318a and NGC 7319).
| || |
X-rays and magnetic field
| || || || |
Remember that neutron stars, unlike planets and ordinary stars, have super powerful magnetic fields. The conditions inside the star, are extreme, and the magnetic field is so intense that it deforms to the atoms that make up matter.
In the absence of magnetic fields, the atoms have a spherical shape, while subjected to magnetic fields super powerful, they take a tapered shape and align themselves along lines of magnetic field, like so many small needles placed end to end.
The chemical atoms exert forces on each other, joining in the thin, long molecular chains.
The material takes a tapered structure in lock of hair.
This is the first critical phase of compression, it is the area of the surface of the star.
Image: Jets of matter and antimatter away from the neutron star at the center of the Crab Nebula.
This image in the X-ray was taken in 2002 by the Chandra satellite.
The central ring has a diameter of about one light year. credit: NASA/CXC/ASU/J. Hester et al.
| || |
X-rays and wind energy
| || || || |
PSR B1509-58 is a relatively young pulsar because the light from the supernova that gave birth to have reached the Earth 1700 years ago.
This pulsar was first detected as X-ray source by the Uhuru satellite, then as a pulsating source by the Einstein satellite in 1982 and observed in radio.
His radio show is relatively low, its discovery in the radio would not have been possible without his prior discovery in the field of X-ray.
This neutron star of only 20 km in diameter, turns on itself seven times per second, this cosmic dynamo powers a wind of charged particles.
In this picture you can see the wind energy that generates X-rays of the nebula at the top of the image of the orbiting Chandra Observatory.
The low energy X-rays are colored red, intermediate energies in green and high energies in blue.
The pulsar itself is the heart of the bright central region at the bottom of the complex structure that irresistibly evokes an outstretched hand or glove.
PSR B1509-58 is located about 17,000 light-years away in the southern constellation of the compass.
At this distance, the Chandra image covers a field of 100 light-years wide.
Image: Credit: P. Slane (Harvard-Smithsonian CfA) et al., CXC, NASA
| || |
X-rays and black holes
| || || || |
This stunning composite image of Arp 147 shows two interacting galaxies, located about 430 million light years from Earth.
It consists of a set of images roses, taken in X-rays by Chandra X-ray and optical data (red, green, blue), the Hubble Space Telescope.
Arp 147 (right) contains the remains of a spiral galaxy, pierced by the collision with the elliptical galaxy on the left. The meeting left a wave of star stands today as a blue ring, hosting young massive stars.
In a few million years, these stars explode as supernovae, leaving behind neutron stars and black holes. The nine X-ray sources (pink), scattered around the blue ring in Arp 147 are so bright they could create black holes, ten to twenty times the mass of the sun.
An X-ray source is also visible in the nucleus of the galaxy rose from the center of the image.
This source could also be powered by a supermassive black hole.
Other objects, unrelated to Arp 147 are also visible on the image, especially in the background, above and left of the galaxy rose you can see, thanks to X-rays, the source of a red quasar.
Image: On this remarkable image of Arp 147, two galaxies have just been through and still interact with many black holes in training.
Credit: X-ray: NASA/CXC/MIT/S Rappaport et al., Optical: NASA/STScI
| || || || |
2400 massive stars are hidden in the center of the Tarantula Nebula (30 Doradus).
These stars produce radiation so intense that the strong winds, blowing off the field. The gas of the nebula, heated to millions of degrees by shock waves stellar radiation, is shown in blue on the X-ray image taken by the Chandra X-ray Observatory. This shock wave is produced by the powerful winds and ultraviolet radiation emitted by young stars of the cluster. These explosions carve in the cloud of dust, huge bubbles of superheated gas, from the cold matter of the nebula. This cold material in orange, is represented here by infrared emission from the Spitzer Space Telescope. RMC 136, is the supercluster of stars near the center of the Tarantula Nebula. It is known as 30 Doradus.
Tarantula Nebula is outside of our galaxy, the Large Magellanic Cloud, at 170 000 light years from the solar system. At the heart of this region of star formation, 30 Doradus, is a gigantic star clusters containing the largest, most massive and hottest known to date.
Image: Image of the Tarantula nebula seen in X-ray telescope Chandra X-ray and infrared by the Spitzer Space Telescope.
Image Credit: NASA | 0.918819 | 4.06835 |
Researchers are one step closer to identifying what lies beyond our galaxy thanks to the Canadian Hydrogen Intensity Mapping Experiment (CHIME).
Located in the Dominion Radio Astrophysical Observatory (DRAO) in Kaleden, CHIME is Canada’s largest radio telescope. Commissioned in 2017, it has already broken new ground in detecting fast radio bursts (FRB) originating 1.5 billion light years away.
“FRBs are fast burst of radio waves that appear to be coming from outside of our galaxy and they currently don’t have a firm explanation for them yet,” said Paul Scholz, research associate at DRAO and member of the CHIME FRB collaboration. “So they’re an open mystery in astrophysics right now.”
Over a three-week period in July and August 2018, CHIME recorded 13 FRBs, one of which was repeating. This is compared to the 50 that have been recorded over the past decade, one of which was also repeating.
Scholz explained that CHIME will “blow the field open” in the next few years because it can detect several FRBs per day.
“We found 13 of these in about a 3-week period this summer in a pre-commissioning phase of the telescope. So this is the iceberg of the results from CHIME,” said Scholz. “In regard to the first recorded repeating FRB, there was a question as to whether this was unique or how rare repeating sources were in the FRB population. So finding a second one means they are not super rare, but are fairly common.”
Prior to CHIME becoming operational, FRBs were only detected at wavelengths of approximately 800 megahertz. CHIME has the capacity to detect FRBs at wavelengths from 400 – 800 megahertz within the electromagnetic spectrum – meaning it has helped narrow down theories about these phenomena and the material around them.
Scholz said these FRBs are “coming from all directions in the sky” which means they are an object or phenomenon that is in a fairly common place in the universe. In addition, because their durations are short they can determine the object must be small because of the speed of the light.
“This means we’re left with dense energetic objects such as neutron stars or blackholes,” said Scholz. “Those are the lines that people are thinking along when coming up with explanations for FRBs.”
Because CHIME is able to detect several FRBs per day, Scholz said the research team will be able to build up a sample of hundreds of them for analysis, giving them a bigger picture as to what could be creating them.
“We’ll be able to transition from a regime where we know of a small amount of sources, so when we look at each individual one, we analyze them like individual snowflakes,” said Scholz. “With a large sample we can step back and analyze the whole population itself and answer questions like how much of the population is repeating, do they look like evolve, do their properties change as a function of cosmic time, things like that.”
Scholz’s responsibility with CHIME is to assist the software pipeline that detects and characterizes FRBs in real time. He explained because the amount of data collected per second by the telescope is so high, it can’t be all saved so the researchers must analyze it as it comes in to detect FRBs and determine whether it is interesting enough to save.
“I’m also involved in the follow-up analysis we perform when we detect exciting events,” said Scholz.
So what do FRBs have to do with the further examination of our galaxy and beyond? Scholz explained it has taken light billions of years to get here from whatever the source of these FRBs are.
“We’re of course very interested in figuring out what is causing FRBs, what exotic phenomenon is creating these energetic bursts. There’s also the promise of them being used as probes for the material between us and the source of the emission,” said Scholz. “We might be able to learn about the structure of our universe and the gas that populates the space between galaxies, which we have very few probes for currently.”
To report a typo, email: [email protected]. | 0.87188 | 3.978721 |
Case Study: Menducia
Ignoring the tricky question of animism (whereby physical "things" have an animating "will" that can manipulate the physical, even against the normal laws of elemental motion), the basics of Menducian physics runs on the elements. Menducian elements are less materials than "the property of a point in space at a point in time". The Menducian cosmos is best visualised as a very complicated - at any given point in time each point in space is assigned a value (element), nothing truly moves, but each configuration gives rise to the next predictably via . The imageis a handy guide to the names of the elements and how they relate to each other.
However, the specifics of this are the Menducian equivalent of molecular physics - we want a slightly broader look. On a larger scale Menducia operates a lot like the real world, at least in that there are "objects" that "move" (like a glider in a cellular automaton) according to certain "forces" (generally derived from the elemental structure of the object, but also related to the elements surrounding an object).
The basic structure of the cosmos Menducia finds itself in is this: Menducia itself is a large central concentration of Earthy elements in a sphere about the size of Earth, with a layer of Watery elements (the oceans, and to a lesser extent the atmosphere) around it. That is suspended in a vast area of Airy elements (outer space). Other, minor bodies are suspended in the Airy layer, including Menducia's many small moons and the sun, a large concentration of Fiery elements that also orbits Menducia. The sun also has two tiny "solar companions" orbiting it, also composed of Fiery elements. Beyond that the specifics are unknown, and fortunately, not relevant.
What heat source(s) does your world have? What causes heat/temperature variation, and why?
In Menducian physics, Heat is a point on the elemental map. The closer an element is to this point (between Fire and Air), the naturally hotter it is. Air and Fire are therefore naturally hotter than Earth and Water, with Mud (sitting opposite Heat) the coolest element. However this only applies to pure elements, which are rare on large scales. Most objects and materials on a human scale are mixtures, which can have more or less Heat and hot elements added or subtracted (resulting in a corresponding change in the object's properties).
The only major source of Hot/Fiery elements on Menducia is its sun (the solar companions are too small to have significant effect). On the whole Heat tends to radiate away from the planet into space, but it travels at such a rate from the sun that it overcomes the general repulsion (partly to do with it being very pure, at least at the outset - as it travels towards Menducia it reacts with the Air and becomes less so, and so slows down. As it reaches the atmosphere (Air/Water boundary) it's often reacted and diffused enough through other elements that the force pushing it away from Menducia has been weakened considerably, but there has still been a considerable shift in the local elemental structure towards Heat.)
Temperature variation comes from two very familiar cycles - the day (the rotation of Menducia on its axis, so that any one point on the surface may be facing towards or away from the sun), and the year. The year is the time it takes for the sun to make a complete orbit of Menducia. It does so on a plane at an angle to the plane of Menducia's equator - this, rather than an incline in Menducia's axis of rotation, causes seasonal variations in the amount of sunlight .
(All this is mathematically relative - what causes seasons, on Menducia or Earth, is the angle between the plane of the ecliptic and the plane of the equator. If we took the Earth as a stationary point, with the axis of rotation at 0 degrees, and measured the movement of the Sun relative to it, we'd end up with a similar picture. Equally you could make the Menducia system heliocentric, in which case its axis of rotation would be inclined relative to the plane of its orbit - just like Earth's).
There is a third cause of large scale temperature variation. The angle of the sun's plane is not fixed, and changes slowly over billions of years. If I wanted to record Menducia's climate over millions of years I would have to take this into account. Fortunately I only want a picture of recorded history, about 10,000 years, and there won't be significant variation over that period.
Do different parts of your world heat and cool at different rates? If so, how and why?
Due to their differing elemental properties, land and sea react to heat differently. While the oceanss are "naturally" warmer than the land, they have less capacity for Heat - the addition of Heat to Water quickly produces light elements that radiate away from the main body of water, keeping its temperature relatively stable. Earthy elements on the other hand can soak up a lot more Heat before elements light enough to float away are formed, but also repel and lose Heat faster than Water. So, the land heats and cools faster than the oceans.
What principles govern atmospheric movement? Does heat drive air movement, or some other force?
Menducia's atmosphere is a mainly Watery/Airy mix of elements. If it was pure Water/Air, its movement would be highly unpredictable. Fortunately, "light"/"hot" (strictly, Fiery) and "heavy"/"cold" (Earthy) elements also play a part. Hotter parts of the atmosphere rise (are repelled by the Earthy core of Menducia), while colder parts sink (are attracted down).
The further hot air rises, the more Fiery elements it loses as they escape into the upper atmosphere and eventually, space. So hot air cools as it rises, then sinks back down where it picks up excess Fiery elements from the land or oceans, and rises again.
Sinking air eventually hits the land or ocean and spreads outwards from there, picking up heat (and over the oceans, moisture) as it goes. This causes a general flow of air from colder areas to hotter ones, at least in the lower atmosphere.
As Menducia is a rotating frame of reference, all this movement will be subject to a Coriolis effect.
What causes rain and other precipitation? Is water vapour carried by the air, or is some entirely different principle at work?
Watery elements are carried in the atmosphere, and fall as rain when they become heavy (less Fiery/more Earthy) enough. This happen particularly when hot air rises and begins to lose its Fiery elements (see above). Cold, sinking air has generally already lost much of its Watery content, and will rarely produce precipitation. Hot air can also carry more Water than cold air, following a similar principle to that which governs how much Heat can be held by Earth vs Water - Hotter mixtures are lighter, and so can bear more heavy elements to be added to them.
In summary, the basic principles driving Menducian climate are:
*All heating comes from the sun
*Water heats and cools more slowly than land
*Hot air rises, cold air sinks
*Winds flow from cold-air areas to hot-air ones
*Corilolis effect deflects winds to the clockwise in the Northern hemisphere and anticlockwise in the Southern hemisphere
*Rising air is conducive to the fall of precipitation, sinking air is not
*Warm air carries more moisture than cold air
This should all look eerily familiar.
"It is quite certain, in particular, that I have always been insane." ~ Aleister Crowley
"Save us all from arrogant men/And all the causes they're for/I won't be righteous again/I'm not that sure any more." ~ Shades of Grey, Billy Joel | 0.825618 | 3.527779 |
A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral atom contains a single positively charged proton and a single negatively charged electron bound to the nucleus by the Coulomb force. Atomic hydrogen constitutes about 75% of the baryonic mass of the universe. In everyday life on Earth, isolated hydrogen atoms are rare. Instead, a hydrogen atom tends to combine with other atoms in compounds, or with another hydrogen atom to form ordinary hydrogen gas, H2. "Atomic hydrogen" and "hydrogen atom" in ordinary English use have overlapping, yet distinct, meanings. For example, a water molecule does not contain atomic hydrogen. Atomic spectroscopy shows that there is a discrete infinite set of states in which a hydrogen atom can exist, contrary to the predictions of classical physics. Attempts to develop a theoretical understanding of the states of the hydrogen atom have been important to the history of quantum mechanics, since all other atoms can be understood by knowing in detail about this simplest atomic structure.
The most abundant isotope, hydrogen-1, protium, or light hydrogen, contains no neutrons and is a proton and an electron. Protium is stable and makes up 99.985% of occurring hydrogen atoms. Deuterium contains one proton. Deuterium is stable and makes up 0.0156% of occurring hydrogen and is used in industrial processes like nuclear reactors and Nuclear Magnetic Resonance. Tritium contains two neutrons and one proton and is not stable, decaying with a half-life of 12.32 years. Because of its short half-life, tritium does not exist in nature except in trace amounts. Heavier isotopes of hydrogen are only created artificially in particle accelerators and have half-lives on the order of 10−22 seconds, they are unbound resonances located beyond the neutron drip line. The formulas below are valid for all three isotopes of hydrogen, but different values of the Rydberg constant must be used for each hydrogen isotope. Lone neutral hydrogen atoms are rare under normal conditions. However, neutral hydrogen is common when it is covalently bound to another atom, hydrogen atoms can exist in cationic and anionic forms.
If a neutral hydrogen atom loses its electron, it becomes a cation. The resulting ion, which consists of a proton for the usual isotope, is written as "H+" and sometimes called hydron. Free protons are common in the interstellar medium, solar wind. In the context of aqueous solutions of classical Brønsted–Lowry acids, such as hydrochloric acid, it is hydronium, H3O+, meant. Instead of a literal ionized single hydrogen atom being formed, the acid transfers the hydrogen to H2O, forming H3O+. If instead a hydrogen atom gains a second electron, it becomes an anion; the hydrogen anion is called hydride. The hydrogen atom has special significance in quantum mechanics and quantum field theory as a simple two-body problem physical system which has yielded many simple analytical solutions in closed-form. Experiments by Ernest Rutherford in 1909 showed the structure of the atom to be a dense, positive nucleus with a tenuous negative charge cloud around it; this raised questions about how such a system could be stable.
Classical electromagnetism had shown that any accelerating charge radiates energy, as shown by the Larmor formula. If the electron is assumed to orbit in a perfect circle and radiates energy continuously, the electron would spiral into the nucleus with a fall time of: t fall ≈ a 0 3 4 r 0 2 c ≈ 1.6 ⋅ 10 − 11 s Where a 0 is the Bohr radius and r 0 is the classical electron radius. If this were true, all atoms would collapse, however atoms seem to be stable. Furthermore, the spiral inward would release a smear of electromagnetic frequencies as the orbit got smaller. Instead, atoms were observed to only emit discrete frequencies of radiation; the resolution would lie in the development of quantum mechanics. In 1913, Niels Bohr obtained the energy levels and spectral frequencies of the hydrogen atom after making a number of simple assumptions in order to correct the failed classical model; the assumptions included: Electrons can only be in certain, discrete circular orbits or stationary states, thereby having a discrete set of possible radii and energies.
Electrons do not emit radiation while in one of these stationary states. An electron can lose energy by jumping from one discrete orbital to another. Bohr supposed that the electron's angular momentum is quantized with possible values: L = n ℏ where n = 1, 2, 3... and ℏ is Planck constant over 2 π. He supposed that the centripetal force which keeps the electron in its orbit is provided by the Coulomb force, that energy is conserved. Bohr derived the energy of each orbit of the hydrogen atom to be: E n = − m e e 4
Austinville is a former town and now a neighborhood within the city of Decatur in Morgan County, United States. It is about 3 miles south from downtown Decatur, centered on the junction of Danville Road and Carridale Street, it was incorporated as a town in 1907 and disincorporated and annexed into the city of Decatur in 1956. Austinville is located at 34.5748149°N 87.0086207°W / 34.5748149. Austinville first appeared on the 1910 U. S. Census three years after it incorporated, it was annexed into Decatur in 1956. See Austinville precinct below. Austinville Precinct was created and first appeared on the 1910 U. S. Census. In 1927, it and the Albany 19th precinct were annexed into the Decatur 1st precinct. In 1960, the Austinville name was attached to a newly-created census division, included the towns of Flint City and Trinity; the division was merged into the Decatur Census Division by 1970
Pennsylvania Impressionism was an American Impressionist movement of the first half of the 20th century, centered in and around Bucks County, Pennsylvania the town of New Hope. The movement is sometimes referred to as the "New Hope School" or the "Pennsylvania School" of landscape painting. Landscape painter William Langson Lathrop moved to New Hope in 1898, where he founded a summer art school; the mill town was located along the Delaware River, about forty miles from Philadelphia and seventy miles from Manhattan. The area's rolling hills were spectacular, the river, its tributaries, the Delaware Canal were picturesque; the natural beauty attracted the artist Edward Redfield. Redfield painted nature in bold and vibrant colors, was “the pioneer of the realistic painting of winter in America.” His thick layering distinguished him from his contemporaries, he amassed more honors and awards than any other artist in the New Hope Colony. His style is distinguished by its color and usual time of day when painting.
The third major artist to settle in the area was Daniel Garber, who came to New Hope in 1907. Garber applied his paint lightly. An instructor at the Pennsylvania Academy of the Fine Arts in Philadelphia, Garber played a huge part of the new colony. Garber made rain paintings popular; as more artists came to the colony, the artists formed art groups with different ideas. The two main groups were the Modernists. Impressionists were painters who did not stay with the traditional pursuit of painting realistically, but instead explored the possibilities of paint and imagination. An important American Impressionist movement is the Pennsylvania Impressionism; the Pennsylvania Impressionist Movement inspired and influenced major artists such as Walter Schofield, George Sotter and Henry Snell. William Lathrop purchased the Phillips Mill property to use as a venue to hold galleries and exhibitions. However, problems occurred in this venue. Modernist Lloyd Ney submitted a painting of the New Hope canal. Lathrop threatened to reject the painting.
Charles Ramsey, Lloyd Ney’s good friend, was disturbed by this comment and formed the “New Group.” This group rebelled against the traditional impressionists having to inaugurate before the Phillips Mill Exhibition on May 16, 1930. Many years a flood of artists came because of the Garber’s influence for constant rain in Pennsylvania; this group consisted of prominent artists such as Robert A. D. Miller, Peter Keenan, Charles Evans. Other important modernist painters to settle in the area after the initial arrivals were Josef Zenk, Bror Julius Nordfeldt, Swiss-born Joseph Meierhans, Clarence Carter and precisionist, Richard Peter Hoffman of Allentown; these fifteen people made a big mark to for Impressionistic society. There was the “Last Ten.” This group stood out. The Ten consisted of Fern Coppedge and M. Elizabeth Price from New Hope, as well as Nancy Maybin Ferguson, Emma Fordyce MacRae, Eleanor Abrams, Constance Cochrane and Theresa Bernstein; these women influenced many other women to join the Pennsylvania Impressionism Movement.
Similar to the French impressionist movement, this style of art is characterized by an interest in the quality of color and the time of day. This group of artists painted in plein air, or out of doors, to capture the moment. According to James A. Michener Art Museum’s Senior Curator Brian Peterson, “what most characterized Pennsylvania impressionism was not a single, unified style but rather the emergence of many mature, distinctive voices: Daniel Garber's luminous, poetic renditions of the Delaware River. Art historian Thomas C. Folk defines the movement as the Late Pennsylvania School, those artists that "came to prominence in Bucks County after 1915 or after the Armory Show and the Panama-Pacific International Exposition." According to Folk, the three most notable artists in this group were John Fulton Folinsbee, Walter Emerson Baum and George Sotter. One of the artists, Walter Emerson Baum, worked as a teacher and educator and through his founding of the Baum School of Art and the Allentown Art Museum, would serve to expand the influence of the movement out of Bucks County and into Lehigh County Allentown and the Lehigh Valley, where the movement continued to flourish into the 1940s and 1950s.
Today, this group of artists is collectively known as the Baum Circle. Eleanor Abrams Faye Swengel Badura Henry Baker Walter Emerson Baum Theresa Bernstein Rae Sloan Bredin Constance Cochrane Morgan Colt Fern Coppedge Nate Dunn Charles Evans Nancy Maybin Ferguson John Fulton Folinsbee Daniel Garber Frederick Harer L. Birge Harrison John Wells James Peter Keenan William Langson Lathrop Harry Leith-Ross Carl Lindborg Emma Fordyce MacRae Robert A. D. "Rad" Miller Roy Cleveland Nuse Mary Elizabeth Price Herbert Pullinger Edward Redfield Charles Rosen Walter Elmer Schofield Henry B. Snell George Sotter Robert Spencer Louis Stone Richard Wedderspoon Impressionism A | 0.864683 | 3.635442 |
Good fortune and cutting-edge scientific equipment have allowed scientists to observe a Gamma Ray Burst jet with a radio telescope and detect the polarization of radio waves within it for the first time – moving us closer to an understanding of what causes the universe’s most powerful explosions.
Gamma Ray Bursts (GRBs) are the most energetic explosions in the universe, beaming out mighty jets which travel through space at over 99.9% the speed of light, as a star much more massive than our Sun collapses at the end of its life to produce a black hole. The study was published in Astrophysical Journal Letters.
Studying the light from Gamma Ray Burst jets as we detect it travelling across space is our best hope of understanding how these powerful jets are formed, but scientists need to be quick to get their telescopes into position and get the best data. The detection of polarized radio waves from a burst’s jet, made possible by a new generation of advanced radio telescopes, offers new clues to this mystery.
The light from this particular event, known as GRB 190114C, which exploded with the force of millions of Suns’ worth of TNT about 4.5 billion years ago, reached NASA’s Neil Gehrels Swift Observatory on Jan 14, 2019.
A rapid alert from Swift allowed the research team to direct the Atacama Large Millimeter/Sub-millimeter Array (ALMA) telescope in Chile to observe the burst just two hours after Swift discovered it. Two hours later the team was able to observe the GRB from the Karl G. Jansky Very Large Array (VLA) telescope when it became visible in New Mexico, USA.
Combining the measurements from these observatories allowed the research team to determine the structure of magnetic fields within the jet itself, which affects how the radio light is polarized. Theories predict different arrangements of magnetic fields within the jet depending on the fields’ origin, so capturing radio data enabled the researchers to test these theories with observations from telescopes for the first time.
The research team, from the University of Bath, Northwestern University, the Open University of Israel, Harvard University, California State University in Sacramento, the Max Planck Institute in Garching, and Liverpool John Moores University discovered that only 0.8% of the jet light was polarized, meaning that jet’s magnetic field was only ordered over relatively small patches – each less than about 1% of the diameter of the jet. Larger patches would have produced more polarized light.
These measurements suggest that magnetic fields may play a less significant structural role in GRB jets than previously thought. This helps us narrow down the possible explanations for what causes and powers these extraordinary explosions.
First author Dr. Tanmoy Laskar, from the University of Bath’s Astrophysics group, said: “We want to understand why some stars produce these extraordinary jets when they die, and the mechanism by which these jets are fuelled – the fastest known outflows in the universe, moving at speeds close to that of light and shining with the incredible luminosity of over a billion Suns combined.
“I was in a cab on my way to O’Hare airport in Chicago, following a visit with collaborators when the burst went off. The extreme brightness of this event and the fact that it was visible in Chile right away made it a prime target for our study, and so I immediately contacted ALMA to say we were going to observe this one, in the hope of detecting the first radio polarization signal.
“It was fortuitous that the target was well placed in the sky for observations with both ALMA in Chile and the VLA in New Mexico. Both facilities responded quickly and the weather was excellent. We then spent two months in a painstaking process to make sure our measurement was genuine and free from instrumental effects. Everything checked out, and that was exciting.
Dr. Kate Alexander, who led the VLA observations, said: “The lower frequency data from the VLA helped confirm that we were seeing the light from the jet itself, rather than from the interaction of the jet with its environment.”
Dr. Laskar added: “This measurement opens a new window into GRB science and the studies of energetic astrophysical jets. We would like to understand whether the low level of polarization measured in this event is characteristic of all GRBs, and if so, what this could tell us about the magnetic structures in GRB jets and the role of magnetic fields in powering jets throughout the universe.”
Professor Carole Mundell, Head of Astrophysics at the University of Bath, added: “The exquisite sensitivity of ALMA and rapid response of the telescopes has, for the first time, allowed us to swiftly and accurately measure the degree of polarization of microwaves from a GRB afterglow just two hours after the blast and probe the magnetic fields that are thought to drive these powerful, ultra-fast outflows.”
The research team plans to hunt for more GRBs to continue to unravel the mysteries of the biggest explosions in the universe. | 0.808478 | 4.041445 |
With real world technology, satellites maintain their gross orbital position through orbital mechanics, maintain precise position (such as geostationary longitude) with station-keeping rockets (ion engines today, monopropellant engines in the past), maintain alignment with reaction wheels, and power themselves with solar panels.
technology, orbital mechanics will still be the cheapest, most reliable way to maintain gross orbital position. Photovoltaic panels may well remain the cheapest and most reliable way to power them (because even with cheap access to space, maintaining a non-photovoltaic power plant requires paid technicians). Reaction wheels might remain the best way to maintain alignment. The only thing that definitely changes is station-keeping; reactionless maneuver drives never need fuel, and if the job can be done with the miniscule thrust of an ion engine, a really small maneuver drive powered by the photovoltaic panels should be able to handle the job, unless they have some inconvenient minimum size.
Nobby-W wrote: ↑
Mon May 29, 2017 6:24 pm
. . .
If you're interested in the physics, the Chelyabrinsk meteor is estimated to have weighed something like 12,000 tons, and was completely vapourised when it entered the atmosphere at approximately 20km/sec. The Tunguska meteor of 1908 made a much bigger bang (estimated about 30MT), but is estimated to have been more like a million tons or so.
From this, we can infer that te-entry at 20km/sec will almost certainly vapourise a starship hull in the upper atmosphere before it does any harm, . . .
The fate of a meteorite depends on a variety of factors, including type (icy-cometary, stony, nickel-iron, fragile space junk, tough space junk, reentry vehicles), velocity (high atmospheric, low orbital, interplanetary, constant-G, relativistic), and angle. Finned tungsten baseball bats are likely to make it through any habitable atmosphere; even if they melt, a blob of high velocity tungsten will ruin your day. By contrast, even a huge cometary object is likely to vaporize if it arrives at an angle just deeper than an atmospheric skip angle. The Arizona Meteor Crater was believed to have been a nickel-iron meteorite that struck at a low angle, and tore into lots of small bits -- but the central bulk of the cluster of small bits made a pretty impressive hole.
To the point, you're not going to find any planetary governments (or balkanized worlds' starport organizations) willing to bet that a failing or suicidal starship will vaporize between space and population or economic targets on the surface. Orbital facilities are even more vulnerable to collisions, so any defense system that can protect a highport will also protect surface targets.
Incidentally, a vacuum or trace atmosphere world is pretty much equivalent to a highport with a structural backbone (and possibly gravity) provided by nature.
Nobby-W wrote: ↑
Mon May 29, 2017 9:10 pm
. . .
Trajectories that hit the ground (sometimes known as Lithobraking) are not generally sensible orbits.
. . .
I love this expression. As a space nerd, I'm surprised I hadn't heard it before. | 0.806583 | 3.264591 |
A violent collision between two neutron stars 4.6 billion years ago showered the as-yet-unformed Solar System with heavy elements, new research has found.
As much as 0.3 percent of Earth’s gold, platinum and uranium (along with other heavy elements) could have been forged in the fire of a merger 1,000 light-years away, when the Solar System was little more than a cloud of gas and dust.
“This means that in each of us we would find an eyelash worth of these elements,” said astrophysicist Imre Bartos of the University of Florida, “mostly in the form of iodine, which is essential to life.”
The famous neutron star collision detected in 2017 taught us many things – not least of which is that such collisions produce heavy elements. In the electromagnetic data produced by GW 170817, scientists detected, for the first time, the production of heavy elements including gold, platinum and uranium.
This is because a powerful explosion, such as a supernova or stellar merger, can trigger the rapid neutron-capture process, or r-process - a series of nuclear reactions in which atomic nuclei collide with neutrons to synthesise elements heavier than iron.
The reactions need to happen quickly enough that radioactive decay doesn’t have a chance to occur before more neutrons are added to the nucleus, which means it needs to happen where there are a lot of free neutrons floating about – like an exploding star.
To figure out where Earth’s heavy elements may have come from – whether a supernova or a neutron star merger – Bartos and his colleague Szabolcs Márka of Columbia University have analysed the radioactive isotopes in early Solar System meteorites.
These are found in actinides – heavy elements with atomic numbers from 89 through 103, from actinium through lawrencium, all of which are radioactive; their traces can be found in meteorites from the early days of the Solar System.
Radioactive isotopes have a half-life. That refers to the period of time it takes for half the atomic nuclei in a sample to decay, and it’s a known quantity for various elements. Radioactive half-life can, therefore, be used as a sort of time capsule to reconstruct specific time periods.
So the researchers were able to use these meteorite actinides, plutonium, uranium and curium, to reconstruct the abundances of heavy elements in the early Solar System.
In and of itself, this doesn’t tell us much more than that, so the team ran numerical simulations of the early Solar System to compare the real-life meteorite abundances against the simulations. And they found that the two didn’t match up without a neutron star smash-up.
The best fit for the observed actinide abundances was a neutron star collision about 1,000 light-years from the Solar System (so, inside the Milky Way galaxy), roughly 100 million years before the Earth formed, when the gas cloud that became the Solar System was still in the process of coalescing.
“If a comparable event happened today at a similar distance from the solar system, the ensuing radiation could outshine the entire night sky,” Márka said.
This event, their research found, sprayed elements out into the surrounding space, contributing 70 percent of the early Solar System’s curium, and 40 percent of its plutonium. Because of radioactive decay, there is much less of it now, 4.6 billion years later.
And it couldn’t have been a supernova, they found – they occur far too often, putting the actinide abundances they would produce beyond the constraints defined by the meteorites.
It’s a result, the researchers said, that can shed some light on the processes that shaped the Solar System. And it has some existential significance, too.
“Our results address a fundamental quest of humanity: Where did we come from and where are we going?” Márka said.
“It is very difficult to describe the tremendous emotions we felt when we realised what we had found and what it means for the future as we search for an explanation of our place in the Universe.”
The research has been published in Nature. | 0.81099 | 4.018358 |
Tidal power has its benefits as a renewable energy source with more predictability than its wind and solar energy sisters being one of them. But it also has its drawbacks, such as the price tag and limited number of tidal sites.
IndustryTap covered tidal power generation in May 2013, “Tidal Power Generation Picking Up, $500 Million Worldwide Market By 2015 (Video)“, with a look at how tidal energy is harnessed, the interaction between the earth and the moon and the different types of tidal wave technology. But tidal power has a long way to go to prove its viability and utility in the renewable energy source space.
Lots of Studies And Small Scale Proof Of Concept Projects Underway
There seem to be as many different ideas about how tidal energy can be harnessed as there are projects around the world. As numbers come in on the performance of different types of tidal-harnessing technology, the number of manufacturers will decline while volume shoots up. Questions such as “where should a tidal power farm be located to get the best results?” are being tested in a variety of environments.
While tidal power technology is young, it may turn out to be a sleeper. After all, most of the earth is covered with ocean, which is subjected to the mysterious powers of the Moon, making this form of energy more predictable than wind or sunshine. What’s more, the environmental impact of tidal power is relatively low because installations are underwater.
Tidal projects are still relatively small compared to more established forms of renewable energy: the largest title power station has a capacity of 254 megawatts (MW) per year while the largest power stations, including nuclear power and dams, produce from 6,000 MW to 22,500 MW.
The following is a list of the largest tidal projects to date. There are many more in the works, which will eclipse these in size and scope.
Where Does A Tide Come From?
The gravitational force of the moon is just one ten-millionth that of the earth. When it is combined with the Earth’s centrifugal force, created by its spin and the gravity of the sun, tides occur.
Tides are not caused by the direct pull of the moon’s gravity but by a combination of the moon’s upward pull and the earth’s downward pull on the oceans. The interaction of these forces causes tides.
Maximum tides occur when the moon, earth and sun are aligned. And spring tides occur when the moon and sun are on the same side of the earth aka “New Moon” or when the sun and moon are on opposite sides of the earth aka “Full Moon.”
An excellent illustration of these relationships is given by Adam Hart Davis of Explain-It:
Recent Project In France, $55 million (40 million euros)
In 2010, Irish tidal technology firm OpenHydro teamed with French utility company EDF to build four 2 MW tidal turbines off the coast of Paimpol-Brehat in Brittany, France. The turbines were installed 115 feet (35 m) below the surface of the water and are 72 feet (22 m) high and weigh 850 tons. | 0.825191 | 3.025586 |
NASA has been credited for sending a number of missions to Mars and Insight is another one on its list. But what sets Insight apart from the other missions is that it is literally a ground-breaking lander. While the previous orbiters have observed the red planet from above, rovers have crept over the surface; the Insight has been designed to explore what’s on inside the planet.
The Insight which is an abbreviated word stand for Interior Exploration using Seismic Investigations will be the first unmanned robotic lander to study the Martian crust, as well as its mantle and core. As stated by Bruce Banerdt, Insight’s principal investigator, the goal of the InSight, is to better understand the birth of our planet Earth and that understanding will be obtained by first understanding the composition of Mars. Scientists also believe that the understanding of Mars from within could help them better understand the evolution of other rocky planets as well as exoplanets.
After its successful landing on the planet’s surface, the 20-feet wide solar-powered robot will use a variety of instruments and try to unlock the hidden secrets of the structure of Mars. Insight’s robotic arm will place an advanced seismometer to listen for and analyze the vibrations of “marsquakes” and asteroid strikes. The seismic waves which have been modified while passing through the different layers will enable the scientists to determine what constitutes the composition of those layers.
In addition to the ultra-sensitive seismometer, Insight is also equipped with a thermal probe which can be hammered 16 feet beneath the surface to measure the heat flow from inside the planet. It will conduct these experiments near the Mars’ equator in a region known as Elysium Planitia. The deeper it will go, higher the temperature will rise-which will help the researchers to calculate the temperature prevailing in Mar’s deep interior. The spacecraft will also measure the shift in the radio signals transmitted between it and Earth. It will help in figuring out how much Mars’ North Pole wobbles over the course of a Martian year. The size and frequency variation will reveal the clues about the red planet’s core, including its size and density.
The NASA robot also carries with itself a microchip containing the names of 2.4 million people etched on it.
The Mars Insight Lander is scheduled to be launched on May 5 at about 4 a.m. The spacecraft will be the first interplanetary mission to be launched from the West Coasts, and so the early birds can expect an aerial treat by briefly watching the spacecraft commencing its journey to the Mars.
Picture provided by NASA | 0.835651 | 3.647574 |
Looking for something spookier than your neighborhood haunted house this Halloween? Then you may want to take a peek at some of the ghostly space images NASA scientists have been able to capture through various missions, like the Hubble Space Telescope and the Spitzer Space Telescope.
The stunning image of our Sun's active regions, lighting up to resemble a blazing Jack-O-Lantern, was captured by NASA's Solar Dynamic Observatory in 2014. According to NASA, "The active regions appear brighter because those are areas that emit more light and energy — markers of an intense and complex set of magnetic fields hovering in the sun’s atmosphere, the corona."
This "ghostly apparition," as NASA calls it, is an image of two galaxies colliding. "Each 'eye' is the bright core of a galaxy, one of which slammed into another," NASA explained on its website. "The outline of the face is a ring of young blue stars. Other clumps of new stars form a nose and mouth." According to the space agency, the phenomenon, captured by the Hubble Space Telescope in June 2019, is extremely rare. Though galaxies often collide, head-on meetings are unusual, and the rings, like the ones captured by the image, are even more so. The scientists expect the two galaxies to merge entirely in about 1 to 2 billion years.
NASA believes this "ghoulish gourd," carved out of gas and dust, was the work of an O-type star — a massive star that is about 15 to 20 times heavier than the Sun. They suspect the star's strong outflow of radiation and particles probably swept the surrounding dust and gas outward, causing deep indentations in the cloud, or nebula. The data used to create the image, released on October 30, 2019, were captured by the Spitzer Space Telescope between 2004 and 2009.
Glowing Cosmic Candy
No Halloween is complete without a treat! This colorful astronomical delight is actually an image of the Saturn Nebula, a complex planetary nebula in the constellation Aquarius. What looks like a candy wrapper is actually the outer layers of a dying star. According to NASA, when stars like our Sun reach retirement age, they transform into unique, stunning works of art! The image of the nebula, which gets its name from its superficial resemblance to the three-ringed planet Saturn, was captured by the Hubble Space Telescope. | 0.903946 | 3.125396 |
The only truth of which we can be certain with regard to life in the universe is that Earth is surely abundant with it. Life can adapt and thrive in many harsh environments from hot geysers to the sun deprived locations deep within our oceans. Common to the existence of life at least as we know it, is a requirement which is that of water…the life-blood of the universe…the vehicle by which organic molecules combine, through which life forms move and nutrients are absorbed.
Beyond Earth, the closest world to us, The Moon, has water and it is thought, a lot of it. The water on the surface is enclosed in volcanic glass beads formed billions of years ago when magma erupted from the Moon’s interior. Was some of it brought by comets or asteroid bombardment …possibly but this is only one source. The water in this encapsulated form can be found throughout the lunar surface. The quantity of water on the lunar surface in this captured volcanic form is estimated to be about 1 quart per cubic meter. The water bearing volcanic beads imply that this water originated from deep within the the interior of the Moon. Water in the form of ice has been found by Nasa radar by an Indian Moon probe. It found evidence of 600 million metric tons of actual water ice spread out on the bottom of the craters at the north lunar pole. Trace amounts of water molecules have also been found above the moon’s surface as well. Nasa found using Nasa Lunar Reconnaissance Orbiter data that the coldest places near the moon’s south pole are the brightest places which might indicate surface frost. All of this data goes a long way in implying that the moon may have had an atmosphere of its own at one time.
In our solar system there are several worlds that are thought to contain water as ice or water vapour such as Jupiter, Saturn, Uranus and Neptune. Mercury shows signs of iced over craters and as discovered by Nasa’s Curiosity Mars Rover, an ancient martian riverbed indicates that once water flowed on it surface.
Europa, Calisto and Ganymede, Jupiter’s moons, show strong evidence of liquid water below their surface as well as essential chemicals to sustain life. In fact Ganymede is thought to have a salt water ocean. Saturn’s moon Europa and Enceladus have not only liquid water but the other factors thought essential for life to exist…essential chemical elements and energy sources.
With the study of exoplanets, the Kepler data confirm the planets about the size of our earth could be entirely covered in water. The Tess mission upcoming will search such exoplanets and the James Webb Space telescope will examine their atmospheres.
Regarding our Moon the question arises…what amount of water could be lurking below its surface and in what form…the answer is a lot and in the form of liquid water quite possibly as in the case of Enceladus for instance, where active geysers spraying water ice particles and water vapor from below its surface give testament to water a plentiful beyond our Earth.
No wonder why Nasa has planned sometime in 2020 to revisit our nearest neighbour. The lunar south pole will be of special interest because the south pole is unique in that sunlight does not reach the botton of the craters which act as permanent cold traps that could reveal a fossil record of the early solar system. Nasa’s Lunar Ice Drill will bore the south pole for analysis during this lunar revisit.
Acquiring the technology to harvest water on the moon and elsewhere will be a crucial step to accomplishing the future goals of Nasa. Its task will be to lay the framework of a moon orbiting space station that will later be serviceable in future interplanetary exploration. As Early as 2033 scientists invision a manned space flight to Mars as a direct result of Nasa’s Orion Program to come.
Further Reading: Brown University
Researchers create first global map of water in Moon’s soil | 0.830526 | 3.057865 |
Authors: Dalya Baron & Brice Ménard
First Author’s Institution: School of Physics and Astronomy, Tel-Aviv University
Status: To be submitted to MNRAS, open access on Arxiv
One of the most infamous solutions to Einstein’s General Relativity, black holes have been realized in the modern era as a fundamental aspect of our Universe. It is now widely believed that a supermassive black hole (SMBH) resides in the center of nearly every galaxy. What’s more is that over the past two decades, evidence has been building which suggests the lives and deaths of galaxies are dictated in part by their SMBH. This may seem obvious, but SMBHs are incredibly tiny compared to the vastness of a galaxy. To put this into perspective in terms of relative size, it is as if a single atom interferes with your balance as you take a morning jog!
A Brief History of Active Galactic Nuclei
Early observations of galaxies revealed a population with intensely bright central regions called Active Galactic Nuclei (AGN). When measured with spectroscopy, the emission line features from the AGN are bizarre. A set of extremely broad lines are thought to be Doppler broadened due to fast-moving gas clouds near the SMBH, and a set of narrow lines from slower moving photo-ionized clouds further out. Hence, these regions are named the Broad Line Region (BLR) and Narrow Line Region (NLR), respectively.
AGN galaxies seen face-on are Type I, from which we can measure both BLR and NLR emission. The mass of the SMBH can then be readily estimated from velocity distribution associated with the BLR emission line width, in addition to the host galaxy properties calculated by carefully subtracting the AGN light. Active galaxies seen edge-on are Type II, and due to a torus of dust and gas around the SMBH region, we cannot directly observe the BLR. Although measurements of the host galaxy are viable, this obscuration makes SMBH masses very difficult to estimate.
These measurements are important because it appears that the mass of the SMBH scales with the stellar velocities and mass of the much larger galaxy bulge, made up of old red stars. Despite this strong indication of co-evolution between tiny SMBHs and their immense host galaxies, the cause of this relationship remains unclear. The fact that we can only measure a given AGN galaxy along one viewing angle has complicated attempts to understand SMBH and host galaxy properties in a consistent way.
Looking for the Pattern with the Sequencer
The authors of today’s astrobite demonstrate a powerful new way to estimate the masses of SMBHs in Type II AGN. By exploiting a previously unknown relationship between the BLR and the NLR emission lines, they obtain SMBH masses for systems which before now only had measurements of galaxy bulge properties.
Figure 1. The resulting sequence of Type I AGN emission line spectra (left) organized by common line profile. The width of the broad Hα component (green box) is found to scale linearly with the flux ratio of the narrow O[III] and Hβ components (green box; right). See Figures 1 & 3 of the paper.
The approach necessitated the development of the Sequencer, an algorithm to organize spectra of AGN by the similarity in their emission line features. In brief, the algorithm attempts to order the spectra by their aggregate spectral features as shown in Figure 1.
They began by considering a large sample of Type I AGN galaxies for which a spectrum has been taken of their central region where it is possible to observe both the BLR and NLR simultaneously. Each spectrum is first shifted to account for cosmological redshift. Then the underlying continuum is subtracted and the resulting spectra are normalized so that the emission line features can be compared fairly. The result is a sequence of neighboring spectra driven by the width of the prominent Hα line. This is not entirely surprising: the Hα line is particularly strong in most galaxy emission spectra.
But there is something more astonishing. The average flux of the narrow NLR component of Hα and Hβ systematically decreases as their BLR component broadens. They explore this relationship using the width of broad Hα and the ratio of narrow O[III] to narrow Hβ fluxes. These selections are convenient as neither is sensitive to the flux normalization, and the latter is both insensitive to dust and traditionally used to estimate the ionization strength of the gas in the NLR. As shown in Figure 1, this relationship is for the most part linear. Hence the take-away: the velocity broadening of the BLR can be estimated from the ratio of NLR narrow lines! The slight nonlinearity can be explained by contamination from luminous stars.
With this linear relation in hand, the BLR gas cloud velocities (and hence SMBH mass) can be obtained for Type II AGN by only measuring their narrow O[III]/Hβ fluxes. As shown in Figure 2, the classical relationship between SMBH mass and bulge region mass for Type I AGN (right) holds for this difficult-to-characterize population of Type II AGN (left).
Figure 2. Black hole mass is known to scale with increasing velocity broadening of the host bulge (σ*). The colored points for Type II AGN (left) and Type I AGN (right) from this work agree well with uncolored points from the literature, and greatly increase the statistical certainty of this poorly understood relation. See Figure 6 of the paper.
Implications for Galaxy Evolution
Galaxy evolution has been a story about expanding horizons. Evidence for the physical cause underpinning the relationship between SMBH mass and bulge properties explored here will most likely come from evaluating this relation during times when galaxies were rapidly assembling, during an epoch known as Cosmic Noon. Earlier times too may reveal startlingly different realities from theories currently proposed.
Future speculation aside, the immediate result of this pioneering method is a new probe with which to study Type II AGN. Like a phoenix arisen from the ashes, the previously disregarded population of edge-on active galaxies may now be used to explore the relationship between the properties of the bulge, and the mass of the minuscule but fantastically powerful beast that lies at its center. | 0.807382 | 4.193044 |
Gibbous ♌ Leo
Moon phase on 20 January 2095 Thursday is Full Moon, 14 days old Moon is in Leo.Share this page: twitter facebook linkedin
Moon rises at sunset and sets at sunrise. It is visible all night and it is high in the sky around midnight.
Moon is passing first ∠0° of ♌ Leo tropical zodiac sector.
Lunar disc appears visually 7.7% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1805" and ∠1950".
The Full Moon this days is the Wolf of January 2095.
There is high Full Moon ocean tide on this date. Combined Sun and Moon gravitational tidal force working on Earth is strong, because of the Sun-Earth-Moon syzygy alignment.
The Moon is 14 days old. Earth's natural satellite is moving through the middle part of current synodic month. This is lunation 1175 of Meeus index or 2128 from Brown series.
Length of current 1175 lunation is 29 days, 11 hours and 55 minutes. It is 1 hour and 45 minutes longer than next lunation 1176 length.
Length of current synodic month is 49 minutes shorter than the mean length of synodic month, but it is still 5 hours and 20 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠317.1°. At the beginning of next synodic month true anomaly will be ∠337.7°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
11 days after point of perigee on 9 January 2095 at 02:21 in ♒ Aquarius. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 4 days, until it get to the point of next apogee on 25 January 2095 at 03:56 in ♍ Virgo.
Moon is 397 104 km (246 749 mi) away from Earth on this date. Moon moves farther next 4 days until apogee, when Earth-Moon distance will reach 405 464 km (251 944 mi).
2 days after its ascending node on 17 January 2095 at 23:02 in ♊ Gemini, the Moon is following the northern part of its orbit for the next 11 days, until it will cross the ecliptic from North to South in descending node on 1 February 2095 at 11:53 in ♐ Sagittarius.
2 days after beginning of current draconic month in ♊ Gemini, the Moon is moving from the beginning to the first part of it.
1 day after previous North standstill on 19 January 2095 at 00:03 in ♋ Cancer, when Moon has reached northern declination of ∠24.116°. Next 12 days the lunar orbit moves southward to face South declination of ∠-24.164° in the next southern standstill on 2 February 2095 at 11:47 in ♑ Capricorn.
The Moon is in Full Moon geocentric opposition with the Sun on this date and this alignment forms Sun-Earth-Moon syzygy. | 0.860247 | 3.189353 |
KOUROU, French Guiana — More than 30 years after the Apollo astronauts walked on the Moon’s surface, a European space probe has been launched to investigate its far side in a mission that could finally answer questions about the origin of Earth’s closest neighbor.
The Ariane-5 spacecraft departs on 27 September 2003, carrying the Moon-bound Smart-1 mission.Smart 1, launched on board an Ariane 5 rocket from the Kourou spaceport in French Guiana on Saturday night (27 September), will map the far side of the Lunar surface, searching for signs of water ice in craters near its poles and gathering data on the chemical composition of its rocks.
The information will be used to test the “giant impact theory”, which suggests that the Moon was created in a collision between Earth and another object not long after our solar system formed.
“We think we know what the Moon is made of because the Apollo astronauts went there and brought back half a ton of rock samples. But they went to the Earth side, on the equator and on the flat bits,” said Professor Manuel Grande of the European Space Agency, who developed Smart 1 with the Swedish Space Corporation and contributions from 11 European countries.
“Those areas aren’t typical and, importantly, they’re not the ancient ones. What we need to do is a global survey of what the Moon is made of, and Smart 1 with our X-ray spectrometer will do that,” he said.
The giant impact theory suggests that an object roughly the size of Mars crashed into Earth 4.5 billion years ago, throwing up vast amounts of debris that then aggregated into the Moon.
The theory has been supported by the similar composition of Earth and Moon rocks, but the probe should find that the Moon contains less iron than Earth, compared with lighter elements such as magnesium and aluminum.
This theory, that the Moon’s core is less massive than the Earth’s, has also been used to explain the Moon’s orbit around the Earth, which is inclined by around 10 degrees relative to the equator. Most other planetary satellites in the solar system have orbital inclinations less than 1 or 2 degrees. By measuring the absolute amounts of these chemical elements comprehensively for the first time, Smart 1 might finally prove or disprove the theory.
The probe, which is about the size of a toaster, and cost just €110-million to develop, is being heralded as a test run for future, high-budget, European space missions.
It will map the Moon using a special x-ray camera developed in Oxfordshire. The photographs will be sent back to mission control where they can be compared to maps of the Earth’s mineral make-up.
As well as using new miniaturized instruments, the probe will test a novel, solar-electric propulsion system that uses a stream of charged ions to create thrust rather than conventional chemical engines.
Although considerably less powerful and slower than a chemical rocket, the ion propulsion system, whose energy comes from solar panels of the probe’s wings, is far more fuel-efficient, allowing the 370kg probe to cover the 385,000 kilometers to the Moon on just 60 liters of fuel.
Once the propulsion system is switched on for the first time tomorrow, it will take the probe 15 months to enter orbit above the Moon.
The Ariane 5 rocket also carried two research satellites from India and France.
The launch comes at a time of heightened public awareness of space exploration after the recent, damning report into safety lapses at NASA that contributed to the Columbia space shuttle crash that killed seven astronauts in February.
China has announced that it plans to launch its first manned mission to space within the next three months, although officials stress it will not be landing on the Moon.
China also confirmed recently that it had struck a deal to invest €230-million in the EU’s Galileo satellite tracking system. The network of 30 satellites is being developed at a total cost of €1.1-billion to provide an alternative to America’s global positioning system, which is favored by the Pentagon. | 0.854945 | 3.788329 |
Something rather bizarre was observed in the asteroid belt on January 6. Ray Villard at Discovery News has just posted an exciting article about the discovery of a comet… but it’s not your average, run-of-the-mill kinda comet. This comet appears to orbit the Sun, embedded in the asteroid belt.
Comets don’t usually do that, they tend to have elliptical and inclined orbits, orbits that carry them close to the Sun (when they start to heat up, creating an attractive cometary tail as volatile ices sublimate into space, producing a dusty vapor). They are then flung back out into the furthest reaches of the Solar System where the heating stops and the comet tail disappears until the next solar approach.
But P/2010 A2 — discovered by the Lincoln Near-Earth Asteroid Research (LINEAR) sky survey — has a circular orbit and it still appears to be venting something into space.
There is the possibility that it is a member of a very exclusive bunch of objects known as main belt comets (MBCs). MBCs are confused asteroid/comet hybrids that appear to spontaneously vent vapor and dust into space and yet stay confined to the asteroid belt. But, if P/2010 A2 is confirmed to be one of these, it will only be the fifth such object to be discovered.
So what else could it be? If the potential discovery of an MBC doesn’t excite you enough, it could be something else entirely: the dust produced by a hyper-velocity impact between two asteroids. If this is the case, it would be the first ever observation of an asteroid impact in the Solar System.
The asteroid belt isn’t the same asteroid belt you might see in science fiction; although there are countless rocky bodies in our asteroid belt, it is rare that these rocky bodies encounter each other. Space is very big, and although the density of asteroids in this region might be considered to be “high”, this is space we’re talking about, you can fly a spaceship through the region without having to worry that you’ll bump into something. The average distance between asteroids is huge, making it a very rare occurrence any two should hit. But given enough asteroids, and enough time, eventually asteroid collisions do happen. And in the case of P/2010 A2, we might have been lucky.
The chatter between comet/asteroid experts is increasing, and on one message board posting, Javier Licandro (Instituto de Astrofísica de Canarias, Spain) reports observing a secondary asteroid traveling with the cloud-like P/2010 A2.
“The asteroid moves in the same direction and at the same rate as the comet,” reports Licandro on The Minor Planet Mailing List. “In addition, the P/2010 A2 (LINEAR) image does not show any central condensation and looks like a ‘dust swarm’.”
“A short lived event, such as a collision, may have produced the observed dust ejecta.”
Therefore, this ‘comet’ may actually be the debris that was ejected after a collision between two asteroids. Although these are preliminary findings and it’s going to take some serious observing time to understand the true nature of P/2010 A2, it’s exciting to think that we may just have observed an incredibly rare event, 250 million miles away.
Source: Discovery News | 0.81444 | 3.852058 |
How about, every 12,000 years or so the Sun micro-nova's and the ensuing output blasts the Earth a bit farther away from the Sun.
Hey, Great post, thanks. I get the feeling that you might find this of interestI guess I'm a bit flummoxed by the title - The Sun is Getting Closer implies that the Earth's orbit is shrinking over time, when of course, it isn't.
Russian dynamicists Gregoriy A. Krasinsky and Victor A. Brumberg calculated, in 2004, that the sun and Earth are gradually moving apart. Not by a great deal – just 15 cm per year – but since that’s 100 times greater than the measurement error, something must really be pushing Earth outward. But what is the mechanism?
One idea is that the Sun is losing enough mass, via fusion and the solar wind, to gradually be losing its gravitational force (see Astronomical unit may need to be redefined) (𝐹 = 𝐺𝑀1𝑀2/𝑟2). Other possible explanations include a change in the gravitational constant G, the effects of cosmic expansion, and even the influence of dark matter. None of the latter have proved satisfactory.
Takaho Miura of Hirosaki University in Japan and three colleagues think they have the answer. In an article submitted to the European journal Astronomy & Astrophysics, they argue that the sun and Earth are literally pushing each other away due to their tidal interaction.
A similar process is gradually propelling the moon’s orbit outward: Tides raised by the moon in our oceans are gradually transferring Earth’s rotational energy to lunar motion. Consequently, each year, the moon’s orbit expands by about 4 cm and Earth’s rotation slows by 0.000017 second.
Likewise, Miura’s team assumes that our planet’s mass, and the mass of the inner two planets - Mercury and Venus, are raising a tiny but sustained tidal bulge in the sun. They calculate that, thanks to just the Earth, the sun’s rotation rate is slowing by 3 milliseconds per century (0.00003 second per year). According to their explanation, the distance between the Earth and sun is growing because the sun is losing its angular momentum.
Read more: https://www.newscientist.com/article/dn17228-why-is-the-earth-moving-away-from-the-sun/#ixzz6JA7ACDBS
Indeed, it's challenging to say the least. I've been absorbed in/by it for the past few months. Velikovsky was one of the pioneers in this area. Good sources here also https://suspicious0bservers.org/Sally -
I think I'm going to need some time to examine this man's credentials, digest this, and look into this so called synchronous process.
We measure a large amount of mass being accelerated from our star to well out pass Neptune. Continuously. Stars shine mass too. Think of the eons of stars. And if stars start out as hydrogen, then a side product is fission into isolated charge. The earth's shield protects us from fission products.
This has to have an effect on the strength of the star's gravity. According to all theory. And it decreases the density of free isolated charge in the star. The other particle ratios go up. Over time, this must have some effect.
First of all, attention must be paid to the proper terms. Are you describing coronal mass ejections when you state "large amount of mass being accelerated from our star to well out pass Neptune?" If so, this must be clearly elucidated. Are coronal mass ejections accelerated beyond Neptune? And, if so, what is the total mass of such an ejection vis a vis the total mass of the sun? Eons of stars are mentioned. An eon is the largest division of geologic time, comprising two or more eras, while in astronomy an eon is equated to one billion years. Are you describing a set of stars through a particular length of time or just a finite number of stars however large?
In any case, not all stars begin as pure hydrogen.
Stars may be classified by their heavy element abundance, which correlates with their age and the type of galaxy in which they are found.
Population I stars include the sun and tend to be luminous, hot and young, concentrated in the disks of spiral galaxies and are usually found in the spiral arms. With the currently accepted model of heavy element formation in supernovae explosions, the gas from which they formed had been seeded with the heavy elements formed from previous giant stellar explosions. About 2% of the total belong to Population I stars.
Population II stars tend to be found in globular clusters and the nucleus of a galaxy. They tend to be older, less luminous and cooler than Population I stars. They have fewer heavy elements, either by being older or being in regions where no heavy-element producing predecessors would normally be found. Astronomers often describe this condition by saying that they are "metal poor", and this coefficient of "metallicity " is used as an indication of stellar age. | 0.942137 | 3.42084 |
ZTF's high-cadence data stream will enable new investigations in a wide variety of fields. The ZTF survey will average more than 300 epoch each year over the entire Northern sky, giving nearly four times the number of exposures of SDSS Stripe 82 over 100 times the sky area. Public access to the ZTF data will provide a wide variety of community science, much unanticipated. Within the partnership, we have six working groups.
The ZTF Northern Sky Survey will be a transformative survey for the study of tidal disruption events (TDEs): outbursts from massive black holes found in the centers of galaxies caught in the act of feasting on an unlucky star that wanders close enough to the black hole to be ripped apart by tidal forces. ZTF is expected to increase the current census of TDEs by an order of magnitude, yielding 30 TDEs per year, some fraction of which will be discovered very early before peak, enabling prompt multiwavelength observations that can probe the geometry of the accreting stellar debris, constrain the mass of the central black hole powering the events, and look for evidence for the launching of outflows and jets.
Because the stellar density is at least a factor of 1000 higher in the Galactic Plane (known as the Milky Way which is visible as the milky strip across the night sky), previous surveys have avoided this area. But to study all the different kinds of stars, the Galactic Plane is the place to look, as that is where the majority of stars live out their lives. As an analogy: Observing stars outside the Galactic Plane is like trying to find a pretty Christmas tree in the desert. If you go to Oregon, there will be lots of them and some will be very unique. The same is true for stars inside the Galactic Plane vs. outside the Galactic Plane. Or another analogy: The galactic plane is largely unexplored, like the ocean, and that instead of only looking at other galaxies, it might be interesting to understand our own a bit more. ZTF is the first optical survey which will observe the visible part of the Galactic Plane every single night in two colors This survey will provide hundreds of observations in the Galactic Plane, an unprecedented dataset that will be analyzed by astronomers for decades. We expect to find millions of new variable stars with periods as short as a few minutes (white dwarfs) or as long as years (pulsating giant stars). We also expect rare objects where a normal star orbits a black hole or a neutron star.
Besides fantastic lightcurves we will get night-to-night variability information for every observed object and will see when objects change their brightness significantly within a single day. For example stars with masses about the half the mass of the sun show strong flares which are sudden flashes of increased brightness of the star similar to a solar flare but 100-1000 times stronger compared to the sun. Another possibility are so-called cataclysmic variables which are binary stars which transfer matter from a low mass companion star that is first accreted onto an accretion disc before it falls onto the more massive primary star. These accretion discs can become unstable and increase their brightness by a factor of 100-1000 within a few hours and come back to quiescence brightness within a few days. ZTF will find all of these. If we are lucky we could possibly witness the rare event when two stars come so close that they merge to form one massive, very dense star. Such a rare stellar merger event is seen due to a rapid brightness increase that takes place during the event.
Thermonuclear explosions of White Dwarf stars, Type Ia supernovae, can be used for accurate distance measurements throughout the Universe and were used to provide the first evidence for dark energy and the accelerated expansion of space-time. The Zwicky Transient Facility will find thousands of such supernovae at a key range where precision distances can be derived and explosion characteristics determined through spectroscopic follow-up. These supernova distances will be used to study how dark matter is distributed in the local universe, how the Milky Way is moving through the Universe and provide the basis for how to use supernovae to search for dark energy variability in the future. The enormous ZTF search volume will also allow the detection of rare supernovae that illuminates details of the detonation or are aligned such that we observe multiple copies of the same object through strong gravitational lensing.
ZTF should promptly and regularly detect bright, blue counterparts now shown to be associated with gravitational waves from neutron star mergers. ZTF is designed to pinpoint exactly which galaxy is the home of the merger among the hundreds of galaxies in the coarse localization by the gravitational wave interferometers. The ZTF localization will enable a quantification of how prolific are these cosmic mines of r-process nucleosynthesis responsible for half the elements in the periodic table heavier than iron. ZTF would quantify how much of the heavy elements (such as gold, platinum, neodymium) are synthesized in a neutron star merging with another neutron stars or a neutron star merging with a black hole.
ZTF will be a valuable tool to conduct a range of science for small bodies, such as detection of fast moving asteroids and/or low elongation objects, search of monolithic asteroids that rotate at a very high rate, and monitoring of outbursting comets.Asteroids that are very close to the Earth usually have high motion rates and leave streaks on typical survey exposures, presenting a challenge for any detection algorithm. ZTF will make use of a streak detection pipeline originally developed at IPAC/Caltech and tested for PTF to search for these fast moving asteroids. The twilight sky is difficult to observe but is known to contain a number of interesting phenomena. The ZTF twilight survey will make use of the twilight hours to repeatedly scan the small elongation region for incoming asteroids and comets from that direction.Most asteroids are gravitationally bounded “rubble-piles”. Rubble-pile asteroids cannot have rotation periods less than a critical limit. It has been found that a small number of asteroids have rotation periods shorter than this limit, implying that they may be monolithic. PTF had discovered 3 of 6 super-fast rotators (SFRs) known to date. With its large sky coverage and high cadence, ZTF can improve our knowledge of the SFR population. Comet outbursts can be spectacular, turning a modestly active comet into a naked eye objects. From Rosetta and Deep Impact we know that smaller outburst may occur daily. Larger outburst happens occasionally, but we do not know the frequency and intensity distribution. Many are caught by amateur astronomers. This will change with ZTF, which will pick up between 30 to 50 comets every time it scans the whole sky. Comets are found all over the sky, so we’re interested in seeing as many of them as we can, in as much detail as possible.
Why and how stars explode as SNe is poorly understood. Previous SN progenitor studies were limited to identifying progenitor stars in pre-explosion Hubble images, if available, or serendipitous spectroscopic observations of massive stars, like in the case of SN1987A?. Flash spectroscopy (Gal-Yam et al., 2014, Nature, 509) offers a new path to systematically study SN progenitors. The carbon copy of this novel technique is iPTF13dyq (SN2013fs), detected by the intermediate Palomar Transient Factory (iPTF) on 13 October 2013 (Yaron et al. 2017, Nature Physics, 13, 510). The short-cadence experiment of the iPTF survey detected this supernova a mere three hours after the massive star exploded. After the second epoch, obtained 50 minutes later, confirmed that the brightness of the transient is rapidly rising, follow-up observations were initiated around the world, with an orchestra of telescopes. About two hours later, the spectrum obtained with the spectrograph LRIS at the 10-m Keck telescope showed highly ionized oxygen and nitrogen recombination lines that vanished over the next 24 hours. Those lines are produced in the circumstellar material that was ionized by the SN shock break-out, before the SN ejecta swept up the circumstellar material. The modelling of the lines provided an unprecedented view on the distribution of material in the immediate environment of the exploding star. This offered a unique opportunity to examine the mass-loss history shortly before the star exploded and therefore information about the progenitor star. Today, only a handful of events have such precious data sets. The high-cadence experiment of the Zwicky Transient Facility will routinely detect such young supernovae and empower us to finally understand not only why but also how massive stars explode as supernovae.
The Andromeda galaxy is our nearest cosmic neighbor; only a few hundred kiloparsecs away. Due to its proximity and the fact that it hosts different stellar populations, including both young ones (in its spiral arms) and old ones (in its bulge), it is an ideal location for the hunt of varied kinds of variable stars and transient events.
As an example, given the sensitivity of ZTF (take R~21mag), at the distance of M31, you can easily track the pulsation of stars brighter than about -4mag---including those of Cepheids, and other giant stars. In fact, during this 3-day-all sky survey, you can look at one of the Cepheids (at Right Ascension of 11.29108 degrees and Declination of 41.50875 degrees) breathe. These stars are also representative of young stellar population, as they evolve from massive stars, and thus by following a (pre-identified) group of them pulsate, you can trace the relatively young parts of the galaxy. The wealth of variable phenomena that can be directly observed in this galaxy makes it a crucial testbed for many astrophysical stellar theories. Furthermore, "guest events" (otherwise invisible to ZTF) tend to easily pop up here, for example, it is likely you will be able to spot a thermonuclear flash from a white dwarf in a binary during the 3-day period. | 0.909445 | 3.972388 |
Video Credit & Copyright: Stéphane Vetter (Nuits sacrées); Music: Eric Aron
Why do some auroras pulsate? No one is sure. Although this unusual behavior has been known for a long time, the cause remains an active topic of research. Featured here is a dramatic video that captured some impressive pulsating auroras in mid-March over Svínafellsjökull Glacier in Iceland. The 48-second video is shown is not time-lapse. The real-time pulsations are exemplified by sequences where the astrophotographer is visible moving about in the foreground. A close inspection of the enigmatic flickering sky colors reveals that some structures appear to repeat, while others do not. The quick rapidity of the pulsations seen here is somewhat unusual -- more common are aurora with pulsations that last several seconds. Recent research shows that pulsations are more common in electron-generated aurora, rather than proton aurora, and that the Earth's local magnetic field may fluctuate in unison.
The Cat's Eye Nebula (NGC 6543) is one of the best known planetary nebulae in the sky. Its haunting symmetries are seen in the very central region of this stunning false-color picture, processed to reveal the enormous but extremely faint halo of gaseous material, over three light-years across, which surrounds the brighter, familiar planetary nebula. Made with data from the Nordic Optical Telescope in the Canary Islands, the composite picture shows extended emission from the nebula. Planetary nebulae have long been appreciated as a final phase in the life of a sun-like star. Only much more recently however, have some planetaries been found to have halos like this one, likely formed of material shrugged off during earlier active episodes in the star's evolution. While the planetary nebula phase is thought to last for around 10,000 years, astronomers estimate the age of the outer filamentary portions of this halo to be 50,000 to 90,000 years.
Have you ever hiked the Queen's Garden trail in Bryce Canyon, Utah, USA, planet Earth? Walking along that path in this dark night skyscape, you can almost imagine your journey continues along the pale, luminous Milky Way. Of course, the name for our galaxy, the Milky Way (in Latin, Via Lactea), does refer to its appearance as a milky band or path in the sky. In fact, the word galaxy itself derives from the Greek for milk. Visible on moonless nights from dark sky areas, though not so bright or quite so colorful as in this image, the glowing celestial band is due to the collective light of myriad stars along the plane of our galaxy, too faint to be distinguished individually. The diffuse starlight is cut by dark swaths of obscuring galactic dust clouds. Four hundred years ago, Galileo turned his telescope on the Milky Way and announced it to be "... a congeries of innumerable stars ..."
These three bright nebulae are often featured in telescopic tours of the constellation Sagittarius and the crowded starfields of the central Milky Way. In fact, 18th century cosmic tourist Charles Messier cataloged two of them; M8, the large nebula left of center, and colorful M20 on the right. The third, NGC 6559, is above M8, separated from the larger nebula by a dark dust lane. All three are stellar nurseries about five thousand light-years or so distant. The expansive M8, over a hundred light-years across, is also known as the Lagoon Nebula. M20's popular moniker is the Trifid. Glowing hydrogen gas creates the dominant red color of the emission nebulae, with contrasting blue hues, most striking in the Trifid, due to dust reflected starlight. This broad skyscape also includes one of Messier's open star clusters, M21, just above and right of the Trifid.
Credit: S. Guisard & Jose Francisco Salgado, ESO, Bulletpeople.com; Music: Arcadia (License: Kevin Macleod)
Why is the Earth moving in the above video? Most time lapse videos of the night sky show the stars and sky moving above a steady Earth. Here, however, the frames have been digitally rotated so that it is the stars that stay (approximately) steady, and the Earth that moves beneath them. The video dramatically shows the actual rotation of the Earth, called diurnal motion, in a clear and moving way, as if the camera were floating free in space. The telescopes featured in the video are the Very Large Telescopes (VLT) in Chile, a group of four of the largest optical telescopes deployed anywhere in the world. A discerning observer of the above time lapse movie may also note the use of laser guide stars, zodiacal light, the Large and Small Magellanic Clouds, and fast-moving, sunlight-reflecting, Earth-orbiting satellites. The original video, on which the above sequences are based, can be found here.
Is the heart and soul of our Galaxy located in Cassiopeia? Possibly not, but that is where two bright emission nebulas nicknamed Heart and Soul can be found. The Heart Nebula, officially dubbed IC 1805 and visible in the above right, has a shape in optical light reminiscent of a classical heart symbol. The above image, however, was taken in infrared light by the recently launched WISE telescope. Infrared light penetrates well inside the vast and complex bubbles created by newly formed stars in the interior of these two massive star forming regions. Studies of stars and dust like those found in the Heart and Soul Nebulas have focussed on how massive stars form and how they affect their environment. Light takes about 6,000 years to reach us from these nebulas, which together span roughly 300 light years.
Will Spirit be able to free itself from soft ground on Mars? The robotic Spirit rover currently rolling across Mars ran into unexpectedly soft ground last month while exploring the red planet. A worry is that the ground is so soft that Spirit won't be able to free itself, will have to stay put and thereafter study what it can from its current position near an unusual martian land feature named Home Plate. Pictured above, the front left wheel appears to be primarily digging itself in when spun, while on the other side, the front right wheel no longer spins and is dragged by the five year old mechanical explorer. In the distance, rocks and rusty dirt fill the alien landscape in front of the distant Husband Hill. NASA continues to study the situation, and engineers and scientists have not yet run out of ideas of how to use Spirit's six wheels. Far across Mars, Spirit's twin Opportunity continues on its two year trek toward Endeavour crater.
Ten Earths could easily fit in the "claw" of this seemingly solar monster. The monster, though, visible on the lower left, is a huge eruptive prominence seen moving out from our Sun. The above dramatic image taken early in the year 2000 by the Sun-orbiting SOHO satellite. This large prominence, though, is significant not only for its size, but its shape. The twisted figure eight shape indicates that a complex magnetic field threads through the emerging solar particles. Differential rotation inside the Sun might help account for the surface explosion. Although large prominences and energetic Coronal Mass Ejections (CMEs) are relatively rare, they are occurred more frequently near Solar Maximum, the time of peak sunspot and solar activity in the eleven-year solar cycle.
M65 is a big, beautiful spiral galaxy, the sixty-fifth object in the famous astronomical catalog compiled by 18th century cosmic tourist Charles Messier. It's also a member of a picturesque trio of large spiral galaxies known as the Leo Triplet, about 35 million light-years away. This sharp view of M65 shows off the galaxy in remarkable detail, with tightly wound spiral arms and dust lanes stretching into a core dominated by the yellowish light from an older population of stars. In fact, M65 seems to be the least disturbed of the Leo Trio, though it is close enough to be interacting gravitationally with the other two galaxies (not seen here). Very nearly edge-on to our line-of-sight, M65 is about 100,000 light-years across, similar in size to our Milky Way Galaxy.
NGC 6188 is an interstellar carnival of young blue stars, hot red gas, and cool dark dust. Located 4,000 light years away in the disk of our Galaxy, NGC 6188 is home to the Ara OB1 association, a group of bright young stars whose nucleus forms the open cluster NGC 6193. These stars are so bright that some of their blue light reflects off of interstellar dust forming the diffuse blue glow surrounding the stars in the above photograph. Open cluster NGC 6193 formed about three million years ago from the surrounding gas, and appears unusually rich in close binary stars. The red glow visible throughout the photograph arises from hydrogen gas heated by the bright stars in Ara OB1. The dark dust that blocks much of NGC 6188's light was likely formed in the outer atmospheres of cooler stars and in supernovae ejecta.
About 1,600 light-years away, in a binary star system fondly known as J0806, two dense white dwarf stars orbit each other once every 321 seconds. Interpreting x-ray data from the Chandra Observatory astronomers argue that the stars' already impressively short orbital period is steadily getting shorter as the stars spiral closer together. Even though they are separated by about 80,000 kilometers (the Earth-Moon distance is 400,000 kilometers) the two stars are therefore destined to merge. Depicted in this artist's vision, the death spiral of the remarkable J0806 system is a consequence of Einstein's theory of General Relativity that predicts the white dwarf stars will lose their orbital energy by generating gravity waves. In fact, J0806 could be one of the brightest sources of gravitational waves in our galaxy, directly detectable by future space-based gravity wave instruments.
Star formation occurs at a faster pace in M82 -- a galaxy with about ten times the rate of massive star birth (and death) compared to our Milky Way. Winds from massive stars and blasts from supernova explosions have created a billowing cloud of expanding gas from this remarkable starburst galaxy. The above scientifically color-coded image highlights the complexity and origin of the plume by combining a wide field image from the WIYN Telescope in Arizona with a smaller high-resolution image from the orbiting Hubble Space Telescope. M82's aspect in optical pictures has led to its popular moniker, the Cigar Galaxy. M82's burst of star formation was likely triggered a mere 100 million years ago in the latest of a series of bouts with neighboring large galaxy M81.
In the center of a swirling whirlpool of hot gas is likely a beast that has never been seen directly: a black hole. Studies of the bright light emitted by the swirling gas frequently indicate not only that a black hole is present, but also likely attributes. The gas surrounding GRO J1655-40, for example, has been found to display an unusual flickering at a rate of 450 times a second. Given a previous mass estimate for the central object of seven times the mass of our Sun, the rate of the fast flickering can be explained by a black hole that is rotating very rapidly. What physical mechanisms actually cause the flickering -- and a slower quasi-periodic oscillation (QPO) -- in accretion disks surrounding black holes and neutron stars remains a topic of much research.
The New General Catalog of star clusters and nebulae really isn't so new. In fact, it was published in 1888 - an attempt by J. L. E. Dreyer to consolidate the work of astronomers William, Caroline, and John Herschel along with others into a useful single, complete catalog of astronomical discoveries and measurements. Dreyer's work was successful and is still important today as this famous catalog continues to lend its "NGC" to bright clusters, galaxies, and nebulae. Take for example this star cluster known as NGC 2266 (item number 2,266 in the NGC compilation). It lies about 10,000 light-years distant in the constellation Gemini and represents an open or galactic cluster. With an age of about 1 billion years, NGC 2266 is old for a galactic cluster. Its evolved red giant stars are readily apparent in this gorgeous three-color image.
From September 2000 through March 2001, astronomer Tunc Tezel patiently photographed the planet Venus on 25 different dates as it wandered through the evening twilight. The pictures were taken from the same spot on the campus of the Middle East Technical University near Ankara, Turkey, and timed so that for each photo the Sun was 7 degrees below the horizon. Carefully registering and combining the pictures, he produced this composite image -- a stunning demonstration of Venus' grand looping sky motion during its recent stint as planet Earth's evening star. As indicated, the first picture, taken September 28, 2000, finds Venus close to the western horizon and drifting south (left) with the passing days. By December however, Venus was climbing well above the horizon after sunset and in January 2001 it reached its maximum apparent distance (elongation) from the Sun. March found Venus falling from the evening sky while moving rapidly north, finally appearing (far right) as a faint dot against the sunset glow on March 24. This month, Venus rises before dawn as the brilliant morning star.
A black hole is supposed to inexorably attract matter. But the intense radiation generated as material swirls and plunges into its high gravity field also heats up surrounding gas and drives it away. In fact, measurements made using this recent Chandra Observatory X-ray spectrum of active galaxy NGC 3783 reveal a wind of highly ionized atoms blowing away from the galaxy's suspected central black hole at a million miles per hour. Displayed in false color, the bright central spot is the X-ray image of NGC 3783 while the lines radiating away represent an X-ray spectrum of this source produced by Chandra's High Energy Transmission Grating (HETG). An X-ray spectrum is the analog to the rainbow spread of colors in a visible light spectrum. It represents a detailed, spread out image of X-ray colors or energies arising from the source. Ionized atoms of iron, magnesium, oxygen, nitrogen and other elements produce patterns of absorption at known X-ray energies. These patterns have been identified in the spectrum of NGC 3783 at slightly shifted energies and the measured shifts indicate the hot wind's velocity.
The deeper you peer into the universe, the harder it is to see straight. The reason is that distant galaxies act as gravitational lenses, deflecting light that passes nearby. These deflections result in the distortion of background sources, and in some cases the creation of multiple images. Pictured above, candidate artifacts of gravitational lensing have been found in images from the Medium Deep Survey being done with the Hubble Space Telescope. Background source images that are lensed by foreground galaxies include quasars, appearing as multiple blue smudges, and galaxies, distorted into curving arcs. Unusual and interesting candidates for gravitational lensing include an edge-on galaxy disk which might be acting as a lens (upper left) and an image nicknamed London Underground (far left) which could well be the distortion of a background galaxy into an optical Einstein ring.
An 11th magnitude quake has been recorded on the Sun, immediately following a moderate solar flare. The quake was the first ever recorded on the Sun, but only because astronomers have only recently figured out when and how to find them using the orbiting SOHO spacecraft. Dark waves from the quake can be seen in the above picture spreading out from an explosive bright flare. The solar ripples are similar in appearance to waves caused by a rock thrown into a pond. The magnitude and evolution of these quakes gives information about the physical nature of solar flares, the surface of the Sun, and even the Sun's interior.
Majestic on a truly cosmic scale, M100 is appropriately known as a Grand Design spiral galaxy. A large galaxy of over 100 billion or so stars with well defined spiral arms, it is similar to our own Milky Way. One of the brightest members of the Virgo Cluster of galaxies , M100 (alias NGC 4321) is 56 million light-years distant in the spring constellation of Coma Berenices. This Hubble Space Telescope image of the central region M100 revealing bright stars and intricate winding dust lanes was made in 1993 with the Wide Field and Planetary Camera 2. Studies of stars in M100 have recently played an important role in determining the size and age of the Universe.
In March and April of 1994 the unmanned Clementine spacecraft demonstrated the technique of prospecting on the Moon from lunar orbit. To accomplish this, Clementine turned an array of cameras sensitive to ultraviolet-visible and near-infrared light toward the lunar surface, producing the first broad-spectrum global imaging of the moon. Using this data, scientists were able to create the above map showing the concentration of iron in the lunar soils. The striking difference between the near (left) and farside (right) hemisphere's offers clues about the Moon's early history. | 0.941004 | 3.923433 |
But if the sun is darting like a comet through the galaxy and the planets are circling around the sun, what keeps the planets circling the sun in a consistent distance from it without flying off out of the solar system?Bruce did a model of the solar system based on RS scalar motion--NO GRAVITATIONAL FORCE in the model, at all. And sure enough, the planets look like they are in orbit!
A simple analogy... take two Deloreans and put them on a 1-lane road, 10 miles apart, so they are facing each other. Get each one going at 88 mph then shift into neutral. Each Delorean weights 2712 pounds. Calculate the gravitation force of attraction that is pulling them together, with eventual collision.
Now you should say "that's nonsense!" There is NO gravitational force pulling the Deloreans together--they are just moving at each other, at constant velocity. Well, that's all the planets are doing with the sun and each other.
As am I. Have you ever heard that the moon's light is cooler than the shadow it produces?Looking forward to the results.
Ok, I'm going to have to spend more time on this one. I still cannot get around the fact that the sun is way high in the sky, say 45 degrees to my left and then there is the moon way high in the sky 45 degrees to the right yet there may only be a small crescent of the moon exposed. I know that is basically what I said before but I'm having trouble with this one.It has to do with triangulation, not shadows. Take a flashlight and put it on the table, pointing at you. Hold a ball in your hand (the moon). Stand behind the ball from the flashlight... it is dark. Slowly move the ball around you and you will see the light from the flashlight lights it up, just like the phases of the moon. It only gets to be "full" just before it crosses into your shadow.
Ok, this makes a little more sense. I will read Beyond Newton and see if it clears it up for me.Gravity is just a 3D, inward scalar motion (read Beyond Newton: An Explanation of Gravitation by Larson). It originates from the 2D inward, magnetic motion coupled with the 1D electric motion. 2D + 1D is 3D... gravity is not an independent "force,"
Quite simply, I don't understand what you are saying here.Water always goes downhill... even if it is a billionth of an inch. The net, inward motion we call "gravity" is perpendicular to the surface of the Earth, all the way around, so it behaves as if it were flat.
Oh? What do you mean exactly?Unfortunately for the Flat Earthers, the "crack in the firmament" is in the "waters below," not above.
Ha, ok. Note to self.Polaris moves; just very slowly. Check its location in about 10,000 years, and you'll see what I mean.
Polaris has been studied and observed for over 10,000 years so wouldn't there be some sort of variance at this point? Our solar system would've moved through the galaxy some 1.7 trillion miles in the last 10,000 years. Surely that is enough to change our perspectives on not only Polaris but the constellations as well. However, they remain just as they were observed well over 10,000 years ago. Still not sure how this is possible.
Lucky for me, camping just like that is on the docket this summer so I will certainly be looking out for it.Go do some camping up in Wyoming, Montana or the Dakotas--"Big Sky country" and you'll see this every morning and evening. It only lasts a short time, as the sun's angle changes quickly (15 degrees an hour) and we've only got a 6-mile gap between the ground and cloud base. But I've even seen it throw chemtrail shadows UP to the clouds above... looks weird, like "black chemtrails."
Ok, thanks for that. This does seem like a flawed model for sure.Bruce did a model of it, using the precise data from the Flat Earth society for sizes and positions. As you can see in this snapshot, the little sun lights roughly 1/3rd of the path it follows. Draw a circle, half way between the center (Arctic) and rim (Antarctic), which would be the location of the equator--and you'll see the lit-up bit is roughly 1/3rd of the distance.
With all the bullsh*t, misinformation, disinformation and psy-ops out there, common sense is increasingly subjective and decreasingly objective.Not if you apply common sense and some basic geometry (which I've noticed seems to lack in most people these days).
100% agreed. No one has the full story. That's why forums like these are so important!Things aren't as we've been told, by mainstream science or Flat Earthers. | 0.895324 | 3.57257 |
The Satellite Path
The path to be followed by satellite (dotted line) does not change due to the fact that the satellite is falling and can be used to assess the trajectory of the object before and after possible fall. In the graph, each point marks the range of 1 minute.
Solar Flux and Other Variables
As much as the institutes and space agencies strive to provide correct data of the point where the space debris will fall, several factors may interfere with the accuracy of the prediction. Among the most important, the solar flux is the most critical because it determines the conditions of the upper atmosphere, increasing or decreasing the drag on the object.
Besides the solar flux acting on the aerodynamic characteristics, another variable rather difficult to be computed is the resistance of materials used in the construction of the object and the shape of the structure. Combined, these factors may determine different altitudes for the moment of rupture, causing errors of more than 30 km in altitude reentry provided.
Other variables that affect the calculation of reentry, although less important, are the gravitational perturbations of the Sun and Moon and also those exercised by large mountain ranges, above or below sea level.
The modeling used by Satview to compute the time of reentry uses solar flux data obtained at the time of modeling, and prediction of the behavior of the sun for the next 5 days. With this, the margin of error of prediction is + / - 3 revolutions for satellites or debris in uncontrolled reentry.
Altitude of Reentry
Spacecraft reentering the atmosphere without control usually break between 72 and 84 km altitude due to temperature and aerodynamic forces acting on the structure.
The nominal breakup altitude is 78 km, but big satellites that have larger and denser structures survive longer and break down at lower altitudes. Usually, solar panels are destroyed before any component, at altitudes between 90 and 95 km. | 0.801125 | 3.218443 |
Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at the Starfish Cluster, otherwise known as Messier 38. Enjoy!
During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.
One of these objects it the Starfish Cluster, also known as Messier 38 (or M38). This open star cluster is located in the direction of the northern Auriga constellation, along with the open star clusters M36 and M37. While not the brightest of the three, the location of the Starfish within the polygon formed by the brightest stars of Auriga makes it very easy to find.
Cruising around our Milky Way some 4200 light years from our solar system, this 220 million year old group of stars spreads itself across about 25 light years of space. If you’re using a telescope, you may have noticed its not alone… Messier 38 might very well be a binary star cluster! As Anil K. Pandey (et al) explained in a 2006 study:
“We present CCD photometry in a wide field around two open clusters, NGC 1912 and NGC 1907. The stellar surface density profiles indicate that the radii of the clusters NGC 1912 and NGC 1907 are 14′ and 6′ respectively. The core of the cluster NGC 1907 is found to be 1′.6±0′.3, whereas the core of the cluster NGC 1912 could not be defined due to its significant variation with the limiting magnitude. The clusters are situated at distances of 1400±100 pc (NGC 1912) and 1760±100 pc (NGC 1907), indicating that in spite of their close locations on the sky they may be formed in different parts of the Galaxy.”
So what’s happening here? Chances are, when you’re looking at M38, you’re looking at a star cluster that’s currently undergoing a real close encounter! Said M.R. de Oliveira (et al) said in their 2002 study:
“The possible physical relation between the closely projected open clusters NGC 1912 (M 38) and NGC 1907 is investigated. Previous studies suggested a physical pair based on similar distances, and the present study explores in more detail the possible interaction. Spatial velocities are derived from available radial velocities and proper motions, and the past orbital motions of the clusters are retrieved in a Galactic potential model. Detailed N-body simulations of their approach suggest that the clusters were born in different regions of the Galaxy and presently experience a fly-by.”
However, it was Sang Hyun Lee and See-Woo Lee who gave us the estimates of M38’s distance and age. As they wrote in their 1996 study, “UBV CCD Photometry of Open Cluster NGC 1907 and NGC 1912“: “The distance difference of the two clusters is 300pc and the age difference is 150 Myr. These results imply that the two clusters are not physically connected.”
So, how do we know they are two clusters passing in the night? The credit for that goes to de Oliveira and colleagues, who also asserted in their 2002 study:
“These simulations also shows that the faster the clusters approach the weaker the tidal debris in the bridge region, which explain why there is, apparently, no evidence of a material link between the clusters and why it should not be expected. It would be necessary to analyse deep wide field CCD photometry for a more conclusive result about the apparent absence of tidal link between the clusters.”
History of Observation:
This wonderful star cluster was originally discovered by Giovanni Batista Hodierna before 1654 and independently rediscovered by Le Gentil in 1749. However, it was Charles Messier’s catalog which brought it to attention:
“In the night of September 25 to 26, 1764, I have discovered a cluster of small stars in Auriga, near the star Sigma of that constellation, little distant from the two preceding clusters: this one is of square shape, and doesn’t contain any nebulosity, if one examines it with a good instrument: its extension may be 15 minutes of arc. I have determined its position: its right ascension was 78d 10′ 12″, and its declination 36d 11′ 51″ north.”
By correcting cataloging its position, M38 could later be studied by other astronomers who would also add their own notes. Caroline, then William Herschel would observe it, where the good Sir William would add to his private notes: “A cluster of scattered, pretty large [bright] stars of various magnitudes, of an irregular figure. It is in the Milky Way.”
Messier Object 38 would then later be added to the New General Catalog by John Herschel, who wasn’t particularly descriptive, either. However, there was an historic astronomer who was determined to examine this star cluster and it was Admiral Symth:
“A rich cluster of minute stars, on the Waggoner’s left thigh, of which a remarkable pair in the following are here estimated. A [mag] 7, yellow; and B 9, pale yellow; having a little companion about 25″ off in the sf [south following, SE] quarter. Messier discovered this in 1764, and described it as ‘a mass of stars of a square form without any nebulosity, extending to about 15′ of a degree;’ but it is singular that the palpable cruciform shape of the most clustering part did not attract his notice. It is an oblique cross, with a pair of large [bright] stars in each arm, and a conspicuous single one at the centre; the whole followed by a bright individual of the 7th magnitude. The very unusual shape of this cluster, recalls the sagacity of Sir William Herschel’s speculations upon the subject, and very much favours the idea of an attractive power lodged in the brightest part. For although the form be not globular, it is plainly to be seen that there is a tendency toward sphericity, by the swell of the dimensions as they draw near the most luminous place, denoting, as it were, a stream, or tide, of stars, setting toward the centre. As the stars in the same nebula must be very merely all at the same relative distance from us, and they appear to be about the same size [brightness], Sir William infers that their real magnitudes must be nearly equal. Granting, therefore, that these nebulae and clusters of stars are formed by their mutual attraction, he concludes that we may judge of their relative age, by the disposition of their component parts, those being the oldest which are the most compressed.”
Perhaps by taking his time and really observing, Smyth gained some insight into the true nature of M38! Observe it yourself, and see if you can also locate NGC 1907. It’s quite a pair!
Locating Messier 38:
Locating Messier 38 is relatively easy once you understand the constellation of Auriga. Looking roughly like a pentagon in shape, start by identifying the brightest of these stars – Capella. Due south of it is the second brightest star which shares its border with Beta Tauri, El Nath. By aiming binoculars at El Nath, go north about 1/3 the distance between the two and enjoy all the stars!
You will note two very conspicuous clusters of stars in this area, and so did Le Gentil in 1749. Binoculars will reveal the pair in the same field, as will telescopes using lowest power. The dimmest of these is the M38, and will appear vaguely cruciform in shape. At roughly 4200 light years away, larger aperture will be needed to resolve the 100 or so fainter members. About 2 1/2 degrees to the southeast (about a finger width) you will see the much brighter M36.
More easily resolved in binoculars and small scopes, this “jewel box” galactic cluster is quite young and about 100 light years closer. If you continue roughly on the same trajectory about another 4 degrees southeast you will find open cluster M37. This galactic cluster will appear almost nebula-like to binoculars and very small telescopes – but comes to perfect resolution with larger instruments.
While all three open star clusters make fine choices for moonlit or light polluted skies, remember that high sky light means less faint stars which can be resolved – robbing each cluster of some of its beauty. Messier 38 is faintest and northernmost of the trio and located almost in the center of the Auriga pentagon. Binoculars and small telescopes will easily spot its cross-shaped pattern.
And here are the quick facts on the Starfish Nebula to help you get started:
Object Name: Messier 38
Alternative Designations: M38, NGC 1912
Object Type: Galactic Open Star Cluster
Right Ascension: 05 : 28.4 (h:m)
Declination: +35 : 50 (deg:m)
Distance: 4.2 (kly)
Visual Brightness: 7.4 (mag)
Apparent Dimension: 21.0 (arc min)
We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects, , M1 – The Crab Nebula, M8 – The Lagoon Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons. | 0.861724 | 3.759465 |
About a month ago, a team of astronomers from different universities around the world discovered a bizarre dwarf galaxy, named Antlia 2 (or Ant 2), orbiting the Milky Way in the constellation Antlia.
Not only was Antlia 2’s enormous proportions atypical of a dwarf galaxy, but it was so dim and pale that it had gone undetected, until now – thanks to the European Space Agency’s Gaia satellite that provided the necessary data for the research team to sift through.
Antlia 2’s dimness, low density and the fact that it is hiding behind the Milky Way’s bright central disk are the reasons why it went undiscovered for as long as it did.
The relatively smaller size of most dwarf galaxies makes them defenseless against the gravitational forces of larger and more massive galaxies in their vicinity.
However, being larger than normal and the fact that it barely emits any light, Antlia 2 is kind of bizarre for a dwarf galaxy.
Researchers attribute Antlia 2’s low luminosity to the gravitational tides of the Milky Way.
Even though the Phantom galaxy is distant enough from the Milky Way to be ripped apart by its gravity, it does get influenced by the huge mass of the larger parent galaxy.
What the researchers have not been able to explain, though, is the disparity in Antlia 2’s mass and size.
With a relatively low mass, the ghost galaxy is vulnerable to the gravitational forces around it, because of which its size should have also been small, which is not the case – something the researchers have, so far, been unable to explain.
Under normal circumstances, the powerful forces of a much larger galaxy would cause the smaller galaxy to lose mass as well as condense, rather than grow.
For now, Antlia 2 may appear to be an “oddball” dwarf galaxy, but if researchers are able to locate more such galaxies, the oddity of Antlia 2 could possibly be better explained.
Parker Solar Probe
Earlier this year, NASA launched it’s $1.5 billion Parker Solar Probe on a seven-year mission that will take it deep into the sun’s atmosphere, the corona.
During this period, the instruments-loaded Parker will orbit the Sun 24 times, collecting important scientific data and beaming it back to earth.
If all goes well, researchers should have ample data by the end of the longish mission – not in space terms, though – to begin understanding the mysterious workings of our star, something that the scientific community has devoted decades towards.
Data such as 3-D images, electric and magnetic field recordings, and high-energy particle catalogs, to mention a few, will go a long way in helping them find long-elusive answers to most of their questions about the Sun and its corona.
It should, and probably will, enable scientists to safeguard spacecraft, astronauts, and sensitive ground equipment through improved space weather forecast, and much more, in times to come.
“It’s of fundamental importance for us to be able to predict this space weather, much like we predict weather here on Earth,” says NASA solar scientist Alex Young of the agency’s Goddard Space Flight Center in Maryland.
Not only is Parker expected to achieve record-breaking speeds of up to 450,000 miles per hour during the course of its multiple revolutions around the sun, it should also be able to get within 3.83 million miles of the star’s fiery surface – which is the closest it will get to it during its 7-year spin, creating yet another record.
The nearest that any spacecraft has ever got was a probe called Helios 2, which was able to make it to within 27 million miles, or 43 million kilometers, of the sun, way back in 1976.
2018 was another great year of photos and science on Mars for NASA’s nuclear-powered Curiosity rover, which was launched in 2011.
In June 2018, Curiosity found organic matter embedded in the sedimentary rocks of the three-billion-year-old Gale Crater on Mars, giving newfound impetus to the possibility that extraterrestrial life existed on the planet at some point in its past.
The organic molecules found in the ancient bedrock suggest that conditions back then may have been ideal to support some form of life, with a good chance that microorganisms once thrived on the red planet.
Despite numerous tests, researchers are unable to give a definitive reason for the formation of the organic matter, leaving open three main possibilities.
- The material had its origin elsewhere in the universe and was carried to Mars in a comet, or other such celestial bodies crashing into the Martian surface.
- They are the remnants of ancient organisms that lived on the planet billions of years ago.
- They are the by-products of chemical reactions that the rocks underwent over time.
Voyager 2 Entered Interstellar Space
NASA’s Voyager 2 spacecraft became the second human-made space plane to enter interstellar space after Voyager 1 achieved the feat in 2012.
Launched way back in in 1977, broke through the Sun’s heliopause and entered the void of interstellar space on Nov 5, 2018 – officially announced by the space agency on Dec 10.
While the heliopause is the boundary separating the Sun’s heliosphere from interstellar space, the heliosphere itself is a vast region surrounding the Sun that is dominated by its continuously expanding plasma known as the solar wind.
It is because of this solar wind that objects within this vast bubble of heliosphere, including Earth, are relatively better protected from the impact of galactic cosmic rays that are far more dominant beyond the heliopause – in interstellar space.
Voyager 2 is currently more than 11 billion miles from earth, getting farther and farther away as it hurtles through the interstellar void at 34,191 miles per hour (55,025 kph).
However, it is still 300 years short of entering the disc-shaped inner Oort cloud and another 30,000 years away from exiting the spherical outer Oort cloud, completely beyond the influence of the solar system.
Although more than a year has passed since a cigar-shaped asteroid came tumbling through our solar system, scientists learned a lot more about this interstellar intruder in 2018.
The cigar-shaped space rock was detected by astronomers at the Pan-STARRS 1 observatory in Hawaii, in Nov 2017, during a routine search of the skies for near-Earth objects on behalf of NASA.
The name Oumuamua is Hawaiian for a messenger from a distant past.
Studies based on the observations made during the 2017 flyby deemed it a strange interstellar object.
Rob Weryk, a postdoctoral researcher at the University of Hawaii Institute for Astronomy (IfA), said, “Its motion could not be explained using either a normal solar system asteroid or comet orbit.”
Further inspection of follow-up images from the European Space Agency’s telescope on Tenerife in the Canary Islands revealed that there was, indeed, something unusual about the object.
Estimated to be a quarter of a mile long, which is ten times its width, OUMUAMUA is dark reddish in color and elongated in shape, somewhat like a cigar, with no gas or dust surrounding it.
According to NASA, “Oumuamua is dense, comprised of rock and possibly metals, has no water or ice, and that its surface was reddened due to the effects of irradiation from cosmic rays over hundreds of millions of years.”
In November 2018, Harvard researchers submitted a paper that suggested Oumuamua could well be a fully operational probe sent to our solar system by some alien civilization.
However, many experts in the field are skeptical about the alien spacecraft theory, something that the authors of the paper, Avi Loeb, chairman of Harvard’s astronomy department, and Shmuel Bialy, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics were also not too sure of, calling it an “exotic scenario.” | 0.948616 | 3.92319 |
On March 14, the ExoMars mission successfully lifted off on a 7-month journey to the planet Mars but not without a little surprise. The Breeze-M upper booster stage, designed to give the craft its final kick toward Mars, exploded shortly after parting from the probe. Thankfully, it wasn’t close enough to damage the spacecraft.
Michel Denis, ExoMars flight director at the European Space Operations, Center in Darmstadt, Germany, said that the two craft were many kilometers apart at the time of the breakup, so the explosion wouldn’t have posed a risk. Still, the mission team won’t be 100% certain until all the science instruments are completely checked over in the coming weeks.
All went well during the takeoff and final separation of the probe, but then something odd happened. Breeze-M was supposed to separate cleanly into two pieces — the main body and a detachable fuel tank — and maneuver itself to a graveyard or “junk” orbit, where rockets and spacecraft are placed at the end of their useful lives, so they don’t cause trouble with operational satellites.
But instead of two pieces, tracking photos taken at the OASI Observatory in Brazil not long after the stage and probe separated show a cloud of debris, suggesting an explosion occurred that shattered the booster to pieces. There’s more to consider. Space probes intended to either land or be crashed into planets have to pass through strict sterilization procedures that rocket boosters aren’t subject to. Assuming the Breeze-M shrapnel didn’t make it to its graveyard orbit, there exists the possibility some of it might be heading for Mars. If any earthly bugs inhabit the remains, it could potentially lead to unwanted consequences on Mars.
And this isn’t the first time a Russian Breeze-M has blown up.
According to Russian space observer Anatoly Zak in a recent article in Popular Mechanics, a Breeze-M that delivered a Russian spy satellite into orbit last December exploded on January 16. Propellant in one of its fuel tanks may not have been properly vented into space; heated by the sun, the tank’s contents likely combusted and ripped the stage apart. A similar incident occurred in October 2012.
ExoMars is a joint venture between the European Space Agency (ESA) and the Russian Federal Space Agency (Roscosmos). One of the mission’s key goals is to follow up on the methane detection made by ESA’s Mars Express probe in 2004 to understand where the gas comes from. Mars’ atmosphere is 95% carbon dioxide with the remaining 5% divided among nitrogen, argon, oxygen and others including small amounts of methane, a gas that on Earth is produced largely by living creatures.
Scientists want to know how martian methane got into the atmosphere. Was it produced by biology or geology? Methane, unless it is continuously produced by a source, only survives in the Martian atmosphere for a few hundreds of years because it quickly breaks down to form water and carbon dioxide. Something is refilling the atmosphere with methane but what?
TGO will also look at potential sources of other trace gases such as volcanoes and map the planet’s surface. It can also detect buried water-ice deposits, which, along with locations identified as sources of the trace gases, could influence the choice of landing sites of future missions.
The orbiter will also act as a data relay for the second ExoMars mission — a rover and stationary surface science platform scheduled for launch in May 2018 and arriving in early 2019.
On October 16, when the spacecraft is still 559,000 miles (900,000 kilometers) from the Red Planet, the Schiaparelli lander will separate from the orbiter and three days later parachute down to the Martian surface. The orbiter will take measurements of the planet’s atmosphere (including methane) as well as any atmospheric electrical fields.
Mars is a popular place. There are currently five active orbiters there: two European (Mars Express and Mars Odyssey), two American (Mars Reconnaissance Orbiter and MAVEN), one Indian (Mars Orbiter Mission) and two rovers (Opportunity and Curiosity) with another lander and orbiter en route! | 0.809765 | 3.262985 |
TEHRAN, Young Journalists Club (YJC) -The interstellar object 'Oumuamua came from somewhere outside the solar system, but where has remained a mystery.
Scientists at the Max Planck Institute for Astronomy, however, have identified four stellar candidates from which the object may have originated.
Astronomers first spotted 'Oumuamua in 2017. Unfortunately, by the time scientists noticed the oblong visitor, it was already moving away from their telescopes, headed back to interstellar space.
Despite the brief visit, scientists were able to gather enough data related to 'Oumuamua's trajectory to retrace its journey through the Milky Way.
Previous attempts to retrace 'Oumuamua's path failed to account for the object's outgassing. Analysis of the interstellar object suggests 'Oumuamua features characteristics of both an asteroid and a comet. And like a comet, 'Oumuamua's ice was sublimated -- heated and turned to gas -- as it passed by the sun.
The outgassing process caused 'Oumuamua to accelerate slightly. The newest attempts to retrace the object's path were the first to account for this outgassing acceleration.
To determine where 'Oumuamua might have come from, astronomers also turned to stellar data collected by the Gaia mission. Scientists modeled the paths of both 'Oumuamua and thousands of stars, looking for crisscrossing trajectories.
Astronomers identified four stellar candidates moving at slow enough speeds. Fast-moving stars don't usually lose orbital control of large objects.
While all of the stars are plausible homes for 'Oumuamua, astronomers acknowledged they have yet to identify a smoking gun. They may be able to identify more candidates after Gaia's third data release, scheduled for 2021, which will feature a wealth of new data on stellar velocities.
Scientists have previously suggested the interstellar object was ejected from a binary star system, while others have argued 'Oumuamua was slung into interstellar space by interactions between giant planets.
"Ejection of 'Oumuamua by scattering from a giant planet in one of the systems is plausible, but requires a rather unlikely configuration to achieve the high velocities found," researchers wrote in their paper. "A binary star system is more likely to produce the observed velocities. None of the four home candidates have published exoplanets or are known to be binaries." | 0.870173 | 3.813705 |
You wouldn’t know it from the asteroid fields in Star Wars, but our asteroid belt is basically empty. If you flew a spaceship through the belt, the odds of crashing into an asteroid are pretty much zero. Plus, no giant space-slugs (we haven’t found them yet, anyway…).
The asteroid belt is huge. It extends from Mars’ orbit all the way to Jupiter, and just the main belt — where most of the asteroids are — has more than twice the surface area of the Solar System interior to Mars’ orbit. But add up all of the asteroids and you get less than a thousandth of Earth (about 0.05% of an Earth to be precise).
My new paper (published Sept 13 in Science Advances) proposes that asteroids are all refugees. They grew across the Solar System but were kicked out of their homes, left to travel the voids of space and finally settle in the asteroid belt.
To explain, I need to discuss how the Solar System formed. So let’s rewind the clock four and a half billion years, back to when the planets were forming from a swirling disk of gas and dust in orbit around the young Sun….
Given how near-empty the asteroid belt is right now, there are two ways to think about its origin. The first is to imagine that the belt once contained a lot more mass than it does now. Say, 1-2 Earth masses in rocky bodies. To arrive at the present-day Solar System, the vast majority of that mass must have been lost.
The second approach envisions an empty primordial asteroid belt. If the belt were born completely empty, then the challenge is to understand how the belt was populated. (Don’t worry, we’ll get to why it’s not crazy to imagine it was born empty.)
Let’s go through these two ideas.
Almost all previous work has focused on a massive primordial asteroid belt. This is the foundation of the “classical model” of rocky planet formation (see animation here). That model has a fatal flaw: it tends to produce gigantic Marses and over-populated asteroid belts (often with normal-sized Marses). There are some other issues, like the lack of planets that look like Mercury (see possible solution here). Here is a cartoon like the planetary systems generally produced by the classical model:
There are ways to rescue the classical model. The most successful to date is the Grand Tack, which proposes that Jupiter’s orbit shifted drastically after its growth. First, Jupiter “migrated” inward to close to Mars’ current orbit, then back outward to near its current orbit. In the process, the asteroid belt was mostly cleared and Mars’ growth was stunted. The model works quite well at matching the inner Solar System, although there are still some issues (see below).
The opposite end of the spectrum is to assume an empty primordial asteroid belt. Before we go any further the question on your mind is probably, why would the asteroid belt have been born empty? Planet-forming disks are mostly gas, which should be nice and smooth. Now remember: planets grow from dust, not gas. Here is a high-resolution image of a nearby disk that we think is forming planets as we speak:
This image only shows the dust (the gas distribution is smooth). As you can see, the dust is clumped into rings. There are gaps — belts — with less dust than the bright rings. This happens because dust grows and drifts through the disk. Asteroid-sized “planetesimals” form in dust pileups. This is a rich-get-richer process: the clumps make lots of planetesimals whereas the gaps can end up with none.
Back to the asteroid belt. It is entirely possible that dust piled up to form planetesimals in the Earth-Venus zone as well as the Jupiter-Saturn region but not in the asteroid belt. Some of the best models we have find exactly this. Punchline: the assumption of an empty primordial asteroid belt is actually not crazy.
Then where did the asteroids come from?
This is the distribution of asteroids in the present-day belt. Almost all of the mass is in the C-types and S-types, so let’s focus on them.
The S-types and C-types have very different chemical properties. The main difference is that the S-types are dry rocks whereas the C-types are rich in water, carbon and other volatiles. S- and C-types are so different that they kind of look like they came from completely different places (foreshadowing….)
In a previous post I explained how the C-types were implanted into the belt during Jupiter and Saturn’s growth. To summarize: planetesimals orbiting near the growing Jupiter and Saturn were gravitationally scattered across the Solar System. A fraction was implanted in the asteroid belt, preferentially in the outer parts. Another portion was launched past the asteroid belt and delivered water to the growing Earth. Here is an animation of the process — you can see Jupiter grow from 100-200 kyr (1kyr = 1000 years) and Saturn from 300-400 kyr.
Now come the S-types. The S-types may simply be leftovers from the inner parts of the Solar System. The terrestrial planets grew from planetesimals, and during the late phases of growth many planetesimals are kicked outward. They often end up on asteroid belt-crossing orbits but these are generally pretty stretched-out (elliptical). Some scattered bodies are transferred onto stable, more circular orbits by gravitational kicks from “rogue planetary embryos“, the Moon- to Mars-sized head honchos of rocky planet growth. Most rogue embryos are on their way to encountering Jupiter and being launched into interstellar space, but on their way out rogue embryos often kick some scattered planetesimals onto stable orbits.
Below is an animation of the implantation of S-types. Since this is a low-probability thing, I’ve combined 50 different simulations into one movie. So this movie shows 50 parallel universes at once! (The black circles are big planetary embryos and the red dots are planetesimals. The grey shaded area is the asteroid belt — you can see when planetesimals get trapped. The embryos at high-eccentricity above the belt are the “rogue embryos” I’ve been talking about.)
By this multiple scattering process, rocky planetesimals are trapped into the main asteroid belt with an efficiency of about 0.1% (1 in 1000). That seems awfully tiny, right? But remember that the asteroid belt is almost empty. The total mass in S-types is only a few hundred-thousandths of an Earth mass — about 0.004% of an Earth mass. And there were a few tenths of an Earth mass in planetesimals at this time. Our simulations usually implanted 3-10 times more S-types than there are today, starting from zero. Over the Solar System’s lifetime the belt has been depleted by about that much, so it’s a match.
Here is what it looks like when we put together the C-type and S-type stories:
This provides a good match to the real belt. S-types dominate the inner main belt and C-types the outer main belt.
This means that the asteroid belt would look like just it does today even if it formed completely empty! The S-types are implanted as byproducts of the growth of the terrestrial planets. Likewise, the C-types (as well as Earth’s water) are just splatter from the growth of the giant planets.
This means that asteroids can be thought of as refugees. They were born in a specific part of the Sun’s planet-forming disk. Then, during the growth of the planets they were kicked out, gravitationally launched into inter-planetary space. Finally, they were trapped onto stable orbits in the belt. The asteroid belt may be a cosmic refugee camp.
The implantation processes for S- and C-types are both very robust. In fact, they are each unavoidable, and simply byproducts of planet formation. S-types are implanted from the rocky planet region and C-types from the giant planet zone even if the asteroid belt was not born empty. No matter the Solar System’s formation history, there must be remnants of the Earth’s building blocks trapped in the asteroid belt, and also planetesimals from the Jupiter-Saturn region and beyond. Since different asteroids condensed across the Solar System, this means that we can explore our entire planetary system within the belt!
Where do we go from here? This is not the final solution to how the Solar System formed. The empty primordial asteroid belt model is on par with the Grand Tack model, which assumes a massive primordial asteroid belt. Each of these models does a good job matching the rocky planets and asteroid belt. And each has a weakness, a feature that, if disproven, would make the whole theory crumble like a pile of wooden blocks. For the Grand Tack model, the weakness is Jupiter’s outward migration. It is not clear whether Jupiter’s orbit really could have expanded from roughly Mars’ present-day orbit out to its current one (technical details here). For the empty primordial asteroid belt model, the weakness is the “empty” part. To get a handle on that we need to better understand how dust drifts and piles up to form planetesimals, and whether that process forms a gap like the one envisioned in this idea. We need to come up with tests to falsify these models, and keep our eyes out for new ones that work even better.
Questions, comments, words of wisdom?
Many thanks to my trusty coauthor Andre Izidoro! | 0.856047 | 3.766314 |
In yesterday’s Part I of this article I explained how there are potentially huge numbers of planets drifting through the cosmos, completely on their own, not orbiting a star. One term for these bodies, the one I’m using, is rogue planets.
Astronomers got their first inklings that these objects existed in the from computer simulations they performed in the 1970s. But it was not until 2000 that the first rogue planet was actually observed. Since then, astronomers have unintentionally found about 50 of these rogue planets. Most are very much like the planets we’re familiar with, have all the characteristics of planets here in our own solar system, they’re just not orbiting a star. Others, however raise questions about the very processes through which stars and planets can form. All of them, the familiar and the peculiar, challenge astronomers’ definitions of what exactly a planet is.
University of Hawaii in Honolulu’s Michael Liu, thinks it’s time we stopped finding and studying rogue planets by accident. He wants to start doing a systematic search for them. “A census of rogues,” says Liu, “is the only way we are going to fully understand the extent of what’s out there in the Milky Way.”
Liu and his colleagues first spotted rogue planet PSO J318.5-22 in 2010; but, wanting to confirm their finding first, they didn’t report the finding until 2013. The team wasn’t looking for rogue planets at the time. They were using the Maui-based Pan-STARRS 1 telescope, looking for failed stars called brown dwarfs. Brown dwarfs appear to start their lives in the same manner that stars do when clump of gas breaks free from a very large cloud of cold, dense gas. The break-away clump collapses, and begins pulling material into a swirling disk around it. At the disk’s center is a baby star, a brown dwarf.
But two traits distinguish brown dwarfs from other stars: mass and the absence of nuclear fusion. Even small stars, are still massive, at least 80 times the mass of Jupiter, and just to give you some scale: keep in mind that Jupiter, the most massive planet in our solar system, is 318 times the mass of Earth. It’s also a standard of measurement used by astronomers to describe the mass of large planets.
Theoretical calculations about how stars work, predict that objects must be at least 80 Jupiter masses to fuse hydrogen nuclei (protons) into helium. This is the process that allows stars to shine. Brown dwarfs on the other hand are not so lucky. They are smaller, anywhere between 13 and 80 Jupiter masses, and therefore not dense enough to fuse hydrogen. But that doesn’t mean they don’t burn. They do sometimes become big and hot enough to fuse deuterium nuclei (a proton plus a neutron) with protons or other nuclei.
Then there are the spheres that form into masses of less than about 13 Jupiter masses. They aren’t large or dense enough to fuse any kind of atomic nuclei, and so they are defined by some astronomers as planets, but without a star to orbit, and so they are: rogue planets. | 0.846062 | 3.935922 |
Evidence is mounting for an ocean at Pluto, buried beneath its frozen heart.
Scientists said Wednesday that Pluto may have rolled over on its axis eons ago, the result of tidal forces with jumbo moon Charon. The extra weight of an underground sea is the most likely explanation, they said.
These latest findings are based on observations by NASA's New Horizons, which made an unprecedented flyby of Pluto last year. The spacecraft is now 365 million miles from Pluto and enroute to a 2019 close approach of another faraway orb.
U.S. & World
Published in this week's journal Nature, the studies focus on a 600-mile basin in the left lobe of Pluto's heart-shaped region. This basin is known as Sputnik Planitia, named after the Russian satellite that launched the Space Age in 1957.
Sputnik Planitia is aligned with Pluto's tidal axis, so much so that it's unlikely to be coincidence, according to the researchers. More likely, the nitrogen ice-coated basin has extra mass — below the surface — to cause Pluto to reorient itself and have Sputnik Planitia on the opposite side of the dwarf planet as Charon.
"It's a big elliptical hole in the ground, so the extra weight must be hiding somewhere beneath the surface. And an ocean is a natural way to get that," lead author Francis Nimmo of the University of California, Santa Cruz, said in a statement.
Nimmo suspects the ocean is primarily water with some ammonia or other "antifreeze" thrown in. Slow refreezing of this ocean would conceivably crack the planet's shell — a scenario consistent with photos taken by New Horizons.
Subsurface oceans may also be on other similarly sized worlds orbiting in the Kuiper Belt, a so-called twilight zone on the fringes of our solar system, according to Nimmo.
"They may be equally interesting, not just frozen snowballs," he noted.
New Horizons is managed from Johns Hopkins University.
Close to the sun, meanwhile, Mercury has a big new valley. Scientists attribute surface buckling, caused by global contraction.
The valley is more than 600 miles long, 250 miles wide and 2 miles deep.
A research team led by Thomas Watters, a senior scientist at the Smithsonian Institution's National Air and Space Museum, discovered the valley from images taken by NASA's Messenger spacecraft. The spacecraft orbited Mercury for four years before crashing deliberately into the innermost planet last year.
Earth has experienced this type of buckling, involving both oceanic and continental plates, Watters said.
"But this may be the first evidence" of it on Mercury, he noted.
This Great Valley, as it's known, was revealed Wednesday. The study was published in Geophysical Research Letters, a journal of the American Geophysical Union. | 0.802128 | 3.667405 |
90 Million LY... in a galaxy known for it (3 in this picture from January)... while many of the other stars in Lynx are hundreds or thousands of LY. That's bright.
2008 January 18
Supernova Factory NGC 2770
Credit: A. de Ugarte Postigo (ESO) et al., Dark Cosmology Centre (NBI, KU),
Instituto de Astrofísica de Andalucía (CSIC), University of Hertfordshire
Explanation: The stellar explosions known as supernovae are among the most powerful events in the universe. Triggered by the collapsing core of a massive star or the nuclear demise of a white dwarf, supernovae occur in average spiral galaxies only about once every century. But the remarkable spiral galaxy NGC 2770 has lately produced more than its fair share. Two still bright supernovae and the location of a third, originally spotted in 1999 but now faded from view, are indicated in this image of the edge-on spiral. All three supernovae are now thought to be of the core-collapse variety, but the most recent of the trio, SN2008D, was first detected by the Swift satellite at more extreme energies as an X-ray flash (XRF) or possibly a low-energy version of a gamma-ray burst on January 9th. Located a mere 90 million light-years away in the northern constellation Lynx, NGC 2770 is now the closest galaxy known to host such a powerful supernova event.
Still cool. And there's a few other groovy astonomy stories in that issue it seems.
have pictures from the SWIFT team itself... if only thumbs.
On January 9, 2008, NASA's Swift observatory caught a bright X-ray burst from an exploding star. Carnegie-Princeton fellows Alicia Soderberg and Edo Berger were on hand to witness this first-of-its-kind event. A few days later, SN 2008D appeared in visible light.
Credit: Image courtesy NASA/Swift Science Team/Stefan Immler | 0.872086 | 3.386699 |
- Paper title: COSMIC TRAIN WRECK BY MASSIVE BLACK HOLES: DISCOVERY OF A KPC-SCALE TRIPLE ACTIVE GALACTIC NUCLEUS
- Authors: Xin Liu , Yue Shen, & Michael A. Strauss
- First author’s affiliation: Harvard-Smithsonian Center for Astrophysics
Fundamental to the field of cosmology is the question, “How did the structure that we see in the Universe come to be?” The commonly accepted answer to this question, at least for galaxy formation, is the hierarchical structure formation model, which says that galaxies are built up through a series of mergers with other galaxies. (This may seem obvious, but for a long time many astronomers were proponents of an opposing theory, known as “top-down structure formation“.) As mentioned in a number of previous astrobites, most massive galaxies are expected to host a supermassive black hole (SMBH) at their center. Thus, hierarchical structure formation predicts that in addition to galaxy mergers, there should be many systems of merging SMBHs in the Universe. In this paper, the authors describe the discovery of a triple system of SMBHs, and go on to derive several properties of the system, as well as an estimate of how many such systems there are.
Detections of merging SMBH systems are made primarily through searches for active galactic nuclei (AGN), because SMBHs are easiest to find (in optical searches) by looking for the characteristic emission lines that arise when they are accreting gas. In some cases, a third galaxy may join a merging pair on timescales short enough that the first interacting pair of SMBHs may not have coalesced, giving rise to a system of three gravitationally interacting SMBHs. Such systems have been suggested as the cause of certain trends noted in large galaxies, such as the large cores of some massive ellipticals (see e.g. Hoffman & Loeb, 2007). In addition, a triple system of SMBH would be a useful dynamic snapshot for investigating three-body interactions in General Relativity – a problem that cannot be solved analytically. However, there is currently little observation evidence for systems of gravitationally interacting SMBH, because their separations are on the order of parsecs, far too small to be resolved with current instruments on cosmic scales. Therefore, the authors of this paper are conducting a survey to investigate the next best thing: kpc-scale merging systems, which are the precursors to gravitationally interacting SMBH systems.
To conduct their search for AGN mergers, the authors use data from the Sloan Digital Sky Survey (SDSS). After selecting a sample of 92 AGN pairs with separations less than 10 kpc, the authors found 7 systems with a third nucleus candidate less than 10 kpc from the first two. In order to determine whether these systems contain three AGN, they conducted optical slit spectroscopy of all three nuclei. Of the 7 candidates they find one system, SDSS J1027+1749, that appears to clearly contain three AGN. The optical image of the system is shown in the figure below.
The authors then used the spectra of each nucleus in SDSS J1027+1749 (shown in the figure below) to determine several important features of the system. By fitting a galaxy template to the continuum (the first line of data in the figure below), they determined the redshift of the stellar component of each nucleus, which gives the projected separation of the AGN. These were all less than 3.0 kpc. The authors then subtract the continuum fit from the total spectrum, which leaves emission lines (the second line of data in the figure). Measuring the ratios of these lines shows that each nucleus is most likely an AGN (as opposed to a star-forming galaxy, for example). In addition, the authors use the velocity dispersions of the stars in the stellar component to compute the stellar mass and black hole mass of each nucleus. The velocity dispersions are computed by measuring the width of the absorption lines in the continuum fit.
Using dynamical friction timescale estimates, the authors conclude that the stellar components of the three nuclei in the system will merge in ~ 40 Myr, while the three SMBHs will inspiral and could become a gravitationally interacting triple in ~ 200 Myr. In addition, the authors use this result to calculate a lower limit for the frequency of kpc-scale triples in optically selected AGNs at a redshift of z ~ 0.1, which is Although it is based on only one system, this result is important because of its power to inform cosmologists about the rates and timescales of SMBH mergers, which can then be applied to cosmological models of structure formation. | 0.884421 | 4.167674 |
At right is a visual image of Sirius, the brightest star as seen from Earth, apart from the Sun.
An example of the differences between visual stellar classification and a possible X-ray classification is the disparity between the image of Sirius A [at above centre in the overexposed Hubble image] with the dim Sirius B [tiny dot at lower left]. [The cross-shaped diffraction spikes and concentric rings around Sirius A, and the small ring around Sirius B, are artifacts produced within the telescope's imaging system.] And, the lower image of the same two stars in X-rays.
This image shows two sources and a spike-like pattern due to the support structure for the transmission grating. The bright source is Sirius B, a white dwarf star that has a surface temperature of about 25,000 degrees Celsius which produces very low energy X-rays. The dim source at the position of Sirius A – a normal star more than twice as massive as the Sun – may be due to ultraviolet radiation from Sirius A leaking through the filter on the detector. In contrast, Sirius A is the brightest star in the northern sky when viewed with an optical telescope, while Sirius B is 10,000 times dimmer.
In the bottom image, Sirius B clearly outshines Sirius A. However, in the visual range the reverse is the case as shown in the top image. The surface effective temperature of Sirius A (spectral type A1V) is only 9,940±210 K, while that of Sirius B (a white dwarf, DA2) is 25,200 K. On the surface temperature of the photosphere alone, Sirius B would be a Class B star.
A variety of elemental violet lines occur in the star Sirius. These include calcium (Ca I & II), iron (Fe I), magnesium (Mg I & II), manganese (Mn I & II), nickel (Ni II), scandium (Sc II), silicon (Si II), strontium (Sr II), titanium (Ti II), vanadium (V II), yttrium (Y II), and zirconium (Zr II).
Around 150 AD, the Hellenistic astronomer Claudius Ptolemy described Sirius as reddish, along with five other stars, Betelgeuse, Antares, Aldebaran, Arcturus and Pollux, all of which are clearly of orange or red hue. The discrepancy was first noted by amateur astronomer Thomas Barker, ... who prepared a paper and spoke at a meeting of the Royal Society in London in 1760. The existence of other stars changing in brightness gave credence to the idea that some may change in colour too; Sir John Herschel noted this in 1839, possibly influenced by witnessing Eta Carinae two years earlier. Thomas Jefferson Jackson See resurrected discussion on red Sirius with the publication of several papers in 1892, and a final summary in 1926. He cited not only Ptolemy but also the poet Aratus, the orator Cicero, and general Germanicus as colouring the star red, though acknowledging that none of the latter three authors were astronomers, the last two merely translating Aratus' poem Phaenomena. Seneca, too, had described Sirius as being of a deeper red colour than Mars. However, not all ancient observers saw Sirius as red. The 1st century AD poet Marcus Manilius described it as "sea-blue", as did the 4th century Avienus. It is the standard star for the color white in ancient China, and multiple records from the 2nd century BC up to the 7th century AD all describe Sirius as white in hue.
In 1985, German astronomers Wolfhard Schlosser and Werner Bergmann published an account of an 8th century Lombardic manuscript, which contains De cursu stellarum ratio by St. Gregory of Tours. The Latin text taught readers how to determine the times of nighttime prayers from positions of the stars, and Sirius is described within as rubeola — "reddish". The authors proposed this was further evidence Sirius B had been a red giant at the time.
Although IK Tauri is far below naked eye visibility even at maximum brightness, due to the low temperature and strong extinction at visual wavelengths, in the infrared, it is brighter than prominent stars such as Rigel (K-band magnitude +0.18) and comparable to Sirius (K-band magnitude −1.35).
Both Al I absorption lines at 394.401±8.5 and 396.152±6.5 have been measured for Sirius.
The chemistry of vanadium includes four adjacent oxidation states 2-5. In aqueous solution the colours are lilac V2+(aq), green V3+(aq), blue VO2+(aq) and, at high pH, yellow VO42-.
Vanadium (V II) has an absorption band, 392.973-403.678 nm, with an excitation potential range of 1.07-1.81 eV.
Chromium has absorption lines that occur at 425.435-428.972 nm from Cr I and 400.333-428.421 nm, 3.09-6.46 eV from Cr II near Sirius.
Manganese (Mn I) has two absorption bands at 403.449±1.4 nm and 405.554±0.8 nm, where the second has an excitation potential of 2.13 eV.
Manganese (Mn II) has an absorption band at 420.638±0.8 nm with an excitation potential of 5.37 eV.
It was not until 31 January 1862 that Alvan Graham Clark observed a previously unseen star close to Sirius, later identified as the predicted companion. Walter Adams announced in 1915 that he had found the spectrum of Sirius B to be similar to that of Sirius.
In the drawing on the right, "Sinuosités observées dans le mouvement propre de Sirius."
On the left is a diagram of the proper motion of Sirius against the background stars.
For locating Sirius use a line through the three stars in Orion's belt to the left into Canis Major per the image on the right.
On the right is a spatial representation of every star within 14 light-years of Sol. There are 32 known stars in this region, including Sol. The stars are coloured according to the spectral type, which may not reflect the actual colour. Please see this Wikipedia article for the listing of stars. If a star is double or triple the stars are shown stacked vertically: the actual position is the star closest to the centre plane. The stars on this map may not all be visible to the naked eye, as many are dwarf stars. Some of this information may be preliminary and not entirely accurate as a result. The coordinate system is right ascension and declination. Hours of RA are marked, as well as distance in multiples of 5 light-years.
- Adelman, Saul J. (July 8, 2004). The Physical Properties of normal A stars. Poprad, Slovakia: Cambridge University Press. pp. 1–11. Bibcode:2004IAUS..224....1A.
- Liebert, J.; Young, P. A.; Arnett, D.; Holberg, J. B.; Williams, K. A. (2005). "The Age and Progenitor Mass of Sirius B". The Astrophysical Journal 630 (1): L69–L72. doi:10.1086/462419.
- Kozo Sadakane and Minoru Ueta (August 1989). "Abundance Analysis of Sirius in the Blue-Violet Region". Publications of the Astronomical Society of Japan 41 (2): 279-88.
- J.B. Holberg (2007). Sirius: Brightest Diamond in the Night Sky. Chichester, UK: Praxis Publishing. ISBN 0-387-48941-X.
- R. C. Ceragioli (1995). "The Debate Concerning 'Red' Sirius". Journal for the History of Astronomy 26 (3): 187–226.
- Whittet, D. C. B. (1999). "A physical interpretation of the 'red Sirius' anomaly". Monthly Notices of the Royal Astronomical Society 310 (2): 355–359. doi:10.1046/j.1365-8711.1999.02975.x.
- 江晓原 (1992). "中国古籍中天狼星颜色之记载" (in Chinese). Ť文学报 33 (4).
- Jiang, Xiao-Yuan (April 1993). "The colour of Sirius as recorded in ancient Chinese texts". Chinese Astronomy and Astrophysics 17 (2): 223–8. doi:10.1016/0275-1062(93)90073-X.
- Schlosser, W.; Bergmann, W. (November 1985). "An early-medieval account on the red colour of Sirius and its astrophysical implications". Nature 318 (318): 45–6. doi:10.1038/318045a0.
- Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues 2237: 0.
- Gobrecht, D.; Cherchneff, I.; Sarangi, A.; Plane, J. M. C.; Bromley, S. T. (2016). "Dust formation in the oxygen-rich AGB star IK Tauri". Astronomy & Astrophysics 585: A6. doi:10.1051/0004-6361/201425363.
- Camille Flammarion (1877). "The Companion of Sirius". Astronomical register 15: 186.
- W. S. Adams (1915). "The Spectrum of the Companion of Sirius". Publications of the Astronomical Society of the Pacific 27: 236. doi:10.1086/122440.
- The One Hundred Nearest Star Systems. RECONS. 2008-01-01. Retrieved 2008-12-08.
- Holberg, J. B.; Oswalt, Terry D.; Sion, E. M. (May 2002). "A Determination of the Local Density of White Dwarf Stars". The Astrophysical Journal 571 (1): 512–518. doi:10.1086/339842.
- Flammarion C., Les étoiles et les curiosités du ciel, supplément de " l’Astronomie populaire ", Marpon et Flammarion, 1882 | 0.827089 | 3.996664 |
June 5, 2019: On June 30, 1908, in broad daylight, a meteoroid hurtled out of the blue sky over Russia’s Tunguska river and exploded, leveling a forest. The event, which researchers are still studying today, kickstarting a new field of astronomy: Daytime meteor showers1.
Most people don’t know it, but some of the strongest meteor showers of the year happen when the sun is up. In fact, one of them is underway now. Today’s sky map from Canada’s Meteor Orbit Radar (CMOR) in western Ontario shows a hot spot in the constellation Aries only 20 degrees from the sun.
“These are Arietid meteors, and they peak every year in early June as Earth passes through a debris stream linked to the unusual comet 96P/Machholz,” says professor Peter Brown of the University of Western Ontario. “At their peak on June 7th, we expect our radar to detect one Arietid every 20 seconds. This makes them the 5th strongest radar shower of the year.”
In fact, people can see daylight meteors–a few at least. The trick is to look just before dawn when the shower’s radiant is barely above the horizon and the sun is barely below.
“The Arietids an observer would see before dawn are quite impressive as they are all Earthgrazers, skimming the atmosphere almost horizontally overhead,” notes Brown. “Earthgrazers tend to be slow and very bright.”
It turns out that June is the best month of the year for daytime meteor showers. When the Arietids subside, another daytime shower will take over: The zeta Perseids peak on June 13th. And then another: The beta Taurids on June 29th.
The beta Taurids are particularly interesting because researchers suspect it may be responsible for the Tunguska explosion of 1908. This June the Taurid debris swarm will make its closest approach to Earth since 1975. Many astronomers, including Brown, will use large telescopes to search for signs of hazardous objects as the swarm passes by.
Stay tuned for updates.
End note: (1) Tunguska was a dramatic example of a daytime meteor. It took 30+ years after the explosion, however, for the field of daytime meteor studies to gain its footing. Brown explains: “The first daytime showers were observed and recognized by astronomers at Jodrell Bank shortly after World War II, really kickstarting the field. As early as 1940, studies of the orbit of the nighttime Taurids suggested the stream should intersect the Earth during the day in June. At that time, predictions were made by Fred Whipple of a daytime component to the Taurid stream in June (the Beta Taurids/Zeta Perseids). In the 1970s, the peak date for the Beta Taurids (about June 30) and the radiant location were matched by Lubor Kresak to the Tunguska fireball–at which time he posited a link between the Beta Taurids and Tunguska.” | 0.836396 | 3.791291 |
The next Mars mission is GO! Nasa will drill deep beneath the red planet's crust for the first time to reveal its hidden secrets
- Construction of Nasa's next mission to Mars, InSight, has been approved
- The mission will launch in March 2016 and arrive in September 2016
- It will be the first lander to drill deep beneath the surface of Mars
- This will provide information on how rocky terrestrial planets form
- The mission is a global endeavour including input from the UK and France
Mars has been roved across, dug into and drilled by various rovers - but so far no machine has delved very deep beneath the surface.
That's all set to change in September 2016, when Nasa's newest mission to the red planet - InSight - will arrive.
The spacecraft completed a successful Mission Critical Design Review last Friday - and Nasa and its international partners have now given the go-ahead for construction of the lander.
NASA's Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport (InSight) mission will pierce deep beneath the Martian surface to study its interior for the first time. The launch is scheduled for March 2016 with arrival at the red planet set for September that year
Nasa’s Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport (InSight) mission will pierce beneath the Martian surface to study its interior.
KEY MISSIONS TO MARS
The first spacecraft to successfully fly by Mars was Nasa's Mariner 4 in 1967, after several failed attempts by the Soviet Union.
But the Soviet Union's Mars 3 probe was the first to successfully land on the surface, on 2 December 1971.
Next, in the latter half of 1976, Nasa's Viking landers touched down on the surface and performed the first search for life on Mars - with results being inconclusive.
The first rover on Mars was Sojourner, carried by Mars Pathfinder, which landed on 27 September 1997.
This was followed by the hugely successful Spirit and Opportunity rovers in 2004, the latter of which is still operational today.
Nasa's Curiosity rover is also still currently hard at work on the surface.
Later this year two new orbiting spacecraft will arrive at Mars, India's Mangalyaan (their first mission to Mars) and Nasa's Maven.
After Insight in 2016, Esa will land a rover called ExoMars on the surface in 2018.
This will be followed by an as yet unnamed Nasa rover similar to Curiosity but with different instruments in 2020.
The mission will investigate how terrestrial rocky planets like Earth formed and developed their layered inner structure of core, mantle and crust.
It will also collect information about those interior zones using instruments that have never been used before on Mars.
InSight will launch from Vandenberg Air Force Base, on the central California coast near Lompoc, in March 2016.
This will be the first interplanetary mission ever to launch from California.
The mission will help inform the agency’s goal of sending a human mission to Mars in the 2030s.
InSight team leaders presented mission-design results last week to a NASA review board, which approved advancing to the next stage of preparation.
The next step will be to begin integrating the various bits of hardware with computer systems, which will begin in November.
'We now move from doing the design and analysis to building and testing the hardware and software that will get us to Mars and collect the science that we need to achieve mission success,' said Tom Hoffman, InSight Project Manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, in a release statement.
Scientists think that by studying the interior of Mars (shown in this illustration) they will have a better understanding of how terrestrial rocky plants like Earth can form. InSight will be capable of drilling up to 15 feet (4.5 metres) beneath the surface and could provide this information
To investigate the planet's interior, the stationary lander will carry a robotic arm that will deploy surface and burrowing instruments contributed by France and Germany.
The national space agencies of France and Germany - Centre National d’Etudes Spatiales (CNES) and Deutsches Zentrum für Luft- und Raumfahrt (DLR) - are partnering with Nasa by providing InSight's two main science instruments.
The Seismic Experiment for Interior Structure (SEIS) will be built by CNES in partnership with DLR and the space agencies of Switzerland and the United Kingdom.
It will measure waves of ground motion carried through the interior of the planet, from 'marsquakes' and meteor impacts.
The Heat Flow and Physical Properties Package, from DLR, will measure heat coming toward the surface from the planet's interior.
'Mars actually offers an advantage over Earth itself for understanding how habitable planetary surfaces can form,' said Bruce Banerdt, InSight Principal Investigator from JPL.
'Both planets underwent the same early processes. But Mars, being smaller, cooled faster and became less active while Earth kept churning.
'So Mars better preserves the evidence about the early stages of rocky planets' development.'
InSight will have a number of instruments designed by agencies across the globe. Germany and France, for example, will be helping to design a seismic experiment that can measure waves of ground motion carried through the interior of the planet
The three-legged InSight lander will go to a site near the Martian equator and provide information for a planned mission length of 720 days - about two years.
InSight adapts a design from the successful NASA Phoenix Mars Lander, which examined ice and soil on far-northern Mars in 2008.
'We will incorporate many features from our Phoenix spacecraft into InSight, but the differences between the missions require some differences in the InSight spacecraft,' said InSight Program Manager Stu Spath of Lockheed Martin Space Systems Company, Denver, Colorado.
'For example, the InSight mission duration is 630 days longer than Phoenix, which means the lander will have to endure a wider range of environmental conditions on the surface.'
Guided by images of the surroundings taken by the lander, InSight's robotic arm will place the seismometer on the surface and then place a protective covering over it to minimize effects of wind and temperature on the sensitive instrument.
The arm will also put the heat-flow probe in position to hammer itself into the ground to a depth of 9 to 15 feet (2.7 to 4.5 metres).
Another experiment will use the radio link between InSight and NASA's Deep Space Network antennas on Earth to precisely measure a wobble in Mars' rotation that could reveal whether it has a molten or solid core.
Wind and temperature sensors from Spain's Centro de Astrobiologia and a pressure sensor will monitor weather at the landing site, and a magnetometer will measure magnetic disturbances caused by the Martian ionosphere.
Most watched News videos
- 'Daddy changed the world' cheers George Floyd's daughter
- Boris Johnson slams fist as he tries to rebuke attacks from Starmer
- Tensions flare as a group of men fight on a London street
- Shocking moment passenger calls taxi driver a 'Muslim c***'
- Alok Sharma appears to fall ill during House of Commons address
- Optical illusion makes it look like PM is wearing an earpiece
- Former police captain seen wounded on ground near St Louis store
- Police sweep scene in Harlesden after four people shot dead
- Woman shows off 'looted' clothing after allegedly starting riot
- California man pulls assault rifle on George Floyd protesters
- Rudy Giuliani clashes with Piers Morgan as he defends Donald Trump
- Crowd jeers as police officer knocked to the ground during protest | 0.821667 | 3.052517 |
Mars has fascinated us for millennia. Almost from the time astronomers first turned their telescopes on the planet shining in the night sky, we've imagined life there. Unlike our other planetary neighbor, Venus, which remains shrouded in cloudy mystery, the red planet has invited speculation and exploration. Since the 1960s, the U.S. and the Soviet Union and, later, Russia and Japan, have launched spacecraft destined to land on or orbit Mars.
The successful missions, like the very first Mars flyby in 1964 by the U.S. Mariner 4, have provided a treasure trove of data and, of course, introduced many new questions. Recently, those data, provided compliments of spacecraft such as the Phoenix Mars Lander, the Curiosity rover, and the Mars Reconnaissance Orbiter, have been arriving at Earth at a dizzying rate. It seems like a golden age for Mars exploration has arrived.
Here's what we've learned about the fourth planet from the sun while orbiting it, landing on it and sampling its contents: It's cold, dusty and dry, but that probably wasn't always the case. Ample data seem to point toward liquid water rushing over its surface in the form of lakes, rivers and an ocean at some undetermined point in the past. Traces of methane have been detected in the atmosphere, but its source is unknown. On Earth, much of the methane is produced by living organisms, like cows, which could bode well for the possibility of life on Mars. On the other hand, the gas could also have nonbiological origins, such as the Martian volcanoes.
One thing we do know: Humans won't be walking on Mars anytime soon. All manner of robots will have cruised its dusty surface long before we do. The next best thing to exploring Mars is reading about it, right? So get ready to launch into the fascinating world of the red planet. How did it form? What's the weather like? And most important, has water or life ever existed on Mars?
As you can see from the accompanying image, Mars has few distinguishing features when viewed from Earth, even with the best telescopes. There are dark and light areas, as well as polar ice caps, but certainly not the clear features that you can see in images from orbiters around Mars. Therefore, we can excuse early astronomers for making mistakes or embellishing their observations. To these scientists searching the sky, Mars was a vastly different world than we know today.
In 1877, Giovanni Schiaparelli, an Italian astronomer, became the first person to map Mars. His sketch showed a system of streaks or channels, which he called canali. In 1910, the U.S. astronomer Percival Lowell made observations of Mars and wrote a book. In his book, Lowell described Mars as a dying planet where the civilizations built an extensive network of canals to distribute water from the polar regions to bands of cultivated vegetation along their banks.
Although Lowell's book captured the public's imagination, the scientific community summarily dismissed it because his observations weren't confirmed. Nevertheless, Lowell's writings sparked generations of science fiction writers. Edgar Rice Burroughs of Tarzan fame wrote several novels about Martian societies, including "The Princess of Mars," "The Gods of Mars" and "The Warlord of Mars." H.G. Wells wrote "The War of the Worlds" about invaders from Mars (Orson Welles' radio play of this book caused a national panic in 1938).
Hollywood has also fueled the public's fascination with the planet in films such as "The Angry Red Planet," "Invaders from Mars" and, more recently, "Mission to Mars," two versions of "Total Recall," and a live-action version of Burroughs' titular hero in "John Carter."
In the 1960s and 1970s, however, the American Mariner, Mars and Viking missions started sending back images of a world very different from that described by Lowell and his literary and silver-screen successors. The photos, snapped during flybys of the planet and eventually during the Viking landings, showed Mars as a dry, barren, lifeless world with variable weather that often included massive dust storms that could whip across a majority of the planet. So with thousands of photos as evidence, Mars was confirmed as a desert planet with rocks and boulders, rather than the home of irritable Martians and man-eating plants a la "The Angry Red Planet."
Now, we have extensively mapped the planet with Mars Global Surveyor, sent rovers to bump over its surface and scoop up soil samples, and launched orbiters to observe the planet from space. More missions are in the works. NASA and the European Space Agency (ESA) have committed to continued robotic and possibly human exploration of Mars.
So far these missions have enabled scientists to hazard a theory about how the red planet formed, and the story would actually make a pretty good movie. Read on to learn how solar system collisions gave Earth its next-door neighbor.
The Origins of Mars
Unfortunately, no human geologist has been to Mars. So the best information that we have about the planet's beginnings 4.6 billion years ago comes from images taken by orbiters and landers, Martian meteorites, and comparisons with its planetary peers (Mercury, Venus, Earth and Earth's moon). The current theory goes like this:
- Mars formed from clumping or accretion of small objects in the early solar system.
- However, unlike Earth and Venus, Mars finished forming within 2-4 million years and never grew beyond the planetary embryo stage.
- Possibly, aluminum 26 decay turned the planet into a magma ocean.
- After cooling, there was a period of intense bombardment from meteors.
- The hot mantle pushed through and lifted portions of the crust.
- One or more periods of intense volcanic activity and lava flows followed.
- The planet cooled and the atmosphere thinned.
Let's look at these steps in more detail.
Mars was created by the accretion of small objects in the early solar system, which took about 2-4 million years. Mars grew and developed a larger gravity field, which attracted more bodies. These bodies would fall into Mars, impact and generate heat. Some models suggest that such heating would not have been enough to bring about large-scale melting on Mars; rather, because the planet formed so quickly, it might have gobbled up enough of the aluminum 26 nuclide, which has a half-life of only 717,000 years, to melt from radioactive decay. Gradually, the material sorted itself out into a core, mantle and crust. Gases released from the cooling formed a primitive atmosphere [source: Dauphas and Pourmand].
But as an embryo planet formed in the solar system's chaotic early days, Mars couldn't catch a break. It was heavily bombarded by meteors in the inner solar system. These bombardments produced craters and multi-ring basins all over the planet, like the 1,400-mile- (2,300-kilometer-) wide Hellas Planitia impact crater in the planet's southern hemisphere. Some geologists think that a huge impact occurred that thinned the crust of the northern hemisphere. Similar impacts occurred on Earth and our moon at this same time. On Earth, the craters were eroded by wind and water. On the moon, the evidence of these great collisions is still visible.
Now imagine Mars is a soft-boiled egg; the inside is hot as the shell cools. If the shell is weak in spots, the egg will crack and the cooked yolk will protrude. A similar occurrence happened with the Tharsis region, a continent-sized land mass in the southern hemisphere. The hot mantle bulged out, pushing up the crust and fracturing the surrounding lava plains (forming Valles Marineris, a network of canyons). In other spots, the mantle pushed through the crust, giving rise to the region's many volcanoes, such as Olympus Mons. (We'll talk about all these Martian landmarks next.)
During this period, there were widespread volcanic eruptions. Lava flowed from volcanoes and filled the low-lying basins. Eruptions released gas that contributed to a thick atmosphere, which could have supported liquid water. Therefore, there might have been rain, flooding and erosion. The erosion would produce sedimentary rocks in the basins and plains, and form channels in the rock. More than one period of widespread volcanic eruptions may have occurred during Mars' history, but eventually the volcanoes stopped rumbling as much.
The bulges that caused the crustal uplifts and the widespread volcanic activity released vast amounts of heat from the inside of Mars. Since Mars isn't as large as the Earth, it cooled much faster, and the surface temperature cooled with it. Water and carbon dioxide from the atmosphere began to freeze and fall to the surface in vast quantities. This freezing removed large amounts of gas from the atmosphere, causing it to thin. In addition, any surface water may have frozen into the ground, forming permafrost layers. Intermittent volcanic eruptions would release more heat that would melt more water ice and cause flooding. The flooding would erode channels and carry more material down to the surrounding plains.
As for the rest of Mars' atmosphere, it was likely blown off under the assault of solar wind. Earth's magnetic field protects us from the worst of such effects, but the Mars equivalent shut down around 4 billion years ago, possibly due to a series of massive asteroid impacts that threw off the temperature gradient powering the planetary electric dynamo [source: Than].
While this is the current theory about the origin of Mars, it needs more data to back it up.
The Surface of Mars
We can divide the surface of Mars into three major regions:
- Southern highlands
- Northern plains (both the plains and the crustal upwarps)
- Polar regions
The southern highlands are extensive. The region's elevated terrain is heavily cratered like the moon. Scientists think the southern highlands are ancient because of the large number of craters. Most cratering in the solar system happened more than 3.9 billion years ago, at which point the rate of meteors bashing into the solar system's planetary bodies dropped steeply.
The northern plains are low-lying regions, much like the maria, or seas, on the moon. The plains show lava flows with small cinder cones -- evidence of volcanoes -- as well as dunes, wind streaks, and major channels and basins similar to dry "river valleys." There is a distinct change in elevation, of several kilometers, between the southern highlands and the northern plains.
Two continent-sized, high regions called crustal upwarps spread over the northern plains. In these upwarps areas the molten rock from the interior mantle pushed up the planet's thin crust, forming a high plateau. These regions are capped with shield volcanoes, where molten rock from the magma broke through the crust. The smaller region, named Elysium, is in the eastern hemisphere, while the larger one, called Tharsis, is located in the western hemisphere.
The highest point in the solar system that we know about rises up in the Tharsis region. This shield volcano called Olympus Mons (Mount Olympus from Greek mythology) towers 16 miles (25 kilometers) above the surrounding plains, and its base spans 370 miles (600 kilometers). In contrast, the largest volcano on Earth is Mauna Loa in Hawaii, which rises 6 miles (10 kilometers) above the ocean floor and is 140 miles (225 kilometers) wide at its base.
At the edge of the Tharsis region is a large system of canyons called Valles Marineris. The canyons stretch for 2,500 miles (4,000 kilometers). That's greater than the distance from New York to Los Angeles. The canyons are 370 miles (600 kilometers) wide and 5 to 6 miles (8 to 10 kilometers) deep. That makes Valles Marineris much larger than the Grand Canyon. Unlike the U.S. national landmark, which formed from water erosion from the Colorado River, Valles Marineris was created by the crust cracking when the Tharsis bulge formed.
We can see the polar regions from the Earth. Surrounded by vast dunes, the northern and southern polar ice caps seem to be made mostly of frozen carbon dioxide (dry ice) with some water ice. Like Earth, Mars has an axial tilt that causes it to experience seasons. The size of the polar ice caps varies with the season. In the summer, the carbon dioxide from the northern ice cap sublimes, or turns directly from ice to steam, revealing a sheet of water ice below. In fact, the water ice in this northern region is the reason why NASA sent the Phoenix lander there. With the help of its robotic arm, Phoenix dug down to the frozen layer and examined soil samples to investigate its composition.
The Interior of Mars
Let's compare the interior of Earth with that of Mars. Earth has a core with a radius of about 2,200 miles (3,500 kilometers) -- roughly the size of the entire planet of Mars. It is made of iron and has two parts: a solid inner core and a liquid outer core. Radioactive decay in the core generates the heat. This heat is lost from the core to the layers above. Convective currents in the liquid outer core along with the rotation of Earth produce its magnetic field.
Mars, the more petite planet, probably has a core radius between 900 and 1,200 miles (1,500 kilometers and 2,000 kilometers). Its core is probably made of a mixture of iron, sulfur and maybe oxygen. The outer part of the core may be molten, but it's unlikely, because Mars has only a weak magnetic field (less than 0.01 percent of Earth's magnetic field). Although Mars doesn't have a strong magnetic field now, it might have had a powerful one long ago.
Surrounding Earth's core is a thick layer of soft rock called the mantle. What do we mean by soft? Well, if the outer core is liquid, then the mantle is a paste, like toothpaste. The mantle is less dense than the core (which explains why it rests above the core). It's made of iron and magnesium silicates, and it stretches about 1,800 miles (3,000 kilometers) thick -- remember that the next time you try to dig a hole to China). The mantle is the source of lava that spews and trickles from volcanoes.
Like Earth, the mantle of Mars (the wide grayish-brown swath in the figure) is probably made of thick silicates; however, it's much smaller, at 800 to 1,100 miles (1,300 to 1,800 kilometers) thick. There must have been convective currents that rose up in the mantle at one time. These currents would account for the formation of the crustal upwarps, such as the Tharsis region, the Martian volcanoes and the fractures that formed Valles Marineris.
On Earth, the crust's continental plates float over the underlying mantle and rub against each other (continental drift). The areas where they rub produce uplift, cracks or faults, such as the San Andreas fault in California. These areas of contact between plates experience earthquakes and volcanoes. On Mars, the crust is also thin, but isn't broken into plates like the Earth's crust. Although we do not know of currently active volcanoes or marsquakes, evidence of quakes occurring as recently as a few million years ago suggest they are possible [source: Spotts].
Do you want to see all this for yourself? You might have difficulty breathing on Mars. Find out why next.
The Atmosphere of Mars
Of all the planets, Mars is our closest relation in terms of makeup (not distance -- Venus is closer), but that's not saying much. And it certainly doesn't mean that it is hospitable. The atmosphere of Mars differs from Earth's in many ways, and most of them don't bode well for humans living there.
- It's composed mostly of carbon dioxide (95.3 percent compared to less than 1 percent on Earth).
- Mars has much less nitrogen (2.7 percent compared to 78 percent on Earth).
- It has very little oxygen (0.13 percent compared to 21 percent on Earth).
- The red planet's atmosphere is only 0.03 percent water vapor, compared to Earth, where it makes up around 1 percent.
- On average, it exerts only 6.1 millibars of surface pressure (Earth's average sea-level atmospheric pressure is 1,013.25 millibars) [source: NASA].
Because the "air" on Mars is so thin, it holds little of the heat that comes from the ground after it absorbs solar radiation. The thin air also is responsible for the wide, daily swings in temperature (almost 100 degrees Fahrenheit or 60 degrees Celsius). Martian atmospheric pressure changes with the seasons. During the Martian summer, carbon dioxide sublimes from the polar ice caps into the atmosphere, increasing the pressure by about 2 millibars. As found by NASA's Mars Reconnaissance Orbiter, during the Martian winter, carbon dioxide refreezes and falls from the atmosphere as carbon dioxide snow! This snowfall causes the pressure to decrease again. Finally, because the Martian atmospheric pressure is so low and the average temperature is so cold, liquid water cannot exist; under these conditions, water would either freeze, evaporate into the atmosphere or, as seen by NASA's 2008 Phoenix Lander mission, fall as snow [source: NASA].
The weather on Mars is pretty much the same each day: cold and dry with small daily and seasonal changes in temperature and pressure, plus a chance of dust storms and dust devils [source: NASA]. Light winds blow from one direction in the morning and then from the reverse direction in the evening. Clouds of water ice hover at altitudes of 12 to 18 miles (20 to 30 kilometers), and clouds of carbon dioxide form at approximately 30 miles (50 kilometers). Because Mars is so dry and cold, it never rains. That's why Mars resembles a desert, much like Antarctica on Earth.
During the spring and early summer, the sun heats up the atmosphere enough to cause small convection currents. These currents lift dust into the air. The dust absorbs more sunlight and heats the atmosphere further, causing more dust to lift into the air. As this cycle continues, a dust storm develops. Because the atmosphere is so thin, great speeds (60 to 120 mph or 100 to 200 kph) are required to stir up the dust. These dust storms spread across large regions of the planet and can last for months. All that dust can be bad for the rovers traversing the surface, but the storms can also clear off dirt caked on their solar panels.
Dust storms are also thought to be responsible for the variable dark regions on Mars that are seen from ground-based telescopes, which were mistaken for canals and vegetation by Percival Lowell and others. The storms are also a major source of erosion on the Martian surface.
Is all that dust making you thirsty? Read on to find out about water on Mars.
Water on Mars
Scientists don't think the liquid was always so scarce. Modern Mars may resemble a barren desert, but very early Mars may have been quite wet, judging from some of the geologic clues left behind. Floods may once have flowed over the planet's surface, rivers may have carved out channels or gullies, and lakes and oceans may have covered large swaths of the planet.
Evidence for this has vastly increased in recent years, with the observations of the Mars Reconnaissance Orbiter, which found thousands of deposits of phyllosilicates at locations around the planet. These claylike minerals arise solely in watery environments -- at temperatures friendly to life -- but were probably laid down in the early days of the solar system, around 4.6 to 3.8 billion years ago. Rovers like Opportunity and Curiosity have revealed that at least some of these lakes maintained salt and acidity levels friendly to life [sources: Rosen; Yeager].
Can't quite picture it? Visit Mono Lake in California, one of the world's oldest lakes at 760,000 years old and an average of 57 feet (17 meters) deep. Now imagine it without water and you'll have the Gusev Crater, a giant basin bisected by a dry riverbed that the Spirit rover searched for evidence of water.
When scientists looked at high-resolution, 3-D images of Mars taken in 2005 and compared them to pictures taken in 1999 of the same area, what they saw excited them: A series of bright, depositary streaks had formed in gullies during the intervening years. These streaks were reminiscent of flash floods that can carve away soil and leave behind new sediments on Earth. A bunch of streaks doesn't sound that monumental, but if water was the recent force behind them, that changes things. (To learn more about the discovery, read "Is there really water on Mars?")
Liquid water may be in short supply, but frozen water isn't. The Phoenix lander investigated the ice in the far north of Mars. The lander's robotic arm dug down into the icy layer for soil samples, which it analyzed with its onboard instruments.
In fact, the lander had three main objectives, all of them water-related:
- Study the history of water in all its phases.
- Determine if the Martian arctic soil could support life.
- Study Martian weather from a polar perspective.
Life on Mars?
This simple question has captivated minds for centuries. We still lack a definitive answer, although evidence has continued to mount as spacecraft carry out increasingly sophisticated tests for life processes, past and present, including analyzing Martian soil for traces of water and looking for the release of gases such as carbon dioxide, methane and oxygen that might suggest bacterial life.
It's possible that we need to revisit our idea of Martian life, exchanging egg-headed humanoids for much smaller organisms. Microbes are hardy little buggers, and there's good reason to believe that they could exist below ground. For example, biologists have unearthed bacteria living in Antarctica as well as a species, dormant for 120,000 years and buried 2 miles (3.2 kilometers) below Greenland's ice, that successfully awoke from its frozen slumber and started multiplying [source: Heinrichs].
There's also plenty of evidence that Mars' environment billions of years ago could have supported them. As we discussed, water is a key ingredient for life, and we know that Mars used to be wet. Curiosity rover was dispatched to Gale Crater because it marks a spot where water flowed for a long period. This history is recorded in the layer after layer of sediment that built its central feature, the 3.4-mile- (5.5-kilometer-) high Mount Sharp (aka Aeolis Mons), over billions of years [sources: Drake; Yeager].
Indeed, 10 years into its mission, Opportunity found another spot like Gale Crater where ancient water was not too acidic or salty for cells to flourish. Moreover, although Curiosity's drill has yet to locate the organic carbon compounds that would form life-related amino acids, it has dug up hydrogen, carbon, sulfur, nitrogen, phosphorous and oxygen -- a well-stocked pantry for single-celled organisms, if they did exist. Back on Earth, scientists have found Mars meteorites with internal structures that are consistent with a biological source [sources: Grant; NASA; Rosen].
In short, there's plenty of evidence that Mars was friendly to life long ago, but no smoking gun. Even if there were, we have to ask: Could it still be hanging around somewhere?
One promising sign of life would be the discovery of large amounts of methane in the Martian atmosphere. Scientists had previously detected the gas -- 90-95 percent of which on Earth is produced by microbes -- in Mars' atmosphere. They hypothesized that trapped methane from buried microorganisms might be released during seasonal ground thaws. So far, Curiosity's measurements indicate levels 1/10,000 of those found in Earth's atmosphere -- in other words, bupkes -- but, given more time, there's a slight chance that the rover might observe such a seasonal bloom. Then again, the methane clouds observed by scientists could arise from a natural process, such as the release of methane trapped in ice [sources: Savage; Wayman].
For more Mars madness, browse the stories and links on the next page.
- How will landing on Mars work?
- Is there really water on Mars?
- How the Mars Exploration Rovers Work
- How the Mars Curiosity Rover Works
- How Mars Odyssey Works
- How Terraforming Mars Will Work
- Mars Image Gallery
- Top 10 Space Conspiracy Theories
- NASA's 10 Greatest Achievements
- How Snakebots Will Work
- How Fusion Propulsion Will Work
- Chaisson, Eric and Steve McMillan. "Astronomy Today." Third edition. Prentice Hall. 1999.
- Dauphas, Nicholas and Ali Pourmand. "Hf–W–Th Evidence for Rapid Growth of Mars and its Status as a Planetary Embryo." Nature. Vol. 473. Page 489. May 26, 2011 (March 19, 2014) http://www.earth.northwestern.edu/people/seth/351/dauphas.pdf
- Drake, Nadia. "Curiosity Goes to Mars." Science News. Dec.13, 2012. (March 20, 2014) https://www.sciencenews.org/article/curiosity-goes-mars
- Encyclopaedia Britannica. "Mars." 2008. (June 9, 2008) http://www.britannica.com/eb/article-54235
- Grant, Andrew. "Life-friendly Environment Confirmed on Mars." Science News. March 12, 2013. (March 20, 2014) https://www.sciencenews.org/article/life-friendly-environment-confirmed-mars
- Heinrich, Allison M. "Researchers at Penn State 'Awaken' Dormant Bacteria." Tribune-Review/Pittsburgh Tribune-Review. June 5, 2008. (June 17, 2008) http://www.redorbit.com/news/science/1417517/researchers_at_penn_state_awaken_dormant_bacteria/
- Jet Propulsion Laboratory. "Mars Rovers Sharpen Questions About Livable Conditions." Press release. Feb. 15, 2008. (June 9, 2008) http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20080215a.html
- Marks, Paul. "Inflatable robots could explore Mars." NewScientist.com. May 30, 2008. (June 9, 2008) http://space.newscientist.com/article/dn14028-inflatable-robots-could-explore-mars.html?feedId=online-news_rss20
- "Mars." World Book at NASA. (June 5, 2008) http://www.nasa.gov/worldbook/mars_worldbook_prt.htm
- NASA. "Mars Extreme Planet: Earth/Mars Comparison." 2006. (June 18, 2008) http://mars.jpl.nasa.gov/facts/
- NASA. "Mars Fact Sheet." July 1, 2013. (March 19, 2014) http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html
- NASA. "NASA Observations Point to 'Dry Ice' Snowfall on Mars." Sept. 11, 2012. (March 19, 2014) http://www.jpl.nasa.gov/news/news.php?release=2012-286
- NASA. "NASA Rover Providing New Weather and Radiation Data About Mars." Nov. 15, 2012. (March 19, 2014) http://www.jpl.nasa.gov/news/news.php?release=2012-361
- NASA. "NASA Scientists Find Evidence of Water in Meteorite, Reviving Debate Over Life on Mars." Jet Propulsion Laboratory. Feb. 27, 2014. (March 20, 2014) http://www.jpl.nasa.gov/news/news.php?release=2014-065
- NASA. "Phoenix Landing: Mission to the Martian Polar North." May 2008. (June 18, 2008) http://www.jpl.nasa.gov/news/press_kits/phoenix-landing.pdf
- Rosen, Meghan. "Old Rover Finds New Evidence of Water on Mars." Science News. Jan. 23, 2014. (March 20, 2014) https://www.sciencenews.org/article/old-rover-finds-new-evidence-water-mars
- Savage, Liz. "For Kids: Either Martians or Mars has Gas." Feb. 13, 2009. (March 20, 2014) https://www.sciencenews.org/article/kids-either-martians-or-mars-has-gas
- Skinner, Brian J. and Stephen C. Porter. "The Dynamic Earth." Second edition. John Wiley & Sons, Inc. 1992.
- Society for General Microbiology. "Where Man Boldly Goes, Bacteria Follow." ScienceDaily. May 30, 2008. (June 18, 2008) http://www.sciencedaily.com/releases/2008/05/080528191418.htm
- Spotts, Pete. "Marsquake? How Rumblings Could Bolster Hope for Life on Mars." Christian Science Monitor. Feb. 23, 2012. (March 19, 2014) http://www.csmonitor.com/Science/2012/0223/Marsquake-How-rumblings-could-bolster-hope-for-life-on-Mars
- Than, Ker. "'Supergiant' Asteroid Shut Down Mars's Magnetic Field." National Geographic News. May 11, 2009. (March 19, 2014) http://news.nationalgeographic.com/news/2009/05/090511-mars-asteroid.html
- Wayman, Erin. "Year in Review: Methane Shortage on Mars." Science News. Dec. 26, 2013. (March 20, 2014) https://www.sciencenews.org/article/year-review-methane-shortage-mars
- Yeager, Ashley. "Wet, Almost, All Over." Science News. July 16, 2008. (March 20, 2014) https://www.sciencenews.org/article/wet-almost-all-over | 0.886652 | 3.859306 |
One of the most burning questions we are faced with when we marvel at the grandness of the universe and the diversity of life on Earth, is: Why the hell can’t we find any aliens?
I’m not talking about bacteria or frozen spores on some asteroid or moon, but intelligent species — interstellar civilizations we can recognize and communicate with. After all, according to the Kardashev scale and given the age of the universe, there should be at least a type II civilization in our own galaxy, and possibly several (or many!) type IIIs throughout the universe. And we ought to be able to observe them with the technology we currently have, as the radiation output of their massive energy conversion would be measurable.
But we’ve found nothing. Nada. Zilch.
Why are they so hard to find? Are we actually alone out here? Or are we, maybe, the first ones to speak up into the void? Or the last? *shudders*
“Why is the galaxy not crawling with self designing mechanical or biological life forms? Why hasn’t the Earth been visited, and even colonised?” ~Stephen Hawking
Maybe the problem lies elsewhere. Maybe we’re expecting the wrong results.
As you probably imagine (or know), many brilliant scientists and inquisitive minds have bent over backwards trying to answer these questions, giving birth to some of the most exciting solutions to the Fermi paradox (high probability of alien life in the universe, apparently no traces of it).
Let’s draw a broad sketch of the issue.
Nicolai Kardashev postulated that as an intelligent species evolves, it will eventually be able to harness and use the entire energy output of its home planet (type I) > then its home star system (by building a Dyson sphere around the star, for example)(type II) > then its home galaxy (type III).
This requires that such a species evolves in an expansionist manner, colonizing its entire galaxy and consuming its entire energy output.
Evidently, such a tremendous evolutionary step requires a phenomenal use of technology on a mind-boggling scale. Enveloping an entire galaxy in an artificial construction, or every single star within it, and using that energy to sustain an enormous, expansionist civilization, will inevitably be detectable. Even if our observational technology is measly by comparison, we’d still be able to detect something by the sheer immensity of its effect on the surrounding universe. By its shadow, so to speak. Or its gargantuan footsteps.
But we’ve found no such civilization out there.
SETI’s G-HAT survey (in which they studied over 100.000 galaxies looking for traces of a type III civilization) has returned a pretty grim result, namely zero. No such thing as a Kardashev type III civilization out there. A real bummer.
Of course, this result says nothing about type Is, for example, which would be far harder to detect. But it still begs a very important question: Was Kardashev wrong?
Why can’t we find any advanced alien civilizations out there?
Let’s go down the rabbit hole and look for possible answers.
Keith Cooper, a freelance science journalist, recently speculated on this topic over at Centaury Dreams. He proposed three possible explanations why civilizations might fall of the Kardashev scale at some point, seemingly never reaching a type III level.
1. They fail to colonize the stars
A strong argument in favor of this explanation is Geoffrey Landis’ percolation theory.
Landis assumes that interstellar travel is short distance only, as travel to far destinations would require hundreds of years and thus be unfeasible. So an interstellar civilizations will expand gradually, in bursts, colonizing the neighboring systems one by one.
Not all of these systems will be colonizable (or warrant the effort), and thus some will become dead ends. Similarly, some systems will be so far away from their next neighbors, they too will become dead ends. Thus, an expanding interstellar civilization will grow outward like the roots (or branches) of a tree, until all its ramifications will meet dead ends and expansion will stop. No type III.
2. Their energy requirements are low
Another theory is that civilizations, as they evolve and become more efficient, will have lower energy demands, not higher. Such civilizations are driven by optimization and specialization, not expansion and comsumption. An optimized society will also not increase in numbers significantly, and thus not need to colonize new worlds to sustain its growth.
Such a civilization will very likely travel to other systems, but to explore and gain knowledge, not to seize and consume. They might very well be galactic, and even inter-galactic, but they wouldn’t occupy a place on the Kardashev scale.
3. Black holes are more interesting
This is the most beautiful puppy theory of all.
If we assume that an evolving civilization will become more efficient and also require more energy, what’s the likeliest target of their interest? Black holes. Infinite energy, condensed into the tiniest possible space. There’s a good reason why all scientists get giddy when one mentions black holes: they’re fascinating and terrifying at the same time (er, the black holes, not the scientists).
Several people have developed theories around the possibility of harnessing energy from black holes, and the results are mind-blowing.
“Paul Davies in his book The Eerie Silence suggests that a spinning black hole could power our present human levels of energy consumption for at least a trillion trillion years, long after the stars have gone out.” ~Keith Cooper, SETI: The Black Hole Alternative
So it makes perfect sense that a sufficiently evolved civilization won’t seek to spend energy painstakingly colonizing an entire galaxy, only to harness the output of volatile stars, if it can focus on harnessing the power of black holes.
They could build Dyson sphere variants around black holes; tap into the blasting energy output of their accretion disks or jets; or use the rotational energy of spinning black holes. There’s also a surprising number of x-ray binaries (black hole plus star) even in our own galaxy, inviting the speculative notion that evolved civilizations create their own black holes in their (or the neighboring) systems to use as an energy source.
But the fascination with black holes as an alternative focus to expansion goes well beyond their energy potential. Black holes could make the most powerful computers imaginable. They could also be gateways to other universes or existential dimmensions, where super-advanced civilizations go to be among their peers, leaving us barbaric beasts behind to crawl across normal space-time at our glacial tempo.
The Transcension Hypothesis speculates on exactly this alternative: that sufficiently advanced civilizations may invariably leave our universe.
The evolution of life on Earth points toward specialization and ever decreasing scales of manipulative dexterity. Extrapolating that to alien civilizations, we’d invariably conclude that they’d much more likely develop toward the micro-, nano-, and subatomic scale, and head inward, into the infinite density and energy of black holes, as opposed to dedicating themselves to greater and larger constructions, hugely growing energy demands and unsustainable scales.
“Evolutionary development guides intelligent life increasingly into inner space and what is referred to as STEM, small scales of space, time, energy and matter.” ~Owen Nicholas, The Transcension Hypothesis
There are some compelling reasons why black holes are attractive to civilizations focused on achieving great STEM density. Miniaturizing civilizations, who re-engineer themselves with femtotechnology (structures at sub-atomic scales) will undoubtedly be intrigued by the challenge of entering and harvesting a black hole without losing structural integrity. All the while, the proximity to black holes essentially fast-forwards them through time, as the rest of the galaxy and universe would speed through its processes in the blink of a subjective eye.
Also, such civilizations—due to their crossing of the computational threshold between noisy, inefficient technologies, and highly specialized, efficient ones—would undoubtedly exist in a sort of “radio silence,” as they would have near zero untargeted, unintentional emissions. So we’d be unable to spot them by their noise.
Just imagine. If you’re a civilization that has created a super dense, super efficient and super fast computational capacity (called ‘computronium’) by relocating to and using black holes, you may increasingly find the rest of the universe slow and boring by comparison. And you’d not be interested in communicating with it or listening to its primitive noise, as such investment on your part would yield no new benefits.
Black holes would be the ultimate tool to exponentially increase your knowledge and power, to essentially blow up the evolutionary scale. Certain classes of accretion discs around super-massive black holes are such monstrously efficient energy harvesters (in some cases 50 times more efficient than stellar nuclear fusion), it begs for speculations about such formations bearing proof that advanced civilizations are at work, rather than coincidental natural phenomena.
And to color our little speculative neuronal explosions even more, such civilizations will invariably evolve non-biological intelligences, which in turn will escape natural evolution and transcend ‘life’ via intentional development. The phenomenal computational capacities facilitated by the manipulation of black holes will invariably yield non-biological organisms that far out-perform and surpas biological life-forms in their development and use of natural resources (such as black holes).
Essentially, we might just as well assume that any civilization that evolves to use black holes will transcend the biological, and
“The hallmark of developmental processes is convergence and unification. A planet of postbiological life forms, if subject to universal development, may increasingly look like one integrated organism, and if so, its entities will be vastly more responsible, regulated, and self-restrained than human beings. If developmental immunity exists, planetary transitions from life to intelligent life, and from intelligent life to postbiological life should be increasingly high-probability.” ~Gregory Stock (biophysicist), The Transcension Hypothesis
It all makes for awesome speculative ideas, doesn’t it?
So to end on a high note, still tasting of wonderful speculation and multi-faceted story material:
The lack of proof of expansionist, consumeristic alien civilizations doesn’t mean we’re alone in the universe. It may just as well mean we have some evolutionary — no, developmental — stages to look forward to that will see us transcend all we currently know to be ‘life,’ and enter a realm of supreme efficiency, computational capacity, and self-realizing potential.
How’s that for science-fiction story material. | 0.831846 | 3.043381 |
Once in a blue moon, an astronomy activity comes along that's both educational and tasty!
While some people may think the Moon is made of cheese, we think using Oreo sandwich cookies makes studying space science even sweeter!
In this simple activity, all it takes is a package of your favorite stuffed cookies and a few household supplies to study phases of the moon and explore astronomy and physics concepts including gravitation and relativity, light, and spectra. By including the Moon as part of your astronomy lessons, you can harness your students' curiosity, imagination, and create a sense of shared exploration and discovery.
But first, a bit about the Moon…
The Moon is our closest neighbor. It's a beautiful, changing, natural satellite that helps us better understand the Earth's past and future.
The Moon goes through 8 major phases approximately every 29.5 days. Talk about a busy month!
These 8 phases are:
- A new moon is when the Moon cannot be seen because we are looking at the unlit half of the Moon. The new moon phase occurs when the Moon is directly between the Earth and the Sun. A solar eclipse can only happen at new moon. To have a successful eclipse watch party make sure you planet!
- A waxing crescent moon is when the Moon looks like crescent and the crescent increases ("waxes") in size from one day to the next. This phase is usually only seen in the west.
- The first quarter moon (or a half moon) is when half of the lit portion of the Moon is visible after the waxing crescent phase. It comes a week after the new moon.
- A waxing gibbous moon occurs when more than half of the lit portion of the Moon can be seen, and the shape increases ("waxes") in size from one day to the next. The waxing gibbous phase occurs between the first quarter and full moon phases.
- A full moon is when we can see the entire lit portion of the Moon. The full moon phase occurs when the Moon is on the opposite side of the Earth from the Sun, called opposition. A lunar eclipse can only happen at a full moon. No wonder the Moon gets so full of itself that day!
- A waning gibbous moon occurs when more than half of the lit portion of the Moon can be seen, and the shape decreases ("wanes") in size from one day to the next. The waning gibbous phase occurs between the full moon and third quarter phases.
- The last quarter moon (or a half moon) is when half of the lit portion of the Moon is visible after the waning gibbous phase. What a great inspiration for the delicious half-moon cookie!
- A waning crescent moon is when the Moon looks like the crescent, and the crescent decreases ("wanes") in size from one day to the next.
The Moon has always been an object of curiosity for humans of all ages. Even though it is 238,900 miles away, it's the perfect astronomical body to study because of its dependability and proximity. Through this simple yet tasteful activity, your students will develop a deeper understanding of the moon.
We're not sure about you, but all this Moon talk is making us hungry. Time for a snack!
Constructing a Moon Phase Calendar Activity
Identify the Moon's phases 365 days a year using photo-realistic images of the Moon for photocopying. For Grades 5-10. Materials for 31 students.
Modeling the Moon's Motion and Phases Lab Activity
Students will use framework concepts of Earth's Place in the Universe (ESS1) to learn about the phases of the Moon, and the difference between a lunar (synodic) month and a sidereal month.
Moon Pops Activity
Miniature moons on a stick illustrate the phases of the moon and how the positions of the Earth, Sun, and Moon cause each phase. | 0.847323 | 3.419769 |
Some supermassive black holes at the centre of galaxies are devouring the surrounding material. They also divert part of it away through powerful winds and jets.
Astronomers studying the supermassive black hole at the centre of the galaxy IRAS F11119+3257 have found proof that the winds blown by the black hole are sweeping away the host galaxy’s reservoir of raw material to form stars.
This finding was made by using ESA’s Herschel space observatory, together with the Suzaku X-ray astronomy satellite. Combining these data, the astronomers could detect the winds driven by the central black hole in X-rays, and their global effect, pushing the galactic gas away, at infrared wavelengths.
This artist's impression shows how the black hole accretes the surrounding matter through a disc (orange). Part of the accreted material is pushed away in a wind (blue), which in turn powers a large-scale galactic outflow of molecular gas (red). | 0.849865 | 3.662628 |
Keywords:organic matter, shock alteration
We systematically investigates shock-induced alteration of planetary organic simulants, which are laboratory analogues of complex organic matter found on primitive planetary bodies, as a function of peak shock pressure and temperature by impact experiments. Our results show that the composition and structure of planetary organic simulants are unchanged upon impacts at peak pressures less than ~5 GPa and temperatures less than ~350ºC. On the other hand, these are dramatically changed upon impacts at pressures higher than 7–8 GPa and temperatures higher than ~400ºC, through loss of hydrogen-related bonds and concurrent carbonization, regardless of the initial compositions of organic simulants. Compared with previous results on static heating of organic matter, we suggest that shock-induced alteration cannot be distinguished from static heating only by Raman and infrared spectroscopy. Our experimental results would provide a proxy indicator for assessing degree of shock-induced alteration of organic matter contained in carbonaceous chondrites. We suggest that a remote-sensing signature of the 3.3–3.6 μm absorption due to hydrogen-related bonds on the surface of small bodies would be a promising indicator for the presence of less-thermally-altered (i.e., temperatures less than 350°C) organic matter there, which will be a target for landing to collect primordial samples in sample-return spacecraft missions to asteroids or icy bodies. | 0.877529 | 3.218326 |
Black holes are strange, seemingly paradoxical objects. By their nature, they are nearly invisible. Yet thanks to their powerful gravitational pull, they draw in matter, which causes some of them to shine brightly enough to be seen across the Universe. Black holes are known for what they devour, but the stuff they don’t eat is even more important, from the point of view of their host galaxies. Material streaming out from a black hole can influence the formation of stars, carve out bubbles in nearby regions, and alter the chemical balance of the galaxy itself.
Case in point: the spiral galaxy NGC 5548, which astronomers have been monitoring off and on for decades. NGC 5548 is an “active galaxy”, which means the huge black hole at its center is surrounded by hot gas that shines brightly in X-ray and ultraviolet (UV) light. However, researchers measured a decrease in X-ray emission last year: something new was blocking the light from reaching us.
Further observations showed that something was an incredibly fast flow of gas blowing outward from the black hole. We happen to be looking straight into that flow, as though a fan were turned on directly in our face. That’s a lucky break: while astronomers have measured similar outflows in other galaxies, this is the first time anyone has seen one from this angle, which provides a lot more detailed data than other viewpoints.
Between that privileged angle and the fact that researchers have watched the galaxy change over decades, we can see how outflows from black holes have shaped NGC 5548. After all, galaxies aren’t static environments, and studying their history is a way to understand the complex processes that control the birth of stars and planets.
Black holes are literally central to that galactic history. Astronomers discovered over the last few decades that nearly every large galaxy, including the Milky Way, harbors a black hole millions or billions of times more massive than the Sun. Gas orbiting these black holes heats up and glows brightly. Some of the matter is ejected away in the form of huge powerful jets (which also emit a lot of light).
For that reason, black holes can influence star formation, both positively and negatively. The flow of gas away from a black hole is called “wind” (not all scientific jargon is complicated!). Winds can either compress other clouds, heating them up and making stars, or break those clouds up. It’s a complex process, and one astronomers are still learning to understand.
A bug-eyed alien astronomer in a galaxy far, far away likely wouldn’t think of the Milky Way’s central black hole as particularly interesting. While it shows signs of past activity, our galaxy is pretty quiet now, but active galaxies like NGC 5548 are another matter.
Like Cookie Monster, many supermassive black holes are messy eaters. Their gravitational pull can draw in huge amounts of gas, which swirls in a thick donut-shaped pattern known as an accretion disk. (“Accretion” just refers to that gravitational gathering. It has the same root as “concrete”, which is a collection of rubble glued together by cement.)
What we actually see of a feeding black hole, then, depends on our viewing angle. If we’re observing it more or less “top down”, then we see the largest area of the accretion disk, maximizing the brightness of the black hole. That’s the case for NGC 5548, so the authors of the new paper were surprised to find that X-ray emissions in 2013 were 25 times weaker—4 percent!—of what they had been in 2002. Normal fluctuations in light are expected, but that’s well past typical.
However, we live in the best era of human history to study black holes. The researchers used an impressive array of observatories to monitor NGC 5548: the X-ray telescopes XMM- Newton, Swift, and Chandra, the Hubble Space Telescope (HST), the Nuclear Spectroscopic Telescope Array (NuSTAR), and the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL). All of these instruments orbit Earth, beyond the atmosphere that blocks X-rays and most ultraviolet light.
They found that in addition to the normal wind, the black hole had spewed out a lumpy cloud of gas, moving 5 times faster than typical outflow. They determined this by measuring absorption: clouds of gas aren’t equally opaque to all kinds of light, and the wavelengths they absorb depend on how fast the gas is moving. In this case, the rapid flow obviously was lying directly between the black hole and us, obscuring our view.
The black hole in NGC 5548 isn’t among the most powerful: other more active galaxies have winds like this flowing out on a more steady basis. However, those galaxies are also more distant, marking a time in the cosmic history when black hole food was more plentiful. (Those are the quasars I wrote about in my earlier column.)
Thanks to the relative proximity of NGC 5548 and the decades of observations astronomers have made of the galaxy, it’s a great place to study the fluctuations in black hole feeding behavior over time. The more we know about how black holes influence their environment, the greater our knowledge of galaxies in general—including perhaps how the chemical components of stars, planets, and life are distributed. | 0.872967 | 4.148957 |
Fullerenes are a class of closed, hollow carbon compounds that comprise only the third form of pure carbon ever discovered. The most remarkable of the fullerenes is the 60-carbon alkene buckminsterfullerene, also known as a Buckyball. This highly unusual molecule was named after the geodesic dome, a structure that exhibits a geometry that approximates a truncated icosohedral soccer ball-shape, invented by visionary engineer, author, and architect R. Buckminster Fuller. The roundest known molecule in the world, the Buckyball has carbon atoms at 60 chemically equivalent vertices that are connected by 32 faces, 12 of which are pentagonal and 20 hexagonal. Due to their unique structure, Buckyballs are remarkably rugged, being capable of surviving collisions with metals and other materials at speeds in excess of 20,000 miles per hour, a pace that would tear most organic molecules apart. Higher and lower order Buckyballs containing different numbers of carbon atoms deviate from the strict geodesic dome structure and are consequently not as stable, but are still composed primarily of pentagons and hexagons. Smaller fullerenes, often termed Buckybabies, are said to have a shape akin to that of asteroids, while larger fullerenes may appear similar in shape to a pentagon.
Edge of a C-60 Thin Film The discovery of fullerenes, which exhibit a number of notable characteristics that make the possibilities of their use seem almost limitless, was an important moment in the history of science. This achievement is generally attributed to Richard Smalley and Robert Curl of Rice University as well as Harold Kroto of the University of Sussex, whose experiments aimed at understanding the mechanisms by which long-chain carbon molecules are formed in interstellar space surreptitiously produced Buckyballs in the mid-1980s. In 1996, Smalley, Curl, and Kroto were awarded the Nobel Prize in Chemistry for their discovery. Yet, the discovery of fullerenes did not necessarily mean that there was a readily available way to study them. For a time, much of the work regarding fullerenes was chiefly theoretical since a practical means of producing significant amounts of the molecules was unknown until 1988, when astrophysicists Donald Huffman and Wolfgang Kratschmer realized that they had already discovered a way to produce them years before, though at that time they did not know the import of their actions. The Huffman/Kratschmer process soon made it possible to generate isolable quantities of fullerenes by causing an arc between two graphite rods to burn in a helium atmosphere and extracting the carbon condensate that resulted utilizing an organic solvent.
C-60 Thin Film In 1991, Science magazine dubbed the Buckyball "molecule of the year," professing it "the discovery most likely to shape the course of scientific research in the years ahead," a statement that, years later, does not appear unsubstantiated. Studies exploring the extraordinary characteristics of Buckyballs and potential uses for them are ongoing and the molecules may eventually wind their way into daily life as practical applications are developed. One of the most promising areas of Buckyball research is in the realm of materials science, many scientists believing that the extremely stable molecules could yield new and improved lubricants, protective coatings, and other materials. But, even more exciting to some are the possible materials that may be produced by combining the carbon framework of the Buckyball with different atoms. The process of knocking one or more carbon atoms out of the Buckyball structure and replacing it with metal atoms is known as doping, and the molecule in its altered form is often referred to as a dopeyball. The electrical and magnetic properties of dopeyballs have been the subject of intense study, which has already resulted in the discovery that potassium-doped Buckyballs are capable of superconducting at 18 K and those doped with rubidium superconduct at 30 K.
Edge of a C-60 Thin Film In addition to doping Buckyballs with other atoms, the hollow structure of the geodesic molecules makes it possible to trap atoms inside them like a molecular cage. This strange capability of Buckyballs has caught the attention of the medical community. Indeed, many researchers believe that eventually Buckyballs may be used to deliver medicines to specific tissues and cells, such as those that have been attacked by a certain bacteria, protecting the rest of the body from the toxic effects of potent pharmaceuticals. This same concept is currently being used to develop improved Medical Resonance Imaging (MRI) contrast agents and image enhancers that exploit the carbon cage of a Buckyball to shield patients from the radioactive materials inside. There are also many non-medical possibilities for atom-filled Buckyballs, which are termed endohedral metallofullerenes (EMFs) when the atoms trapped inside are metallic. For instance, EMFs are well on their way to being utilized in organic solar cells and may one day be crucial components of nanoelectronic devices, which many predict will eventually revolutionize the modern communications industry. Some EMFS have also shown potential for use as chemical catalysts that could be delivered to support surfaces in novel ways.
C-60 Thin Film What is perhaps most amazing about Buckyballs is that despite their circuitous discovery in the laboratory, they have been naturally present on Earth all along. The earliest evidence that Buckyballs occur in nature was discovered by Arizona State University researchers Semeon Tsipursky and Peter Buseck, who found that a sample of rare, carbon-rich rock called shungit, estimated to have been formed between 600 million and 4 billion years ago, contained both C60 and C70 fullerenes. Since then, the fascinating molecules have also been identified in meteorites, impact craters, and materials struck by lightning. This new information has led some scientists to speculate about the role that fullerenes may have played in the development of life on Earth. Indeed, gases are known to become readily trapped inside the hollow molecules, and one research group has already found evidence of a form of helium in Buckyballs taken from the Sudbury crater (which contains the greatest known concentration of fullerenes in the world) that likely originated not inside of our own solar system, but within a red giant star. Thus, many consider it to be theoretically possible that Buckyballs carried from their stellar origin both the carbon essential to life and the volatiles that helped produce the planetary conditions necessary for life to begin. ______________________________________...
The fullerenes are a recently-discovered family of carbon allotropes named after Buckminster Fuller. They are molecules composed entirely of carbon, in the form of a hollow sphere, ellipsoid, or tube. Spherical fullerenes are sometimes called buckyballs, the C60 variant is often compared to the typical white and black soccer football, the Telstar (football) of 1970. Cylindrical fullerenes are called buckytubes. Fullerenes are similar in structure to graphite, which is composed of a sheet of linked hexagonal rings, but they contain pentagonal (or sometimes heptagonal) rings that prevent the sheet from being planar.
Prediction and discovery In molecular beam experiments, discrete peaks were observed corresponding to molecules with the exact mass of sixty or seventy or more carbon atoms. In 1985, Harold Kroto (of the University of Sussex), James Heath, Sean O'Brien, Robert Curl and Richard Smalley, from Rice University, discovered C60, and shortly after came to discover the fullerenes. Kroto, Curl, and Smalley were awarded the 1996 Nobel Prize in Chemistry for their roles in the discovery of this class of compounds. C60 and other fullerenes were later noticed occurring outside of a laboratory environment (e.g. in normal candle soot). By 1991, it was relatively easy to produce grams of fullerene powder using the techniques of Donald Huffman and Wolfgang Krätschmer. Fullerene purification remains a challenge to chemists and determines fullerene prices to a large extent. So-called endohedral fullerenes have ions or small molecules incorporated inside the cage atoms. Fullerene is an unusual reactant in many organic reactions such as the Bingel reaction discovered in 1993.
Naming Buckminsterfullerene (C60) was named after Richard Buckminster Fuller, a noted architect who popularized the geodesic dome. Since buckminsterfullerenes have a similar shape to that sort of dome, the name was thought to be appropriate. As the discovery of the fullerene family came after buckminsterfullerene, the name was shortened to illustrate that the latter is a type of the former.
Buckminsterfullerene C60Buckminsterfullerene (IUPAC name (C60-Ih)[5,6]fullerene) is the smallest fullerene in which no two pentagons share an edge (which is destabilizing — see pentalene). It is also the most common in terms of natural occurrence, as it can often be found in soot.
The structure of C60 is a truncated icosahedron, which resembles a round soccer ball of the type made of hexagons and pentagons, with a carbon atom at the corners of each hexagon and a bond along each edge.
The C60 molecule has two bond lengths. The 6:6 ring bonds (between two hexagons) can be considered "double bonds" and are shorter than the 6:5 bonds (between a hexagon and a pentagon).
Nanotubes are cylindrical fullerenes. These tubes of carbon are usually only a few nanometres wide, but they can range from less than a micrometre to several millimetres in length. Their unique molecular structure results in unique macroscopic properties, including high tensile strength, high electrical conductivity, high resistance to heat, and chemical inactivity.
Properties For the past decade, the chemical and physical properties of fullerenes have been a hot topic in the field of research and development, and are likely to continue to be for a long time. In April 2003, fullerenes were under study for potential medicinal use: binding specific antibiotics to the structure to target resistant bacteria and even target certain cancer cells such as melanoma. The October 2005 issue of Chemistry and Biology contains an article describing the use of fullerenes as light-activated antimicrobial agents.
In the field of nanotechnology, heat resistance and superconductivity are some of the more heavily studied properties.
A common method used to produce fullerenes is to send a large current between two nearby graphite electrodes in an inert atmosphere. The resulting carbon plasma arc between the electrodes cools into sooty residue from which many fullerenes can be isolated.
Chemistry Fullerenes are stable, but not totally unreactive. The sp2-hybridized carbon atoms, which are at their energy minimum in planar graphite, must be bent to form the closed sphere or tube, which produces angle strain. The characteristic reaction of fullerenes is electrophilic addition at 6,6-double bonds, which reduces angle strain by changing sp2-hybridized carbons into sp3-hybridized ones. The change in hybridized orbitals causes the bond angles to decrease from about 120 degrees in the sp2 orbitals to about 109.5 degrees in the sp3 orbitals. This decrease in bond angles allows for the bonds to bend less when closing the sphere or tube, and thus, the molecule becomes more stable.
Other atoms can be trapped inside fullerenes to form inclusion compounds known as endohedral fullerenes. Recent evidence for a meteor impact at the end of the Permian period was found by analysing noble gases so preserved. Metallofullerene-based inoculates using the rhonditic steel process are beginning production as one of the first commercially-viable uses of buckyballs.
Fullerenes are sparingly soluble in many solvents. Common solvents for the fullerenes include toluene and carbon disulfide. Solutions of pure Buckminsterfullerene have a deep purple color. Fullerenes are the only known allotrope of carbon that can be dissolved in common solvents at room temperature.
Solubility Solvents that are able to dissolve a fullerene extract mixture (C60 / C70) are listed below in order from highest solubility. The value in parentheses is the approximate saturated concentration.
Diffraction In 1999, researchers from the University of Vienna demonstrated that the wave-particle duality applied to macro-molecules such as fullerene.
Quantum mechanics Researchers have been able to increase the reactivity by attaching active groups to the surfaces of fullerenes. Buckminsterfullerene does not exhibit "superaromaticity": that is, the electrons in the hexagonal rings do not delocalize over the whole molecule.
A spherical fullerene of n carbon atoms has n pi-bonding electrons. These should try to delocalize over the whole molecule. The quantum mechanics of such an arrangement should be like one shell only of the well-known quantum mechanical structure of a single atom, with a stable filled shell for n = 2, 8, 18, 32, 50, 98, 128, etc, i.e. twice a perfect square; but this series does not include 60. As a result, C60 in water tends to pick up two more electrons and become an anion. The nC60 described below may be the result of C60's trying to form a metallic bonding type loose combination.
Safety issues Although buckyballs have been thought in theory to be relatively inert, a presentation given to the American Chemical Society in March 2004 and described in an article in New Scientist on April 3, 2004, suggests the molecule is injurious to organisms. An experiment by Eva Oberdörster at Southern Methodist University, which introduced fullerenes into water at concentrations of 0.5 parts per million, found that largemouth bass suffered a 17-fold increase in cellular damage in the brain tissue after 48 hours. The damage was of the type lipid peroxidation, which is known to impair the functioning of cell membranes. There were also inflammatory changes in the liver and activation of genes related to the making of repair enzymes. At the time of presentation, the SMU work had not been peer reviewed.
Pristine C60 can be suspended in water at low concentrations as large clusters often termed nC60. These clusters are spherical clumps of C60 between 250-350 nm in diameter. Thus, nC60 represents a different chemical entity than solutions of C60 in which the fullerenes exist as individual molecules. Recently, results presented at the ACS meeting in Anaheim, CA suggest that nC60 is moderately toxic to water fleas and juvenile largemouth bass at concentrations in water of around 800 ppb. The first study of its kind on marine life, these preliminary results quickly spread across the scientific community. However, the overwhelming evidence of the essential non-toxicity of C60 (not nC60) in previously peer-reviewed articles of C60 and many of its derivatives indicates that these compounds are likely to have little (if any) toxicity, especially at the very low concentration at which it is used (~1-10 µM).
A new study published in December 2005 in Biophysical Journal raises a red flag regarding the safety of buckyballs when dissolved in water. It reports the results of a detailed computer simulation that finds buckyballs bind to the spirals in DNA molecules in an aqueous environment, causing the DNA to deform, potentially interfering with its biological functions and possibly causing long-term negative side effects in people and other living organisms.
Mathematics behind fullerenes In mathematical terms, the structure of a fullerene is a trivalent convex polyhedron with pentagonal and hexagonal faces. In graph theory, the term fullerene refers to any 3-regular, planar graph with all faces of size 5 or 6 (including the external face). Using Euler's polyhedron formula, |V|-|E|+|F| = 2, (where |V|, |E|, |F| indicate the number of vertices, edges, and faces), one can easily prove that there are exactly 12 pentagons in a fullerene.
The smallest fullerene is the dodecahedron--the unique C20. There are no fullerenes with 22 vertices. The number of fullerenes C2n grows with increasing n = 12,13,14... For instance, there are 1812 non-isomorphic fullerenes C60. Note that only one of the C60's, the buckminsterfullerene alias truncated icosahedron, has no pair of adjacent pentagons (the smallest such fullerene). To further illustrate the growth, there are 214,127,713 non-isomorphic fullerenes C200, 15,655,672 of which have no adjacent pentagons.
At first they were considered laboratory-created freaks. Then some of them turned up in outer space. Now they're being sent to ORNL from the frozen reaches of northern Russia. What's going on here?
RNL's Bob Hettich was on the case. He analyzed. He checked. He double checked. His conclusion?
"Buckyballs. Definitely buckyballs."
Buckyballs Video Clip (QuickTime, 2.3 minutes, 3 MB)
These enigmatic clusters of carbon atoms have been puzzling scientists since 1985 when they were discovered in a research laboratory among the by-products of laser-vaporized graphite. Their hollow spherical structure, reminiscent of the geodesic domes of eccentric architect Buckminster Fuller, earned them the names "buckyballs" and "fullerenes."
Qualities, such as their unique structure, heat resistance, and electrical conductivity, have fueled speculation about their possible applications in high-temperature lubricants, microfilters, more efficient semiconductors, and manufacturing processes.
To learn more about buckyballs and how they are formed, researchers began to look for naturally occurring fullerenes, particularly on the earth. The first evidence that fullerenes occur naturally on the earth came to light when Arizona State University researchers Semeon Tsipursky and Peter Buseck examined a sample of shiny black rock, known as shungite, from northeastern Russia. Shungite is a rare, carbon-rich variety of rock believed to have been formed between 600 million and 4 billion years ago, although how it was formed is debatable. Electron microscopy of the shungite samples revealed a pattern of white circles with black centers--similar to micrographs Tsipursky had seen of laboratory-produced fullerenes.
To confirm their suspicions, Buseck and Tsipursky sent a trace of powdered rock between two glass slides to Bob Hettich of ORNL's Chemical and Analytical Services Division for examination by mass spectroscopy, a technique that sorts molecules by weight and electric charge. Hettich had previously worked with Buseck to analyze samples from both meteorites and terrestrial rocks for evidence of fullerenes, but they had found none. The shungite sample was different, however; Hettich's analysis confirmed the presence of fullerenes in the rock.
"We wanted to make sure we were looking at only what was in the sample and not distorting it in any way," says Hettich. So, he conducted two separate analyses of the sample. In the initial analysis, he used a pulsed laser to vaporize and ionize the sample, preparing it for analysis by mass spectroscopy. Hettich also analyzed carbon samples known not to contain fullerenes to ensure that none were being created by the laser vaporization process itself. The initial analysis confirmed the presence of both C60 and C70, two common fullerenes, in the shungite sample.
To dispel any lingering doubt, Hettich repeated the analysis without a laser, this time using a 400°C stainless steel probe to vaporize the sample and introduce it into the mass spectrometer for ionization. This technique, known as thermal desorption, cannot create fullerenes in fullerene-free graphite material, yet it yielded identical results, confirming the presence of the two types of buckyballs in the sample.
When Buseck and Tsipursky told Hettich that the rock had come from Russia and not a meteorite, he was somewhat surprised. "In the laboratory," says Hettich, "fullerenes are created in an atmosphere of inert gases, like helium, because common diatomic gases, like nitrogen and oxygen inhibit fullerene growth. This is why fullerenes are not found in ordinary soot, like that in household fireplaces. It seemed more likely to find naturally occurring fullerenes in meteorites, where interaction with these gases would be less of a problem."
The discovery of fullerenes in the shungite sample has provided some hard information for buckyball hunters who have been working mostly on educated guesses and speculation. "We've been working with Peter Buseck for quite a while analyzing various samples, but until now we hadn't found any fullerenes," Hettich notes, "This discovery helps us redefine where to look." More recently, C60 and C70 have also been found in a sample of glassy rock from the mountains of Colorado. Known as a fulgurite, this type of rock structure is formed when lightning strikes the ground. Busek, Tsipursky, and Hettich speculated in a 1992 paper that lightning strikes could provide conditions that are favorable for the formation of buckyballs.
The shungite fullerenes are notable not only for their earthly origin, but also because they may have been formed as solids--most laboratory-created fullerenes are grown in the gas phase. "This is the first example of solid-phase fullerene growth," says Hettich, "It has raised a lot of questions about how the rock was formed, how old it is, and how its composition may have changed over time. Because the shungite sample may be volcanic in origin, you can imagine conditions, like those in a volcano, that would be hot enough to form fullerenes and, at the same time, have little or no oxygen or nitrogen present. But right now, no one is sure exactly how these fullerenes were produced."
"This kind of discovery raises more questions than it answers," says Hettich, "but that's not necessarily a bad thing."--Jim Pearce
Sizing Up Fullerenes--"SANS Doute" "Sans doute!" a confident Frenchman might say--"without a doubt!" But in the brand new world of fullerenes, this sort of certainty is sometimes in short supply. Much of the uncertainty surrounding these newly discovered carbon clusters stems from their size--you could line up 25 million C60 molecules on a ruler before passing the inch mark.
So, although tools like mass spectrometers can be used to distinguish heavier fullerenes from lighter ones--separating C120 from C180, for instance--researchers still have trouble answering some of the most basic questions about them. How big are they? Are they shaped like spheres, dumbbells, or what? How and where do other atoms bond to their inner and outer surfaces?
Using a time-tested analysis technique of small-angle neutron scattering, appropriately labeled SANS, a team of researchers from ORNL's Biology, Chemical Technology, Health Sciences Research, and Solid State divisions is working to dispel some of the mystery surrounding fullerenes, including how they interact and bond with other elements and with each other.
The preferred method of studying the structure of most materials is crystallography. This technique enables researchers to pinpoint the location of every atom in a sample. "Even though C60 has been crystallized, this is not always possible with other materials," says Stephen Henderson of ORNL's Biology Division. "Other techniques, like SANS, are more accessible, though they give less structural information." SANS requires only that the material be dissolved, rather than crystallized; then scattered neutrons are counted for several hours and the data are analyzed.
The SANS research facility, located at ORNL's High Flux Isotope Reactor, is operated by George Wignall of the Solid State Division. There, dissolved fullerene samples are placed in the path of a neutron beam. As the beam passes through the sample, neutrons are deflected, or scattered, by carbon molecules in the solvent. This scattering is recorded by a detector, providing a two-dimensional pattern, or "signature," for the material, which can then be analyzed to determine the size and shape of the dissolved molecules.
"The greatest significance of using SANS to analyze fullerenes is its ability to discern shapes," says Bob Haufler, a postdoctoral fellow in the Health Sciences Research Division (HSRD). "This is clearly fertile ground for new chemistry. I think it will be especially helpful in situations where atoms of hydrogen or metals are attached to the inside of the fullerenes." "It's also interesting to see how the fullerenes interact with the solvents," says Kathleen Affholter of the Solid State Division, "to see if polymers are forming, for example."
The SANS facility "sees" objects in its neutron beam by keeping track of the neutrons the objects scatter. This scattering varies with the square of an object's volume, so when its diameter decreases by half, it scatters only one-quarter as many neutrons. As a result, the smallest fullerenes are near the lower limit of what the SANS can see--a factor in the past reluctance of researchers to use SANS in this type of research.
Even though the outcome was in doubt, Wignall encouraged Affholter and others to pursue the project because the potential scientific payoff was so high. "If it hadn't been for George," Affholter says, "the project wouldn't have started in the first place." When Affholter introduced the idea of using the SANS facility for fullerene studies to Bob Compton of HSRD, he said his group was making some C120 and C180 molecules and they didn't know what they looked like--whether they were dumbbell-shaped or just bigger versions of the more or less round C60 and C70 balls. "We decided to look at the C60 and C70 balls first," says Affholter, "because they were available and their sizes and shapes were already known."
Because of the relatively small sizes of these fullerenes, the researchers sought to optimize several factors in the experiments. First, the distance the neutron beam traveled through the fullerene solution was increased from a typical 2 mm to 20 mm, increasing the likelihood of interactions between the fullerenes and the neutron beam. "As a result," says Henderson, "we got incredibly good statistics after an hour or so. Often, for solution work, differences are hard to see even after 10 hours of counting."
Second, the fullerenes were dissolved in a solvent that is relatively transparent to neutrons to maximize the contrast between the two. "A visual analogy," says Henderson, "would be observing blue balls in a transparent solvent, rather than in a blue solvent." Fortunately, the solvent that provided the best contrast also dissolved C60 and C70 most effectively, again putting more molecules in the path of the beam.
The team hopes to expand its work to include further explorations of the basic chemistry of buckyballs, including imaging fullerenes that have been combined with other elements, such as hydrogen, fluorine, and various metals. They expect to be able to determine how many and where these "piggyback" atoms are attached to the inner and outer surfaces of the fullerenes. They also expect to be able to produce and analyze larger fullerenes.
"It is difficult to get this kind of information from other techniques," Henderson says. "We also expect to be able to see whether these additional atoms have expanded the structure of the fullerenes. The actual mechanics and chemistry of adding other atoms to these molecules helps us understand how they react and combine with other elements. It could be that these materials--hydrogenated fullerenes, for instance--are better starting points for making other products."
"This project was an excellent example of cooperation among four research divisions," says Affholter. "Everybody had something to add to the project. Everybody talked and pulled together to make it work." The success of this group bodes well for the future of the informal collaboration. "We've gotten together to determine what we want to do next," Affholter says. "We like doing this kind of work, and if we don't do it, people at other labs will."
* Original Yahoo link: https://answers.yahoo.com/question/index?qid=20060808105315AATxiZT&guccounter=1 | 0.875565 | 3.772612 |
Yesterday (on May 8th, 2017), an asteroid swung past Earth on its way towards the Sun. This Near Earth Object (NEO), known as 2017 HX4, measures between 10 and 33 meters (32.8 and 108 feet) and made its closest approach to Earth at 11:58 am UT (7:58 am EDT; 4:58 am PT). Naturally, there were surely those who wondered if this asteroid would hit us and trigger a terrible cataclysm!
But of course, like most NEOs that periodically make a close pass to Earth, 2017 HX4 passed us by at a very safe distance. In fact, the asteroid’s closest approach to Earth was estimated to be at a distance of 3.7 Lunar Distances (LD) – i.e. almost four times the distance between the Earth and the Moon. This, and other pertinent information was tweeted in advance by the International Astronomical Union’s Minor Planet Center (IAU MPC) on April 29th.
This object was first spotted on April 26th, 2017, using the 1.8 meter Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), located at the summit of Haleakala in Hawaii. Since that time, it has been monitored by multiple telescopes around the world, and its tracking data and information about its orbit and other characteristics has been provided by the IAU MPC.
With funding provided by NASA’s Near-Earth Object Observations program, the IAU MPC maintains a centralized database that is responsible for the identification, designation and orbit computations of all the minor planets, comets and outer satellites of the Solar System. Since it’s inception, it has been maintaining information on 16,202 Near-Earth Objects, 729,626 Minor Planets, and 3,976 comets.
But it is the NEOs that are of particular interest, since they periodically make close approaches to Earth. In the case of 2017 HX4, the object has been shown to have an orbital period of 2.37 years, following a path that takes it from beyond the orbit of Venus to well beyond the orbit of Mars. In other words, it orbits our Sun at an average distance (semi-major axis) of 1.776 AU, ranging from about 0.88 AU at perihelion to 2.669 AU at aphelion.
Since it was first spotted, the object has been viewed a total of 41 times between April 26th and May 4th. In addition to the Pan-STARRS-1 survey, observations were also provided by the Cerro Tololo Observatory, the Mauna Kea Observatories, the Steward Observatory and the Kitt Peak-Spacewatch Telescopes, the Astronomical Research Observatory, the Apache Point Observatory, and the Mount John Observatory.
From these combined observations, the IAU MPC was able to compile information on the object’s orbital period, when it would cross Earth’s orbit, and just how close it would come to us in the process. So, as always, there was nothing to worry about here folks. These objects are always spotted before they cross Earth’s orbit, and their paths, periods and velocities and are known about in advance.
Even so, it’s worth noting that an object of this size was nowhere near to be large enough to cause an Extinction Level Event. In fact, the asteroid that struck Earth 65 millions year ago at the end of Cretaceous era – which created the Chicxulub Crater on the Yucatan Peninsula in Mexico and caused the extinction of the dinosaurs – was estimated to measure 10 km across.
At 10 to 33 meters (32.8 to 108 feet), this asteroid would certainly have caused considerable damage if it hit us. But the results would not exactly have been cataclysmic. Still, it might not be too soon to consider getting off this ball of rock. You know, before – as Hawking has warned – a single event is able to claim all of humanity in one fell swoop!
The MPC is currently tracking the 13 NEOs that were discovered during the month of May alone, and that’s just so far. Expect to hear more about rocks that might cross our path in the future.
Further Reading: IAU Minor Planet Center | 0.849746 | 3.750978 |
His Name In Lights is set on Jupiter’s moon Io, which has captured my interest for some time. I have at least one other Io story in the making. Expect an announcement about A Perfect Day Off The Farm fairly soon. In that story, I explain the concept of stick farms, which is something that would actually work.
Io is a body slightly bigger than Earth’s Moon which orbits Jupiter at roughly the same distance as the Moon orbits Earth. It is the closest of the larger moons of that planet. Jupiter, of course, is much, much bigger than Earth, and this has all sorts of consequences for its neighbourhood.
Io was discovered in 1610 by Galileo when he was looking at Jupiter and noticed three little dots close to it. Moreover, the dots were placed in a straight line (that’s a dead giveaway for a planetary or any kind of system that involves things orbiting each other), and on top of that, the next day, the dots were in different positions. The discovery of the four Galilean moons (Io, Europa, Ganymede and Callisto – the god Jupiter’s lovers in ancient mythology), proved Galileo’s hypothesis that other planet-moon systems existed and that, by extrapolation, the Earth was not the centre of the universe, nor the centre of the solar system.
You can see Jupiter and its dancing dots with a decent set of binoculars in the night sky. Because Jupiter is so large and has so much gravity, the moons race around the planet like bats out of hell, and their positions are visibly different every day.
Being the closest moon, Io orbits Jupiter every 42 hours. Since the circle it describes is the same size as the Moon’s orbit around Earth, it means it’s moving at a speed of over 17 kilometres per second. By comparison, the Moon moves at a speed of one kilometre a second. This thing is racing!
The same applies for the other three moons, Europa (3.5 days), Ganymede (7.15 days) and Callisto (16 days). All move at comparatively high speed, which is why they’re so much fun to observe. You can see them move.
The moons’ gravities also interact with each other, since all of them are roughly the size of our Moon and quite close together, astronomically speaking. They have developed a pattern of orbital resonance, where Io will orbit exactly twice within one orbit of Europa, and Europa will orbit twice with each orbit described by Ganymede. Which also means that Io will orbit exactly four times for one orbit of Ganymede. Callisto is the odd one out and isn’t playing this game.
This orbital resonance means that the three moons will frequently line up in a straight path and will be at cross-angles to each other at other times. This means that there are huge tidal forces exerted on each of those moons, but especially on poor little Io.
When telescopes became good enough to observe very fuzzy details of the surface, scientists thought at first that there were two moons. Sections of the surface are highly reflective, and later pictures of the moon show a kaleidoscope of colours in yellows, greens and reds, leading to the nickname ‘pizzaface’.
We now know that Io is made primarily of sulphur and silicates (aka ‘rock’). The atmosphere is very thin and patchy and when present consists of sulphur dioxide. There is no water at all, in contrast to the other three Galilean moons, which have significant percentages of water on their surface. It is thought that radiation from Jupiter has evaporated any water present on the surface.
Because of the huge tidal forces, Io is the most volcanic body in our solar system. On Earth, we think of tides as something that affects water, but that is just because water can easily move, so we notice the effect. Rock can’t move, so it gets hot in response to tidal forces. This is why the interior of Io consists of molten rock.
Geologists on Earth define an active volcano as one that has been known to exhibit activity within the last 400 years. Under that definition, every single feature on the 400-long list of mountains, depressions and rifts on Io is an active volcano.
In fact, the moon is so volcanic that there are no impact craters, like we can see on the Moon or Mars. That’s not because nothing’s ever hit Io, but because the evidence gets covered up pretty quickly. Essentially, Io is continuously being turned inside-out by its own fart-holes.
The spread of volcanic ash across the surface of Io amounts to an average of 1cm per year. At a geological scale, that’s massive.
It also means that any robotic craft or permanent fixture you were to put on the surface would need some sort of mechanism to keep itself un-buried from this material. To make matters worse, it’s most sulphur as well as Sodium and other elements that are Not Conducive to effective mechanical operation of equipment.
Mountains on Io are up to 8 kilometres in height. Some are volcanoes, but many are not, at least not at the top. The volcanic outlets are more likely to be at the bottom of the mountain.
Why? Well, imagine a layer of ice floating on water. Now pile ice chips on, and more ice chips and more ice chips… and eventually the layer of ice will start to protest, to buckle and twist and break, sink in one place and tilt upwards at another. Ah! Now we have mountains. The logic then also dictates that the breaks (= places where magma can rise to the surface) are next to the mountains.
What else would be special about Io?
The day on Io is 42 hours, the same as its orbital period. Because the moon is tidally locked with Jupiter, like our Moon, it always shows the same side to the planet. Which in turn means that a day on the moon is the same length as one orbit around the planet. On Io, however, this has an interesting complication.
As it races around Jupiter, Io experiences an eclipse every day when it goes into the shadow of Jupiter. The eclipse lasts 2.5 hours and in that dark time it gets so cold that the pathetic cover of sulphur dioxide that passes for atmosphere condensates on the surface as snow, only to sublimate again when the sun returns.
In fact, it is highly likely that the time of the eclipse is the darkest time of day on Io. At night, the Jupiter-facing (subjovian) side would have Jupiter in the night sky. To be honest, Jupiter will take up a very significant portion of the night sky. Think of the light it would reflect back to Io.
This only applies for the side that always faces Jupiter, though. On the other side, you would never see the planet, but you probably get some interesting views of the other moons.
No discussion about Io is complete without mentioning radiation. Every celestial body that has a magnetic field has Van Allen radiation belts. A magnetic field traps particles, either from the solar wind or cosmic radiation, in a donut-shaped torus around the planet. Crossing those belts at between 1000 and 60,000km from the Earth was one of the main concerns for the Moon astronauts. At about 370km, the International Space Station stays well clear of them.
Io orbits–you guessed it–smack bang in the middle of Jupiter’s Van Allen belt. Jupiter is the second-most magnetic object in the solar system (after the Sun). Io helps the particle soup along a bit by constantly spewing volcanic stuff into space.
All this amounts to a massive radiation load. So much that if you were to step onto the surface unprotected, you’d be dead in minutes. Radiation would also affect the operation of any robotic equipment you’d send there.
So, as you can see, there are serious challenges to doing anything on Io, and a lot of places in the solar system that are easier to visit. But Io is also one of the most interesting places in the solar system.
Reference: Io After Galileo, A New View of Jupiter’s Volcanic Moon. Rosaly M.C. Lopes and John R. Spencer (2006). Springer. 366pp. ISBN 978-3540346814.
Be warned, this book is pretty darn expensive. For those with a more casual interest, Io’s Wikipedia page has an extensive list of scientific references, some of which can be read or downloaded for free online. If you are interested in buying this book, you can get a copy here: Io After Galileo: A New View of Jupiter’s Volcanic Moon (Springer Praxis Books / Geophysical Sciences)
Patty writes hard Science Fiction, space opera and fantasy. Her latest book is Trader’s Honour, in the space opera series The Return of the Aghyrians. If you’d like to be kept up-to-date with new releases, remember to sign up for Patty’s new release newsletter. | 0.870832 | 3.402759 |
NASA Sun-Gazing Spacecraft Spots Unusual Eruptions
By NASA.gov // July 2, 2014
ejection of a massive burst of solar material
A suite of NASA’s sun-gazing spacecraft have spotted an unusual series of eruptions in which a series of fast puffs forced the slow ejection of a massive burst of solar material from the sun’s atmosphere.
The eruptions took place over a period of three days, starting on Jan. 17, 2013.
Nathalia Alzate, a solar scientist at the University of Aberystwyth in Wales, presented findings on what caused the puffs at the 2014 Royal Astronomical Society’s National Astronomy Meeting in Portsmouth, England.
The sun’s outermost atmosphere, the corona, is made of magnetized solar material, called plasma, that has a temperature of millions of degrees and extends millions of miles into space.
On Jan. 17, the joint European Space Agency and NASA’s Solar and Heliospheric Observatory, or SOHO, spacecraft observed puffs emanating from the base of the corona and rapidly exploding outwards into interplanetary space. The puffs occurred roughly once every three hours.
After about 12 hours, a much larger eruption of material began, apparently eased out by the smaller-scale explosions.
“We still need to understand whether there are shock waves, formed by the jets, passing through and driving the slow eruption,” said Alzate.
“Or whether magnetic reconfiguration is driving the jets allowing the larger, slow structure to slowly erupt. Thanks to recent advances in observation and in image processing techniques we can throw light on the way jets can lead to small and fast, or large and slow, eruptions from the sun.”
By looking at high-resolution images taken by NASA’s Solar Dynamics Observatory, or SDO, and NASA’s Solar Terrestrial Relations Observatory, or STEREO, over the same time period and in different wavelengths, Alzate and her colleagues could focus on the cause of the puffs and the interaction between the small and large-scale eruptions.
“Looking at the corona in extreme ultraviolet light we see the source of the puffs is a series of energetic jets and related flares,” said Alzate.
“The jets are localized, catastrophic releases of energy that spew material out from the sun into space. These rapid changes in the magnetic field cause flares, which release a huge amount of energy in a very short time in the form of super-heated plasma, high-energy radiation and radio bursts. The big, slow structure is reluctant to erupt, and does not begin to smoothly propagate outwards until several jets have occurred.”
Because the events were observed by multiple spacecraft, each viewing the sun from a different perspective, Alzate and her colleagues were able to resolve the three-dimensional configuration of the eruptions. This allowed them to estimate the forces acting on the slow eruption and discuss possible mechanisms for the interaction between the slow and fast phenomena. | 0.849748 | 3.773884 |
Berkeley, Calif.—Astronomers say they may have detected a second planet around Proxima Centauri, our solar system’s nearest neighboring star.
Announced at Breakthrough Discuss, an annual invitation-only interdisciplinary meeting held by the Breakthrough Initiatives (a scientific research organization primarily bankrolled by the Silicon Valley billionaire Yuri Milner), the planet’s existence remains unconfirmed—for now. Dubbed Proxima c, it would be a so-called super-Earth, with a minimum mass roughly six times that of our planet’s. Its approximately 1900-day orbit would likely make it a frigid, inhospitable place, orbiting some 1.5 times the Earth-sun distance from Proxima Centauri—which is a red dwarf star some four light-years away that is much smaller and dimmer than our familiar yellow sun. If confirmed, the newfound world would join Proxima b, a roughly Earth-mass planet discovered in 2016 in a more clement orbit around Proxima Centauri.
According to the scientists making the presentation—Mario Damasso of the Astrophysical Observatory of Turin and Fabio Del Sordo of the University of Crete—the tentative detection is based upon the same expansive multi-year dataset that first revealed Proxima b, with the addition of more than 60 further measurements of the star taken in 2017. Primarily gathered through the European Southern Observatory’s (ESO) HARPS instrument, the measurements look for planets by the telltale wobbling such worlds induce upon their host stars. The strength of such wobbles provides an estimate of a world’s mass; the wobble’s period yields a planet’s orbit. Among other incidental evidence, the wobble of Proxima c—a subtle swerve in the position of Proxima Centauri by slightly more than a meter per second—appeared in earlier observations to be of borderline significance, but was pushed into firmer territory by the last few years of additional measurements. The search for Proxima Centauri's planets has been spearheaded by the international Pale Red Dot planet-hunting team. The results are summarized in a paper that has been submitted to a peer-reviewed journal.
“It is only a candidate,” Damasso said during the presentation. “This is very important to underline.” Del Sordo offered similar cautions in his remarks, comparing the candidate world to a “castle in the air,” one that “we should keep working to put even stronger foundations under.” (Neither Damasso nor Del Sordo would make further comments on the record outside of their presentation, citing concerns about the embargo policies of the journal to which they submitted their paper.)
Further measurements with HARPS, the pair said, could ultimately confirm the planetary nature of Proxima c, as could follow-up studies with other facilities on the ground and in space. ESO’s next-generation planet-hunting ESPRESSO instrument on the Very Large Telescope in Chile, for example, would be able to detect the wobble caused by the candidate world with even higher fidelity. But most promising would be observations from the European Space Agency’s Milky-Way-mapping Gaia satellite, which is monitoring the motions and positions of more than a billion stars in our galaxy—including, it turns out, Proxima Centauri. Gaia could detect the planet’s presence by watching for wobbles, too. By the conclusion of its nominal five-year mission later this year, Del Sordo said, Gaia could provide “a decisive answer” as to whether or not Proxima c is real.
Beyond mere detection, the candidate planet would offer exciting opportunities for follow-up studies to characterize its nature, the presenting scientists said. According to Del Sordo, Proxima c would be “a spectacular laboratory for direct imaging”—astronomers’ parlance for snapping a planet’s picture across the vast gulfs of interstellar space. Proxima b has been discussed as a fruitful target for direct imaging as well. But because Proxima c is farther out from the star than b, it should be easier to see. Potentially within reach of future space observatories such as NASA’s James Webb Space Telescope and Webb’s planned successor, the Wide-Field Infrared Survey Telescope, the planet could become the first world beyond the solar system imaged in reflected light. (Previous direct images of planets have been in infrared light, where the glare of a planet’s star is less overwhelming.)
Any image of Proxima c—presuming the planet proves genuine—would likely reveal a chilly, gas-dominated orb, but could still prove extremely useful for astronomers struggling to understand what super-Earths are actually like. Despite being the most common known variety of planet in the Milky Way, super-Earths are entirely absent from our own solar system. Midway in mass and size between Earth and Neptune, super-Earths may either be mostly gassy planets offering slim chances for life as we know it, or instead super-sized versions of our own habitable, rocky world.
Images of planets in the Proxima Centauri system might also help resolve lingering debates over the potential for red dwarf stars to harbor habitable planets; such stars are often more active than solar-type stars, blasting accompanying worlds with showers of high-speed particles and hard radiation that can strip away atmospheres like so much sand-blasted paint. Pictures could resolve the fates of such worlds—provided, that is, astronomers manage to secure time on Earth’s most powerful telescopes to go look. | 0.898171 | 3.73542 |
Monster colliding black holes might lurk on the edge of spiral galaxies
The outskirts of spiral galaxies like our own could be crowded with colliding black holes of massive proportions and a prime location for scientists hunting the sources of gravitational waves, said researchers at Rochester Institute of Technology in an upcoming paper in Astrophysical Journal Letters.
The RIT study identifies an overlooked region that may prove to be rife with orbiting black holes and the origin of gravitational-wave chirps heard by observatories in the United States and Italy. Identifying the host galaxies of merging massive black holes could help explain how orbiting pairs of black holes form.
Conditions favorable for black-hole mergers exist in the outer gas disks of big spiral galaxies, according to Sukanya Chakrabarti, assistant professor of physics at RIT and lead author of “The Contribution of Outer HI Disks to the Merging Binary Black Hole Populations,” available online at
Until now, small satellite or dwarf galaxies were thought to have the most suitable environment for hosting black-hole populations: a sparse population of stars, unpolluted with heavy metals like iron, gold and platinum—elements spewed in supernovae explosions—and inefficient winds that leave massive stars intact.
Chakrabarti realized the edges of galaxies like the Milky Wavy have similar environments to dwarf galaxies but with a major advantage—big galaxies are easier to find.
“The metal content in the outer disks of spiral galaxies is also quite low and should be rife with black holes in this large area,” Chakrabarti said.
A co-author on the paper, Richard O’Shaughnessy, assistant professor of mathematical sciences at RIT and a member of the LIGO Scientific Collaboration, said: “This study shows that, when predicting or interpreting observations of black holes, we need to account not only for differences between different types of galaxies but also the range of environments that occur inside of them.”
A deeper understanding of the universe is possible now that scientists can combine gravitational wave astronomy with traditional measurements of bands of light. Existing research shows that even black holes, which are too dense for light to escape, have a gravitational wave and an optical counterpart, remnants of matter from the stellar collapse from which they formed.
“If you can see the light from a black-hole merger, you can pinpoint where it is in the sky,” Chakrabarti said. “Then you can infer the parameters that drive the life cycle of the universe as a whole and that’s the holy grail for cosmology. The reason this is important is because gravitational waves give you a completely independent way of doing it so it doesn’t rely on astrophysical approximations.” | 0.816577 | 4.037303 |
Australia and India reaching for the stars together
What is out there? Are we alone? How did the universe begin? These are questions that have baffled humankind for millennia. Space may be the final frontier, but every day we get a little closer to solving its mysteries. We may not have the answers to the big questions just yet, but we're finding out a lot of other useful information–about the universe, our planet and ourselves–along the way.
India's rapid growth has had a positive impact on so many areas of innovation, and now it too is reaching for the stars–literally. In 2015, India launched the Astrosat: its first dedicated multi-wavelength space observatory. In simple terms, it is a satellite that monitors frequencies in space. The huge potential of the Astrosat has fostered collaboration across continents, with a joint research project being undertaken by the University of Western Australia (UWA), in Perth, and the Indian Institute of Astrophysics (IIA), in Bangalore.
The aim of the research is to figure out how stars and galaxies form, and to learn why some stars continue to form in distant parts of space, while elsewhere they dwindled billions of years ago. The project is supported by a grant from the Australia-India Council (AIC), and will form an important partnership between India and Australia in the field of space science. It combines Indian leadership in the development of ultraviolet space-telescopes with Australia's internationally recognised expertise in galaxy evolution studies.
We recently spoke to AIC grant recipient, Dr. Luca Cortese, a Senior Research Fellow at UWA who's central to the project. Though it's early days for the research, Luca's optimistic about not just the scientific discoveries he expects to make, but the longer-term partnerships between the two countries and where they will lead in the future. "We consider the AIC grant more as a seed fund to start getting people together and to gain momentum," he says. "The real success of the project will be if we can have a serious collaboration, and serious engagement, that lasts for the next decade."
The project is a large-scale collaboration that is allowing experts in the field to travel between India and Australia to share knowledge and coordinate their research. The visits are important because they allow scientists to meet in person, ensuring it's not just skills and data being shared, but cultural experiences and understanding. As with any long-term, multi-year research, strong relationships are critical to the success of the project. There is an added benefit as well–India has a growing number of students interested in astronomy, many of whom want to undertake a portion of their study in Australia. A successful collaboration between the two countries will go a long way to helping support the next generation of space scientists.
While the short-term aim of the project is to combine observations of galaxies from different Australian and Indian facilities to get the best possible picture of how stars and galaxies form, the long-term vision would see Australia become a significant partner supporting the Indian presence in space. So, says Luca, "you could call this the beginning of a long and prosperous collaboration with our friends in India."
The project is a win-win scenario–forming strong cross-cultural connections here on Earth, while solving the mysteries of the universe above.
Read the full interview with Luca from our 'Australia & India. A Dynamic Mix' series.
Learn more about the economic potential of the Australia-India partnership in An India Economic Strategy to 2035 – Navigating from potential to delivery | 0.820477 | 3.323474 |
Clear November night skies offer incredible celestial sights for stargazers, so bundle up and get outside for stargazing fun!
- Pre-Dawn Planetary Pairing - Look just above the southeastern horizon a few hours before sunrise on November 2nd to see a close conjunction between bright Venus and reddish-orange Mars. Earth's two next-door neighbor planets will appear just 0.7° apart before they fade into the light of sunrise.
- Big and Bright, Jupiter Season is here - In early November the gas giant planet Jupiter rises in the east about 1:30AM, but by the end of the month it will rise before 11:00 PM and be quite high in the eastern sky by midnight - a perfect position to get great views. Jupiter will be the brightest object in the eastern sky. Nearly any telescope, and even a pair of good astronomy binoculars, will show the four brightest Galilean Moons (discovered by Galileo, the inventor of the telescope) and a 3" or larger refractor will show detail on the planet itself with moderate to high power. Use a blue Jupiter Observation Filter to enhance contrast of the planet's major equatorial cloud bands.
- Leonids Meteor Shower - Go outside around midnight on Tuesday, November 17th into the early morning hours of the 18th to see the peak of the annual Leonids Meteor Shower. The best viewing will be after midnight, after the first quarter Moon sets. Look for meteors as they appear to radiate out from the constellation Leo. The Leonids meteors are left-over debris of comet Temple-Tuttle, a comet that orbits the Sun every 33 years. Grab a warm blanket or coat and enjoy the show!
- Best Star Cluster - M45, the Pleiades. November is sometimes called "the month of the Pleiades," since the star cluster is visible all night long for observers in the Northern hemisphere. From a dark sky site, it is easy to see with the unaided eye and resembles a small "teaspoon" pattern in the sky, but this open star cluster is best appreciated in a good pair of astronomy binoculars or a telescope with a lower-power eyepiece.
- Best Galaxy - M31, The Andromeda Galaxy. If you view the sky often, you've been watching this object for months now; around 9 PM in early November the Andromeda Galaxy is just north of the constellation Andromeda and positioned high in the eastern sky for great telescopic views. M31 is the nearest neighboring galaxy to our home galaxy, the Milky Way.
- A Bright Spot in the Milky Way - High in the northern sky at 10 PM is a brighter knot in the Milky Way, between the constellations of Perseus and Cassiopeia. With astronomy binoculars you can tell that it is really two open star clusters side by side, the famous Double Cluster in Perseus. Also called NGC 884 & NGC 889, these star clusters are relatively very close to Earth, about 7-8,000 light years away. They're also very young star clusters. Astronomers believe these are only about 3-5 million years old, just youngsters on the cosmic timescale!
- A Dark Sky Test - On the opposite side of Andromeda is another nearby galaxy, M33. Use a star chart to look for it in 50mm or larger astronomy binoculars. If you have a dark sky site to observe from, you can even detect this galaxy with the unaided eye. In fact, M33 is used as a test by many experienced observers to judge the darkness and transparency of a potential observing site.
- Catch a Dying Star - High in the western skies of November, early in the evening, the constellation Cygnus is still prominently visible and topped off by the bright star Deneb at the top of the "Northern Cross." Use a star chart to track down the Veil Nebula on the eastern side of Cygnus near the star 52 Cygni. Use an Oxygen-III filter and low power while you scan for this object. The Veil is a remnant of a supernova explosion, where a star has died! We recommend a 4" or larger telescope to catch it (but it has been seen in smaller scopes from good dark sky locations with excellent seeing conditions).
- November's Challenge Object - Low in the southern sky, in the constellation Grus, lies a BIG planetary nebula called IC5148. You'll need at least a 6" telescope to see it, and an Oxygen-III filter really helps. This 13th magnitude planetary is 120" x 120" of arc across, so it's nice and big, but it's tough for most observers to catch since it is so low in the south and the surface brightness is low. IC5148 is about 3000 light years away and is sometimes called the "Spare Tire" Nebula.
ESO Photograph of IC5148 with the New Technology Telescope
All objects described above can easily be seen with the suggested equipment from a dark sky site, a viewing location some distance away from city lights where light pollution and when bright moonlight does not overpower the stars. | 0.935836 | 3.382101 |
Table of contents
About this book
Sirius - A Diamond in the Night will tell two stories. The first and most obvious is why the star known as Sirius has been regarded as an important fixture of the night sky by many civilizations and cultures since the beginnings of history. A second, but related, narrative is the prominent part that Sirius has played in how we came to achieve our current scientific understanding of the nature and fate of the stars. These two topics have a long intertwined history, and the telling of one story eventually leads back to the other. Presently, new observations from space are revealing, in precise terms, how stars like Sirius and the Sun have evolved and what they will ultimately become, while at the same time answering some of the age-old questions about Sirius.
The book is divided into five parts. The first (Chapters 1 and 2) describes how Sirius was viewed by the ancient civilizations of Egypt, Greece and Rome. The second part (Chapters 3-5) describes how early astronomers sought to determine the nature of the stars, including the prediction that Sirius possessed an unseen companion and the eventual discovery of this white dwarf companion 18 years later. The third part (chapters 6-9) describes the major discoveries in stellar astrophysics revealed by observations of Sirius. The fourth part (chapters 10 and 11) probes the modern scientific and pseudo scientific controversies involving Sirius, including the ‘Red Sirius’ and Dogon tribe stories. The final part (Chapters 12 and 13) highlights modern observations made with the Hubble Space Telescope and other spacecraft of the white dwarf companion. | 0.865261 | 3.131963 |
This year’s Nobel Prize winning finding that the ‘Universe is accelerating’ is being subjected to another validation test in the USA to confirm whether the expansion is “even or uneven”.
“We are testing the acceleration theory through another experiment to find whether the expansion is even or multi-directional. We are confident it would be ‘even’,” says eminent cosmologist Prof.Robert Kirshner who guided two of the three-member team of researchers that bagged the Nobel Prize in Physics – 2011 for the revolutionary finding recently.
With the experimental study now on, this time using the MMT telescope in Arizona and the Magellan Telescope in Northern Chile, he said, the researchers would, within two years, be in a position to collect enough data to determine whether the expansion of the Universe is even or in all directions, Kirshner said.
Kirshner of the Centre for Astrophysics, Harvard University (USA) was interacting with this Indian Science Writers Association(ISWA) representative in South Goa on the sidelines of the just concluded week-long VII International Conference on “Gravitation and Cosmology” organised by the International Centre for Theoretical Sciences(ICTS) under the prestigious Tata Institute of Fundamental Research, Mumbai.
As many as 300 astrophysicists from across the world had participated in the conference and shared their findings and experiences on black holes,gravitation wave experiments and need for international collaborations to promote research in astrophysics of the 21st century.
His researchers – Adam Riess and Brian Schmidt – along with Perl mutter, had recently received the Nobel Prize in Physics for their stellar discovery in 1998, used the Panstars Telescope with big array of detectors with a gigapixel resolution to capture the image of many galaxies at the same time for the study.
“I am also confident that such high resolution and higher sensitive telescopes enable us trace the history of their shifts by recognizing what is known as their “Red Shifts” as the galaxies move away from us,” he said.
The on-going studies may also throw light on the ‘fossils of light” emitted when stars exploded during what is known as the “Big Bang” 14 billion years ago that led to the creation of the Universe.
“We expect data we gather could unlock the secrets of the origin of the Universe including the history of the first galaxies, stars and the supernovae and their death,” he said.
Scientists believe that the Universe contain galaxies, each composed of about 100 billion stars observable enough and 100 billion unobservable galaxies.
Earlier in his plenary talk in the conference on “Exploding Stars and the Accelerating Universe,” Kirshner said observations of exploding stars halfway across the universe show that the expansion of the universe is speeding up.
“We attribute this to a pervasive ‘dark energy’ whose properties we would like to understand. This work was recently honoured by the 2011 Nobel Prize in Physics to Perl Mutter, Schmidt and Riess.”
He had also presented the most recent evidence from supernovae, Cosmic Microwave Background (CMB) fluctuations, and galaxy clustering. The present state of knowledge on dark energy is completely consistent with a modern version of the cosmological constant, but with a ridiculously low value.
He also discussed ways to use infrared observations to make the supernova measurements with better accuracy and higher precision.
Kirshner also explained how improved supernova measurements and the matrix of evidence from other observations can help us understand whether modifications to general relativity or a time-varying component of dark energy can be ruled out.//EOM// | 0.844985 | 3.62534 |
By Greg Crinklaw
Major professional observatories, such as ESO, use mathematical models of their telescope and instruments to plan their observations. It is useful to know the image scale, what exposure times to use, whether a star will bloom or if the signal will become nonlinear, and how many exposures are required to reach a given Signal to Noise Ratio (SNR).
I have long thought that amateurs could greatly benefit from such a tool, but many of the difficulties in doing so seemed insurmountable. The professional apps tend to focus on one telescope, one instrument, and a specific type of work such as spectroscopy. To be truly useful to the amateur, an app would have to work with any telescope, camera, and filter. Most difficult of all, it would have to handle a range of target objects such as stars, galaxies, and emission nebulae.
My previous software product, SkyTools 3, is primarily aimed at visual observers. It does have an imaging capability, but it uses a crude imaging model that suffers from many shortcomings. The model was originally developed by Bradly Schaeffer and it makes many simplifying assumptions, such as filters that must be approximately Gaussian, and it has no means of handling emission line objects, such as HII regions and supernovae.
It was a first step, but only that. In order to be more useful, I would need a much better model, and I would have to invent ways to approximate both the spatial and spectral energy distribution of everything from comets to planetary nebulae.
In the end, SkyTools 4 Imaging took over four years of full-time work and introduces an entirely new imaging system model. It begins with the target object and ends with an accurate prediction of the target object signal, sky signal, system noise, and finally SNR. Any set of observing conditions can be simulated, including the effects of seeing, airmass, twilight, and moonlight.
So how does it do it?
Spectral-Energy Distribution of the Target Object
Stars and other stellar sources (quasars, minor planets, etc.) are modeled based on the continuum, which can be described by their UBVRI color indices (see Figure 1).
Reflection nebulae, galaxies, and comets are modeled similarly, using UBVRI colors representative of these objects. For galaxies, the type of galaxy determines the color characteristics.
Planetary nebulae, HII regions and supernova remnants are modeled via their emission line spectrum (see Figure 2). The primary emission lines used in SkyTools are H-Alpha, H-Beta, OIII, NII, and SII. Other lines are included when data is available.
For some objects, (HII regions and supernova remnants in particular) there is no catalog data available for the required emission line strengths. To obtain data for these objects I have scoured the scientific literature. For those that remained without sufficient data I have initiated an observing campaign using narrow band filters to measure the emission.
For a given object, the total energy as well as the energy distribution is modified as it passes through the atmosphere. The degree to which it is modified depends on the airmass, atmospheric conditions (temperature, humidity), and time of year.
The brightness of the sky background depends on the amount of light pollution, moonlight, twilight, altitude of the target, and atmospheric conditions.
The area of the telescope objective, minus what may be obstructed by the presence of a secondary mirror, determines how much total energy is collected. The optics also modify the spectral distribution, depending on the optical coatings. In the case of reflecting optics, the time since the mirror was last cleaned has a significant effect.
A filter is modeled by combining the spectral transmission curve of the filter with the energy distribution of the target object, as modified by the atmosphere and optical system (see Figure 3).
At the final step, the number of photons counted by each pixel is the integral over wavelength of the spectral energy distribution of the light that reaches the detector, combined with the spectral quantum efficiency of the detector. The quantum efficiency tells us how many electrons are produced for each photon detected (see Figure 4).
As a result of the previously mentioned steps, the signal in e- (electrons) can be predicted. For extended objects it is predicted on a per pixel basis, along with the signal from the sky background. The signal measured by each pixel in e- is converted to ADU via the camera gain. The SNR can be estimated per pixel based on the signal and the total noise (primarily composed of detector readout noise and sky noise).
For stellar objects the total signal in e- is predicted. The atmospheric conditions and limitations of the telescope optics determine how this signal is spread over the detector, as modeled by a point spread function. The photometric SNR is computed for the total signal and noise over a circular aperture. The peak SNR is computed for the peak signal (peak of the point spread function) and the estimated noise at the peak.
Diffuse objects such as galaxies, nebulae, and comets, are not uniform. For example, a spiral galaxy may consist of a bright central core, spiral arms, and a faint outer halo.
So, when estimating the SNR, it is important to specify what part of the galaxy we are exposing for. Do you wish to merely detect the bright core? Or do you wish to obtain a high-quality (high SNR) image of the spiral arms? The surface brightness corresponding to each part of the galaxy is estimated by a combination of the overall brightness of the galaxy and statistics for galaxy type.
A similar process is used for other diffuse objects, such as reflection nebulae. For comets, the size of the coma and degree of concentration from recent observations are used.
The model has been tested extensively using the many imaging systems available at iTelescope.net.
The primary testing was done with Landolt UBVRI standard star fields. I developed an image analysis app that uses the information from the FITS header along with photometry extracted from the image data. The photometry was tested against software from the AAVSO to ensure its accuracy. For each image the actual signal is compared to the signal predicted by the model for the time and conditions of the image.
Interestingly, several additional significant effects were uncovered in testing, such as the age and cleanliness of the mirrors, and the optical transmission of the camera window.
In the end we can compute the SNR for any exposure at any time during the night. But what if the conditions are changing rapidly? E.g. what if the sky brightness is changing during the exposure? Or for an image of a comet at high airmass, the airmass can change quickly as it sets.
Standard SNR calculators implicitly assume that conditions don’t change during the exposure. But the SkyTools Imaging calculator integrates the signal, sky brightness, and other factors, over time. As a result, it can estimate the SNR of an image even when the conditions are changing rapidly during the exposure.
Finally, we can create a model with real world inputs that are based on the properties of the target object, location, weather conditions, airmass, sky brightness, and imaging system. This can be very useful by itself, but we can take it a step further. For any time of night the SNR can be computed for an arbitrary exposure. We can also compute the SNR for the same exposure, but under the ideal conditions at the same location. When we compare the two by dividing the SNR computed for the test exposure by the SNR under ideal conditions, we have an index that can be used to estimate the imaging quality (IQ) at any time. This is extremely useful for planning when to image in each filter.
It has been a long journey, and I faced many apparently insurmountable problems, but I am very happy with the result. I can’t imagine planning my own imaging without it. I use SkyTools 4 Imaging to select targets that are appropriate for an imaging system, determine the number of exposures and sub exposure times required to meet a target SNR, maximize my SNR by planning my images during the best time of the night, and even to select which available telescope is best for a given target.
Greg Crinklaw operates Skyhound and is the developer of SkyTools. He is a life-long amateur astronomer, who is also trained as a professional astronomer, holding a BS, MS in astronomy, and an MS in astrophysics. He also worked for NASA as a Software Engineer on a Mars orbital mission. Greg and his family live in the mountains of Cloudcroft, New Mexico. | 0.912766 | 3.885402 |
Invariably when we write about living on Mars, some ask why not go to the Moon instead? It’s much closer and has a generous selection of minerals. But its lack of an atmosphere adds to or exacerbates the problems we’d experience on Mars. Here, therefore, is a fun thought experiment about that age-old dream of living on the Moon.
Inhabiting Lava Tubes
The Moon has even less radiation protection than Mars, having practically no atmosphere. The lack of atmosphere also means that more micrometeorites make it to ground level. One way to handle these issues is to bury structures under meters of lunar regolith — loose soil. Another is to build the structures in lava tubes.
A lava tube is a tunnel created by lava. As the lava flows, the outer crust cools, forming a tube for more lava to flow through. After the lava has been exhausted, a tunnel is left behind. Visual evidence on the Moon can be a long bulge, sometimes punctuated by holes where the roof has collapsed, as is shown here of a lava tube northwest from Gruithuisen crater. If the tube is far enough underground, there may be no visible bulge, just a large circular hole in the ground. Some tubes are known to be more than 300 meters (980 feet) in diameter.
Lava tubes as much as 40 meters (130 feet) underground can also provide thermal stability with a temperature of around -20°C (-4°F). Having this stable, relatively warm temperature makes building structures and equipment easier. A single lunar day is on average 29.5 Earth days long, meaning that we’ll get around 2 weeks with sunlight followed by 2 weeks without. During those times the average temperatures on the surface at the equator range from 106°C (224°F) to -183°C (-298°F), which makes it difficult to find materials to withstand that range for those lengths of time.
But living underground introduces problems too.
One problem with living underground is that makes it difficult to communicate from one location to another, perhaps even between different lava tubes. To overcome this, cables could be run through the tubes and antennas could be located on the surface.
Lava tubes are often found on the boundaries between the highlands and the mares. Lunar mares are the uniform dark areas visible from Earth with the naked eye, mare being Latin for “sea”. The antennas could be located high up in those highlands. Ideally, there would always be at least one communications satellite within communications range and a network of them for transmitting anywhere on the Moon.
Electrical Ground And Charged Dust
The moisture in Earth soil aids conductivity by helping ions move around, making for a good electrical ground. Lunar soil, however, is dry and therefore is a poor electrical ground. Connecting structures together with cables can at least bring those structure to a common potential, creating a sort of ground.
But a bigger problem than that is moon dust. Apollo astronauts found that the dust clung to everything and they brought it with them into the lander. Harrison “Jack” Schmitt of Apollo 17, reacted to it strongly, saying that it caused his turbinates (long, narrow bone in the nose) to swell, though the effect diminished after a few hours. Even the vacuum cleaner they used to clean up the dust became clogged.
This dust also becomes charged by solar storms, only to then be discharged when solar radiation knocks the extra electrons off, but that discharging doesn’t happen during the long nights. Inferring from data collected by the Lunar Prospector during orbits in 1998-1999, charging also happens when the Moon passes through the Earth’s magnetic wake created by the solar wind. This happens in 18-year cycles and is currently at its peak.
With the Earth’s and Mars’ atmospheres, built up charge can be bled off to the atmosphere using sharp metal points which ionize the surrounding air. On the Moon, that approach is far less effective. Using all dwellings as a ground at least provides a large capacitor to take up stray charge. If you know of a good solution to this problem, we’d like to hear it.
Producing Oxygen From Soil
We’ll of course need oxygen to breathe and one source is the lunar soil. The process usually involves reacting certain oxygen-bearing minerals with hydrogen while heating to around 1000°C. Much work has been done with the mineral ilmenite (FeTiO3), making the process:
FeTiO3 + H2 + heat -> Fe + TiO2 + H2O
This gives us water vapor which would be separated from the other components. We could then use the water as is, or we could use electrolysis to split apart the hydrogen and oxygen. We’d condense the oxygen for storage, and recycle the hydrogen back into the process. Hydrogen is scarce on the Moon and so the hydrogen could initially be shipped from Earth and then continuously recycled.
This ilmenite is abundant on the Moon, first having been found in moon rocks returned by the Apollo astronauts, and then other locations have been inferred by the Hubble Space Telescope, one such being in the area of Aristarchus crater. Luckily that’s also near the lava tubes with collapsed pits which we’d mentioned above near Gruithuisen crater. However, for abundant water, we’ll need to look to the north and south poles.
Water From The Poles
The evidence is very strong that there’s a mix of hydroxyl (OH) and water (H2O) on the Moon’s surface. The theories are that it comes from comets impacting on the Moon and from hydrogen ions created when the solar wind interacts with oxygen in the soil.
But for most of the Moon, solar radiation would then free the hydrogen and oxygen atoms from their molecules and they would escape to space. However, the lunar poles have areas which are in perpetual shadow, forever free of the hydrogen-liberating solar radiation. After decades of spacecraft probing these regions, the evidence for water and hydroxyls there is very strong, though the quantity of it is still uncertain.
This means that a good location for a lunar mining outpost would be in sunlit areas adjacent to these areas of perpetual shadow. There are even some such locations around the poles that are high enough to be in perpetual sunlight. And that perpetual sunlight is ideal for generating electricity using solar panels which we could manufacture on the Moon from mined minerals.
Mining And Manufacturing
The Moon is lacking in volatile chemicals, ones that have a low boiling point, having negligible amounts of hydrogen, nitrogen, and carbon. But it is rich in many other chemicals and minerals. Mining them is important for two reasons: for building the things we need and for exporting to the other off-Earth colonies either in raw form or in manufactured products.
We’ve already mentioned using ilmenite (FeTiO3) to produce oxygen, but the byproducts of that are iron (Fe) and titanium (Ti), both of which can be used for the construction of living spaces, vehicles and other rigid objects.
Examining a table of Earth and lunar crustal composition, you’ll see that the Moon contains an abundance of useful minerals.
The silicon can be used for producing solar cells along with phosphorus and boron for the dopants. The study that produced the table doesn’t include boron, but other studies have found it in Moon rock, albeit in the 25 PPM and lower range and so it may have to be imported.
Helium 3 is another valuable substance that can be mined on the Moon. The Chinese Chang-E1 lunar satellite estimated the amount in lunar regolith as 660 billion kg. It’s hoped that it can be used for future fusion reactors due to that fusion producing no radiation and more energy than other fusion reactions. However, it also requires a higher temperature. Just 6,700 kg would be required to power the US for one year. Luckily helium 3 is in abundance in the same area where we’ll be mining ilmenite.
We’ve already mentioned that there are areas around the poles that are in perpetual sunlight. So during the long nights, solar power farms in those areas could generate electricity as a product to sell throughout the Moon.
Geothermal energy isn’t an option for the Moon, at least not for the colonies’ early days as you’d have to drill down around 45 km (28 miles) before the temperature reaches the boiling point of water. Geothermal energy has been used to generate electricity in Chena Hot Springs, Alaska with only 57°C (135°F) but that’s still around 20 km (12.5 miles) deep.
If helium 3 fusion is ever made to work then it could be used to provide electricity through the long lunar night when the local solar farms are down. And it might have to, because uranium is in short supply on the Moon.
Home Sweet Home
And so we’ll have a central colony in the lava tubes near Gruithuisen crater. Some of the inhabitants will spend time mining ilmenite just a little south around the Aristarchus crater to produce oxygen and mineral byproducts. Meanwhile, others will spend time working on the water mines at the north pole and maintaining the solar power farms there which sit in the perpetual sunlight.
When will you be ready to move? What would you do differently? We haven’t even touched on growing food, which will have its own challenges given the lack of volatiles such as nitrogen. What other issues can you think of? Let us know in the comments below. | 0.822416 | 3.806855 |
November 17, 2016 – A liquid ocean lying deep beneath Pluto’s frozen surface is the best explanation for features revealed by NASA’s New Horizons spacecraft, according to a new analysis. The idea that Pluto has a subsurface ocean is not new, but the study provides the most detailed investigation yet of its likely role in the evolution of key features such as the vast, low-lying plain known as Sputnik Planitia (formerly Sputnik Planum).
Sputnik Planitia, which forms one side of the famous heart-shaped feature seen in the first New Horizons images, is suspiciously well aligned with Pluto’s tidal axis. The likelihood that this is just a coincidence is only 5 percent, so the alignment suggests that extra mass in that location interacted with tidal forces between Pluto and its moon Charon to reorient Pluto, putting Sputnik Planitia directly opposite the side facing Charon. But a deep basin seems unlikely to provide the extra mass needed to cause that kind of reorientation.
“It’s a big, elliptical hole in the ground, so the extra weight must be hiding somewhere beneath the surface. And an ocean is a natural way to get that,” said Francis Nimmo, professor of Earth and planetary sciences at UC Santa Cruz and first author of a paper on the new findings published November 16 in Nature. Another paper in the same issue, led by James Keane at the University of Arizona, also argues for reorientation and points to fractures on Pluto as evidence that this happened.
Like other large basins in the solar system, Sputnik Planitia was most likely created by the impact of a giant meteorite, which would have blasted away a huge amount of Pluto’s icy crust. With a subsurface ocean, the response to this would be an upwelling of water pushing up against the thinned and weakened crust of ice. At equilibrium, because water is denser than ice, that would still leave a fairly deep basin with a thin crust of ice over the upwelled mass of water.
“At that point, there is no extra mass at Sputnik Planitia,” Nimmo explained. “What happens then is the ice shell gets cold and strong, and the basin fills with nitrogen ice. That nitrogen represents the excess mass.”
Nimmo and his colleages also considered whether the extra mass could be provided by just a deep crater filled with nitrogen ice, with no upwelling of a subsurface ocean. But their calculations showed that this would require an implausibly deep layer of nitrogen, more than 25 miles (40 kilometers) thick. They found that a nitrogen layer about 4 miles (7 km) thick above a subsurface ocean provides enough mass to create a “positive gravity anomaly” consistent with the observations.
“We tried to think of other ways to get a positive gravity anomaly, and none of them look as likely as a subsurface ocean,” Nimmo said.
Coauthor Douglas Hamilton of the University of Maryland came up with the reorientation hypothesis, and Nimmo developed the subsurface ocean scenario. The scenario is analogous to what occurred on the moon, where positive gravity anomalies have been accurately measured for several large impact basins. Instead of a subsurface ocean, however, the dense mantle material beneath the moon’s crust pushed up against the thinned crust of the impact basins. Lava flows then flooded the basins, adding the extra mass. On icy Pluto, the basin filled with frozen nitrogen.
“There’s plenty of nitrogen in Pluto’s atmosphere, and either it preferentially freezes out in this low basin, or it freezes out in the high areas surrounding the basin and flows down as glaciers,” Nimmo said. The images from New Horizons do show what appear to be nitrogen glaciers flowing out of mountainous terrain around Sputnik Planitia.
As for the subsurface ocean, Nimmo said he suspects it is mostly water with some kind of antifreeze in it, probably ammonia. The slow refreezing of the ocean would put stress on the icy shell, causing fractures consistent with features seen in the New Horizons images.
There are other large objects in the Kuiper belt that are similar to Pluto in size and density, and Nimmo said they probably also have subsurface oceans. “When we look at these other objects, they may be equally interesting, not just frozen snowballs,” he said. | 0.876406 | 3.865429 |
A pink supermoon greets this time of full moon. We are in times of coronavirus, and the planets indicate restriction, lockdown, curfew, social distancing; all this. Yet, other planets deliver energy that we must learn to manage. We can do best when we chant – internally – “I am the light; I am the love, I am the truth, I AM!
A supermoon occurs when a full moon happens on the same night the moon reaches perigee, or the closest point to Earth in its orbit. (Apogee is its furthest point from Earth in its orbit.) In April, in the US the full moon peaks at 10:35 EDT. Though the moon is called a “pink” moon, its color won’t be any different than normal. It will be golden orange when low in the sky, and brighten to white as it rises. The name comes from pink wildflowers called creeping phlox that bloom in early spring, under April’s full moon, per Catherine Boeckmann at the Old Farmer’s Almanac. That “pink” reference is from botany in the USA.
Supermoons are only about seven percent bigger and 15 percent brighter than the average full moon, so the difference may not be obvious. The slight change in size happens because the moon follows an eccentric orbit around Earth that isn’t perfectly circular. On March 24, for example, Earth’s lunar companion reached its furthest apogee of the year, about 252,707 miles away. On April 7th, it will be about 30,000 miles closer, only 221,772 miles from Earth. That’s only a few hundred miles further than the closest supermoon in recent history, which occurred in November 2016.
Supermoon isn’t a scientific term for the astronomical event-that term is “perigee-syzygy.” Rather, the term supermoon was introduced by astrologer Richard Noelle in 1979.
The Full Moon
The April Full Moon occurs in Virgo, in Chitra nakshatra Pada 1.
Virgo is the natural 6th house, has both kapha and unhealthy vata. Earth sign, ruled by Air planet. Dusthana sign. However, at this time, it is not the 6th house, for the Ascendant – lagna is in Gemini, Mercury is Lord of 1st and 4th houses and debilitated in midheaven, the 10th house. Mercury is very weak and cannot offer much intelligence nor swift movement at this point in time. This moon is in the 4th house in this time of lockdown, Janata Curfew; the enforced stay at home for many peoples in many nations.
The situation here is that people may begin to feel ambitious, and start planning on resuming their lives, for the Moon is in pada 1 of Chitra nakshatra, wherein lies the drive, the planning for perfection. Tvashtar – the divine architect – is the devata of this nakshatra. And living in lockdown with a lot of people will turn the mind inwards to plan a the perfect escape. Unfortunately, for those who escape, the authorities are not so kind. We need to put down roots (this nakshatra helps), and bide our time. An interesting Full Moon, aspected at this point in time from Capricorn by Jupiter, who brings the inner resources to soften the hard crash of lockdown. Jupiter makes matters a little gentler.
We began by saying that Virgo is the natural 6th house, has both kapha and unhealthy vata.. This signifies multiplication of fluid on the lungs and vata needing relief: people will be on ventilators, and with the weak aspect of Mercury on its own sign, the ventilators will not be in sufficient quantity when needed. It is a most challenging time, beefed up by Rahu with the Ascendant.
Rahu in Gemini (vata sign, signifies lungs).
Rahu in Gemini somewhat multiplies the desire to escape lockdown. Rahu conjunct the Ascendant has a passion for mobility and supremacy. Rahu will seek admiration by risk-taking and driving people flout the boundaries of the coronavirus lockdown. It certainly doesn’t help this time of full moon with similar energy flowing from Virgo! Rahu loves to over-extend social norms; we need to practice self-awareness with a dash of self-control when the urge to break free and flout the social distancing norms arises within. Yes, Rahu will drive many stir-crazy, a condition well-known in prisons which makes people want to escape captivity no matter what. It is really time to slow down, to go within, to take space for the soul and get in contact with the soul at this time, rather than let the excitement of risk-taking lead us astray.
Kaal Sarp Yoga
We must point out that all planets except the Moon are between the head and tail of the dragon, what is called the Kaal Sarp Yoga, the serpent of time. The Moon – the presiding deity of the mind, feels threatened by malefics on either side – Rahu and Ketu, and so has nervousness until it passes Ketu in transit. Kaal Sarp Yoga tends to affect nations more so than individuals, and analysis of national charts is needed to ascertain the effects. Astro Cartography may also help in this instance. Here, examine the transit of the 40° parallel, and the nations involved:
Jupiter, Saturn Mars in 8th House
Jupiter has transited out of Sagittarius, where it was conjunct Ketu in this time of pandemic; the energy of Jupiter was multiplying the pandemic – auspiced by Ketu and Rahu.
Now that Jupiter is in Capricorn, it will behave a little bit like Saturn and actually slow things down. The energy of Jupiter in this time and place will actually help “flatten the curve”. Let’s look at this. Jupiter is normally debilitated in Capricorn; here, today, will not be debilitated. The neechabanga rules, the one that says Neecha is cancelled if the debilitated planet is aspected by a planet in exaltation or own sign. So we have Saturn in its own sign (Saturn is Lord of Capricorn) which is the first cancellation or neechabanga. Then we have Mars: Mars is exalted, fulfilling the second neechabanga condition for Jupiter, thus making Jupiter strong in this sign. We also note that Jupiter is vargottama; it is in the same sign in the Navamsha chart. This strengthens the role of Jupiter as a benign influence on Saturn and Mars – thus generating an energy of resilience instead of wartime tension and suffering.
This is reinforced by the role of Mars in the 8th house: here, Mars rejuvenates, discovering secret sources of regeneration and rebirth. Mars will aid the purgation of the various realms of experience: physical, emotional, mental, spiritual, to bring about resilience that looks to yesterday, today and tomorrow with confidence and rebounding back.
Saturn in the 8th house indicates resilience and resistance to danger. Saturn explores narratives, stories, legends and family history about survival, rigidity, structure, statutory law, and persistence in the face of obstruction. Saturn – manda, the slow one – will rely in inner experience and learning, draw strength from bildungsroman – the coming of age in this time of coronavirus – and slowly map a path to recovery, resilience and danger. Saturn will take up the script of control, boundaries, restriction and prohibition and turn them into assets that create the future -slowly, with endurance, with confidence in the outcome.
Here, we need to talk about the planets in our lives. We often tell here that the planets can raise us up, they can pull us down. You may propitiate the planets with puja, hommam, stotram and mantram; you may propitiate the planets with trikarana suddhi, the purity of thought, word and action. You take to these matters, these current conditions with awareness of what your inner talk is about, and manage that, then you will be a mastermind and draw the positive energy, the positive magnetism of the planets. We are speaking of nava-graha, the nine seizers. Graha means to seize, you want the energy, the refracted light, the magnetism of the planet to have a positive effect within. Recall that grace (anugraha) requires effort; you put in your part with trikarana suddhi, self management of time, talents and resources, and you will attract the right energy around yourself. Ditto with planets.
Sun in 10th House
The Sun receives dig-bala (additional strength) when it is in the 10 house, the mid-heaven. Here, the Sun finds itself at the centre of affairs, handicapped and perhaps restrained by restrictions and conditions. However, the Sun will seek to preserve as much personal freedom as possible whilst fulfilling the karma of following strict conditions and restriction. The influence of the Sun here does not want to be engaged in penury nor durance vile of lockdown. Where the personality, the naisargika atmakaraka seeks to be strong and dramatic and the centre of attention and activity, it takes a significant effort for the Sun in 8th house to express native intelligence, and “see” beyond government institutional bureaucratic hierarchies. The Sun seeks to shine with customary brilliance. It takes time… and patience.
Venus in Taurus
Venus is home, grounded in swarthy, earthy, loamy Taurus. Visible in the morning sky, Venus, the Earth mother, will help many emotional, physical and spiritual problems to melt away when we engage in activities which draw the drishti, the light, the magnetism of Venus. (All during a time of coronavirus and lockdown, here is the raising up of planet Venus available, the seizing of harmony and gracefulness of Venus …) Venus will be very strong in the sky in Taurus for 4 months and afflicted by the Sun from May 29-June 8th and turning retrograde May 11th. So Venus’s strong qualities come out most of the time.
Full Moon Meditation:
We spoke earlier about managing our inner self-talk and how important this is for human integrity and purity.
In this wise, we must recall, “As you think, so you become”; we must recall yad bhavati, tad bhavatum, as the feeling, so the result. We must also watch our words, for words affect the cells in the body; what we say out loud becomes a spell that affects every cell, every electron, proton, neutron in the cell. Words are powerful. In Sanathana Dharma, we have the principle of true humanness, which is built on trikarana suddhi, the unity of thoughts, words and actions. This is human integrity.
For the full moon meditation this month, we recommend inner chanting of the following mantra. It recalls your I AM essence, that is, the essence of the Soul. It recalls the statement that the universe is based on truth, and therefore, your life is based on truth. It reminds you that you are an embodiment of love, and that you carry the eternal love of the Creator within your heart. It states you are light, you emerged from light, that this world is light, light, light. Share your light with others, let them see the light within your eyes.
Repeat this mantra with inner chanting any time of your day, start the day with I AM THE LIGHT. I AM THE LOVE. I AM THE TRUTH. I AM. Fill the day with I AM THE LIGHT. I AM THE LOVE. I AM THE TRUTH. I AM. Spend the day with I AM THE LIGHT. I AM THE LOVE. I AM THE TRUTH. I AM. End the day with I AM THE LIGHT. I AM THE LOVE. I AM THE TRUTH. I AM.
You will change this world, you will raise this world to the light. You will raise this world to the Love. You will raise this world to the truth.
I AM THE LIGHT. I AM THE LOVE. I AM THE TRUTH. I AM.
I AM THE LIGHT. I AM THE LOVE. I AM THE TRUTH. I AM.
I AM THE LIGHT. I AM THE LOVE. I AM THE TRUTH. I AM.
263 total views, 4 views today | 0.810313 | 3.175271 |
’s orbit around the Sun) and/or the Earth
Both of these planes are in motion and their positions are difficult to specify
precisely. In practice, therefore, a model ecliptic and/or equator are used instead.
These, together with the point on the sky that defines the coordinate origin (the
intersection of the two planes termed the
" mean equinox
" ) move with time according to
some model which removes the more rapid fluctuations. The SkyFrame class supports both
the FK4 and FK5 models.
The position of a fixed source expressed in any of these coordinate systems will appear
to change with time due to movement of the coordinate system itself (rather than motion
of the source). Such coordinate systems must therefore be qualified by a moment in time
" epoch of the mean equinox
" for short) which allows the position of
the model coordinate system on the sky to be determined. This is the role of the
The Equinox attribute is stored as a Modified Julian Date, but when setting or getting its value you may use the same formats as for the Epoch attribute (q.v.).
The default Equinox value is B1950.0 (Besselian) for the old FK4-based coordinate systems (see the System attribute) and J2000.0 (Julian) for all others.
Care must be taken to distinguish the Equinox value, which relates to the definition of
a time-dependent coordinate system (based on solar system reference planes which are in
motion), from the superficially similar Epoch value. The latter is used to qualify
coordinate systems where the positions of sources change with time (or appear to do so)
for a variety of other reasons, such as aberration of light caused by the observer
See the description of the System attribute for details of which qualifying attributes apply to each celestial coordinate system. | 0.860139 | 3.22507 |
演者: Prof. Justin Erik Halldór Smith (Professeur des Universités Département d’Histoire et Philosophie des Sciences Université Paris Diderot – Paris VII Paris, France)
タイトル：Lunar Astronomy and Philosophy from Plutarch to Kepler
Why did so many philosophers in antiquity and the early modern period deploy thought experiments involving the moon?
What were their systematic and conceptual ends in this exercise?
In ancient astronomy,the moon served as an important boundary between two very different domains of nature, sometimes called the ‘superlunar’ and the ‘sublunar’ (or the ‘celestial’ and the ‘terrestrial’), which were subject to very different laws, not least the laws of generation, corruption, and motion.
The moon was also presumed, unlike the higher celestial bodies, to be in at least some traffic with the earth, with elements, and perhaps also beings, presumed to travel back and forth.
So to which side of the boundary did the moon itself belong?
In this talk, I would like to argue that it was precisely thisquestion that made the moon a fertile source of *Gedankenexperimente.*
From the utopian political subtexts of lunar science fiction of such authors as Cyrano de Bergerac, to the arguments for relativity in Johannes Kepler’s * Somnium*, the moon facilitated the
conceptualization of models of reality that could not be nearly so easily constructed on earth.
Thus people were effectively going into outer space, in the name of advancing theoretical understanding, long before such a feat was actually technically possible.
The way such thought experiments proceed,and what their real utility and pay-off are, may be important, I shall argue, for our understanding of the method of science more generally. | 0.848786 | 3.004117 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.