text
stringlengths 286
572k
| score
float64 0.8
0.98
| model_output
float64 3
4.39
|
|---|---|---|
Maunakea, Hawaii – When it comes to extrasolar planets, appearances can be deceiving. Astronomers have imaged a new planet, and it appears nearly identical to one of the best studied gas-giant planets. But this doppelgänger differs in one very important way: its origin.
“We have found a gas-giant planet that is a virtual twin of a previously known planet, but it looks like the two objects formed in different ways,” said Trent Dupuy, astronomer at the Gemini Observatory and lead author of the study.
Emerging from stellar nurseries of gas and dust, stars are born like kittens in a litter, in bunches and inevitably wandering away from their birthplace. These litters comprise stars that vary greatly, ranging from tiny runts incapable of generating their own energy (called brown dwarfs) to massive stars that end their lives with supernova explosions. In the midst of this turmoil, planets form around these new stars. And once the stellar nursery exhausts its gas, the stars (with their planets) leave their birthplace and freely wander the Galaxy.
Because of this exodus, astronomers believe there should be planets born at the same time from the same stellar nursery, but are orbiting stars that have moved far away from each other over the eons, like long-lost siblings.
“To date, exoplanets found by direct imaging have basically been individuals, each distinct from the other in their appearance and age. Finding two exoplanets with almost identical appearances and yet having formed so differently opens a new window for understanding these objects,” said Michael Liu, astronomer at the University of Hawaii Institute for Astronomy, and a collaborator on this work.
Dupuy, Liu, and their collaborators have identified the first case of such a planetary doppelgänger. One object has long been known: the 13-Jupiter-mass planet beta Pictoris b, one of the first planets discovered by direct imaging, back in 2009. The new object, dubbed 2MASS 0249 c, has the same mass, brightness, and spectrum as beta Pictoris b.
After discovering this object with the Canada-France-Hawaii Telescope (CFHT), Dupuy and collaborators then determined that 2MASS 0249 c and beta Pictoris b were born in the same stellar nursery. On the surface, this makes the two objects not just lookalikes but genuine siblings.
However, the planets have vastly different living situations, namely the types of stars they orbit. The host for beta Pictoris b is a star 10 times brighter than the Sun, while 2MASS 0249 c orbits a pair of brown dwarfs that are 2000 times fainter than the Sun. Furthermore, beta Pictoris b is relatively close to its host, about 9 astronomical units (AU, the distance from the Earth to the Sun), while 2MASS 0249 c is 2000 AU from its binary host.
These drastically different arrangements suggest that the planets’ upbringings were not at all alike. The traditional picture of gas-giant formation, where planets start as small rocky cores around their host star and grow by accumulating gas from the star’s disk, likely created beta Pictoris b. In contrast, the host of 2MASS 0249 c did not have enough of a disk to make a gas giant, so the planet likely formed by directly accumulating gas from the original stellar nursery.
“2MASS 0249 c and beta Pictoris b show us that nature has more than one way to make very similar looking exoplanets,” says Kaitlin Kratter, astronomer at the University of Arizona and a collaborator on this work. “beta Pictoris b probably formed like we think most gas giants do, starting from tiny dust grains. In contrast, 2MASS 0249 c looks like an underweight brown dwarf that formed from the collapse of a gas cloud. They’re both considered exoplanets, but 2MASS 0249 c illustrates that such a simple classification can obscure a complicated reality.”
The team first identified 2MASS 0249 c using images from CFHT, and their repeated observations revealed this object is orbiting at a large distance from its host. The system belongs to the beta Pictoris moving group, a widely dispersed set of stars named for its famous planet-hosting star.
The team’s observations using the Near-Infrared Camera, second generation (NIRC2) instrument and laser guide star adaptive optics at W. M. Keck Observatory determined that the host is actually a closely separated pair of brown dwarfs. So altogether, the 2MASS 0249 system comprises two brown dwarfs and one gas-giant planet.
“We were surprised to learn that this doppelgänger planet is orbiting a binary,” said Dupuy. “It’s the first brown dwarf binary in the beta Pictoris moving group, and one of only a handful of brown dwarf binaries known among all the young moving groups.”
Follow-up spectroscopy of 2MASS 0249 c with the NASA Infrared Telescope Facility and the Astrophysical Research Consortium 3.5-meter Telescope at Apache Point Observatory demonstrated that it shares a remarkable resemblance to beta Pictoris b.
The 2MASS 0249 system is an appealing target for future studies. Most directly imaged planets are very close to their host stars, inhibiting detailed studies of the planets due to the bright light from the stars. In contrast, the very wide separation of 2MASS 0249 c from its host binary will make measurements of properties like its surface weather and composition much easier, leading to a better understanding of the characteristics and origins of gas-giant planets.
This work has been supported by the National Science Foundation under Grant No. AST-1518339. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. | 0.893979 | 3.898193 |
The planet-hunting Kepler space telescope has found its first extrasolar planets: three alien worlds that had been previously discovered with ground-based telescopes. The finds confirm that Kepler’s instruments are sensitive enough to detect Earth-like planets around sun-like stars – but they might also be unexpectedly sensitive to charged particles in space that can zap circuitry.
Kepler launched on 6 March with a simple charge: Stare at a swatch of sky for three and a half years, and look for Earths. The telescope will hunt transiting exoplanets, planets that pass in front of their stars and dim their brightness at regular intervals.
It’s focused on a 100-square-degree patch of the Milky Way between the constellations Cygnus and Lyra that contains about 4.5 million stars, 100,000 of which are prime candidates for planets.
In the first 10 days of its calibration period, Kepler collected data on 52,496 stars, three of which were known to have transiting planets. “We expected to be able to see those instantly from the first data that we took,” says project manager Jim Fanson at NASA’s Jet Propulsion Laboratory. “Any planet that you can detect from the ground will be very obviously visible to Kepler.”
One of these planets, HAT-P-7b, provided some good news: Kepler is indeed sensitive enough to detect alien Earths.
HAT-P-7b is so hot – more than 2300 °Celsius – that it radiates its own light. Deputy principal investigator David Koch, of NASA’s Ames Research Center, says: “The planet is glowing red.”
Kepler detects the light emitted by both the sun and the planet. This means it can tell when the planet passes behind the star as well as in front of it. When the planet is in front, it blocks a bit of the star’s brightness; but when the star is in front, the planet’s light disappears.
Kepler measured the dip in brightness when HAT-P-7b hid behind its star with extreme precision – more than enough to detect other Earths, Koch says.
“Kepler is operating at the level required to detect Earth-size planets,” Koch and colleagues write in a new study. “The signal from a Sun-Earth analogue will be at a comparable level of statistical significance.”
But Earth-sized planets aren’t the only thing Kepler is sensitive to. It may be more susceptible to harmful cosmic rays than scientists had hoped.
Kepler’s computer has mysteriously entered a standby, or “safe”, mode twice since launch, once on 15 June and once on 2 July. This happens when the computer unexpectedly fails to communicate with the telescope’s electronics, and automatically reboots itself as a precaution.
“It’s like if you’re driving your car and your ‘check engine’ light comes on, you don’t want to start your cross-country trip. You want to open the hood and have a look at the engine,” Fanson told New Scientist.
Scientists are investigating several possible causes for the hiccups, both of which probably had the same root source.
The prime suspects are energetic charged particles known as cosmic rays. Earth’s atmosphere shields us from these particles’ potentially dangerous effects, but they bombard spacecraft at a rate of thousands per second.
If a cosmic ray hits a vulnerable spot in Kepler’s electronics, it could cause a voltage spike that mimics a request from ground controllers to reboot the spacecraft’s computer. “It could be that the computer is just chugging along doing everything fine, and then a cosmic ray comes sailing through,” Fanson says. “All of a sudden it thinks it’s been asked to reset, so it resets.”
Alternatively, cosmic rays could toggle chips in the computer’s memory, making it misinterpret instructions. The reboots could also be caused by a bug in the software, or half a dozen other things, Fanson says. “There are many, many things you have to look at that could be causing it. These systems are very complex,” he says.
Scientists will begin testing duplicates of Kepler’s electronics in September, bombarding them with charged particles from an accelerator beam at Texas A&M University.
If the culprit does turn out to be cosmic rays, mission managers could tell the telescope not to shut down all the way when it sees this sort of signal. That would reduce the time it takes to start back up. “We can’t modify the electronics now, so we’d just have to live with it, and modify the way the spacecraft responds to mitigate the impact to the timeline,” Fanson says.
But not to worry – the time spent in safe mode “basically has had no impact” on data collection. The mission team allocated 12 days per year as a buffer in case anything happened. Of the 150 days in the mission so far, only three and a half have been lost to safe mode.
“We expected that we would spend some time in safe mode. Every mission does,” Fanson says. “Even if we did nothing [to mitigate the problem], it would not affect the mission.”
Journal reference: Science (vol 325, p 709) | 0.847869 | 3.807738 |
This is an image of Neptune.
Click on image for full size
An Overview of Neptune's Atmosphere
Neptune's atmosphere shows a striped pattern of clouds, just like that of Jupiter and Saturn. Neptune even has a Great Dark Spot similar to the Great Red Spot of Jupiter.
The history of Neptune's atmosphere is like that of the other Giant planets.
The clouds of Neptune are thought to be made of a complex molecule called methane.
Motions in the cloud patterns of Neptune give clues about Neptune's weather, which is like that of Jupiter and Saturn.
You might also be interested in:
Like Jupiter and all the giant planets, Neptune's appearance shows a striped pattern of clouds. Other cloud shapes seen over time include a small dark spot, the "scooter" and the Great Dark Spot. The Great...more
The giant planets have definitely changed since their formation. But how much remains to be seen. Most of the original air of the giant planets remains in place. (The earth-like planets lost most of their...more
This image shows the new Great Dark Spot of Neptune, which was discovered using the Hubble Space Telescope. The image shown here, shows a large "hole" in the clouds of Neptune in pink, in the northern...more
This image shows some clouds known as "cirrus" clouds, extending for many kilometers across the face of Neptune. These clouds are very high up, for they can be seen to cast shadows on the lower clouds,...more
This image of Neptune uses false colors to show where the smog is. The smog of Neptune can be seen in red along the edge of the image. This smog haze is found very high up in the atmosphere, over the clouds...more
Scientists think that the solar system formed out of a spinning cloud of hydrogen and helium molecules. Because the cloud was spinning, it flattened into a frisbee shape, just like a ball of pizza dough...more
Neptune was discovered in 1846. But it wasn't discovered using a telescope. Scientists used math instead! They watched Uranus and saw that its orbit was doing weird things. They knew another planet had...more
Neptune's atmosphere shows a striped pattern of clouds, just like that of Jupiter and Saturn. Neptune even has a Great Dark Spot similar to the Great Red Spot of Jupiter. The history of Neptune's atmosphere...more | 0.842944 | 3.168581 |
"Earth has captured an asteroid that's spending time in space acting as a mini-moon, or baby moon, to our planet. "Orbit integrations...indicate that this object is temporarily bound to the Earth," the IAU filing reads. "No evidence of perturbations due to solar radiation pressure is seen, and no link to a known artificial object has been found. Further observations and dynamical studies are strongly encouraged."
"You read that right: no link to artificial objects has been found meaning this is likely a straggler space rock hurtling through the solar system, and not a gift from aliens or smugglers in space."
"They had long thought there was something strange about Ophiuchus galaxy cluster, which is a giant aggregation containing thousands of individual galaxies intermingled with hot gas and dark matter. X-ray telescopes had spied a curious curved edge to it."
"Black holes are famous for gorging on infalling matter, but they will also expel prodigious amounts of material and energy in the form of jets. Scientists at first doubted their explanation however, because the cavity was so big; you could fit 15 of our own Milky Way galaxies in a row into the hole. And that meant any black hole explosion would have to have been unimaginably prodigious."
"In some ways, this blast is similar to how the eruption of Mount St Helens (volcano) in 1980 ripped off the top of the mountain," said Simona Giacintucci of the Naval Research Laboratory in Washington, DC, and lead author of the study."
“It’s the kind of behaviour that’s more often associated with domesticated animals or those kept in captivity.”
"The orbit isn’t stable, so eventually 2020 CD3 will be flung away from Earth. “It is heading away from the Earth-moon system as we speak,” says Grigori Fedorets at Queen’s University Belfast in the UK, and it looks likely it will escape in April."
"However, there are several different simulations of its trajectory and they don’t all agree – we will need more observations to accurately predict the fate of our mini-moon and even to confirm that it is definitely a temporary moon and not a piece of artificial space debris. “Our international team is continuously working to constrain a better solution,” says Fedorets."
There Will Be More. | 0.88965 | 3.42604 |
Say hello to the black hole deep inside the Messier 87, a galaxy located in the Virgo cluster some 55 million light years away. It may seem underwhelming at first, but it’s one of four images of the supermassive spacetime deforming structure — marking the first time such an object has been photographed.
The shots were captured using a combination of eight radio observatories spread out along four continents, creating what MIT refers to as a “virtual, Earth-sized telescope.” There’s light surrounding the object — a so-called “ring of fire.” True to its name, the black hole’s shadow is the dark region in the center. That, mind you, is the spot where gravity’s pull is so strong not even light can escape.
“This black hole is much bigger than the orbit of Neptune, and Neptune takes 200 years to go around the sun,” Geoffrey Crew, a research scientist at MIT’s Haystack Observatory, said in a statement. “With the M87 black hole being so massive, an orbiting planet would go around it within a week and be traveling at close to the speed of light.”
In fact, the black hole is massive, even by black hole standards. “It has a mass 6.5 billion times that of the Sun,” Prof. Heino Falcke of Radboud University in the Netherlands told the BBC. “And it is one of the heaviest black holes that we think exists. It is an absolute monster, the heavyweight champion of black holes in the Universe.”
The light surrounding the object is much brighter than that of surrounding galaxies, allowing it to be captured at such an incredible distance. | 0.874907 | 3.254981 |
2010 Odyssey Dark Spot V2 is now followed by 2010 Odyssey Dark Spot and Monolith V3
2010: Odyssey Two is a best-selling science fiction novel by Arthur C. Clarke,
which was published in January 1982.
An apparition of Bowman appears before Floyd (shaping itself from dust),
warning him that they must leave Jupiter within fifteen days.
Floyd has difficulty convincing the rest of the crew, at first,
but then the monolith vanishes from orbit
and a mysterious dark spot on Jupiter begins
to form and starts growing.
HAL’s telescope observations reveal that the Great Black Spot is,
in fact, a vast population of monoliths, increasing at a geometric rate,
which appear to be eating the planet.
Comet Shoemaker-Levy 9 (SL9,
formally designated D/1993 F2) was a comet
that broke apart and collided with Jupiter in July 1994,
providing the first direct observation
of an extraterrestrial collision of solar system objects.
This generated a large amount of coverage in the popular media,
and SL9 was closely observed by astronomers worldwide.
The collision provided new information about Jupiter and highlighted
its role in reducing space debris in the inner solar system.
Observers soon saw a huge dark spot after the first impact.
This impact created a giant dark spot over 12,000 km across,
and was estimated to have released an energy equivalent
to 6,000,000 megatons of TNT
(600 times the world’s nuclear arsenal).
The visible scars from the impacts could be seen on Jupiter
for many months.
They were extremely prominent, and observers described them
as more easily visible even than the Great Red Spot.
A search of historical observations revealed that the spots
were probably the most prominent transient features ever seen
on the planet, and that while the Great Red Spot is notable
for its striking color, no spots of the size and darkness
of those caused by the SL9 impacts have ever been recorded before.
On July 19, 2009, a new black spot about the size of the Pacific Ocean
appeared in Jupiter’s southern hemisphere.
Thermal infrared analysis showed it was warm
and spectroscopic methods detected ammonia.
JPL scientists concluded that another impact event had occurred,
probably a small undiscovered comet or other icy body.
The extraterrestrial species that built the monoliths is never described in much detail, but some knowledge of its existence is given to Dave Bowman after he is transported by the stargate to the “cosmic zoo”, as detailed in the novels 2001: A Space Odyssey and 2010: Odyssey Two. The existence of this species is only hypothesized by the rest of humanity, but it is obvious because the monolith was immediately identified as an artefact of non-human origin.
The extraterrestrial species that built the monoliths developed intergalactic travel millions or perhaps billions of years before the present time. In the novels, Clarke refers to them as the “Firstborn” (not to be confused with the identically-named race in Arthur C. Clarke’s and Stephen Baxter‘s Time Odyssey Series) since they were quite possibly the first sentient species to possess a significant capability of interstellar travel. Members of this species explored the universe in the search of knowledge, and especially knowledge about other intelligent species.
In Clarke’s Novel , humans discover the monolith buried in the Moon.
In actual events humans discovered a monolith or what apparently seems one on Phobos :
..and they planned and plan to reach that surface to further investigations about it. | 0.920534 | 3.869458 |
The Gaia spacecraft has new predictions regarding the future collision with the nearest Andromeda galaxy
Our galaxy was initially predicted to collide with its neighboring Andromeda galaxy 3.9 billion years from now according to astronomers that used the Hubble Space Telescope and measured the sideways motions of the Andromeda years back. However, recent new measurements have been made by the European Space Agency’s Gaia space telescope, that state that instead of a head-on collision there will be an initial glancing blow and also pushed back the date to 4.5 billion years from now.
The Gaia spacecraft was launched in December 2013 in order to help researchers create the best 3D map of the Milky Way. Since then it has been precisely monitoring the positions and movements of stars in our galaxies and neighboring galaxies, as well as other cosmic objects.
The neighboring galaxies are the Andromeda, also known as M31, and the spiral Triangulum, known as M33. These are situated at a distance of 2.5 million to 3 million light-years of our galaxy and may even be interacting with each other, according to scientists. Researchers also mapped out how M31 and M33 have moved through space so far and where they will likely go over the next billion years. Gaia project scientist Timo Prusti stated:
“Gaia was designed primarily for mapping stars within the Milky Way – but this new study shows that the satellite is exceeding expectations and can provide unique insights into the structure and dynamics of galaxies beyond the realm of our own. The longer Gaia watches the tiny movements of these galaxies across the sky, the more precise our measurements will become.”
Andromeda is currently hurtling toward us at nearly 250,00 miles per hour, but when the two galaxies will finally meet, it will actually be more of a sideswipe than a head-on collision that will liven up the night sky for any creatures living on Earth 4.5 billion years from now. Moreover, scientists claimed the galaxies will actually collide several times, pass through one another and then collide again until eventually they will become one galaxy.
Scientists say that by then the Earth will be orbiting the sun on a more randomly oriented orbit within a large elliptical galaxy. The sun will be on its way to becoming a red giant star anyway, which is a natural stage in stellar evolution, it will brighten and balloon outward, engulfing Mercury and Venus and turning Earth into a roasted bit of planetary charcoal. | 0.895773 | 3.471243 |
March 12, 2015 – Following a successful launch at 8:44 p.m. MDT Thursday, NASA’s four Magnetospheric Multiscale (MMS) spacecraft are positioned in Earth’s orbit to begin the first space mission dedicated to the study of a phenomenon called magnetic reconnection. This process is thought to be the catalyst for some of the most powerful explosions in our solar system.
The spacecraft, positioned one on top of the other on a United Launch Alliance Atlas V 421 rocket, launched from Cape Canaveral Air Force Station, Florida. After reaching orbit, each spacecraft deployed from the rocket’s upper stage sequentially, in five-minute increments, beginning at 10:16 p.m. MDT Thursday, with the last separation occurring at 10:31 p.m. MDT. NASA scientists and engineers were able to confirm the health of all separated spacecraft at 10:40 p.m. MDT.
“I am speaking for the entire MMS team when I say we’re thrilled to see all four of our spacecraft have deployed and data indicates we have a healthy fleet,” said Craig Tooley, project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Over the next several weeks, NASA scientists and engineers will deploy booms and antennas on the spacecraft, and test all instruments. The observatories will later be placed into a pyramid formation in preparation for science observations, which are expected to begin in early September.
“After a decade of planning and engineering, the science team is ready to go to work,” said Jim Burch, principal investigator for the MMS instrument suite science team at the Southwest Research Institute in San Antonio (SwRI). “We’ve never had this type of opportunity to study this fundamental process in such detail.”
The mission will provide the first three-dimensional views of reconnection occurring in Earth’s protective magnetic space environment, the magnetosphere. Magnetic reconnection occurs when magnetic fields connect, disconnect, and reconfigure explosively, releasing bursts of energy that can reach the order of billions of megatons of trinitrotoluene (commonly known as TNT). These explosions can send particles surging through space near the speed of light.
Scientists expect the mission will not only help them better understand magnetic reconnection, but also will provide insight into these powerful events, which can disrupt modern technological systems such as communications networks, GPS navigation, and electrical power grids.
By studying reconnection in this local, natural laboratory, scientists can understand the process elsewhere, such as in the atmosphere of the sun and other stars, in the vicinity of black holes and neutron stars, and at the boundary between our solar system’s heliosphere and interstellar space.
The spacecraft will fly in a tight formation through regions of reconnection activity. Using sensors designed to measure the space environment at rates100 times faster than any previous mission.
“MMS is a crucial next step in advancing the science of magnetic reconnection – and no mission has ever observed this fundamental process with such detail,” said Jeff Newmark, interim director for NASA’s Heliophysics Division at the agency’s Headquarters in Washington. “The depth and detail of our knowledge is going to grow by leaps and bounds, in ways that no one can yet predict.”
MMS is the fourth mission in the NASA Solar Terrestrial Probes Program. Goddard built, integrated and tested the four MMS spacecraft and is responsible for overall mission management and operations. The principal investigator for the MMS instrument suite science team is based at the SwRI. Science operations planning and instrument commanding are performed at the MMS Science Operations Center at the University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics. | 0.828287 | 3.153977 |
Despite the emptiness of outer space, cosmic collisions between galaxies are fairly common. One of the best examples is Messier 51, which consists of a large spiral galaxy, M51a, known more commonly as the Whirlpool, and a smaller companion galaxy, M51b, with a bridge of stars connecting them. The two galaxies collided in the dim, distant past, and M51b is inexorably spiralling into the Whirlpool. Both the Whirlpool and M51b have central supermassive black holes and, since each is viewed face on from earth, the system provides an outstanding opportunity to study how galaxy collisions help feed supermassive black holes. Scientists think that such titanic collisions should drive material into the maws of the central supermassive black holes, increasing their size and making them shine brightly in X-rays. Oddly enough, observations with the Chandra X-ray Observatory and other X-ray observatories have shown that the supermassive black holes in the M51 galaxies are unexpectedly faint. However, material near the black holes might block some of the X-ray emission, so that the observed emission might severely underestimate the true activity. The NuSTAR X-ray observatory provides the unique capability to make images at very high X-ray energies, and these high energy ("hard") X-rays can penetrate through huge amounts of absorbing material and give us an unobscured view of the supermassive black holes in M51. The image above shows the NuSTAR image of M51 in green, superimposed on an optical image. The NuSTAR observations show that both central black holes are hard X-ray sources, but confirm that the supermassive black holes in M51 are actually intrinsically faint, and apparently dainty eaters. This is a puzzle to astronomers, and perhaps suggests that supermassive black holes in interacting galaxies only feed sporadically, with X-ray active periods interspersed with long periods of inactivity. Interestingly, NuSTAR also shows that one of the brightest X-ray sources in the Whirlpool, the green dot near the outer spiral arm of the galaxy on the left of the image, is a neutron star. This X-ray source is so bright that it is classified as a rare ultra-luminous X-ray source, or ULX. Its not clear why this neutron star, about a million times less massive than the supermassive black holes, is such a bright hard X-ray source. Astronomers think that perhaps the X-ray emission is produced somehow by the neutron star's superstrong magnetic field, though the details are not yet fully understood.
NuSTAR: In Colliding Galaxies, a Pipsqueak Shines Bright
|<< Previous HEAPOW||High Energy Astrophysics Picture of the Week||Next HEAPOW >>| | 0.819178 | 4.1207 |
The path of a light beam is bent by the presence of mass, as explained by General Relativity. A massive body can therefore act like a lens — a so called “gravitational lens” — to distort the image of an object seen behind it. Microlensing is a related phenomenon: a short flash of light is produced when a moving cosmic body, acting as a gravitational lens, modulates the intensity of light from a background star as it fortuitously passes in front of it. About fifty years ago scientists predicted that if it ever became possible to observe a microlensing flash from two well-separated vantage points, a parallax measurement would pin down the distance of the dark object. The Spitzer Space Telescope, orbiting the Sun at the distance of the Earth but trailing behind the Earth by about one-quarter of the orbital path, had been working with ground-based telescopes to do just that until it was shut down last month by NASA as a cost-savings measure.
CfA astronomer Jennifer Yee is a member of a large international team of astronomers making parallax microlensing measurements of small stellar objects. The technique is a powerful tool for probing isolated objects like free-floating planets, brown dwarfs, low-mass stars, and black holes. At the low-mass end, microlensing has already detected several free-floating planet candidates including several possible Earth-mass objects. Such discoveries are crucial for testing theories about the origin and evolution of free-floating planets. Similarly, microlensing observations of more massive objects like isolated brown dwarf stars have identified some objects orbiting in a sense opposite to that of normal disk stars. Stellar-mass sized objects found via microlensing reveal stellar-mass black holes and neutron stars.
New microlensing parallax observations have been able to determine the masses of, and distances to, two small, isolated stars. One has a mass of about 0.6 solar-masses and is about 23,700 light-years away from us; modeling for the second is ambiguous, concluding that it is either 0.40 solar-masses at about 24,800 light-years or 0.38 solar-masses at 24,300 light-years distant. Both stars are red giants, and lie in the peanut-shaped bulge of old stars (about ten billion years old) in the Milky Way, about seven thousand light-years in radius in the central region of our galaxy. The new results, together with six earlier parallax microlensing measurements, lend strong support to current models of the Galaxy and its bulge formation.
Reference: “Spitzer Microlensing Parallax Reveals Two Isolated Stars in the Galactic Bulge” by Weicheng Zang, Yossi Shvartzvald, Tianshu Wang, Andrzej Udalski, Chung-Uk Lee, Takahiro Sumi, Jesper Skottfelt, Shun-Sheng Li, Shude Mao, Wei Zhu (Leading Authors), Jennifer C. Yee, Sebastiano Calchi Novati, Charles A. Beichman, Geoffery Bryden, Sean Carey, B. Scott Gaudi, Calen B. Henderson (The Spitzer Team), Przemek Mróz, Jan Skowron, Radoslaw Poleski, Michal K. Szymanski, Igor Soszynski, Pawel Pietrukowicz, Szymon Kozlowski, Krzysztof Ulaczyk, Krzysztof A. Rybicki, Patryk Iwanek (The OGLE Collaboration), Etienne Bachelet, Grant Christie, Jonathan Green, Steve Hennerley, Dan Maoz, Tim Natusch, Richard W. Pogge, Rachel A. Street, Yiannis Tsapras (The LCO and µFUN Follow-up Teams), Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Cheongho Han, Kyu-Ha Hwang, Youn Kil Jung, Yoon-Hyun Ryu, In-Gu Shin, Sang-Mok Cha, Dong-Jin Kim, Hyoun-Woo Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, (The KMTNet Collaboration), Ian A. Bond, Fumio Abe, Richard Barry, David P. Bennett, Aparna Bhattacharya, Martin Donachie, Akihiko Fukui, Yuki Hirao, Yoshitaka Itow, Iona Kondo, Naoki Koshimoto, Man Cheung Alex Li, Yutaka Matsubara, Yasushi Muraki, Shota Miyazaki, Masayuki Nagakane, Clément Ranc, Nicholas J. Rattenbury, Haruno Suematsu, Denis J. Sullivan, Daisuke Suzuki, Paul J. Tristram, Atsunori Yonehara (The MOA Collaboration), Martin Dominik, Markus Hundertmark, Uffe G. Jørgensen, Sohrab Rahvar, Sedighe Sajadian, Colin Snodgrass, Valerio Bozza, Martin J. Burgdorf, Daniel F. Evans, R. Figuera Jaimes, Yuri I. Fujii, Luigi Mancini, Penelope Longa-Peña, Christiane Helling, Nuno Peixinho, Markus Rabus, John Southworth, Eduardo Unda-Sanzana, Carolina von Essen and (The MiNDSTEp Collaboration), 27 February 2020, The Astrophysical Journal. | 0.868563 | 4.075475 |
NASA's Voyager 2, launched to study the Solar System's outer planets, has had its first readings from interstellar space, collected after travelling more than 11 billion miles over forty years, analyzed by scientists.
It was the second human-made probe known to have sailed beyond the heliosphere – the expansive region made of plasma and magnetic fields generated by the Sun. It finally broke free from the Solar System to enter interstellar space last year, joining its twin companion Voyager 1, which exited in 2012. For what it's worth, NASA's Pioneer 10 and 11 are somewhere out there, lost in space, and may have left the Solar System by now.
The data transmitted by Voyager 2 was analysed by a large team of physicists, and their findings were published in five papers in Nature Astronomy on Monday this week. Specifically, the studies assessed Voyager 2's measurements of the cosmic rays, magnetic fields, the density of plasma and particles within and beyond the heliosphere.
A lot of the findings confirmed what was discovered when Voyager 1 left our tiny back yard in the universe, which is useful in itself. "The Voyager probes are showing us how our Sun interacts with the stuff that fills most of the space between stars in the Milky Way galaxy," said Ed Stone, lead author on one of the papers and a project scientist for the Voyager mission.
"Without this new data from Voyager 2, we wouldn't know if what we were seeing with Voyager 1 was characteristic of the entire heliosphere or specific just to the location and time when it crossed."
The heliosphere is a giant protective bubble that shields the Solar System from galactic cosmic rays. Made from plasma, it’s often described as the solar wind that flows throughout the system and blocked from going further by pressure in the interstellar medium. The small region in between both regions is known as the heliosheath, and the edge of the bubble is known as the heliopause.
A diagram describing the different parts of the heliosphere, the interstellar medium, and where the Voyager spacecrafts have travelled to. Image credit: NASA/JPL-Caltech
Voyager 2 found that the temperature of the plasma in the surrounding interstellar medium is lower than that in the heliosphere. Measurements also confirmed that the density of the plasma is higher outside, compared to inside, the heliosphere.
As the plucky probe passed through the inner edge of heliopause, the plasma density suddenly shot up for some unknown reason. The researchers believe that the plasma is being compressed, and aren’t quite sure what’s squeezing the particles.
Interestingly enough, Voyager 2 detected a stream of particles within the heliosphere leaking out into interstellar space – and the leak was larger than what was previously observed with Voyager 1.
Voyager 1 left the planet 41 years ago – and SpaceX hopes to land on Earth this SaturdayREAD MORE
One remaining mystery is the direction of the magnetic field on either side of the heliopause. They seem to be in parallel, or aligned in other words, but no one quite knows why. This alignment was discovered by Voyager 1, and has now been confirmed by the Voyager 2 data.
“In a historical sense, the old idea that the solar wind will just be gradually whittled away as you go further into interstellar space is simply not true," said Don Gurnett, co-author of a second plasma density paper and a professor emeritus of physics and astronomy at The University of Iowa in the US. "We show with Voyager 2 – and previously with Voyager 1 – that there's a distinct boundary out there. It's just astonishing how fluids, including plasmas, form boundaries."
Voyager 1 has traveled more than 13.6 billion miles (22 billion kilometres) from the Sun, while Voyager 2 is 11.3 billion miles (18.2 billion kilometres) away. Both probes will continue speeding into the depths of the Milky Way galaxy virtually indefinitely.
"The two Voyagers will outlast Earth," said Bill Kurth, co-author of one of the papers and a research scientist at the University of Iowa. "They're in their own orbits around the galaxy for five billion years or longer. And the probability of them running into anything is almost zero." ®
Sponsored: Webcast: Ransomware has gone nuclear | 0.851225 | 3.94609 |
Every study using transit methods to detect objects around other stars is looking for planets. But a paper by Luc Arnold (Observatoire de Haute-Provence, France), soon to be published in The Astrophysical Journal, suggests that the same methods could be employed to find artificial planet-sized objects in orbit around stars. Arnold sees this as a possible SETI ploy, for transits of multiple objects could be used to emit signals that might be detected by other civilizations.
What would such objects be? Giant solar sails, perhaps, or huge low-density structures of other configuration built purposely as a means of interstellar communication. Arnold’s work inevitably recalls Freeman Dyson’s 1960 Science article “Search for Artificial Stellar Sources of Infrared Radiation,” which developed the idea that would later be known as a Dyson Sphere, an artificial cluster of rotating objects the size of a planetary orbit that would collect almost all the solar energy available and create a vast habitat for life.
But Arnold falls back on Jill Tarter’s suggestion that advanced technologies might try to send signals that would be discovered by other civilizations in the course of their normal astronomical observations. So he is developing a new spin on ‘optical SETI,’ while noting that the light-curves of objects from spheres to triangles and even more exotic shapes will have their own distinctive signature, even as multiple objects could send a ‘message’ whose timing and number would announce the willingness of their makers to communicate.
Upcoming missions like Kepler and the European Corot may be able to detect such objects as they look for planetary transits. “Transit of artificial objects also could be a mean for interstellar communication from Earth in the future,” Arnold concludes. “We therefore suggest to future human generations to have in mind, at the proper time, the potential of Earth-size artificial multiple structures in orbit around our star to produce distinguishable and intelligent transits.”
A preprint of Arnold’s paper “Transit Lightcurve Signatures of Artificial Objects” can be accessed at the ArXiv site.
The study of Dyson Spheres remains intriguing. None has as yet been observed (the paper to consult is Bradbury, R.J. “Dyson Shells: A Retrospective,” which appeared in The Search for Extraterrestrial Intelligence (SETI) in the Optical Spectrum III, 2001 Proc. SPIE Vol. 4273, pp. 56-62). But it is also true that some stars do display an excess of infrared that has not been explained. The most likely cause is a hitherto unknown natural process, but the data also fit a possible Dyson signature.
Image: A Dyson Sphere would consist provide a vast amount of habitable space, while taking advantage of almost all the solar energy available. Credit: Steve Bowers.
That work was done at the University of California at Berkeley. Charles Conroy (working with SETI@Home chief scientist Dan Werthimer) determined that a Dyson Sphere would radiate with an excess temperature of about 300 degrees Kelvin, which would translate to surplus radiation at the 12 micron wavelength. Using a list of candidate stars, each one billion years of age or older (those whose protoplanetary disks would have dissipated, thus eliminating a possible source of excess infrared), Conroy found 33 stars whose infrared radiation seemed excessive in the 12 micron range.
Followup studies using the SETI resources at Berkeley yielded no unusual radio emissions or light signals, leaving the mystery of the excess infrared unsolved. You can read more about Conroy’s work with Dyson sphere candidates in this article by Amir Alexander.
The original paper on these objects is Dyson, F.J. “Search for artificial stellar sources of infrared radiation,” Science 131, pp. 1667-1668 (3 June 1960). The Bradbury paper mentioned above, “Dyson Shells: A Retrospective,” offers refinements to the Dyson concept, an analysis of earlier work, and extrapolations on new signatures for optical SETI study. Bradbury is particularly valuable in discussing the distinction between an all-encompassing Dyson ‘sphere’ and a Dyson ‘shell.’
Maybe the term ‘swarm’ is even better: In a later letter to Science, Dyson noted that his concept of a ‘sphere’ had been misunderstood: “The form of ‘biosphere’ which I envisaged consists of a loose collection or swarm of objects traveling on independent orbits around the star. The size and shape of the individual objects would be chosen to suit the inhabitants. I did not indulge in speculations concerning the constructional details of the biosphere, since the expected emission of infrared radiation is independent of such details.” | 0.877491 | 3.993913 |
Exomoons are drawing more interest all the time. It may seem fantastic that we should be able to find moons around planets circling other stars, but the methods are under active investigation and may well yield results soon. Now David Kipping (Harvard-Smithsonian Center for Astrophysics) and colleagues have formed a new project called HEK — the Hunt for Exomoons with Kepler. We thus move into fertile hunting ground, for there has never been a systematic search for exomoons despite the work of ground-breaking researchers like Kipping, Gaspar Bakos (Princeton) and Jean Schneider (Paris Observatory). It’s definitely time for HEK as Kepler’s exoplanet candidate list grows.
Kepler, of course, works with transit methods, noting the dip in starlight as an exoplanet passes in front of the star under observation. HEK will use Kepler photometry to look for perturbations in the motion of the host planet that could flag the presence of a moon. Variations in transit timing (TTV) and duration (TDV) should be the most observable effects, the former being variations in the time it takes the planet to transit its star, while transit duration variation is caused by velocity changes induced by the fact that the planet and moon orbit a common center of mass.
The team will also look for eclipse features, where the moon might occult the planet during a planet-star eclipse. Back in 2009, Kipping and team ran a feasibility study on Kepler’s ability to find the moon of a gas giant in the habitable zone of a star (see Habitable Moons and Kepler). Assuming moons on circular, coplanar orbits around the host planet, the results showed that Kepler could detect exomoons down to 0.2 Earth masses. This is a large moon indeed, for as Kipping’s new paper on this work points out, the most massive moon in our Solar System, Ganymede, is 0.025 Earth masses (our own Moon is 0.0123 Earth masses). No question, then, that HEK will be looking for large moons, moons bigger than any we see in our own system.
Image: The view from a large exomoon would be like nothing we’ve seen in our own system, especially if that world proved suitable for life. Credit: Dan Durda.
Of course, binary planets also fall within the scope of this study — Kipping draws the line between a binary planet and a true planet-moon pair at the point where the center of mass of the two bodies is outside the radius of both bodies, but HEK can work comfortably with both scenarios. The paper runs through the likelihood that such large objects might exist, forming either around the host planet as it undergoes planetary growth, or (more likely) being captured by the host — here we think of moons like Triton in our own system, or of impact scenarios between planetesimals or young planets like that thought to have produced our own Moon.
Other scenarios are also possible, as the paper announcing HEK notes:
For planets which do not migrate through a proto-Kuiper belt or under the assumption that such objects will never reach sufficient mass to qualify as large moons, an alternative source of terrestrial mass objects is required. This object could be an inner terrestrial planet encountered during the gas giant’s inward migration or even a large, unstable Trojan which librates too close to the planet. Indeed, Eberle et al. (2010) have shown that a gas giant planet (in their case HD 23079b) can capture an Earth-mass Trojan into a stable satellite orbit, occurring in 1 out of the 37 simulations they ran.
How long would such a system be stable? The capture process would produce what the paper describes as ‘very loosely-bound initial orbits,’ but there has been work showing that captured moons have relatively high survival rates, as high as 50 percent in various configurations. Producing binary planets through the same methods is plausible, and the paper notes that a Jupiter orbited by an Earth-class planet could be considered an example of an extreme binary.
Examining these origin scenarios as well as the evolution of large moons in detail, the paper goes on to note the project’s objectives:
1. The primary objective of HEK is to search for signatures of extrasolar moons in transiting systems.
2. The secondary objective of HEK will be to derive posterior distributions, marginalised over the entire prior volume, for a putative exomoon’s mass and radius, which may be used to place upper limits on such terms (where conditions permit such a deduction).
3. The tertiary objective of HEK is to determine… the frequency of large moons bound to the Kepler planetary candidates which could feasibly host such an object (in an analogous manner to η⊕ – the frequency of Earth-like planets).
We know that in our own system, Europa, Titan and even tiny Enceladus are possible candidates for life. The Hunt for Exomoons with Kepler project won’t be able to tell us anything about astrobiology on an exoplanet’s moon, but if we begin to find Earth-sized objects orbiting gas giants in the habitable zone, we’ll have taken a first step toward learning whether exomoons could be just as viable a place for life as a planetary surface. The HEK home page goes so far as to speculate that planet-based life could actually be outnumbered by life on habitable moons. Step one, of course, is to find out if such moons actually exist, using Kepler’s crucial data.
The paper is Kipping et al., “The Hunt for Exomoons with Kepler (HEK): I. Description of a New Observational Project,” submitted to the Astrophysical Journal (preprint). The 2009 study is Kipping et al., “On the detectability of habitable exomoons with Kepler-class photometry,” Monthly Notices of the Royal Astronomical Society, published online 24 September, 2009 (abstract). | 0.853015 | 3.955624 |
Newswise — One year ago, the Event Horizon Telescope (EHT) Collaboration published the first image of a black hole in the nearby radio galaxy M 87. Now the collaboration has extracted new information from the EHT data on the distant quasar 3C 279: they observed the finest detail ever seen in a jet produced by a supermassive black hole. New analyses, led by Jae-Young Kim from the Max Planck Institute for Radio Astronomy in Bonn, Germany, enabled the collaboration to trace the jet back to its launch point, close to where violently variable radiation from across the electromagnetic spectrum arises.
The results are published in the coming issue of “Astronomy & Astrophysics”, April 2020.
The EHT collaboration continues extracting information from the groundbreaking data collected in its global campaign in April 2017. One target of the observations was a galaxy 5 billion light-years away in the constellation Virgo that scientists classify as a quasar because an ultra-luminous source of energy at its center shines and flickers as gas falls into a giant black hole. The target, 3C 279, contains a black hole about one billion times more massive than our Sun. Twin fire-hose-like jets of plasma erupt from the black hole and disk system at velocities close to the speed of light: a consequence of the enormous forces unleashed as matter descends into the black hole’s immense gravity.
To capture the new image, the EHT uses a technique called very long baseline interferometry (VLBI), which synchronizes and links radio dishes around the world. By combining this network to form one huge virtual Earth-size telescope, the EHT is able to resolve objects as small as 20 micro-arcseconds on the sky — the equivalent of someone on Earth identifying an orange on the Moon. Data recorded at all the EHT sites around the world is transported to special supercomputers at the Max Planck Institute for Radio Astronomy in Bonn and at MIT’s Haystack Observatory in Westford, Massachusetts, where they are combined. The combined data set is then carefully calibrated and analyzed by a team of experts, which then enables EHT scientists to produce images with the finest detail possible from the surface of the Earth.
The newly analyzed data show that the normally straight jet has an unexpected twisted shape at its base. Jae-Young Kim, lead author of the paper, is enthusiastic and at the same time puzzled: “We knew that every time you open a new window to the universe you can find something new. Here, where we expected to find the region where the jet forms by going to the sharpest image possible, we find a kind of perpendicular structure. This is like finding a very different shape by opening the smallest matryoshka doll.”
“The results are very surprising,” said Kazunori Akiyama, a Jansky Fellow of the National Radio Astronomy Observatory (NRAO) at MIT Haystack who developed imaging techniques for the EHT to create the first images of the black hole in M87, and which were also used to create the images of quasar 3C 279. “When we observed the quasar for four days within one week, we assumed that we would not see these dynamical changes because the source is so far away (100 times further from Earth than M87). But the EHT observations were so sharp that for the first time we could see tiny changes in motions of the jets within this time frame.”
3C 279 has a very active nucleus that can be observed across all wavelengths. The jet in the nucleus has already been monitored for over two decades with the National Science Foundation’s Very Long Baseline Array (VLBA). Astronomers Alan Marscher and Svetlana Jorstad of Boston University lead a project called VLBA-BU-BLAZAR, to relate outbursts of gamma-rays and X-rays to changes in the jet seen in VLBA images at a wavelength of 7 millimeters.
The VLBA images reveal that 3C 279 shoots “blobs” of high-energy particles and magnetic fields down a jet at velocities up to 99.96% of the speed of light. “Surprisingly, the speeds vary over time, as does the direction that the blobs move when they first appear,” said Marscher. “This implies that the jets are propelled in a complex way from a jet launching region about 0.4 light-years across, which can be explored by shorter wavelength observations with the Event Horizon Telescope. The EHT observations have the potential to see how the blobs form and accelerate as they move farther from the black hole into the jet seen in the VLBA images.”
Avery Broderick, an astrophysicist working at the Perimeter Institute and University of Waterloo in Ontario, Canada, said: “For 3C 279, the combination of the transformative resolution of the EHT and new computational tools for interpreting its data have proved revelatory. What was a single radio ‘core’ is now resolved into two independent complexes. And they move – even on scales as small as light-months, the jet in 3C 279 is speeding toward us at more than 99.5% of light speed!”
Because of this rapid motion, the jet in 3C 279 appears to move at about 20 times the speed of light. “This extraordinary optical illusion arises because the material is racing toward us, chasing down the very light it is emitting and making it appear to be moving faster than it is,” clarifies Dom Pesce, a postdoctoral fellow at the Center for Astrophysics | Harvard & Smithsonian (CfA). The unexpected geometry suggests the presence of traveling shocks or instabilities in a bent, rotating jet, which might also explain emission at high energies such as gamma-rays.
“This result is a dream come true for anyone studying how jets are launched,” says Violette Impellizzeri, lead astronomer for the Atacama Large Millimeter/submillimeter Array (ALMA) VLBI observations. “I am particularly thrilled to have been supporting these observations. I did my PhD with this group and we were already working hard on resolving the jet foot point already 15 years ago. With the help of ALMA and all others telescopes in the array, the EHT is really getting there!”
The EHT array is always improving, explains Shep Doeleman, EHT Founding Director. “These new quasar results demonstrate that the unique EHT capabilities can address a wide range of science questions, which will only grow as we continue to add new telescopes to the array. Our team is now working on a next-generation EHT array that will greatly sharpen the focus on black holes and allow us to make the first black hole movies.”
The telescopes contributing to this result were ALMA, Atacama Pathfinder Experiment (APEX), the IRAM 30-meter telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope, the Submillimeter Array, the Submillimeter Telescope, and the South Pole Telescope.
J.Y. Kim, T.P. Krichbaum, A.E. Broderick, et al.: Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution, in: Astronomy & Astrophysics, April 2020. https://doi.org/10.1051/0004-6361/202037493
The international collaboration announced the first-ever image of a black hole at the heart of the radio galaxy Messier 87 on April 10, 2019 by creating a virtual Earth-sized telescope. Supported by considerable international investment, the EHT links existing telescopes using novel systems — creating a new instrument with the highest angular resolving power that has yet been achieved.
The individual telescopes involved in the EHT collaboration are: the Atacama Large Millimetre Telescope (ALMA), the Atacama Pathfinder EXplorer (APEX), the Greenland Telescope (since 2018), the IRAM 30-meter Telescope, the IRAM NOEMA Observatory (expected 2021), the Kitt Peak Telescope (expected 2021), the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope (LMT), the Submillimeter Array (SMA), the Submillimeter Telescope (SMT), and the South Pole Telescope (SPT).
The VLBA-BU-BLAZAR project has been supported by the National Science Foundation and NASA’s Fermi guest investigator program.
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. | 0.82783 | 3.815889 |
One of the fundamental ideas of cosmology is that everything looks the same in all directions if you look over large enough distances. A new study using data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton is challenging that basic notion.
Astronomers using X-ray data from these orbiting observatories studied hundreds of galaxy clusters, the largest structures in the universe held together by gravity, and how their apparent properties differ across the sky.
"One of the pillars of cosmology — the study of the history and fate of the entire universe — is that the universe is 'isotropic,' meaning the same in all directions," said Konstantinos Migkas of the University of Bonn in Germany, who led the new study. "Our work shows there may be cracks in that pillar."
Astronomers generally agree that after the Big Bang, the cosmos has continuously expanded. A commonly analogy is that this expansion is like a baking loaf of raisin bread. As the bread bakes, the raisins (which represent cosmic objects like galaxies and galaxy clusters) all move away from one another as the entire loaf (representing space) expands. With an even mix the expansion should be uniform in all directions, as it should be with an isotropic universe. But these new results may not fit that picture.
"Based on our cluster observations we may have found differences in how fast the universe is expanding depending on which way we looked," said co-author Gerrit Schellenberger of the Center for Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Massachusetts. "This would contradict one of the most basic underlying assumptions we use in cosmology today."
Scientists have previously conducted many tests of whether the universe is the same in all directions. These included using optical observations of exploded stars and infrared studies of galaxies. Some of these previous efforts have produced possible evidence that the universe is not isotropic, and some have not.
This latest test uses a powerful, novel and independent technique. It capitalizes on the relationship between the temperature of the hot gas pervading a galaxy cluster and the amount of X-rays it produces, known as the cluster's X-ray luminosity. The higher the temperature of the gas in a cluster, the higher the X-ray luminosity is. Once the temperature of the cluster gas is measured, the X-ray luminosity can be estimated. This method is independent of cosmological quantities, including the expansion speed of the universe.
Once they estimated the X-ray luminosities of their clusters using this technique, scientists then calculated luminosities using a different method that does depend on cosmological quantities, including the universe's expansion speed. The results gave the researchers apparent expansion speeds across the whole sky — revealing that the universe appears to be moving away from us faster in some directions than others.
The team also compared this work with studies from other groups that have found indications of a lack of isotropy using different techniques. They found good agreement on the direction of the lowest expansion rate.
The authors of this new study came up with two possible explanations for their results that involve cosmology. One of these explanations is that large groups of galaxy clusters might be moving together, but not because of cosmic expansion. For example, it is possible some nearby clusters are being pulled in the same direction by the gravity of groups of other galaxy clusters. If the motion is rapid enough it could lead to errors in estimating the luminosities of the clusters.
These sorts of correlated motions would give the appearance of different expansion rates in different directions. Astronomers have seen similar effects with relatively nearby galaxies, at distances typically less than 850 million light years, where mutual gravitational attraction is known to control the motion of objects. However, scientists expected the expansion of the universe to dominate the motion of clusters across larger distances, up to the 5 billion light years probed in this new study.
A second possible explanation is that the universe is not actually the same in all directions. One intriguing reason could be that dark energy — the mysterious force that seems to be driving acceleration of the expansion of the universe — is itself not uniform. In other words, the X-rays may reveal that dark energy is stronger in some parts of the universe than others, causing different expansion rates.
"This would be like if the yeast in the bread isn't evenly mixed, causing it to expand faster in some places than in others," said co-author Thomas Reiprich, also of the University of Bonn. "It would be remarkable if dark energy were found to have different strengths in different parts of the universe. However, much more evidence would be needed to rule out other explanations and make a convincing case."
Either of these two cosmological explanations would have significant consequences. Many studies in cosmology, including X-ray studies of galaxy clusters, assume that the universe is isotropic and that correlated motions are negligible compared to the cosmic expansion at the distances probed here.
The team used a sample of 313 galaxy clusters for their analysis, containing 237 clusters observed by Chandra with a total of 191 days of exposure, and 76 observed by XMM-Newton, with a total of 35 days of exposure. They also combined their sample of galaxy clusters with two other large X-ray samples, using data from XMM-Newton and the Japan-US Advanced Satellite for Cosmology and Astrophysics (ASCA), giving a total of 842 different galaxy clusters. They found a similar result using the same technique.
A paper describing these results will appear in the April 2020 issue of the journal Astronomy and Astrophysics and is available online. In addition to Migkas, Schellenberger and Reiprich, the authors of this paper are Florian Pacaud and Miriam Elizabeth Ramos-Ceja (University of Bonn), and Lorenzo Lovisari (CfA).
NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science and flight operations from Cambridge and Burlington, Massachusetts. | 0.816619 | 4.12858 |
If our eyes could see high-energy radiation called gamma rays, the Moon would appear brighter than the Sun! That's how NASA's Fermi Gamma-ray Space Telescope has seen our neighbor in space for the past decade.
Gamma-ray observations are not sensitive enough to clearly see the shape of the Moon's disk or any surface features. Instead, Fermi's Large Area Telescope (LAT) detects a prominent glow centered on the Moon's position in the sky.
These images show the steadily improving view of the Moon's gamma-ray glow from NASA's Fermi Gamma-ray Space Telescope. Each 5-by-5-degree image is centered on the Moon and shows gamma rays with energies above 31 million electron volts, or tens of millions of times that of visible light. At these energies, the Moon is actually brighter than the Sun. Brighter colors indicate greater numbers of gamma rays. This image sequence shows how longer exposure, ranging from two to 128 months (10.7 years), improved the view.
Credit: NASA/DOE/Fermi LAT Collaboration
Mario Nicola Mazziotta and Francesco Loparco, both at Italy's National Institute of Nuclear Physics in Bari, have been analyzing the Moon's gamma-ray glow as a way of better understanding another type of radiation from space: fast-moving particles called cosmic rays.
"Cosmic rays are mostly protons accelerated by some of the most energetic phenomena in the universe, like the blast waves of exploding stars and jets produced when matter falls into black holes," explained Mazziotta.
Because the particles are electrically charged, they're strongly affected by magnetic fields, which the Moon lacks. As a result, even low-energy cosmic rays can reach the surface, turning the Moon into a handy space-based particle detector. When cosmic rays strike, they interact with the powdery surface of the Moon, called the regolith, to produce gamma-ray emission. The Moon absorbs most of these gamma rays, but some of them escape.
Mazziotta and Loparco analyzed Fermi LAT lunar observations to show how the view has improved during the mission. They rounded up data for gamma rays with energies above 31 million electron volts -- more than 10 million times greater than the energy of visible light -- and organized them over time, showing how longer exposures improve the view.
"Seen at these energies, the Moon would never go through its monthly cycle of phases and would always look full," said Loparco.
As NASA sets its sights on sending humans to the Moon by 2024 through the Artemis program, with the eventual goal of sending astronauts to Mars, understanding various aspects of the lunar environment take on new importance. These gamma-ray observations are a reminder that astronauts on the Moon will require protection from the same cosmic rays that produce this high-energy gamma radiation.
While the Moon's gamma-ray glow is surprising and impressive, the Sun does shine brighter in gamma rays with energies higher than 1 billion electron volts. Cosmic rays with lower energies do not reach the Sun because its powerful magnetic field screens them out. But much more energetic cosmic rays can penetrate this magnetic shield and strike the Sun's denser atmosphere, producing gamma rays that can reach Fermi.
Although the gamma-ray Moon doesn't show a monthly cycle of phases, its brightness does change over time. Fermi LAT data show that the Moon's brightness varies by about 20% over the Sun's 11-year activity cycle. Variations in the intensity of the Sun's magnetic field during the cycle change the rate of cosmic rays reaching the Moon, altering the production of gamma rays.
Francis Reddy | EurekAlert!
Convenient location of a near-threshold proton-emitting resonance in 11B
29.05.2020 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences
A special elemental magic
28.05.2020 | Kyoto University
In living cells, enzymes drive biochemical metabolic processes enabling reactions to take place efficiently. It is this very ability which allows them to be used as catalysts in biotechnology, for example to create chemical products such as pharmaceutics. Researchers now identified an enzyme that, when illuminated with blue light, becomes catalytically active and initiates a reaction that was previously unknown in enzymatics. The study was published in "Nature Communications".
Enzymes: they are the central drivers for biochemical metabolic processes in every living cell, enabling reactions to take place efficiently. It is this very...
Early detection of tumors is extremely important in treating cancer. A new technique developed by researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from normal tissue. The work is published May 25 in the journal Nature Nanotechnology.
researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from...
Microelectronics as a key technology enables numerous innovations in the field of intelligent medical technology. The Fraunhofer Institute for Biomedical Engineering IBMT coordinates the BMBF cooperative project "I-call" realizing the first electronic system for ultrasound-based, safe and interference-resistant data transmission between implants in the human body.
When microelectronic systems are used for medical applications, they have to meet high requirements in terms of biocompatibility, reliability, energy...
Thomas Heine, Professor of Theoretical Chemistry at TU Dresden, together with his team, first predicted a topological 2D polymer in 2019. Only one year later, an international team led by Italian researchers was able to synthesize these materials and experimentally prove their topological properties. For the renowned journal Nature Materials, this was the occasion to invite Thomas Heine to a News and Views article, which was published this week. Under the title "Making 2D Topological Polymers a reality" Prof. Heine describes how his theory became a reality.
Ultrathin materials are extremely interesting as building blocks for next generation nano electronic devices, as it is much easier to make circuits and other...
Scientists took a leukocyte as the blueprint and developed a microrobot that has the size, shape and moving capabilities of a white blood cell. Simulating a blood vessel in a laboratory setting, they succeeded in magnetically navigating the ball-shaped microroller through this dynamic and dense environment. The drug-delivery vehicle withstood the simulated blood flow, pushing the developments in targeted drug delivery a step further: inside the body, there is no better access route to all tissues and organs than the circulatory system. A robot that could actually travel through this finely woven web would revolutionize the minimally-invasive treatment of illnesses.
A team of scientists from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart invented a tiny microrobot that resembles a white blood cell...
19.05.2020 | Event News
07.04.2020 | Event News
06.04.2020 | Event News
29.05.2020 | Materials Sciences
29.05.2020 | Materials Sciences
29.05.2020 | Power and Electrical Engineering | 0.872039 | 4.071453 |
India’s first dedicated space observatory has begun collecting data with its suite of instruments, studying Ultraviolet and X-Ray emissions from galactic targets to contribute to addressing some of the outstanding questions in high-energy astrophysics.
AstroSat was launched on September 28 atop a Polar Satellite Launch Vehicle, successfully placing the 1,513-Kilogram satellite into an equatorial orbit of 630 by 650 Kilometers at an inclination of six degrees – an orbital setup carefully selected for this mission to limit the duration of passages through the South Atlantic Anomaly where radiation levels peak and can cause damage to the delicate instrument detectors.
The AstroSat spacecraft is outfitted with five co-aligned instruments to conduct studies by imaging targets in the ultraviolet wavelengths as well as a broad X-ray energy range. One day after its launch, AstroSat activated its first payload systems beginning with the Charged Particle Monitor – a sensor designed to detect changes in proton and electron flux to determine when the satellite’s instruments have to be switched off to protect them from radiation-related damage, e.g. when flying through the South Atlantic Anomaly. The initial spacecraft checks also revealed that the data handling systems, the communications systems, the spacecraft controller and all platform systems were functioning as planned.
Working through a methodical process, Indian mission controllers initially powered up the Soft X-Ray Telescope which covers an energy range of 0.3 to 8 kilo-Electronvolt utilizing a Wolter I design that makes use of grazing incidence optics to focus the incoming X-rays onto a 600 by 600-pixel CCD detector. Once activated, SXT showed good voltages and switched to its calibration mode.
The next instrument to be activated was the Large Area Xenon Proportional Counter (LAXPC) that aims to detect X-rays at energies of 3 to 80 keV by using a chamber filled with Xenon gas which, when struck by a high-energy x-Ray photon, generates ion-and-electron pairs detected via their electrical current that is in proportion to the energy the original X-ray possessed.
The Scanning Sky Monitor was commanded to begin rotating its sensors on the third flight day, following a similar detection principle as LAXPC but using a rotating sensor to cover a large area of the sky for the detection of X-rays at energies between 2 and 10 keV.
By October 1, the Charged Particle Monitor was declared operational, actively controlling the operation of the other instruments and triggering deactivation commands in case particle flux levels rise above a programmed threshold. The Cadmium-Zinc-Telluride Imager powered up its electronics to begin checkouts of the instrument. CZTI puts to use an array of detector elements to image X-rays from 10 to 150 keV and conduct photometric studies for hard X-rays up to 1 mega-Electronvolt. The initial data returned by CZTI showed a good powered state of the instrument, allowing controllers to activate the high-voltage detector systems. On October 5, CZTI was declared operational and began collecting science data with a one-day integration on Cygnus X-1, a well known X-Ray source that represents one of the most studied astronomical objects, making it suitable for calibrations of the CZTI instrument.
CZTI was oriented to point at Crab Nebula on October 6, a supernova remnant that includes the Crab Pulsar, the brightest source in the sky for hard X-rays and therefore often used for calibration measurements of space and Earth-based instruments. The initial attempt to collect data on Crab Nebula was not successful because the satellite’s instruments were deactivated by the onboard safeguard when detecting the observatory was passing through the South Atlantic Anomaly. Analysis of data showed that Crab Nebula was captured later in the observation session when it emerged from behind Earth, causing detector count rates to rise above their background level of around 9 counts per detector to approximately 20 counts per second, providing operators with a confirmation that the instrument was picking up a bright X-ray source.
Processing of the data from the 42-minute Crab Nebula observation yielded the First Light image for the AstroSat mission. The image displays only the hard X-ray spectrum above 25 keV and shows Crab Nebula as a bright object surrounded by artifacts that will be removed as part of data processing. CZTI reached an image resolution of 10 arcmin which will be improved over the course of instrument commissioning to around 8 arcmin. Additional work will be carried out to bring down the lower energy threshold to 10 keV as part of the commissioning phase.
Starting on October 12, the Scanning Sky Monitor became operational and joined the observation of Crab Nebula. AstroSat will complete coordinated observations with other space observatories including NASA’s Swift and NuSTAR satellites to provide additional data for the calibration of the instruments and an assessment of detector drifts.
Commissioning of the remaining AstroSat instruments will continue over the course of the next three weeks to prepare the X-ray instruments to begin regular operations in November when several coordinated observation campaigns are planned, focused on back holes and black hole candidates. | 0.908749 | 3.621642 |
The primary objective of the OSIRIS-REx mission is to collect a sample from an asteroid and return it to Earth but the spacecraft will also carry out an extensive remote-sensing campaign at asteroid Bennu using a suite of scientific instruments. These include cameras and various spectrometers to learn about the composition and appearance of the asteroid’s surface while gravity science will reveal what lies beneath.
The OSIRIS-REx spacecraft is outfitted with six payloads – five remote-sensing instruments and the TAGSAM sample collection mechanism, plus the spacecraft’s communications equipment that doubles as a science payload when performing gravity science.
This page deals with the remote-sensing instruments and gravity science; for details TAGSAM, the Touch-And-Go Sample Acquisition Mechanism, refer to its dedicated page.
OCAMS – OSIRIS-REx Camera Suite
OCAMS – the OSIRIS-REx Camera Suite – is comprised of three separate cameras:
PolyCam collecting telescopic images during the approach to Bennu and high resolution once in formation,
MapCam tasked with collecting color imagery and the search for satellites around the asteroid, and
SamCam, a dedicated camera to deliver context imagery during the Touch-and-Go sample collection.
OCAMS was designed and built by the University of Arizona’s Lunar and Planetary Laboratory.
The first camera to pick up Bennu will be PolyCam that becomes active from a distance of around 2 Million Kilometers. It is a 20.3-centimeter telescope with a focal length of 63.5 centimeters and a narrow field of view of 0.8 degrees.
The telescope uses a Richey-Chretien arrangement which employs a hyperbolic primary mirror and a hyperbolic secondary mirror to eliminate off-axis optical errors compared to traditional reflecting telescopes which also have a smaller field of view.
PolyCam can detect stars down to the 12th magnitude, limited by spacecraft jitter. Its first task is to acquire the asteroid when OSIRIS-REx is still at great distance, providing assistance in optical navigation. Closer in, PolyCam can resolve surface features which helps in the exclusion of dangerous sites where sample collection will not be possible.
PolyCam’s name has been chosen because it can fulfill a pair of important tasks, collecting telescopic imagery from great distance and delivering high-resolution surface imagery during the close proximity phase of the mission – enabled by a refocusing mechanism.
PolyCam will deliver high-resolution imagery to characterize rock and pebble sizes on the surface for at least a dozen prospective sampling sites to help in the selection of the sampling location. The camera’s resolution will enable pebble sizes down to two centimeters to be identified.
MapCam is a medium-range camera tasked with the search for satellites and outgassing plumes on Bennu as well as mapping the asteroid in full color. It uses a five-lens optical design and a filter wheel between the optical elements and the focal plane to enable wide-band multispectral image acquisition.
The filter wheel has eight slots containing filters for full-color imaging (blue, green, red) and near-infrared, an empty slot for monochromatic imaging and a diopter lens to permit imaging at close range to the asteroid. MapCam has a field of view of 4 degrees.
MapCam’s primary task is the mapping of the entire asteroid surface in the various wavelength ranges enabled by the filter wheel. From a five-Kilometer distance, MapCam can see the asteroid make one full rotation every 4.3 hours and collect images at a resolution of 0.17 degrees. The refocusing lens allows MapCam to focus the surface from a distance of 30 meters for image collection of the sampling site.
SamCam is a close-range camera that serves a twofold task – collecting context imagery of the sampling site and verifying that the sampling process worked by imaging the sampling device.
It offers a wide field of view of 21 degrees and has a filter wheel with three identical filters plus an diopter filter. Three filters allow SamCam to restore its vision after a sample collection event in case the stream of nitrogen gas from the sampling device kicks dust into the camera assembly. This allows the camera to support at least three sampling attempts to make sure OSIRIS-REx fulfills its primary mission goal. The diopter is rotated into the optical path when focused images of the sample mechanism are needed (at very close range).
All three OCAMS cameras use identical focal plane assemblies with 1024 by 1024-pixel detectors manufactured by Teledyne Dalsa, Inc. Each has a mass of 0.6 Kilograms and draws 5.3 Watts of electrical power.
The detectors use an electronic frame-transfer shutter. All three cameras share a Camera Control Module installed underneath the payload deck and responsible for the analog to digital conversion, image compression and storage as well as commanding all camera sequences.
OCAMS completes extensive calibration after OSIRIS-REx arrives in space using multiple sources. Geometric calibration is accomplished by the collection of star cluster images to get a handle on the geometric distortion in the images, radiometric calibration is completed by star imaging, blocking filters are used for dark current monitoring, illumination lamps are available to assess pixel noise and imaging of the Earth-Moon system during flyby provides operational preparation for the mission at Bennu.
During approach to Bennu, PolyCam is the first to acquire the asteroid from a distance of 2 Million Kilometers as the asteroid begins to become visible against the star-filled sky. Imagery is used for optical navigation and the approach phase can be used for the measurement of the precise rotation rate, phase curve and other properties to verify data collected using ground-based sensors. Additionally, PolyCam will deliver initial data to develop a preliminary shape model of the asteroid.
Arriving at the asteroid, OSIRIS-REx enters a Survey Phase during which flybys of the polar regions are completed and images are collected from different positions with the asteroid at various phase angles. This phase will cover at least 80% of the asteroid’s surface generating high-resolution monochromatic images and full-color data. These initial maps will be used to construct a refined shape model, delineate craters, large boulders and identify surface features.
The Survey Phase will deliver 12 potential sampling locations.
After the Survey Phase, OSIRIS-REx is to enter a polar orbit around the terminator where the gravitational attraction and radiation pressure from the sun offset. Orbiting one Kilometer around the center of gravity of the asteroid places OSIRIS-REx several hundred meters above the surface from where imagery of 5-centimeter resolution can be collected by PolyCam. These images will narrow the search for a sample location from a dozen to only four sites.
The Reconnaissance Phase sets up flyovers of the four finalist sites and uses PolyCam with its refocusing mechanism, essentially converting the telescope into a microscope. Imagery captured by PolyCam during the flyovers provides information on the properties of the sample site candidates, resolving any dangers and confirming that the sites contain a sufficient amount of small regolith particles under two centimeters in diameter.
A final site is selected based on PolyCam imagery and will mark the start of a series of rehearsals of the sampling operation during which MapCam monitors the surface from a 30-meter distance using its refocusing capability. At this standoff distance, OSIRIS-REx matches the rotational period of the asteroid, providing an opportunity of extended monitoring of the sampling site.
During the actual Touch-and-Go Sample Collection, SamCam collects imagery at around one frame per second. The approach to sampling delivers context imagery of the undisturbed surface while imagery collected after the touch provides a look at the morphology of the site after contact with the probe. The final and possibly most critical task of SamCam is imaging the sample head to deliver a visual confirmation that material has entered the system.
OLA – OSIRIS-REx Laser Altimeter
OLA, the OSIRIS-REx Laser Altimeter, is a scanning and LIDAR instrument to generate high-resolution topographical maps of the Bennu asteroid. The instrument will create a global topographic map of Bennu, local maps of candidate sampling sites, and support data collection from other instruments as well as proximity navigation around the asteroid.
OLA scans the surface of Bennu at specific intervals in the mission to rapidly map out the entire surface of the asteroid and support the calculation of the asteroid’s center of mass to refine gravitational studies conducted later in the mission.
The Laser Altimeter is funded by the Canadian Space Agency and was developed and built by MDA and Optec Inc. The instrument uses heritage from the XSS-11 satellite that practiced autonomous rendezvous operations in Earth orbit, and the landing radar of NASA’s Phoenix lander that touched down on Mars in 2008.
LIDARs and laser altimeters function by sending laser pulses toward a target and recording the reflected pulse in order to calculate the distance to the target or gain information on its shape.
OLA employs a pair of laser sources and a single receiver, expanding the previous LIDAR/Altimeter systems by adding a second laser source optimized for measurements at longer distances.
Both laser sources make use of 1064-nanometer Nd:YAG lasers (neodymium-doped yttrium aluminum garnet). The High-Energy Laser operates at a frequency of 100 Hz (sending 100 pulses per second) with a pulse energy of 1 milli-Joule while the Low-Energy laser operates at a frequency of 10 kHz (10,000 pulses per second) and a pulse energy of 10 micro-Joule.
The laser beams are directed onto a flexure mounted scanning mirror driven by Electro-Magnetic Actuators supporting a high-speed pointing capability. With this mechanism – and a high-accuracy read-out circuit, OLA can make 10,000 measurements per second, permitting range pictures to be taken by having the mirror sweep out a 2-dimensional path on the surface. The maximum beam deflection is 7° to either direction (X/Y).
OLA has a maximum operational range of 7.5 Kilometers and delivers accurate readings up to a distance of 200 meters. The accuracy of the measurement depends on the distance to the target and varies from 5 to 30 centimeters. This is also true for the size of the laser spot on the surface, varying from 1.5 centimeters to 2 meters.
Over the course of the OSIRIS-REx mission, OLA will map Bennu to a spatial resolution of 7 centimeters.
The High-Energy Laser source is in use at distances of 1 to 7.5 Kilometers while the Low-Energy laser operates for all distances inside 1 Kilometer.
OLA will generate a high-density 3D point cloud data to reconstruct the asteroid shape model at the highest density yet for a small body. It also delivers the slope information needed in the selection of potential sampling sites. Another important task of OLA is keeping track of the distance of OSIRIS-REx to the asteroid for processing of Gravity Science Data.
OLA will first acquire Bennu at a distance of 7 Kilometers and complete a detailed scanning campaign at the mission’s 5-Kilometer survey position. When OSIRIS-REx is in its 1km orbit, OLA will be operating continuously to support gravity science and complete a high-resolution mapping campaign to yield a global map at the best possible resolution. During reconnaissance passes a few hundred meters from the surface, OLA will yield very high-resolution maps of targets of interest.
OLA data will contribute to the study of Bennu’s interior, including its density and heterogeneity, revealing clues on its formation and evolution. Vertical roughness measurements will be used in an assessment of the evolution of local and regional surfaces.
OVIRS – OSIRIS-REx Visible and Infrared Spectrometer
OVIRS is the OSIRIS-REx Visible and Infrared Spectrometer, one of three spectrometers that look at asteroid Bennu across the electromagnetic spectrum to reveal its surface composition, determining its mineralogy and supporting the search of organics.
The OVIRS instrument is a point spectrometer, is collects the VIS/IR wavelengths from a single spot on the surface, sweeping out image strips by combining the rotation of the asteroid and the rotation of the spacecraft around the optical axis of the spectrometer.
OVIRS covers a wavelength range of 0.4 to 4.3 micrometers and aims to generate a global spectral map of Bennu at a resolution of 20 meters with sufficient spectral accuracy to identify a variety of compounds including carbonates, silicates, sulfates, oxides, absorbed water and different organics.
Light entering the OVIRS instrument falls onto an off-axis parabolic mirror that images the surface of the asteroid onto a field stop which selects a 4-milliradian angular region of the image. The light from the 4-milliradian area is then re-collimated by a second off-axis parabolic mirror and sent to the Focal Plane.
OVIRS employs linear variable filters (wedge filters) placed in front of the detector to create the spectrum. The wavelength passing these two-dimensional filters varies with the position along one of the filter’s spatial dimensions, essentially assigning each detector region a specific wavelength.
This design was chosen for its flexibility and relative design simplicity compared to slit-type spectrometers that have complex optics and require dispersive elements, or Fourier-transform spectrometers with their elaborate scanning mechanisms.
The detector of the OVIRS instrument uses a 510 by 512-pixel region of a 1024 x 1024-pixel Mercury-Cadmium-Telluride H1RG array. This type of array is constructed by hybridizing the photosensitive pixel elements to a CMOS Read Out Integrated Circuit via Indium bonds.
The instrument delivers a spectral resolution of better than 7.5 nanometers for wavelengths between 400 and 900 nanometers (visible), better than 13nm for the 0.9 to 1.9-micrometer range (near infrared), and better than 22nm for the infrared range from 1.9 to 4.3 μm.
In addition, the 2.9 to 3.6 μm range is covered by a second filter to yield a resolution of under 10nm in order to resolve organic spectral signatures that have recently been discovered on asteroids.
The OVIRS filter is comprised of five segments 102 by 512 pixels in size and bound in a single assembly attached less than one millimeter from the detector array. The transmitted wavelength varies along the 512 pixel row dimension with each 102-pixel column covering a specific wavelength, creating the spectrum along the length of the detector. Pixels that fall within the central wavelength of their respective filter segments (at least 30) will be summed and averaged to reduce noise effects.
The detector element is coupled to a two-stage passive radiator pointing to space to maintain a focal plane temperature of 105 Kelvin in an effort to reduce dark currents. A cold baffle in the optical path limits thermal noise from the instrument enclosure showing up in the spectrum and the optics are cooled to under 160K by dedicated radiators. The thermal design has been optimized to ensure source photon noise dominates over thermal noise with the exception of low asteroid surface temperatures.
OVIRS is supported by a single electronics box containing three boards – a Low-Voltage Power Supply and a Command & Data Handling board that deliver regulated, filtered power to the instrument and control all instrument functions, executing commands and accepting housekeeping data. The third board hosts the System for Image Digitization, Enhancement, Control and Retrieval which controls all focal plane functions – analog-to-digital conversion, signal amplification, and detector clocking. All boards are functionally redundant.
In-flight calibration of OVIRS can use different sources. Spectral calibration will be completed with gratings that provide monochromatic scanned radiation with high repeatability while radiometric calibration is accomplished with blackbodies and flood sources as well as solar calibration via a dedicated calibration port. Dark currents will be assessed via dark sky observations.
OTES – OSIRIS-REx Thermal Emission Spectrometer
OTES, the OSIRIS-REx Thermal Emission Spectrometer, is the second spectrometer of the spacecraft covering the thermal infrared region of the spectrum to deliver complementing measurements to OVIRS to help mineralogical assessments, and to assess the thermal emission of the asteroid surface.
Like OVIRS, OTES is a point spectrometer – looking at a single point on the asteroid and using its and the spacecraft’s rotation to sweep out imaging strips. However, unlike OVIRS, OTES makes use of a Fourier Transform Interferometer with heritage from the OTES instruments on the Mars Global Surveyor and Mars Exploration Rovers.
The instrument was developed at the School of Earth and Space Exploration at Arizona State University.
Covering the 4 to 50-micrometer wavelength range, OTES can pick up fingerprint signatures of all major minerals expected to be found on Bennu and also delivers data on the water content of the minerals.
This spectral range also covers the bulk of thermal emissions from the asteroid which can yield valuable surface properties such as the mean grain size within the regolith.
The Fourier Transform Interferometer (FIT) is fed by a 15.2-centimeter Ritchey-Chretien telescope with a hyperbolic primary mirror and a hyperbolic secondary mirror to eliminate off-axis optical errors. The telescope arrangement creates a narrow instrument field of view of 8 millirad.
The basic working principle behind a Michelson Interferometer as used by OTES is splitting the incoming light with one half reflected off a fixed mirror and directed to the detector while the other beam is bounced off a translating mirror and then passed to the detector to introduce a time delay.
This will create optical interference on the detector which is different for each different time delay setting by moving the mirror – essentially converting the time domain into a spatial coordinate.
Fourier transform algorithms allow an entire spectrum to be reconstructed from many data points for the interference patterns at different mirror positions.
This spectrometer arrangement is more complex than traditional slit-type spectrometers or the design used by OVIRS, but yields a much higher resolution.
OTES uses a beam splitter made of chemical vapor deposited (CVD) diamond providing the stability and water resistance needed for the OSIRIS-REx mission.
The instrument captures one spectrum every two seconds and reaches a spectral resolution of 10cm^-1. Its spatial resolution depends on the distance of the spacecraft to the asteroid and varies from 40 meters at the 5-Kilometer surveying position to 4 meters for close reconnaissance passes.
OTES is an uncooled spectrometer system and features an optical baffle on its entrance to reduce the noise effects caused by solar radiation. Calibration is accomplished with an internal, conical blackbody target and dark space observation.
The OTES instrument electrics responsible for power supply, instrument control, and data read-out reside in an electronics box mounted directly under the spectrometer.
REXIS – Regolith X-Ray Imaging Spectrometer
REXIS is the Regolith X-Ray Imaging Spectrometer and represents a student collaboration experiment that is the result of a joint venture between MIT and Harvard University. The instrument is tasked with the creation of a global X-Ray map of asteroid Bennu to enhance the mission’s remote-sensing capabilities.
The 4.4-Kilogram REXIS instrument measures the composition of the asteroid surface and the distribution of select elements through the measurement of soft X-Rays caused by solar-induced fluorescence. This observation complements the other two spectrometers of the OSIRIS-REx mission at a the high end of the electromagnetic spectrum.
REXIS can characterize the elemental abundances at the global scale down to a 50-meter resolution, allowing for an assessment of local variations in surface composition. Of particular interest for REXIS are magnesium, iron, sulfur and silicon which are a key focus point in the classification of meteorites.
Because REXIS relies on solar-induced X-Ray fluorescence for its measurements, the current state of the sun has to be known with high accuracy to extract elemental information from the X-Ray spectra – removing the effect of solar emission variability.
The REXIS instrument is comprised of three subassemblies, the Main Detector and Collimator Assembly, the electronics box and a Solar X-Ray Monitor installed on the sun-facing side of the spacecraft.
The Soft X-Ray Imaging Spectrometer is 32 by 14 by 20 centimeters in size and houses four Charged Coupled Devices in a 2 x 2 arrangement serving as the detectors of the instrument. The detectors reside underneath a Coded Aperture Mask with 64 pixels.
Imaging is accomplished by placing a pinhole mask over the detector array so that the shift in the shadow pattern can be put through a deconvolution procedure to encode the location of the X-ray source on the asteroid.
The instrument has a field of view of 30 degrees and reaches a spatial resolution of 5.6 meters when OSIRIS-REx is in the one-Kilometer orbit around Bennu.
The mask is placed 20 centimeters from the detector, sitting atop the instrument entrance. It is 100 micrometers thick and consists of stainless steel. Each of the 64 repeating pixels is 98.3 millimeters in diameter with a 1.5mm pixel pitch, creating an open hole fraction of 50%. Sitting atop the mask is a radiation cover that protects the detector during the lengthy cruise phase and opens at the start of the observation campaign at Bennu.
The detector module is 37 by 20 centimeters in size, hosting the four detector elements, Iron-55 calibration sources and electronics support systems for instrument readout.
Each of the four MIT-Lincoln Lab CCDs consists of 1024 by 1024 pixels and covers an energy range of 0.3 to 10 kilo-Electronvolt, though the instrument’s operational range is given as 0.5 to 7.5 keV. The energy resolution achieved by the detector is 130 eV.
Deposited atop the detector is a 220-nanometer layer of Aluminum responsible for optical blocking, only allowing X-rays to strike the detector.
When being struck by an X-Ray photon, the photo-effect in a CCD pixel will create free electrons that create an output signal when the detector is being read out. This signal – provided sufficient calibration information is available – can be translated into the energy the photon possessed when striking from which the material that emitted the photon can be deduced.
The REXIS CCD is operated at a fixed integration time of four seconds and employs two frame store areas, read out by one of four output nodes on each CCD. Digitization is completed by a 12-bit analog to digital converter and the instrument converts the images to event lists with time tags, reducing the downlink data volume by orders of magnitude as only frames with data will be sent to Earth. Another measure to reduce data volume is binning pixels in an 8 x 8 array to super pixels 0.192 millimeters in size.
While a collimator-based instrument could achieve an angular resolution of 28 centimeters, REXIS’ maximum resolution from 730 meters will be lower by a factor of 7.3 taking into account the integration time of the instrument, spacecraft and asteroid motion, and limitations in the coded-mask design.
Calibration of the detector is accomplished with a source of Iron-55 placed around the CCD to fully saturate the detector with photons at an energy of 5.89 keV. Measuring the detector gain for a well known and calibrated X-Ray energy allows the instrument to determine the energy of any other photon.
Another calibration technique is measuring the cosmic background simultaneously with imaging operations since the asteroid will not occupy the entire field of view, allowing the background to be measured on the detector edges.
The measurement of the solar X-ray spectrum is accomplished by a separate Solar X-Ray Monitor SXM because the highly variable input from the sun has to be tracked for all asteroid measurements to be able to calculate the fluorescence energy emitted by the different elements.
SXM is installed on the side of the spacecraft facing the sun when REXIS is in nadir-pointed observation mode.
The heart of SXM is a commercial-off-the-shelf Silicon Drift Detector (SDD) provided by Amptek with a custom read-out circuit. The detector has a 25mm² active area with a detection depth of 500 microns. It is housed in an 0.5-millimeter thick Berryllium housing for optical blocking. A thermoelectric cooler is necessary to keep the detector at under 0°C while in direct solar illumination.
SXM covers an energy range of 1 to 20 keV with an energy resolution around 125 eV at 5.9keV.
The solar X-Ray spectrum can vary greatly on time periods of only ten minutes up to several days with flux variation up to three orders of magnitude, requiring constant SXM readings to put the main spectrometric measurements into context.
The main spectrometer of REXIS is thermally decoupled from the main spacecraft structure and hosts a radiator pointed towards deep space when in observation attitude to be able to cool the focal plane to below -60°C. In a typical orbit around the asteroid, taking 27 hours for one lap, OSIRIS-REx will be nadir-pointing for at least 11 hours for operation of the remote sensing instruments.
To reveal the interior structure of Bennu, OSIRIS-REx makes detailed measurements of the planet’s gravitational field which will point to internal structures down to the core.
Like many other planetary missions, OSIRIS-REx will use its radio system to conduct sensitive measurements using Deep Space Network (DSN) Doppler, and Delta-DOR
(delta – Differential One-way Ranging) techniques. Radio science can yield a detailed gravity field measurement, accurate mass estimate, asteroid ephemeris and other physical characteristics of asteroid Bennu.
Local variations in gravity can act on the spacecraft in orbit and cause it to speed up or slow down – those changes in spacecraft motion can be detected using the Doppler Shift in the X-band transponders used by the radio sub-system. For the gravity experiment, the High Gain Antenna needs to be pointed directly at Earth so that Ranging Signals can be sent and received at the Deep Space Network Stations.
Turnaround ranging using the Deep Space Network involves the DSN station that sends a signal to the spacecraft containing ranging tones that it imposes on a carrier using phase modulation. When the spacecraft receives the tones, it sends them right back via X-Band downlink. The DSN station records the timing of the ranging tones uplink and the timing of the tone’s reception order to calculate the line-of-sight distance to the spacecraft.
After processing of the data taking into account delays by the electronics on the spacecraft and the ground, atmospheric and ionospheric properties, interplanetary plasma, and relativistic effects, the ranging method achieves sub-meter accuracy. | 0.880293 | 3.700464 |
(BIVN) – On Monday, scientists announced the discovery of 20 new moons orbiting Saturn, making the gas giant the planet with the most moons in the Solar System.
“Move over Jupiter; Saturn is the new moon king,” declared the media release circulated by the Carnegie Institution for Science. Jupiter is known to have 79 moons.
The discovery was made using the Subaru Telescope on Maunakea. Here is the media release issued by Subaru:
Each of the newly discovered moons is about five kilometers, or three miles, in diameter. Seventeen of them orbit the planet backwards, or in a retrograde direction, meaning their movement is opposite of the planet’s rotation around its axis. The other three moons orbit in the prograde—the same direction as Saturn rotates.
Two of the prograde moons are closer to the planet and take about two years to travel once around Saturn. The more-distant retrograde moons and one of the prograde moons each take more than three years to complete an orbit.
“Studying the orbits of these moons can reveal their origins, as well as information about the conditions surrounding Saturn at the time of its formation,” Sheppard explained.
The outer moons of Saturn appear to be grouped into three different clusters in terms of the inclinations of the angles at which they are orbiting around the planet. Two of the newly discovered prograde moons fit into a group of outer moons with inclinations of about 46 degrees called the Inuit group, as they are named after Inuit mythology. These moons may have once comprised a larger moon that was broken apart in the distant past. Likewise, the newly announced retrograde moons have similar inclinations to other previously known retrograde Saturnian moons, indicating that they are also likely fragments from a once-larger parent moon that was broken apart. These retrograde moons are in the Norse group, with names coming from Norse mythology. One of the newly discovered retrograde moons is the farthest known moon around Saturn.
“This kind of grouping of outer moons is also seen around Jupiter, indicating violent collisions occurred between moons in the Saturnian system or with outside objects such as passing asteroids or comets,” explained Sheppard.
The other newly found prograde moon has an inclination near 36 degrees, which is similar to the other known grouping of inner prograde moons around Saturn called the Gallic group. But this new moon orbits much farther away from Saturn than any of the other prograde moons, indicating it might have been pulled outwards over time or might not be associated with the more inner grouping of prograde moons.
If a significant amount of gas or dust were present when a larger moon broke apart and created these clusters of smaller moon fragments, there would have been strong frictional interactions between the smaller moons and the gas and dust, causing them to spiral into the planet.
“In the Solar System’s youth, the Sun was surrounded by a rotating disk of gas and dust from which the planets were born. It is believed that a similar gas-and-dust disk surrounded Saturn during its formation,” Sheppard said. “The fact that these newly discovered moons were able to continue orbiting Saturn after their parent moons broke apart indicates that these collisions occurred after the planet-formation process was mostly complete and the disks were no longer a factor.”
The new moons were discovered using the Subaru Telescope. The observing team included Sheppard, David Jewitt of UCLA, and Jan Kleyna of the University of Hawaii.
“Using some of the largest telescopes in the world, we are now completing the inventory of small moons around the giant planets,” says Scott Sheppard. “They play a crucial role in helping us determine how our Solar System’s planets formed and evolved.”
Last year, Sheppard discovered 12 new moons orbiting Jupiter and Carnegie hosted an online contest to name five of them.
“I was so thrilled with the amount of public engagement over the Jupiter moon-naming contest that we’ve decided to do another one to name these newly discovered Saturnian moons,” Sheppard said. “This time, the moons must be named after giants from Norse, Gallic, or Inuit mythology.” Contest details are available here. | 0.859926 | 3.492841 |
Where did Earth's global ocean come from? A team of Arizona State University geoscientists led by Peter Buseck, Regents' Professor in ASU's School of Earth and Space Exploration (SESE) and School of Molecular Sciences, has found an answer in a previously neglected source. The team has also discovered that our planet contains considerably more hydrogen, a proxy for water, than scientists previously thought.
So where is it? Mostly down in our planet's core, but more about that in a minute. The bigger question is where did all this come from in the first place.
"Comets contain a lot of ices, and in theory could have supplied some water," says Steven Desch, professor of astrophysics in SESE and one of the team scientists. Asteroids, he adds, are a source as well, not as water-rich yet still plentiful.
"But there's another way to think about sources of water in the solar system's formative days," Desch explains. "Because water is hydrogen plus oxygen, and oxygen is abundant, any source of hydrogen could have served as the origin of Earth's water."
In the beginning
Hydrogen gas was the major ingredient in the solar nebula -- the gases and dust out of which the Sun and planets formed. If the abundant hydrogen in the nebula could combine with Earth's rocky material as it formed, that could be the ultimate origin of Earth's global ocean.
Jun Wu, the lead author of the paper the team has published in the Journal of Geophysical Research, is an assistant research professor in both SESE and the School of Molecular Sciences. He says, "The solar nebula has been given the least attention among existing theories, although it was the predominant reservoir of hydrogen in our early solar system."
But first, some geochemical detective work.
To distinguish between sources of water, scientists turn to isotope chemistry, measuring the ratio between two kinds of hydrogen. Nearly all hydrogen atoms have a nucleus that's a single proton. But in about one in 7,000 hydrogen atoms, the nucleus has a neutron in addition to the proton. This isotope is called "heavy hydrogen," or deuterium, symbolized as D.
The ratio of the number of D atoms to ordinary H atoms is called the D/H ratio, and it serves as a fingerprint for where that hydrogen came from. For example, asteroidal water has a D/H of about 140 parts per million (ppm), while cometary water runs higher, ranging from 150 ppm to as much as 300 ppm.
Scientists know that Earth has one global ocean of water on its surface and about two more oceans of water dissolved in its mantle rocks. That water has a D/H ratio of about 150 ppm, making an asteroidal source a good match.
Comets? With their higher D/H ratios, comets are mostly not good sources. And what's worse, the D/H of hydrogen gas in the solar nebula was only 21 ppm, far too low to supply large quantities of Earth's water. In fact, asteroidal material is such a good match that previous researchers have discounted the other sources.
But, say Wu and co-workers, other factors and processes have changed the D/H of Earth's hydrogen, starting back when the planet was first beginning to form. Wu says, "This means we shouldn't ignore the dissolved solar nebula gas."
The key lies in a process combining physics and geochemistry, which the team found acted to concentrate hydrogen in the core while raising the relative amount of deuterium in Earth's mantle.
The process began quite early as the Sun's planets were starting to form and grow through the merger of primitive building blocks called planetary embryos. These Moon-to-Mars-size objects grew very quickly in the early solar system, colliding and accreting material from the solar nebula.
Within the embryos, decaying radioactive elements melted iron, which grabbed asteroidal hydrogen and sank to form a core. The largest embryo experienced collisional energy which melted its entire surface, making what scientists call a magma ocean. Molten iron in the magma snatched hydrogen out of the developing primitive atmosphere, which derived from the solar nebula. The iron carried this hydrogen, along with hydrogen from other sources, down into the embryo's mantle. Eventually the hydrogen became concentrated in the embryo's core.
Meanwhile another important process was going on between molten iron and hydrogen. Deuterium atoms (D) do not like iron as much as their H counterparts, thus causing a slight enrichment of H in the molten iron and leaving relatively more D behind in the magma. In this way, the core gradually developed a lower D/H ratio than the silicate mantle, which formed after the magma ocean cooled.
All this was stage one.
Stage two followed as embryos collided and merged to become the proto-Earth. Once again a magma ocean developed on the surface, and once more, leftover iron and hydrogen may have undergone similar processes as in stage one, thus completing the delivery of the two elements to the core of the proto-Earth.
Wu adds, "Besides the hydrogen that the embryos captured, we expect they also caught some carbon, nitrogen, and noble gases from the early solar nebula. These should have left some isotope traces in the chemistry of the deepest rocks, which we can look for."
The team modeled the process and checked its predictions against samples of mantle rocks, which are rare today at Earth's surface.
"We calculated how much hydrogen dissolved in these bodies' mantles could have ended up in their cores," says Desch. "Then we compared this to recent measurements of the D/H ratio in samples from Earth's deep mantle." This let the team set limits on how much hydrogen is in Earth's core and mantle.
"The end result," says Desch, "is that Earth likely formed with seven or eight global oceans' worth of hydrogen. The majority of this indeed came from asteroidal sources. But a few tenths of an ocean's worth of hydrogen came from the solar nebula gas."
Adding up the quantities cached in several places, Wu says, "Our planet hides the majority of its hydrogen inside, with roughly two global oceans' worth in the mantle, four to five in the core, and of course, one global ocean at the surface."
Not just for our solar system
The new finding, says the team, fits neatly into current theories for how the Sun and planets formed. It also has implications for habitable planets beyond the solar system. Astronomers have discovered more than 3,800 planets orbiting other stars, and many appear to be rocky bodies not greatly different from our own.
Many of these exoplanets might have formed far from the zones where water-rich asteroids and other building blocks might have arisen. Yet they still could have collected hydrogen gas from their own stars' solar nebulas in the way that Earth did.
The team concludes, "Our results suggest that forming water is likely inevitable on sufficiently large rocky planets in extrasolar systems."
The authors of the paper are Jun Wu, Steven Desch, Laura Schaefer, Linda Elkins-Tanton, Kaveh Pahlevan, and Peter Buseck, all affiliated with SESE; Wu and Buseck are also affiliated with ASU's School of Molecular Sciences. The research was funded by the Keck Foundation.
Based in Los Angeles, the W. M. Keck Foundation was established in 1954 by the late W. M. Keck, founder of the Superior Oil Company. The Foundation's grant-making is focused primarily on pioneering efforts in the areas of medical research, science and engineering and undergraduate education. The Foundation also maintains a Southern California Grant Program that provides support for the Los Angeles community, with a special emphasis on children and youth. | 0.802105 | 3.9023 |
This chart provides the detail for the posting 2016-2017, Venus Evening Star.
The chart was plotted using data from the U.S. Naval Observatory’s MICA computer program. All points on the chart are calculated for Chicago, Illinois . The sunset line is the line across the bottom of the chart. The chart shows the setting times of the objects compared to sunset, beginning June 6, 2016 (Venus’ superior conjunction) and ending March 24, 2017 (Venus’ inferior conjunction). The latest setting time difference for any object on the chart is 5 hours after sunset.
When the Lines Cross
For all the objects that lie outside our planet’s orbital path, their setting times start at the top of the chart and set earlier each night until they disappear into the sun’s glare. Mercury and Venus move from evening sky to morning sky and back again. They pass behind the sun and move into the evening sky, setting higher until they reach their maximum separations from the sun and then dive between the earth and sun and move into the morning sky. This chart has two complete evening appearances for Mercury and the start of the third as Venus moves between earth and the sun.
When the setting lines of the celestial wonders cross, this indicates they are setting at the same time. It does not indicate that they are closest in their approaches to each other. The companion article, linked above describes close passings of the objects on this chart. An excellent example of this occurs early in October 2016. The setting chart above indicates that the moon and Venus set at nearly the same time on October 2, although they are closer on the next evening.
When the setting times of the celestial objects cross, they are setting at the same time, and they are likely to be close together sometime around the date of the cross. One exception is Antares. While it is near the orbital plane of the solar system, the closest approach dates can be several days before or after the simultaneous setting time. For example, the chart indicates that Mars and Antares set at the same time on August 19, 2016, they are closest on August 24 (1.75 degrees).
Planets and Stars on the Chart
Venus is represented by the green line between its two conjunction dates. During mid-January 2017, it sets nearly 4 hours after the sun. It sets during twilight until late October 2016. Locally (for Chicago) this 9 p.m. CDT. Venus reaches its greatest separation from the sun (Greatest Elongation East — GEE on the chart) on January 12, 2017. As it approaches our planet, it reaches its maximum brightness (GB) on February 17, 2017.
Mercury is represented by the brown lines that show its setting times during the Venus apparition; that is, two full evening appearances and the start of the third. It is best to observe Mercury near the time when is it near its maximum setting time difference relative to the sun. This speedy planet usually sets during evening twilight and is never seen high in the sky when the sky is completely dark.
The setting time of the moon is represented by circles (moon dots). The evening appearance of the moon starts near sunset and then sets later each night. Dates are indicated for each lunar cycle at least twice.
The stars Pollux, Regulus, Spica, and Antares make a starry background for the visible planets. They are near the plane of the solar system and the planets appear to move past them. Antares is several degrees from the plane. When a planet’s setting line intersect’s or a moon circle appears near Antares setting time, the objects set at the same time. This does not necessarily indicate that they are in conjunction.
Civil twilight is defined to begin in the morning, and to end in the evening when the center of the Sun is 6 degrees below the horizon. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished. In the morning before the beginning of civil twilight and in the evening after the end of civil twilight, artificial illumination is normally required to carry on ordinary outdoor activities.
Nautical twilight is defined to begin in the morning, and to end in the evening, when the center of the sun is 12 degrees below the horizon. At the beginning or end of nautical twilight, under good atmospheric conditions and in the absence of other lighting, general outlines of ground objects may be distinguishable. During nautical twilight the illumination level is such that the horizon is still visible even on a Moonless night.
Astronomical twilight is defined to begin in the morning, and to end in the evening when the center of the Sun is 18 degrees below the horizon. Before the beginning of astronomical twilight in the morning and after the end of astronomical twilight in the evening, light from the Sun is less than that from starlight and other natural sources. For a considerable interval after the beginning of morning twilight and before the end of evening twilight, sky illumination is so faint that it is practically imperceptible. (Source) | 0.838968 | 3.535985 |
We explain everything about the Sun, its component parts, its temperature and other characteristics. In addition, the Solar System.
What is the sun?
The Sun is the closest star to the planet Earth, located 149.6 million kilometers away. All the planets of the Solar System orbit around them at different distances, attracted by their gigantic gravity, as well as the comets and asteroids we know. The Sun is commonly known as Astro Rey .
It is a fairly common star of our galaxy, the Milky Way: it is neither too big nor too small compared to its millions of sisters. Scientifically, the Sun is classified as a yellow dwarf star, of type G2 .
It is currently in its main sequence of life. It is located in an outer region of the galaxy, in one of its spiral arms, 26, 000 light years from the galactic center.
However, the size of the Sun is such that it represents 99% of the entire mass of the Solar System, equivalent to about 743 times the total mass of each and every planet combined, and about 330, 000 times the mass of our planet.
Its diameter is 1.4 million kilometers, so it is the largest and brightest object in the earth's sky. That is why their presence makes the difference between day and night.
Moreover, the Sun is a huge plasma ball, almost round. It consists mostly of hydrogen (74.9%) and helium (23.8%), as well as a small portion (2%) of heavier elements such as oxygen, carbon, neon and iron.
Hydrogen is the main fuel of the Sun. However, due to combustion it becomes helium, leaving behind a layer of "ashes" of helium as the star progresses in its main life cycle.
Structure and parts of the Sun
The Sun is a spherical star, with a slight flattening at its poles, the result of its rotation movement. In spite of being a gigantic and continuous atomic bomb of fusion of atoms of hydrogen, the enormous force of gravity that its mass grants compensates the thrust of the internal explosion, reaching thus a balance that allows the continuity of its existence.
The Sun is structured in layers, more like an onion. These layers are:
- The core The innermost region of the Sun, which occupies a fifth of the star's total: about 139, 000 kilometers of its total radius. It is there where the gigantic atomic explosion of hydrogen merging takes place; but the gravity in the solar nucleus is such that it takes about a million years for the energy produced in this way to surface.
- The radiant zone It is composed of plasma, that is, of gases such as helium and / or ionized hydrogen, and is the region that allows the easiest radiation of energy towards the outer layers, which considerably decreases the temperature recorded in this place.
- The convective zone It is a region where gases cease to be ionized, making it more difficult for energy (in the form of photons) to escape out of the Sun. This causes energy to A can escape only by caloric convection, much more slowly. Thus, the solar fluid heats unevenly, causing dilation, loss of density and ascending or descending currents, such as an interior tide.
- The photosphere The region of the Sun where visible light is emitted, which is perceived as bright granules on a darker surface, although it is a transparent layer about 100 to 200 km deep. The surface of the star is considered, and it is where the sunspots appear.
- The chromosphere The outer layer of the photosphere itself is so called, much more translucent and still difficult to appreciate, since it is opaque due to the brightness of the previous layer. It has a size of around 10, 000 km and seen during an eclipse, it has an exterior reddish hue.
- The solar corona The weakest layers of the outer atmosphere of the Sun are thus known, in which the temperature rises considerably with respect to the inner layers. This is a mystery of solar nature. However, there are low densities of matter along with intense magnetic fields, crossed by energy and matter at very high speeds, as well as by numerous X-rays.
As we have seen, the temperature of the Sun varies according to the region of the star, although for our standards it is, in all, incredibly high.
Temperatures close to 1.36 x 10 6 degrees Kelvin (i.e. about 15 million degrees Celsius) can be recorded in the solar core, while on the surface the temperature drops to just barely 5, 777 K (around 5, 505 C), and rise again in the solar corona to 2 x 10 5 degrees Kelvin.
Importance of the Sun for life
Due to its continuous emission of electromagnetic radiation, including the light perceptible by our eyes, the Sun provides heat and illumination to our planet, making life possible as we know it. For this reason, the Sun is irreplaceable.
Its light allows photosynthesis, without which the atmosphere would not contain the oxygen levels we need, nor the plant life to sustain the different trophic chains. On the other hand, its heat keeps the climate stable, allows the existence of liquid water and energizes the different climatic cycles.
Finally, solar gravity keeps the planets orbiting around them, including Earth. Without him there would be no day and night, there would be no seasons, and the Earth would surely be a cold and dead planet, as are many of the outer planets.
This is reflected in human culture: the Sun usually occupies a central place in the religious imaginary, as a fertile father god, throughout almost all known mythologies. All the great gods, kings or messiahs have been in one way or another associated with their brightness, while death, nothingness and the evil or secret arts are associated with night and night.
We call the planetary neighborhood where the Earth is located, that is, the circuit of eight planets that constantly orbit the Sun. This neighborhood is part of the Local Interstellar Cloud, part of the Local Bubble of the Ori n arm. It is estimated that it emerged 4, 568 million years ago, as a result of the collapse of a molecular cloud.
It consists of the following objects:
- The Sun, the only star located in its center.
- The inner planets, smaller in size and solid: Mercury, Venus, Earth and Mars. Next to them, their respective moons or satellites.
- The outer planets, gigantic balls of icy gas: Saturn, J piter, Neptune and Uranus. Next to them, their respective moons or satellites.
- Dwarf planets, such as Pluto, Ceres or Shovels.
- The asteroid belt that separates the inner planets from the outer ones.
- The belt of Kuiper and the Oort cloud, two sets of trans- Neptunian objects from which comets come.
More in: Solar System | 0.861414 | 3.731622 |
Figuring for Yourself
Show that no matter how big a redshift (z) we measure, v/c will never be greater than 1. (In other words, no galaxy we observe can be moving away faster than the speed of light.)
If a quasar has a redshift of 3.3, at what fraction of the speed of light is it moving away from us?
If a quasar is moving away from us at v/c = 0.8, what is the measured redshift?
In the chapter, we discussed that the largest redshifts found so far are greater than 6. Suppose we find a quasar with a redshift of 6.1. With what fraction of the speed of light is it moving away from us?
Rapid variability in quasars indicates that the region in which the energy is generated must be small. You can show why this is true. Suppose, for example, that the region in which the energy is generated is a transparent sphere 1 light-year in diameter. Suppose that in 1 s this region brightens by a factor of 10 and remains bright for two years, after which it returns to its original luminosity. Draw its light curve (a graph of its brightness over time) as viewed from Earth.
Large redshifts move the positions of spectral lines to longer wavelengths and change what can be observed from the ground. For example, suppose a quasar has a redshift of At what wavelength would you make observations in order to detect its Lyman line of hydrogen, which has a laboratory or rest wavelength of 121.6 nm? Would this line be observable with a ground-based telescope in a quasar with zero redshift? Would it be observable from the ground in a quasar with a redshift of
Once again in this chapter, we see the use of Kepler’s third law to estimate the mass of supermassive black holes. In the case of NGC 4261, this chapter supplied the result of the calculation of the mass of the black hole in NGC 4261. In order to get this answer, astronomers had to measure the velocity of particles in the ring of dust and gas that surrounds the black hole. How high were these velocities? Turn Kepler’s third law around and use the information given in this chapter about the galaxy NGC 4261—the mass of the black hole at its center and the diameter of the surrounding ring of dust and gas—to calculate how long it would take a dust particle in the ring to complete a single orbit around the black hole. Assume that the only force acting on the dust particle is the gravitational force exerted by the black hole. Calculate the velocity of the dust particle in km/s.
In the Check Your Learning section of Example 27.1, you were told that several lines of hydrogen absorption in the visible spectrum have rest wavelengths of 410 nm, 434 nm, 486 nm, and 656 nm. In a spectrum of a distant galaxy, these same lines are observed to have wavelengths of 492 nm, 521 nm, 583 nm, and 787 nm, respectively. The example demonstrated that z = 0.20 for the 410 nm line. Show that you will obtain the same redshift regardless of which absorption line you measure.
In the Check Your Learning section of Example 27.1, the author commented that even at z = 0.2, there is already an 11% deviation between the relativistic and the classical solution. What is the percentage difference between the classical and relativistic results at z = 0.1? What is it for z = 0.5? What is it for z = 1?
The quasar that appears the brightest in our sky, 3C 273, is located at a distance of 2.4 billion light-years. The Sun would have to be viewed from a distance of 1300 light-years to have the same apparent magnitude as 3C 273. Using the inverse square law for light, estimate the luminosity of 3C 273 in solar units. | 0.838365 | 3.861172 |
Like Oedipus, Macbeth, or a minor character in a Final Destination movie, our planet faces a grim, inescapable fate. And now we have a chance to see what that might look like.
In about 5 billion years, the sun will run out of hydrogen to feed the nuclear reactions burning at its core and become a red giant. Our star’s atmosphere will push out into the solar system, swallowing up Mercury, Venus, and finally Earth before it stops its cataclysmic expansion just short of Mars, according to astronomers.
Eventually, the sun will collapse into a small, dense point of light: a white dwarf. For several billion years, it will cast a smoldering glow over the spot where life as we know it used to exist.
Astronomers from the UK’s University of Warwick have announced they found evidence of an Earth-like planet that met a similar fate. What remains of the planet orbits a white dwarf 410 lightyears from Earth, spinning perilously close to its spent host star.
A closer relationship, in the end
Although the distant star used to be twice the mass of our sun, it has now collapsed into a dense ember roughly the size of Earth. The planetary fragment circles the white dwarf so closely that its orbit would have fit inside the star before it collapsed.
“The white dwarf’s gravity is so strong—about 100,000 times that of the Earth’s—that a typical asteroid will be ripped apart by gravitational forces if it passes too close,” lead author Christopher Manser said in a statement.
The researchers theorize that the object they’ve found is no typical asteroid. It’s an iron-rich hunk of heavy metal that used to make up the core of a larger, rocky planet like our own. Sometime after the star collapsed, a disturbance may have nudged the planet into a tight orbit around the white dwarf, where intense gravitational forces stripped away its outer layers until only its sturdy iron core remained.
We’ll always have Mars
The findings paint a grisly portrait for the future of our planet. “The general consensus is that 5-6 billion years from now, our Solar System will be a white dwarf in place of the Sun, orbited by Mars, Jupiter, Saturn, the outer planets, as well as asteroids and comets,” Manser said.
If our species survives to see the sun die, Earth won’t float through space as a graveyard or monument to humanity’s past. Every possible trace that we have been here will be incinerated or gravitationally shredded—unless billions of years from now we find some way to bury a sign about 3,200 miles (5,100 km) below the surface in our planet’s inner core. | 0.912891 | 3.758463 |
The Parkes Radio Telescope picks up faint signals from distant pulsars (Image: David Nunuk/Science Photo Library)
We’re homing in on the blobs from outer space.
In the past three decades astronomers have seen dips in the radio signals from quasars and pulsars, seemingly caused by a dark object passing by. These events don’t all look the same, so it isn’t clear if they share a cause. Sometimes different radio frequencies are delayed by different amounts, while other times the radio signal twinkles.
Now new observations are giving us a clearer picture. Bill Coles of the University of California, San Diego, and his colleagues used the Parkes Pulsar Timing Array, which carefully measures pulsar signals in an attempt to detect gravitational waves. The team used it to look for radio waves held up by a passing blob.
Violently turbulent clouds
They saw both time delays and twinkles from pulsars at the same time. That suggests the different phenomena may be coming from the same thing – violently turbulent clouds.
“This is an interstellar cloud way out in the middle of nowhere,” Coles says. “It makes a person wonder – what the hell is that out there?”
The short duration of the events suggests the blobs would fill the distance between the Earth’s orbit and the sun, which sounds big but is small in interstellar terms.
To affect radio signals as much as they do, the blobs must be filled with plasma that is at least a hundred times denser than normal interstellar space. That also means they must be hot, so it’s strange they don’t puff into nothingness.
Shock wave or pressure point?
“You need something that can create these and confine them,” says Jim Cordes of Cornell University in New York. He thinks the blobs are created by eddies from supernova shock waves that have compressed regions of interstellar gas. The compression strengthens their inherent magnetic fields to hold plasma inside.
Coles disagrees and thinks instead that they might form at pressure points when two regions of the thin dust and gas between stars brush up against each other, with no supernova blast involved.
Even stranger theories have been suggested, including that the blobs are nuggets of dark matter. More data from pulsar timing arrays should clear things up, says Cordes.
More on these topics: | 0.881276 | 3.928478 |
When I read about the sun’s magnetic field reversing its polarity within the next several months, part of me felt a little nervous. How will the sun’s changes affect the earth? Does this mean that our earthly days are numbered? Actually, astronomers and meteorologists have indicated that we have little to worry.
The sun’s shift in polarity will not lead to more solar storms or other events that might spell doom and gloom for the residents of earth. Such an event occurs every eleven years—and given what we have seen in the past, we are still here—alive and well.
The change in polarity may actually have some positive benefits for all us. For one thing, the shift in the sun’s magnetic field will make our planet’s radiation belt more effective as a barrier against dangerous cosmic rays emanating from distant galaxies.
Not bad, no?
In practical terms, the earth’s storms should be less intense since the lightning storms will diminish comparatively.
At any rate, the changes in our sun’s magnetic field illustrate just how finely attuned the universe is calibrated to enhance life on this planet.
In spiritual terms, we may say that God carefully preordained the movement of the heavenly bodies in the cosmos. Had the Earth been closer to the sun or larger than it presently became, the sun’s rays would have incinerated the earth. Had the earth been just slightly farther away from the sun than its present orbit, life on our planet would have frozen. Had the earth’s circular orbit (with a 3% variance) been like the elliptical orbit of the planet Mars, which varies by 42 million kilometers in its distance from the sun, the earth would incinerate annually once it came closest to the sun. Nothing is fortuitous about the Earth’s orbit. Bar-Ilan University physicist Nathan Aviezer observes how fortunate this planet was in the cosmological scheme of the universe:
- Our planet Earth is very hospitable to life, abundant with air and water essential to life. Our neighbors Mars and Venus, however, have no water or air. Yet shortly after they were formed about 4.6 billion years ago, all three planets (Earth, Mars, and Venus) had comparable amounts of surface water. In fact, the deep channels that are observed today on the surface of Mars were carved out long ago by the copious, fast-flowing Martian primordial surface waters. Venus was once covered by deep oceans which contained the equivalent of a layer of water 3 kilometers deep over the entire surface of the planet. Why, then, are the two planets so completely different today?
- The difference in the subsequent development of Mars and Venus was due to their proximity to the Sun. Mars is somewhat more distant from the Sun than the Earth. This caused the temperature of Mars to drop in the course of time. Eventually, Mars became so cold that all its surface water froze, and as a result, the planet Mars has become completely devoid of all liquid water, thus preventing the existence of life as we know it on that planet. Venus, on the other hand, is somewhat closer to the Sun than the Earth, which caused it to gradually become hotter. As a result, Venus became so intensely hot, all its oceans and seas completely evaporated and then decomposed into hydrogen gas and oxygen gas, both of which later dissipated. Why did the Earth escape these catastrophes?
- The answer is that the Earth escaped these catastrophes by sheer accident! The Earth just happened to be sufficiently distant from the Sun that the runaway greenhouse effect did not occur and therefore all our surface water neither evaporated nor decomposed. Moreover, the Earth just happened to be sufficiently near the Sun that it remained warm enough to prevent all the oceans from freezing permanently into ice caps. Therefore, the Earth alone, of all the planets of the solar system, is capable of supporting life. This balance in the carbonate‑silicate geochemical cycle is so delicate that if the Earth were only a few percent closer to or further from the Sun, the possibility for life could not exist. This enigmatic situation has become known among scientists as the “Goldilocks problem of climatology.”
The recent discovery of extrasolar planets orbiting other nearby stars, has given us a new appreciation as to the perfect conditions that exist on this planet, which produce life. One interesting planet, classified as Upsilon Andromeda b, orbits a star that is approximately 40 light-years away in the constellation Andromeda. It is a Jupiter-sized planet that circles closely around its scorching star every 4.6 days—is a world composed of fire and ice. Some planets float eerily through space with heat sources that someday may produce a new solar system, while others orbit pulsar stars, which emit such powerful bursts of energy—life as we know it would prove impossible. Paul Davies refers to our world as hitting the “cosmic jack-pot,” and argues that the “cosmos” appears to have played a “conscious” role in the formation of life, and continues to play a pivotal role in the evolution of the cosmos.
Nathan Aviezer, In The Beginning: Biblical Creation and Science (Hoboken, NJ: Ktav, 1990), 37.
Last modified on | 0.909554 | 3.397242 |
Space and planetary Probes
The International Cometary Explorer (ICE) spacecraft was launched in 1978 into heliocentric orbit to measure study the interaction between the Earth's magnetic field and the solar wind. It was the first probe to visit a comet, passing through the plasma trail of comet Giaobini-Siner in 1985. Routine contact was suspended in 1997 with status checks in 1999 and 2008. In 2014 the ISEE-3 Reboot Project regained communication but contact was lost later that year.
The Luna program was a series of spacecraft missions sent to the Moon by the Soviet Union between 1959 and 1976. Twenty-four spacecraft were given the Luna designation, with 15 successful missions as an orbiter or lander. Many more were launched but failed to reach orbit. There were many types of spacecraft: impactors, flybys, soft landers, orbiters, rovers, and sample returns. The program ended due to a lack of funding.
The Venera program was a series of space probes developed by the Soviet Union between 1961 and 1984 to research Venus. Ten probes landed on the surface of the planet while 13 entered the atmosphere. The probes could only survive a short time on the surface but they acheived many accomplishments. Venera 4 was the first device to enter the atmosphere of another planet in 1967, Venera 7 was the first to make a soft landing on another planet in 1970, and Venera 9 was the first to return images from another planet's surface in 1975.
The Mariner program was a 10-mission NASA program that launched robotic interplanetary probes from 1962 to 1973 to investigate Mars, Venus, and Mercury. They include the first planetary flyby, the first planetary orbiter, and the first gravity assist maneuver. Seven of the ten launches were successful, and plans for future Mariner probes were adapted into the Voyager, Viking, and Magellan programs. | 0.893173 | 3.004248 |
Without help from a comet. . . I will give you a receipt for growing tree ferns at the pole, or if it suits me, pines at the equator; walruses under the line, and crocodiles in the arctic circle.' Charles Lyell
I n science as in life, timing is everything. A correct theory proposed before the time is ripe for its acceptance goes nowhere. The history of science is replete with theories ignored for years, decades, even centuries before their eventual acceptance. The most famous example is that of Aristarchus of Samos who anticipated by '8 centuries Copernicus's theory that the sun and not the earth is at the center of the solar system. In Aristarchus's day, however, Earth-centered astronomy did a good enough job of explaining the then rudimentary knowledge of the solar system, so that Aristarchus's theory was not "required." In '866, the monk Gregor Mendel published his work on the laws of genetics in the proceedings of a local society of naturalists, but no one took notice. In '900, '6 years after his death, Mendel's results were rediscovered. Continental drift had to wait half a century from Alfred Wegener's initial formulation in '9'5 to the plate tectonics revolution of the '960s and '970s.
Why do ideas that eventually prove worthy often have to wait? Typically it is because they go against the grain of the current paradigm, leaving other scientists with no way even to think about them. When first proposed, they are often little more than inspired guesses with no supporting evidence. (Mendel was an exception; he had the evidence but published it where no one saw it.] The apparatus and techniques that will eventually provide experimental support often have yet to be invented. For example, only a few years prior to '980, the Gubbio iridium anomaly could not have been detected, even if someone had been looking for it, because none of the available instruments were sensitive enough to detect iridium at the parts per trillion level.
The idea that a giant impact could cause mass extinctions, though consistently rejected by geologists, has a surprisingly long history, dating back at least to 1742, when Frenchman Pierre-Louis Moreau de Maupertuis suggested that comets have struck the earth and caused extinction by changing the atmosphere and the oceans.2 His countryman, astronomer Pierre-Simon Laplace, wrote in 1813 that a meteorite of great size striking the earth would produce a cataclysm that would wipe out entire species.3 In our own century, the distinguished paleontologist Otto Schindewolf sought an extraterrestrial cause for mass extinction. In 1970, Digby McLaren used his presidential address to the Paleontological Society to present the idea once again, leading some uniformitarians to assume that he could only have been speaking tongue-in-cheek.4 American Harold Urey, winner of the Nobel Prize in chemistry, proposed in 1973 in the widely read journal Nature that impact was responsible for mass extinctions and the periods of the geologic time scale on which they are based.5 Urey, who had published a variety of important research papers, had developed enough of a reputation in the earth and planetary sciences to be taken seriously, yet still no one paid any attention. These suggestions were catastrophist, unorthodox, and without evidence or predictions; therefore, even when made by distinguished scientists in important journals, they languished.
By 1980, when the Alvarez theory appeared, conditions had begun to improve. Iridium at the parts per trillion level was not easily measured, but it could be done at several laboratories around the world. The space age was nearly two decades old and the surfaces of other heavenly bodies were known in great detail—the map of the moon was more complete and accurate (when the ocean basins were included) than any map of the earth. It was impossible not to notice that, whatever its effect on the earth, impact had scarred every other object in the inner solar system innumerable times.
Was this article helpful? | 0.865664 | 3.575876 |
Skywatchers had high hopes that a comet called ATLAS would light up the night sky this spring, with forecasts suggesting it could become bright enough to see with the unaided eye.
Instead, the icy object crumbled to pieces — but it's still putting on a spectacular show for scientists. Ye Quanzhi, an astronomer at the University of Maryland, snagged some time with NASA's Hubble Space Telescope to take a look at Comet ATLAS on Monday (April 20) and caught a stunning image of its fragments that he shared on Twitter as a preview of his research.
"We have been following the break-up of ATLAS since it was first detected in early April, but with ground-based telescopes we couldn't resolve most of the debris field," Ye told Space.com in an email, adding that he was excited to see the new images. "With Hubble, we are finally able to resolve individual mini-comets."
Ye hopes those mini-comets will help scientists understand what caused ATLAS to fall apart. In particular, astronomers rely on the distance between fragments to reconstruct events, since that distance increases as more time passes since a specific fracture.
Previous observations had identified four main fragments from Comet ATLAS. In the Hubble image, Ye said, he believes two of those fragments have broken down even more, yielding the two pairs of bright spots on the right, which represent the four largest fragments at the time.
The two clouds of brightness on the left may represent where older fragments have broken up into smaller pieces. Before beginning the observations, which lasted for one of Hubble's orbits around Earth, Ye had hoped that Hubble would be able to spot more mini-comets in those regions, but it would appear those fragments had already disintegrated too far by the time the observations began.
Comet ATLAS is hardly the first icy space rock to break up within scientists' view, but there are a few special conditions that make these new observations particularly exciting, Ye said. First, ATLAS happened to break up when it was quite close to Earth and quite bright, giving astronomers an especially clear view.
And ATLAS hails from the Oort Cloud, a distant sphere of icy rubble enveloping the solar system as much as 9.3 trillion miles (15 trillion kilometers) away from Earth. That vast distance makes it quite difficult for astronomers to study the Oort Cloud directly, but watching Comet ATLAS's antics will help scientists develop new hypotheses about what's happening out there.
ATLAS is only the second bright Oort cloud comet whose fragments Hubble has been able to observe in its 30 years of work, Ye said.
- Photos: Spectacular comet views from Earth and space
- Interstellar Comet Borisov shines in incredible new Hubble photos
- Comet Atlas is falling apart, new photos confirm | 0.854647 | 3.687705 |
Sunday, June 05, 2011
Kepler's Harmony of the Worlds Might Also Be a Dance of the Planets...
Planetary scientists have long wondered why Mars is only about half the size and one-tenth the mass of Earth. As next-door neighbors in the inner solar system, probably formed about the same time, why isn't Mars more like Earth and Venus in size and mass? A paper published in the journalNature this week provides the first cohesive explanation and, by doing so, reveals an unexpected twist in the early lives of Jupiter and Saturn as well.
Dr. Kevin Walsh, a research scientist at Southwest Research Institute® (SwRI®), led an international team performing simulations of the early solar system, demonstrating how an infant Jupiter may have migrated to within 1.5 astronomical units (AU, the distance from the Sun to the Earth) of the Sun, stripping a lot of material from the region and essentially starving Mars of formation materials.
"If Jupiter had moved inwards from its birthplace down to 1.5 AU from the Sun, and then turned around when Saturn formed as other models suggest, eventually migrating outwards towards its current location, it would have truncated the distribution of solids in the inner solar system at about 1 AU and explained the small mass of Mars," says Walsh. "The problem was whether the inward and outward migration of Jupiter through the 2 to 4 AU region could be compatible with the existence of the asteroid belt today, in this same region. So, we started to do a huge number of simulations.
"The result was fantastic," says Walsh. "Our simulations not only showed that the migration of Jupiter was consistent with the existence of the asteroid belt, but also explained properties of the belt never understood before."
The asteroid belt is populated with two very different types of rubble, very dry bodies as well as water-rich orbs similar to comets. Walsh and collaborators showed that the passage of Jupiter depleted and then re-populated the asteroid belt region with inner-belt bodies originating between 1 and 3 AU as well as outer-belt bodies originating between and beyond the giant planets, producing the significant compositional differences existing today across the belt.
The collaborators call their simulation the "Grand Tack Scenario," from the abrupt change in the motion of Jupiter at 1.5 AU, like that of a sailboat tacking around a buoy. The migration of the gas giants is also supported by observations of many extra-solar planets found in widely varying ranges from their parent stars, implying migrations of planets elsewhere in universe.
The paper, "A Low Mass for Mars from Jupiter's Early Gas-Driven Migration," published in the June 5 issue of the journal Nature, was written by Walsh; Alessandro Morbidelli of the Université de Nice, France; Sean N. Raymond of Université de Bordeaux, France; David P. O'Brien of Planetary Science Institute in Tucson, Ariz.; and Avi M. Mandell of NASA's Goddard Space Flight Center. The research was funded by the Helmholtz Alliance, the French National Center for Scientific Research and NASA.
Posted by Thingumbobesquire at 11:54 AM
- ► 2019 (14)
- ► 2018 (16)
- ► 2017 (14)
- ► 2016 (29)
- ► 2015 (30)
- ► 2014 (28)
- ► 2013 (58)
- ► 2012 (162)
- Hooray! Happy Days Are Here Again.
- From The Mouth of Babes
- More on Seeding the Cosmos with Life's Precursors
- Impeach Tin Pot Obama!
- The Light of Time: A Theodicy of Sorts
- Aaron Burr and Derivatives
- Plus ça change, plus c'est la même chose
- Toroidal Shockwaves and Life
- Obama's Sense of Timing: Curiouser and Curiouser!
- Statistics Say the Darnedest Things!
- Obama: Being a dad is sometimes my hardest job
- Union leader compares NJ gov to Hitler at rally
- ‘Nothing More Impeachable' Than War Without Author...
- Greece: Tragedy or Hope?
- Entropic Gravity Wins The Prize This Time
- The IMF Hacked!!!
- Who Is Nuttier Weiner or Obama?
- On The Other Hand...
- Yet More Crocodile Tears from Paul Krudman
- This Kind of Stuff Must Make Prince Phillip and Co...
- E. coli: The Legacy of Rachel Carson and Friends
- 2 and 2 together
- But How Did This Actual Climate Science Get Past T...
- Pure Crapola
- The Wonder of Life
- Kepler's Harmony of the Worlds Might Also Be a Da...
- Hope For A Future If You Can Win It
- Americans' Obsession with Folly or the Tale of the...
- A Diversionary Tack?
- The World of Edgar Allan Poe: The Poetic Principle...
- Please Pardon The Doggerel, But Sometimes I Get A ...
- Things We Would Like to See More Of
- The Harbinger of the E Coli Mutation
- ▼ June (34)
- ► 2010 (139)
- ► 2009 (30)
- ► 2008 (22)
- ► 2007 (16) | 0.902239 | 3.825982 |
For a long time, many imagined conditions on Venus to be similar to Earth. But space probes have since discovered a burning hell instead of a tropical paradise on the planet’s surface. The first European mission to Venus, our closest neighbour, helps explain some of the reasons for this hostile environment.
Spring is the season when nature awakes from a cold and dark winter.
The warmth of the sun shining high in the sky brings nature and Man back to life.
Since ancient times, this season has been linked to beauty and love.
These virtues lent their name to a celestial object that resembled Earth so much it was believed to be our planet’s twin sister.
Håkan Svedhem, Venus Express Project Scientist, ESA: ”The planet Venus got its name from the goddess of love and beauty Venus. And it’s of course a very beautiful planet – just as the goddess is beautiful. But Venus can also be a hellish place.”
Many imagined Venus as some kind of tropical paradise.
Dimitri Titov, Science Coordinator for the Venus Express mission: ”A tropical paradise. That’s what people imagined Venus to be at the start of the 20th century. As it’s quite near to us, people expected to find a similar environment there – until the first space flights to Venus proved them wrong.”
At the dawn of the space age, Venus, also known as the ‘Morning Star’, was a very popular destination. This interest was fuelled by hopes of finding similar conditions to Earth on Venus, which is the planet closest to us.
Since the early 60s, more than 20 American and Soviet space probes have been sent to Venus.
Unfortunately, the data collected has unveiled a very hostile planet which has proved extremely difficult to study.
Uli Christensen, Planetary Director, Max Planck Institute for Solar System Research: ”You can’t see its surface from the outside, because Venus is covered in a close layer of clouds -which lie at an altitute of about 60 kilometres. They are made up of sulfuric acid and cover the entire planet. You can’t see through them – at least not in visible light.”
This acid cloud blanket has long prevented Man from studying Venus’s complex environment – its atmosphere, its surface, and its geology.
For more than 15 years, following several failed missions, the “Morning Star” and its mysteries seemed forgotten.
But today, the search has resumed, in the hope of finding answers to our own past and future.
Håkan Svedhem: ”Venus is covered by a thick cloud cover which is impossible to look through with a human eye… But now, with the help of modern technology – in infrared wavelenghs – we’re able to look through this cloud cover down to the surface.”
Some of the planet’s secrets have been uncovered by new high-tech equipment onboard the Venus Express mission.
Built around the design of its predecessor Mars Express, the Venus probe was quicker and cheaper to develop.
Dimitri Titov: “Venus Express is the European Space Agency’s first mission to the planet. It’s been orbiting our closest neighbour for three years now, studying its atmosphere, its plasma mantle and its surface”.
Equipped with state-of-the-art instruments, Venus Express has been able to delve into the secrets of the planet’s atmosphere.
Thanks to the stream of data pouring in from the orbit, scientists have been able to explain to some extent why Venus has become so inhospitable compared to its sister Earth.
The Venus Express mission was launched in November 2005.
Each piece of equipment onboard is thoroughly tried and tested before being sent into space.
Here, the ‘Venus monitoring camera’, which spans near-infrared, ultraviolet and visible wavelengths, is being tested in a vacuum furnace which simulates open space conditions.
Dimitri Titov: ”When we travel, we usually have a camera along to take pictures of what we see. Well, scientists do the same when they send a spacecraft to distant planets. There’s a camera just like this one onboard Venus Express.”
The camera’s images show Venus’s atmosphere is even more dynamic than expected.
Influenced by the gigantic hurricane-like vortices at its poles, the upper atmosphere rotates around the planet at a formidable speed, with wind reaching 360 kilometres an hour.
They then drop to almost zero at the planet’s surface.
Håkan Svedhem: ”When you get deeper into the atmosphere and down to the surface, it’s really a hellish place because of the high temperature and high pressure that crushes everything that gets in there and burns it at 460 degrees Celsius.”
With this data, scientists have been able to model the dynamics of the atmosphere on Venus.
They hope that by better understanding what’s going on under Venus’ clouds, they might find out why Earth and Venus’ destinies differed so wildly from the very birth of our Solar System.
Uli Christensen: “It’s thought Venus’ entire surface was completely altered by some kind of sudden and catastrophic event around 500 million years ago, and tremendous lava flows covered the planet’s surface. There’s been a lot of speculation, but we don’t really know what happened.”
Astronomers of the past could be forgiven for suggesting that Venus’s climate was once similar to the Earth’s.
Our sister planet wasn’t always that different.
Håkan Svedhem: “Likely, in the early days of the Solar system Venus may well have had as much water as the Earth had, and of course in that time the climate would have been very different, the temperature much lower. And slowly then, probably because Venus is closer to the Sun, it received more sunlight, the water slowly boiled up and out of the atmosphere.”
What Venus Express has been able to measure is the way Venus is losing its hydrogen and oxygen, which are stripped away by solar winds.
In contrast, the Earth is protected by its magnetic field.
But the slowly rotating Venus doesn’t have such a shield and is therefore gradually losing what’s left of its water.
To make matters worse, water vapor and carbon dioxide trapped inside the atmosphere act as a huge greenhouse ceiling, warming it up and speeding up the process.
Dimitri Titov: “Climate change on Venus is strongly influenced by a very powerful greenhouse effect, like the one we have on Earth on a much smaller scale – it only warms up our outside atmosphere by 30 to 40 degrees. However, we should bear in mind that by raising CO2 and water vapor levels in the atmosphere, we could one day have a climate as hostile as the one we see on Venus”.
Although there’s still a long way to go before that happens, perhaps the findings of the Venus Express mission will in some way spark reflexion about climate change on its unlikely twin, planet Earth. | 0.860816 | 3.589864 |
Moon ♈ Aries
Moon phase on 28 March 2063 Wednesday is Waning Crescent, 28 days old Moon is in Pisces.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 6 days on 21 March 2063 at 20:16.
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 ∠21° of ♓ Pisces tropical zodiac sector.
Lunar disc appears visually 7.4% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1785" and ∠1922".
Next Full Moon is the Pink Moon of April 2063 after 15 days on 13 April 2063 at 02:34.
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 28 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 781 of Meeus index or 1734 from Brown series.
Length of current 781 lunation is 29 days, 17 hours and 12 minutes. It is 3 hours and 10 minutes longer than next lunation 782 length.
Length of current synodic month is 4 hours and 28 minutes longer than the mean length of synodic month, but it is still 2 hours and 35 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠204.9°. At the beginning of next synodic month true anomaly will be ∠234.9°. 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°).
3 days after point of apogee on 25 March 2063 at 07:06 in ♒ Aquarius. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 12 days, until it get to the point of next perigee on 10 April 2063 at 05:55 in ♍ Virgo.
Moon is 401 550 km (249 512 mi) away from Earth on this date. Moon moves closer next 12 days until perigee, when Earth-Moon distance will reach 365 244 km (226 952 mi).
1 day after its ascending node on 27 March 2063 at 21:01 in ♓ Pisces, the Moon is following the northern part of its orbit for the next 12 days, until it will cross the ecliptic from North to South in descending node on 10 April 2063 at 07:03 in ♍ Virgo.
1 day after beginning of current draconic month in ♓ Pisces, the Moon is moving from the beginning to the first part of it.
6 days after previous South standstill on 21 March 2063 at 12:26 in ♐ Sagittarius, when Moon has reached southern declination of ∠-28.488°. Next 7 days the lunar orbit moves northward to face North declination of ∠28.415° in the next northern standstill on 4 April 2063 at 23:41 in ♊ Gemini.
After 1 day on 30 March 2063 at 00:50 in ♈ Aries, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.1535 |
The Hubble telescope has been searching the heavens for decades, finding one amazing discovery after another. This time, it appears to have found a surprising new example of a Hot Jupiter exoplanet, complete with a stratosphere. What is perhaps even more important, is that the team found signatures of water around that planet.
This Hot Jupiter Exoplanet has a Cooler Interior
The planet is a gas giant about 880 light years from Earth, known as WASP-121b. It was noted to orbit very close to its parent star, completing a revolution every 1.3 days. It is called a hot Jupiter exoplanet because, while it is of similar size to our own king of planets, its upper atmosphere reaches temperatures of 2,500 degrees Celsius or 4,500 degrees Fahrenheit.
One of the most interesting inferences made by this discovery is that this planet seems to get cooler as you head toward the interior. The outer layers of the stratosphere are highly excited, probably from the intense solar radiation the planet receives. That is how the water signatures were discovered.
“The question [about] whether stratospheres do or do not form in hot Jupiters,” said mission leader, Thomas Evans from the University of Exeter, “has been one of the major outstanding questions in exoplanet research since at least the early 2000s. Currently, our understanding of exoplanet atmospheres is pretty basic and limited. Every new piece of information that we are able to get represents a significant step forward.”
That is another exciting part of this discovery, the knowledge that we can determine atmosphere compositions of distant exoplanets. Hubble was able to examine the various spectra of light off of the planet to gauge what elements surround it. Science has yet to develop the technology needed for exploring smaller, rocky bodies like Earth and Mars, but the team has no doubt that future astronomers will develop the techniques and tools.
Image Credits: NASA | 0.825854 | 3.759824 |
There are several distinguishing properties of craters that help lunar scientists determine their ages. As craters get older their appearance changes through exposure to solar wind bombardment and other impacts (collectively called space weathering), and even gravity has an effect. Effects of the solar wind lower the reflectance of the surface; so regolith (soil) that was excavated by recent impacts has higher reflectance than the background surface, this is why small young craters have visible crater rays. New impacts pulverize rocks that were ejected during the formation of an older crater and disturb the shape by causing moonquakes. Also, gravity works to alter the shape of a crater by pulling material down its walls in a process called slumping, this causes craters to have a smoother appearance.
Today's Featured Image showcases two similarly sized adjacent craters (each ~500 m in diameter) located in Mare Tranquillitatis (see WAC context image below) with very different appearances. The area surrounding the top crater is littered with boulders in all directions. Wheras the more southerly crater has only a few rocks near its rim. Where did the boulders come from in the first place? And did the lower crater originally have boulders?
Since the mare basalt formed from layers of lava that hardened into solid rock, it is likely the boulders are coherent fragments of those thick layers (a few to tens of meters thick) that were broken up and ejected during the impact event. Since these two craters are so close and both formed in the mare it is very likely that the lower crater also had a large grouping of boulders in its ejecta field. The dissimilarity between these two craters is most likely due to age difference. Over time (perhaps a couple of billion years) the original boulders around the lower crater were slowly ground down by micro-meteorite bombardment - think of this process as cosmic sand-blasting! The boulders around the younger crater (top) have not had time to be pulverized by other impacts, but stick around for a billion years and you can watch these boulders slowly disappear!
Explore the full resolution NAC here:
Back to Images | 0.817572 | 3.982311 |
Map of Milky Way Galaxy reveals presence of stellar nurseries wave
Washington D.C. [USA], Jan 8 : Astronomers from Harvard University have found the presence of a wave-shaped gaseous structure named ‘Radcliffe Wave’ in the Milky Way Galaxy.
According to the research which has been published in the journal – Nature – the wave structure is the largest ever seen in the galaxy and is made up of interconnected stellar nurseries.
This discovery by the university transforms the 150-year-old vision of the nearby stellar nurseries as an expanding ring in one featuring a star-forming filament that reached trillions of miles below and above the galactic disk.
The study was enabled through a relatively new analysis of data from the European Space Agency’s Gaia spacecraft which was launched in 2013 along with the mission of precisely measuring the distance, position, and motion of the stars.
The researchers combined the data from Gaia which was super-accurate, with other measurements for constructing a detailed, 3D map of interstellar matter in the Milky Way, and noticed an unexpected pattern in the spiral arm which is closest to the Earth.
The researchers further discovered a thin, long structure, about 9,000 light-years long and 400 light-years wide, having a shape that of a wave, cresting 500 light-years above and below the mid-plane of our galaxy’s disk.
The wave consists of stellar nurseries that have been previously thought to form a part of the ‘Gould’s Belt’, which is a band of star-forming regions and is believed to have an orientation around the Sun in a circular or ring-like fashion.
“No astronomer expected that we live next to a giant, wave-like collection of gas — or that it forms the Local Arm of the Milky Way,” said the researcher, Alyssa Goodman.
“We were completely shocked when we first realized how long and straight the Radcliffe Wave is, looking down on it from above in 3D — but how sinusoidal it is when viewed from Earth. The Wave’s very existence is forcing us to rethink our understanding of the Milky Way’s 3D structure,” Goodman added.
“Gould and Herschel both observed bright stars forming in an arc projected on the sky, so for a long time, people have been trying to figure out if these molecular clouds actually form a ring in 3D,” said another researcher, Joao Alves.
“Instead, what we’ve observed is the largest coherent gas structure we know of in the galaxy, organized not in a ring but in a massive, undulating filament. The Sun lies only 500 light-years from the Wave at its closest point. It’s been right in front of our eyes all the time, but we couldn’t see it until now,” Alves added.
The newly developed three-dimensional map shows Earth’s galactic neighborhood in a new light, which gives researchers a revised view of the Milky Way and is also opening the door to some of the major discoveries.
“We don’t know what causes this shape but it could be like a ripple in a pond as if something extraordinarily massive landed in our galaxy,” said Alves.
“What we do know is that our Sun interacts with this structure. It passed by a festival of supernovae as it crossed Orion 13 million years ago, and in another 13 million years it will cross the structure again, sort of like we are ‘surfing the wave,” Alves added.
A long-standing challenge for astronomy and astronomers is disentangling structures that are present in the ‘dusty’ galactic neighbourhood. In previous studies, a group of researchers mapped the three-dimensional distribution of dust using a vast survey of stars.
Using the new data researchers recently augmented these techniques, which dramatically improves the ability of astronomers for measuring the distances to star-forming regions. The work which was led by the researcher Zucker has been published in the Astrophysical Journal.
“We suspected there might be larger structures that we just couldn’t put in context. So, to create an accurate map of our solar neighborhood, we combined observations from space telescopes like Gaia with astrostatistics, data visualization, and numerical simulations,” said Zucker.
“We pulled this team together so we could go beyond processing and tabulating the data to actively visualizing it — not just for ourselves but for everyone. Now, we can literally see the Milky Way with new eyes,” she added.
“Studying stellar births is complicated by imperfect data. We risk getting the details wrong because if you’re confused about distance, you’re confused about size,” another researcher Finkbeiner said.
Agreeing to the claims by Zucker and Finkbeiner, Goodman said, “All of the stars in the universe, including our Sun, are formed in dynamic, collapsing, clouds of gas and dust. But determining how much mass the clouds have, how large they are — has been difficult, because these properties depend on how far away the cloud is.” | 0.859109 | 3.637322 |
Mars’ carbon dioxide ‘snowflakes’ are about the size of red blood cells.
In the dead of a Martian winter, clouds of snow blanket the Red Planet’s poles — but unlike our water-based snow, the particles on Mars are frozen crystals of carbon dioxide. Most of the Martian atmosphere is composed of carbon dioxide, and in the winter, the poles get so cold — cold enough to freeze alcohol — that the gas condenses, forming tiny particles of snow.
Now researchers at MIT have calculated the size of snow particles in clouds at both Martian poles from data gathered by orbiting spacecraft. From their calculations, the group found snow particles in the south are slightly smaller than snow in the north — but particles at both poles are about the size of a red blood cell.
“These are very fine particles, not big flakes,” says Kerri Cahoy, the Boeing Career Development Assistant Professor of Aeronautics and Astronautics at MIT. If the carbon dioxide particles were eventually to fall and settle on the Martian surface, “you would probably see it as a fog, because they’re so small.”
Cahoy and graduate student Renyu Hu worked with Maria Zuber, the E.A. Griswold Professor of Geophysics at MIT, to analyze vast libraries of data gathered from instruments onboard the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO). From the data, they determined the size of carbon dioxide snow particles in clouds, using measurements of the maximum buildup of surface snow at both poles. The buildup is about 50 percent larger at Mars’ south pole than its north pole.
Over the course of a Martian year (a protracted 687 days, versus Earth’s 365), the researchers observed that as it gets colder and darker from fall to winter, snow clouds expand from the planet’s poles toward its equator. The snow reaches halfway to the equator before shrinking back toward the poles as winter turns to spring, much like on Earth.
“For the first time, using only spacecraft data, we really revealed this phenomenon on Mars,” says Hu, lead author of a paper published in the Journal of Geophysical Research, which details the group’s results.
Diving through data
To get an accurate picture of carbon dioxide condensation on Mars, Hu analyzed an immense amount of data, including temperature and pressure profiles taken by the MRO every 30 seconds over the course of five Martian years (more than nine years on Earth). The researchers looked through the data to see where and when conditions would allow carbon dioxide cloud particles to form.
The team also sifted through measurements from the MGS’ laser altimeter, which measured the topography of the planet by sending laser pulses to the surface, then timing how long it took for the beams to bounce back. Every once in a while, the instrument picked up a strange signal when the beam bounced back faster than anticipated, reflecting off an anomalously high point above the planet’s surface. Scientists figured these laser beams had encountered clouds in the atmosphere.
Hu analyzed these cloud returns, looking for additional evidence to confirm carbon dioxide condensation. He looked at every case where a cloud was detected, then tried to match the laser altimeter data with concurrent data on local temperature and pressure. In 11 instances, the laser altimeter detected clouds when temperature and pressure conditions were ripe for carbon dioxide to condense. Hu then analyzed the opacity of each cloud — the amount of light reflected — and through calculations, determined the density of carbon dioxide in each cloud.
To estimate the total mass of carbon dioxide snow deposited at both poles, Hu used earlier measurements of seasonal variations in the Martian gravitational field done by Zuber’s group: As snow piles up at Mars’ poles each winter, the planet’s gravitational field changes by a tiny amount. By analyzing the gravitational difference through the seasons, the researchers determined the total mass of snow at the north and south poles. Using the total mass, Hu figured out the number of snow particles in a given volume of snow cover, and from that, determined the size of the particles. In the north, molecules of condensed carbon dioxide ranged from 8 to 22 microns, while particles in the south were a smaller 4 to 13 microns.
“It’s neat to think that we’ve had spacecraft on or around Mars for over 10 years, and we have all these great datasets,” Cahoy says. “If you put different pieces of them together, you can learn something new just from the data.”
Since carbon dioxide makes up most of the Martian climate, understanding how it behaves on the planet will help scientists understand Mars’ overall climate, says Paul Hayne, a postdoc in planetary sciences at the California Institute of Technology.
“The big-picture question this addresses is how the seasonal ice caps on Mars form,” says Hayne, who was not involved in the research. “The ice could be freezing directly at the surface, or forming as snow particles in the atmosphere and snowing down on the surface … this work seems to show that at least in some cases it’s snowfall rather than direct ice deposition. That’s been suspected for a long time, but this may be the strongest evidence.”
What can the size of snow tell us?
Hu says knowing the size of carbon dioxide snow cloud particles on Mars may help researchers understand the properties and behavior of dust in the planet’s atmosphere. For snow to form, carbon dioxide requires something around which to condense — for instance, a small silicate or dust particle. “What kinds of dust do you need to have this kind of condensation?” Hu asks. “Do you need tiny dust particles? Do you need a water coating around that dust to facilitate cloud formation?”
Just as snow on Earth affects the way heat is distributed around the planet, Hu says snow particles on Mars may have a similar effect, reflecting sunlight in various ways, depending on the size of each particle. “They could be completely different in their contribution to the energy budget of the planet,” Hu says. “These datasets could be used to study many problems.”
This research was funded by the Radio Science Gravity investigation of the NASA Mars Reconnaissance Orbiter mission.
Jennifer Chu, MIT News Office | 0.864628 | 3.880824 |
It is a commonplace of conversation that for some months past the weather conditions have been abnormal, particularly in the matter of rainfall, in the battle-zones and elsewhere. Detailed data from regions close to the firing lines are not available; and we have only general statements of inclemency in so far as they affect military operations. But in districts not far away,—the British Isles, for instance,—the records of excessive raininess during the winter of 1914-15 and at subsequent times have not escaped comment; and others besides meteorologists are discussing the possibility of a connection between the heavy cannonading and the rainfall. The professional meteorologist is called upon to answer whether there is any rational explanation of what appears to be a marked departure from the usual sequence of weather conditions. Is it possible that the tremendous expenditure of ammunition—an expenditure which the layman may well regard as an experiment in concussion sufficiently vast to be decisive—has facilitated condensation and its later stage, precipitation? In concise terms, has the bombarding not only caused clouds but forced the clouds to send down rain?
It is conceivable that such could be the case; and stranger things have happened than the revelation through war of fresh progress in man's effort to comprehend and master the processes of Nature. And here, as is so often the case, Nature herself has suggested the relation, for we have all noticed that after an exceptionally near and heavy clap of thunder, the raindrops fall with a rush, as if the very tumult had shaken the clouds and caused the downpour. Later we shall see how this well-known phenomenon is to be interpreted.
Three separate lines of inquiry suggest themselves as throwing light on the problem. First, the underlying principles of the formation and flotation of a drop of rain; second, the causes of excessive rainfall in certain places at certain times; and third, the direct relation, if any, which exists between the use of high explosives and showery or rainy weather. To most of us the raindrop is an ordinary, commonplace drop of clean water, or rather it seems to be clean. It is one of the most common phenomena of everyday life, and most of us never stop to think that its life-history could be eventful; in fact we are sure that there can be nothing unusual about a drop of water falling through the air. On the contrary there is much that is wonderful in the wanderings of the little visitor; and the structure of each minute globe is in its way as marvelous as the structure the great nebula in Andromeda.
Probably no two raindrops are exactly alike. Photographs of snow crystals make it plain that no two flakes even in the same storm have identical shapes and structures. Raindrops are formed under somewhat similar conditions of strain, with forces more energetic, but never quite permanently balanced. Drops change incessantly, even those that seem to be quiescent. Many have made long journeys and undergone modification at every turn of the road; but large or small, each globule is a complex of ionic infinitesimals wrapped in a blanket of water vapor. It is an elastic blanket, beyond measure, and changes its size and sometimes its form, with every variation in pressure, temperature, and electrification. The process of wrapping the ions in the blanket of vapor still baffles science, although man has had recourse to certain small messengers, waves of light, wave-lengths little larger than a millionth of a millimeter, and sent these among the ions to do his bidding.
Generally speaking, a raindrop or any water-drop is an aggregation of hydrogen and oxygen atoms combining in the value of two to one. In a gram of hydrogen (that is, about fifteen grains), there are six million million million million atoms. But still smaller than atoms are these carriers of electric charge called electrons, oscillating many million times per second and as constantly colliding with one another. An English physicist who has worked much along these lines, once said that unless we had a better test for a man than we have for an unelectrified atom we could never detect that the earth was inhabited.
But larger than the electrons are certain foreign bodies called nuclei or centers of condensation; and if ever man succeeds in making rain artificially it will be by increasing the number of nuclei. In fact, the vortex guns or smoke-ring firers used in the grape growing regions of the West to dissipate hail have a certain scientific value in that they furnish nuclei at critical times. Notwithstanding the belief of the vineyard owners, however, the efficacy of these Steiger guns remains unproved. Without nuclei, condensation does not occur even when space is saturated with vapor. And here a word of caution, and a bit of information that rain-makers in general do not know. While textbooks speak of the capacity of air for vapor, they overlook the fact that it is space rather than air which contains the vapor, for air and water vapor are two separate entities and must be considered as such.
The man who has most studied the behavior of the nuclei and who therefore comes nearest to being a genuine rain-maker, though he would be surprised to hear himself so designated, is John Aitken of Edinburgh. His well-known dust-counter is a very practical means of studying the formation of fog or the first step in rain-making. His experiments show that the size of the nuclei or inorganic centers varies considerably; and also the number present at different times. In one of his papers Aitken speaks of the number of nuclei in a puff of smoke from a lighted cigarette as 4,000,000,000,000 per cubic centimeter. Now each of these little particles may serve as a foundation for a raindrop. On a much larger scale, the factory chimney as it belches forth its clouds of smoke is furnishing material for the building of raindrops; and, provided enough vapor is present and certain temperature changes occur, there is no uncertainty about the result.
Aitken, Barus, Wilson, Thomson, Langevin, Pollock, and other physicists have taught us a great deal about the building of a drop of water. There is no difficulty in making rain on a small scale. The moisture on the outside of an ice-water pitcher on a warm day proves how easily water-vapor may be condensed and dew or rain made. Nature makes rain by cooling a given volume of vapor. While there is no change in the weight of the individual atoms, the comparatively gross nuclei do change in size and weight because of physical changes, gravitational attraction, and probably electrical attraction and repulsion. These forces bring about cohesion, and a drop acquires sufficient weight to begin its downward movement against air resistance. The cooling of the vapor (and this is the effective agency) may be due to expansion, as when a stream of mixed air and vapor is carried up in a mighty cumulonimbus cloud or thunder-head; or the cooling may be due to radiation, or to contact and loss of heat by conduction, or, again, by mixing. This may throw interesting light on the many degrees of cloudiness, from the far-distant cirrus or feather to the towering cumulus, from the valley fog of dusk to the black-browed nimbus that precedes the cloudburst.
Sometimes Nature conducts a rainmaking experiment in very dramatic fashion, as when a volcano blows its head off. Thus, when Mont Pelée, Krakatoa, Asama Yama, Katmai, and even little Lassen were in eruption, there were produced the heavy rolling clouds, the lightning, the wind-rush, and the downpour. And not only is there direct rain-making close to the volcano: indirectly and at a distance eruptions cause rain, since the gases and fine ash or dust are carried far and wide by the winds, and, serving as nuclei, they increase the rainfall in countries far removed from the scene of outbreak. Someone will say, do not these facts prove that the claims of 'rain-makers' regarding explosions and rains are correct? The answer is, not quite. The explosive output and the atmospheric disturbance in the two cases are not comparable. For example, during one of the recent eruptions of Asama Yama, pressure disturbances were recorded on all the barographs in Japan; but the daily noon gun fired close to the Observatory in Tokyo never affects the instruments.
The idea that concussion alone produces rain, then, may be dismissed, as there is no removal or transportation of either water-vapor or nuclei by these compressional waves. And here we may explain the seeming relation of thunder-clap and rain-gush. There is probably marked electrical action facilitating the formation of big drops before, during, and after a flash of lightning. But the lightning, the beginning of the thunder, and the downward start of the raindrops, even if simultaneous, would appear to a person below as occurring one after the other, because of different speeds of propagation. We see the lightning as soon as it occurs because the velocity of light is 300,000 kilometers per second; we hear the thunder five or six seconds later, because the velocity of sound is only 0.33 kilometers per second, and we note the rain-gush still later because its velocity is, perhaps, only 0.03 kilometers. The rain may well have started before the flash occurred or the thunder began. It is also of interest to know that estimates have been made of the amount of energy represented in a thunder tone, if one may use this phrase for what is really a noise and not a tone. In nearly all loud thunder-claps there is one violent or shock wave, a sound wave that travels out in all directions from the path of discharge or core of incandescent air. Dr. Wilhelm Schmidt has shown us how the prolongation of the sound is largely a reflection, not so much from the clouds and sheets of falling rain, as from the 'interfaces' between atmospheric strata of different temperatures, largely by the action of wind. Thus the original sharp report becomes a prolonged roll. In a certain peal which he analyzed, the thunder lasted thirteen seconds.
A word or two is in order regarding the claims of those who insist that explosions, particularly gunfire, are accompanied by or cause rain. Edward Powers published a book in 1890 proving to his own satisfaction that the great battles of the Civil War were followed by heavy rain. A wider study of the facts does not bear out the statement. This volume, War and the Weather, led to an appropriation by Congress of the sum of $10,000 for experiments in producing rain by the use of high explosives. The writer witnessed some of these experiments, made under favorable conditions. There was no evidence of a causal relation between the detonations of the dynamite and the showers. Again in the course of a long residence in California he had occasion to follow closely the operations of certain much talked-of 'rain-makers.' Evidence of the production of rain directly or indirectly was lacking. An incident may be referred to here since it illustrates how popular opinion is formed and passes. During the course of a prolonged dry spell a meeting of prominent citizens of a certain town was held to consider the acceptance of an offer from a temporary resident to furnish enough explosives to produce rain. The visitor claimed that he had caused rain on his ranch in Texas by such means. While the meeting was in progress the long deferred rain began falling, and interest in the question waned. If the meeting had been held a day or two earlier and the explosives been used, credit for making the rain would naturally have gone to the visitor; and it would have been a difficult matter to convince the citizens that the test was not a valid one. It would be a rash man who would say that condensation and precipitation on a commercial scale are beyond human control; but certainly we lack conclusive evidence that any of man's efforts have produced rain in measurable amount. Finally, if the war is not the cause of the abnormal weather, what is? We do not know. The weather map tells only a part, and a very small part at that, of atmospheric motion; and it frequently misleads the forecaster. The writer speaks feelingly, for he has had the unique experience of forecasting the weather in Washington for all of the Eastern states, again at New Orleans for the Gulf section; and for many years at San Francisco for the Pacific and Inter-mountain states. Sometimes it has seemed to him that it was the valor of the forecaster rather than the value of the forecast which deserved commendation. But the time is coming when our information will be extended to all atmospheric levels available, and not limited to one,—that near the ground,—as at present. The newer meteorology, which may well be called aerography or the science of the structure of the air, will undoubtedly throw light on cloudiness and rain formation. At present we can only correlate the excessive rains and certain temperature departures over wide areas with displacements of the major pressure areas,—'hyperbars' and 'infrabars,' as they are termed. And we know, too, that excessive rains have occurred in previous years when there were no wars; and in all probability will occur again, regardless of the prevalence of gunfire.
We want to hear what you think about this article. Submit a letter to the editor or write to [email protected]. | 0.835473 | 3.00327 |
The Moon and Jupiter will share the same right ascension, with the Moon passing 3°53' to the north of Jupiter. The Moon will be 17 days old.
From Cambridge, the pair will be visible in the morning sky, becoming accessible around 23:08, when they rise to an altitude of 7° above your south-eastern horizon. They will then reach its highest point in the sky at 03:18, 30° above your southern horizon. They will be lost to dawn twilight around 06:06, 19° above your south-western horizon.
The Moon will be at mag -12.5, and Jupiter at mag -2.4, both in the constellation Libra.
The pair will be too widely separated to fit within the field of view of a telescope, but will be visible to the naked eye or through a pair of binoculars.
A graph of the angular separation between the Moon and Jupiter around the time of closest approach is available here.
The positions of the two objects at the moment of conjunction will be as follows:
|Object||Right Ascension||Declination||Constellation||Magnitude||Angular Size|
The coordinates above are given in J2000.0. The pair will be at an angular separation of 142° from the Sun, which is in Pisces at this time of year.
|The sky on 03 April 2018|
17 days old
All times shown in EDT.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|26 Oct 2017||– Jupiter at solar conjunction|
|08 May 2018||– Jupiter at opposition|
|26 Nov 2018||– Jupiter at solar conjunction|
|10 Jun 2019||– Jupiter at opposition| | 0.895513 | 3.445133 |
An announcement from NASA/ESA Hubble Telescope program:
Smallest exoplanet ever found to have water vapour
Astronomers using data from the NASA/ESA Hubble Space Telescope, the Spitzer Space Telescope, and the Kepler Space Telescope have discovered clear skies and steamy water vapour on a planet outside our Solar System. The planet, known as HAT-P-11b, is about the size of Neptune, making it the smallest exoplanet ever on which water vapour has been detected. The results will appear in the online version of the journal Nature on 24 September 2014.
This is an artist’s concept of the silhouette of the extrasolar planet HAT-P-11b
as it passes its parent star. The planet was observed as it crossed in front of its star in order to learn more about its atmosphere.
In this method, known as transmission or absorption spectroscopy, starlight filters through the rim of the planet’s atmosphere and into the telescope. If molecules like water vapour are present, they absorb some of the starlight, leaving distinct signatures in the light that reaches our telescopes. Using this technique, astronomers discovered clear skies and steamy water vapour on the planet.
The discovery is a milestone on the road to eventually finding molecules in the atmospheres of smaller, rocky planets more akin to Earth. Clouds in the atmospheres of planets can block the view of what lies beneath them. The molecular makeup of these lower regions can reveal important information about the composition and history of a planet. Finding clear skies on a Neptune-size planet is a good sign that some smaller planets might also have similarly good visibility.
“When astronomers go observing at night with telescopes, they say ‘clear skies’ to mean good luck,” said Jonathan Fraine of the University of Maryland, USA, lead author of the study. “In this case, we found clear skies on a distant planet. That’s lucky for us because it means clouds didn’t block our view of water molecules.”
This image, taken with the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3, shows the star HAT-P-11.
Not visible here is a Neptune-sized planet named HAT-P-11b which orbits the star. Astronomers have discovered clear skies and steamy water vapour on the planet. It is the smallest planet ever for which water vapour has been detected.
The small bright object next to the star is not the planet in question; in fact it is not a planet at all, but another star.
The reason for the graininess in this image is that it is a very short exposure. The star itself is so bright that it is saturated, it would otherwise be a small dot like the faint star next to it. The rings and the cross are caused by the diffraction — the bouncing of light — inside the telescope.
HAT-P-11b is a so-called exo-Neptune — a Neptune-sized planet that orbits another star. It is located 120 light-years away in the constellation of Cygnus (The Swan). Unlike Neptune, this planet orbits closer to its star, making one lap roughly every five days. It is a warm world thought to have a rocky core, a mantle of fluid and ice, and a thick gaseous atmosphere. Not much else was known about the composition of the planet, or other exo-Neptunes like it, until now.
Part of the challenge in analysing the atmospheres of planets like this is their size. Larger Jupiter-like planets are easier to observe and researchers have already been able to detect water vapour in the atmospheres of some of these giant planets. Smaller planets are more difficult to probe — and all the smaller ones observed to date have appeared to be cloudy.
The team used Hubble’s Wide Field Camera 3 and a technique called transmission spectroscopy, in which a planet is observed as it crosses in front of its parent star. Starlight filters through the rim of the planet’s atmosphere and into the telescope. If molecules like water vapour are present, they absorb some of the starlight, leaving distinct signatures in the light that reaches our telescopes.
“We set out to look at the atmosphere of HAT-P-11b without knowing if its weather would be cloudy or not,” said Nikku Madhusudhan, from the University of Cambridge, UK, part of the study team. “By using transmission spectroscopy, we could use Hubble to detect water vapour in the planet. This told us that the planet didn’t have thick clouds blocking the view and is a very hopeful sign that we can find and analyse more cloudless, smaller, planets in the future. It is groundbreaking!”
Before the team could celebrate they had to be sure that the water vapour was from the planet and not from cool starspots — “freckles” on the face of stars — on the parent star. Luckily, Kepler had been observing the patch of sky in which HAT-P-11b happens to lie for years. Those visible-light data were combined with targeted infraredSpitzer observations. By comparing the datasets the astronomers could confirm that the starspots were too hot to contain any water vapour, and so the vapour detected must belong to the planet.
The results from all three telescopes demonstrate that HAT-P-11b is blanketed in water vapour, hydrogen gas, and other yet-to-be-identified molecules. So in fact it is not only the smallest planet to have water vapour found in its atmosphere but is also the smallest planet for which molecules of any kind have been directly detected using spectroscopy . Theorists will be drawing up new models to explain the planet’s makeup and origins.
Zoom in on the star:
Although HAT-P-11b is dubbed as an exo-Neptune it is actually quite unlike any planet in our Solar System. It is thought that exo-Neptunes may have diverse compositions that reflect their formation histories. New findings such as this can help astronomers to piece together a theory for the origin of these distant worlds.
“We are working our way down the line, from hot Jupiters to exo-Neptunes,” said Drake Deming, a co-author of the study also from University of Maryland, USA. “We want to expand our knowledge to a diverse range of exoplanets.”
The astronomers plan to examine more exo-Neptunes in the future, and hope to apply the same method to smaller super-Earths — massive, rocky cousins to our home world with up to ten times the mass of Earth. Our Solar System does not contain a super-Earth, but other telescopes are finding them around other stars in droves and the NASA/ESA James Webb Space Telescope, scheduled to launch in 2018, will search super-Earths for signs of water vapour and other molecules. However, finding signs of oceans and potentially habitable worlds is likely a way off.
This work is important for future studies of super-Earths and even smaller planets. It could allow astronomers to pick out in advance the planets with atmospheres clear enough for molecules to be detected. Once again, astronomers will be crossing their fingers for clear skies.
Molecular hydrogen has been inferred to exist in many planets, including planets smaller than HAT-P-11b, but no molecule has actually been detected, using spectroscopy, in a planet this small, until now. | 0.84776 | 3.724485 |
The small satellite 'ABRIXAS' (A BRoad-band Imaging X-ray All-sky Survey Satellite) was planned as a follow-up of the successful ROSAT-mission and was intended to perform the first complete survey of the sky with an imaging telescope in the X-ray energy range from 0.5- up to 10-keV. During its planned life-time of 3 years, ABRIXAS was expected to discover more than 10.000 new X-ray sources, mainly active galaxies above 2-keV. In the centres of these galaxies, persumably black holes convert gravitational energy into high energy radiation. Very often, like in our galaxy, the centres are covered by cloudes of gas and dust, which can be penetrated by high energy X-rays.
The scientific responsibility was with the Leibniz-Institut für Astrophysik Potsdam (AIP), the Max-Planck-Institut for Extraterrestrial Physics (MPE), and the Institute for Astronomy and Astrophysics of the University of Tübingen (IAAT). The German Space Agency - DARA - took over the project management. Main contractor for development, construction and launch of the satellite was the OHB-System GmbH, Bremen.
The X-ray optics system consisted of seven twentysevenfold nested Wolter-I mirror-modules with a focal length of 1.6 m, which were built by Carl Zeiss and tested at the X-ray test facility PANTER of MPE. The focal instrumentation was a novel pn-CCD X-ray detector having high efficency and a good spectral resolution. It was developed by MPE/IAAT. With respected to the scientific and technological achievments ABRIXAS was expected to have a pathfinder role for further X-ray missions.
The satellite was launched into an orbit of 580 km, 51 deg inclination with a COSMOS rocket from the Russian launch centre Kapustin Yar on April 28. 1999.
The mission finally failed due to a faulty satelite power system.
|Total mass:||550 kg|
|Payload Mass:||Approx. 160 kg|
|Dimensions:||Height 2500 mm |
Width 1800 mm
Depth 1150 mm
|Energy Supply:||2 battery packages |
|Capacity:||200 W (average)|
|Board Computer:||Transputer T 800/805 INMOS|
|Mass Memory:||64 Mbyte|
|Software:||Parallel C, RTXC Real Time Kernel|
|Telemetry:||S-Band, 500 kbps|
|Redundancy:||Parallel on-board electronic with cross coupling|
|Attitude Control:||Magnetic, momentum wheel| | 0.84181 | 3.394986 |
This is “Looking UP! in southern Colorado,” from the Colorado Springs Astronomical Society. I’m Hal Bidlack, and there are lots of reasons to look up in the night sky right now.
We have a special visitor, Comet Lovejoy, streaking through the inner solar system. Comets are balls of mostly rock and ice, with other materials mixed in, that are some of the oldest things in our solar system. Astronomers speculate that all the water on Earth comes from comets that smashed into the Earth billions of years ago. So when you take a drink, you may be drinking comet juice!Comet Lovejoy is well positioned in the sky for Southern Colorado right now. It’s not an especially bright object, but it isn’t too hard to find if you are in a dark location, but even if you live in a city it is easy to spot with binoculars. When you look at a star, you see a bright point of light. Comet Lovejoy, however, will look like a fuzzy ball of light. As comets near the Sun, the Sun’s energy does two things: it blows the dirt and dust of the comet into a long tail, and it causes the ice in the comet to slowly vaporize. Some of that vapor forms a huge bubble in space around the comet, which is called the “coma”. Comet Lovejoy has a particular type of carbon in it that glows green. Seeing green in the night sky is very rare – as is this comet – so it is definitely worth taking the time to take a peek.
Look for the comet pretty much due South around 8 pm, roughly 3/4th of the way up between the southern horizon and the spot directly over your head. It is nearing the Pleiades, a beautiful cluster of fairly young stars that are nearly overhead by early and mid evening.
We’ve placed a link on our website, CSASTRO.ORG and at KRCC.ORG that will take you to maps showing where Comet Lovejoy is each night for the next few weeks. Please visit csastro.org for information on lots of interesting things worth looking up for, and to get information on our monthly meetings. And, our free public star parties in the warmer months.
Do you have an old telescope in the closet you are not sure how to use? Get a new telescope or binoculars for Christmas? Come to our meeting and we’ll be happy to help you learn to use your scope. Who knows? Maybe someday we’ll be telling people to look up at a comet you discovered!
This is Hal Bidlack for the Colorado Springs Astronomical Society, telling you to keep looking up, Southern Colorado! | 0.818854 | 3.458183 |
The European Space Agency (ESA) has announced a new mission that will have the goal of intercepting a comet with a special composite spacecraft in order to shoot photos of it.
Called “Comet Interceptor,” the spacecraft “will be the first spacecraft to visit a truly pristine comet or other interstellar object that is only just starting its journey into the inner Solar System,” ESA writes.
The plan is for the spacecraft to wait around at the Sun-Earth Lagrange point L2 about 1.5 million kilometers (932,000mi) behind Earth as viewed from the Sun. The spacecraft will then fly to an as-yet-undiscovered comet for a flyby when the comet is headed to Earth’s orbit.
Initially a single composite spacecraft, the Comet Interceptor will split into three separate spacecraft a few weeks before intercepting the comet. Those spacecraft will then surround the comet and shoot photos from different perspectives.
Those photos will then be used to create 3D models of the comet, which will contain “unprocessed material surviving from the dawn of the Solar System.”
“Pristine or dynamically new comets are entirely uncharted and make compelling targets for close-range spacecraft exploration to better understand the diversity and evolution of comets,” says ESA science director Günther Hasinger. “The huge scientific achievements of Giotto and Rosetta – our legacy missions to comets – are unrivaled, but now it is time to build upon their successes and visit a pristine comet, or be ready for the next ‘Oumuamua-like interstellar object.”
Previous comet missions were all to short-period comets that orbit the Sun in less than 200 years — Comet Interceptor will target a comet visiting the inner parts of our Solar System for the first time. In the past, these “new” comets were discovered too late for scientists to launch a mission to reach and study them, but since Comet Interceptor will be standing by in space, it’ll be ready to meet a new comet when it’s discovered.
Comet Interceptor is designated a fast-class mission, meaning it will be implemented from selection to launch readiness in just 8 years. If all goes according to plan, the spacecraft will catch a ride to space aboard ESA’s exoplanet-studying Ariel spacecraft in 2028 before turning on its own propulsion system. | 0.85485 | 3.302748 |
Japan has launched a miniature space elevator
- It will be used to test the viability of a full-sized space elevator.
- Questions still remain about what materials could be used to build the elevator.
- If successful, a space elevator would be a cheaper way of reaching space.
On September 22nd — after waiting out a delay imposed by Typhoon Mangkhut — a satellite launched containing a miniature space elevator designed by researchers at Shizuoka University. It intends to serve as a test model of a future space elevator that the Obayashi Corp. hopes to construct in the next 30 years.
The idea of a space elevator was first inspired by a Russian recluse scientist named Konstantin Tsiolkovsky who, in observing the Eiffel Tower, imagined a "celestial castle" attached to it in geosynchronous Earth orbit.
Though there is a practical draw to consider here — a space elevator is an appealing project because it would, in theory, cost less to send something up a space elevator than via a rocket — there are other hard practical realities to consider as well. As Jason Daley notes in Smithsonian, there is currently no material strong enough to work as the elevator's cables are supposed to work. "Even carbon nanotubes," he writes, "the strongest material we've devised so far, would shred under the stress."
How should a space elevator work, anyway? Well — the further we get from the earth, the greater the likelihood that whatever is escaping earth will encounter centrifugal force. There is a point between earth and space where the gravitational tug and centrifugal force are perfectly balanced against each other. That's called the 'geosynchronous equatorial orbit.' It's here that Obayashi imagines a space station of some kind. Beyond the floating structure occupying this point — at the other end of the line — would be a weight. The combination of this weight and the centrifugal force of the weight pulling on the other end of this line would keep the 'elevator' line in place.
Though this isn't explicitly stated, one would imagine that one benefit of testing a mini-space elevator would be in testing how well this machine in miniature works at a certain level of gravity.
What else would need to be tested? What sort of elevator cable material could withstand space debris, be strong enough to hold weights going up and down the line, and also potentially change size the further it gets away from the reach of the gravity of the planet, for one. Perhaps there can be a collaboration with the British RemoveDebris Mission, where a net is fired out into space to wrap itself web-like around any potential passing debris.
The full extent of Obayashi's plans are ambitious. It isn't just the elevator they're building; if the video on their landing page is any indication, they're planning to build a slew of things. From a structure at the Mars Gravity Center — a point above the earth where the gravity is the same as it is on Mars — to a "Low Earth Orbit" gate from which one can deploy satellites back to earth.
The goal is to have the elevator completed, up and running, by 2050.
- Elevator to the Stars - Video | Big Think ›
- Will Someone Please Design A Better Space Elevator? ›
- Bill Nye: Could We Build a Space Elevator Using Giant Magnets? ›
- People Are Serious About Building A Space Elevator | Big Think ›
- Going up! Japan to test mini 'space elevator' - Channel NewsAsia ›
- Japan Is Launching a Mini Space Elevator Into Orbit This Month ›
- Japan is about to launch a mini space elevator that could be a sign ... ›
- Japan Will Soon Conduct The First Test of Elevator Movement in ... ›
- Japan's mini space elevator goes to space - CNET ›
- Japan has launched a miniature space elevator | Science News ›
- Why the world still awaits its first space elevator - The Economist ... ›
- Going up! Japan to test mini 'space elevator' ›
- Japan Takes Tiny First Step Toward Space Elevator | Smart News ... ›
Universities claim to prepare students for the world. How many actually do it?
- Many university mission statements do not live up to their promise, writes Ben Nelson, founder of Minerva, a university designed to develop intellect over content memorization.
- The core competencies that students need for success—critical thinking, communication, problem solving, and cross-cultural understanding, for example—should be intentionally taught, not left to chance.
- These competencies can be summed up with one word: wisdom. True wisdom is the ability to apply one's knowledge appropriately when faced with novel situations.
This is what the world will look like, 250 million years from now
To us humans, the shape and location of oceans and continents seems fixed. But that's only because our lives are so short.
A new study may help us better understand how children build social cognition through caregiver interaction.
Researchers at UT Southwestern noted a 47 percent increase in blood flow to regions associated with memory.
- Researchers at UT Southwestern observed a stark improvement in memory after cardiovascular exercise.
- The year-long study included 30 seniors who all had some form of memory impairment.
- The group of seniors that only stretched for a year did not fair as well in memory tests. | 0.830811 | 3.277381 |
A galaxy lacking dark matter
Publication date: 30 March 2018
Authors: van Dokkum, P., et al.
Copyright: © 2018 Macmillan Publishers Limited, part of Springer Nature
Studies of galaxy surveys in the context of the cold dark matter paradigm have shown that the mass of the dark matter halo and the total stellar mass are coupled through a function that varies smoothly with mass. Their average ratio Mhalo/Mstars has a minimum of about 30 for galaxies with stellar masses near that of the Milky Way (approximately 5 × 1010 solar masses) and increases both towards lower masses and towards higher masses. The scatter in this relation is not well known; it is generally thought to be less than a factor of two for massive galaxies but much larger for dwarf galaxies. Here we report the radial velocities of ten luminous globular-cluster-like objects in the ultra-diffuse galaxy NGC1052–DF2, which has a stellar mass of approximately 2 × 108 solar masses. We infer that its velocity dispersion is less than 10.5 kilometres per second with 90 per cent confidence, and we determine from this that its total mass within a radius of 7.6 kiloparsecs is less than 3.4 × 108 solar masses. This implies that the ratio Mhalo/Mstars is of order unity (and consistent with zero), a factor of at least 400 lower than expected. NGC1052–DF2 demonstrates that dark matter is not always coupled with baryonic matter on galactic scales.Link to publication | 0.829511 | 3.564118 |
The study looked at a substance found on the Moon called pyroclastic deposits, which are made mostly of volcanic glass beads formed during ancient explosive eruptions. In the past, these have been thought of as potentially useful sources for elements like iron and titanium.
Now we have reason to believe they also contain water, that could be extracted by astronauts on the Moon.
Our Moon formed as the result of a giant impact with Earth, billions of years ago. This was a very high energy and high temperature process, and it is hard to envision how water could have survived it.
Because of this, it had been presumed that the interior of the Moon would have little water in it. But that view started to change in 2008 when professor Alberto Saal of Brown University studied volcanic glass beads brought back from the Moon by the Apollo mission, finding trace amounts of water.
The biggest question was whether or not these glass beads were representative of the interior of the Moon, or if they just happened to contain water in an otherwise dry body.
Now researchers have used satellite data to study more of the Moon’s surface, and found water-rich deposits spread across it. "By looking at the orbital data, we can examine the large pyroclastic deposits on the Moon that were never sampled by the Apollo or Luna missions,” said Ralph Milliken, from Brown University, lead author of the study.
“The fact that nearly all of them exhibit signatures of water suggests that the Apollo samples are not anomalous, so it may be that the bulk interior of the Moon is wet."
The presence of water on the Moon, and water in the deep interior in particular, is important because it tells us something about the fundamental processes that occurred during the formation of the Moon, and the earliest days of our solar system.
“The water somehow had to survive this process or, and perhaps more likely, the water was delivered to the Earth-Moon system by water-rich asteroids and comets after the impact event but before the Moon had completely cooled down and solidified,” Milliken told WIRED.
To determine how much water is in a planet or moon, astronomers use spectrometers to measure the light that bounces off the planetary surface. By looking at the wavelengths of light absorbed or reflected by a surface, scientists can work out which compounds are present. This was made trickier on the Moon, because its surface is warmed during each day.
Milliken says the most exciting part of this discovery is the potential use for humans. “The amount of water in a given glass bead is not very much, but the pyroclastic deposits are huge, so you have a lot of material to work with,” he told WIRED.
“Water is heavy and expensive to carry with you from Earth, so any water that can be extracted at the lunar surface is a huge help for developing a sustained presence beyond Earth.”
The research is published in Nature Geoscience. | 0.846571 | 3.985701 |
This image of the inner galaxy color codes different types of emission sources by merging microwave data (green) mapped by the Goddard-IRAM Superconducting 2-Millimeter Observer (GISMO) instrument with infrared (850 micrometers, blue) and radio observations (19.5 centimeters, red). Where star formation is in its infancy, cold dust shows blue and cyan, such as in the Sagittarius B2 molecular cloud complex. Yellow reveals more well-developed star factories, as in the Sagittarius B1 cloud. Red and orange show where high-energy electrons interact with magnetic fields, such as in the Radio Arc and Sagittarius A features. An area called the Sickle may supply the particles responsible for setting the Radio Arc aglow. Within the bright source Sagittarius A lies the Milky Way’s monster black hole. The image spans a distance of 750 light-years.Credit: NASA’s Goddard Space Flight Center
A feature resembling a candy cane appears at the center of this colorful composite image of our Milky Way galaxy’s central zone. But this is no cosmic confection. It spans 190 light-years and is one of a set of long, thin strands of ionized gas called filaments that emit radio waves.
This image includes newly published observations using an instrument designed and built at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Called the Goddard-IRAM Superconducting 2-Millimeter Observer (GISMO), the instrument was used in concert with a 30-meter radio telescope located on Pico Veleta, Spain, operated by the Institute for Radio Astronomy in the Millimeter Range headquartered in Grenoble, France.
“GISMO observes microwaves with a wavelength of 2 millimeters, allowing us to explore the galaxy in the transition zone between infrared light and longer radio wavelengths,” said Johannes Staguhn, an astronomer at Johns Hopkins University in Baltimore who leads the GISMO team at Goddard. “Each of these portions of the spectrum is dominated by different types of emission, and GISMO shows us how they link together.”
GISMO detected the most prominent radio filament in the galactic center, known as the Radio Arc, which forms the straight part of the cosmic candy cane. This is the shortest wavelength at which these curious structures have been observed. Scientists say the filaments delineate the edges of a large bubble produced by some energetic event at the galactic center, located within the bright region known as Sagittarius A about 27,000 light-years away from us. Additional red arcs in the image reveal other filaments.
“It was a real surprise to see the Radio Arc in the GISMO data,” said Richard Arendt, a team member at the University of Maryland, Baltimore County and Goddard. “Its emission comes from high-speed electrons spiraling in a magnetic field, a process called synchrotron emission. Another feature GISMO sees, called the Sickle, is associated with star formation and may be the source of these high-speed electrons.”
Two papers describing the composite image, one led by Arendt and one led by Staguhn, were published on Nov. 1 in the Astrophysical Journal.
The image shows the inner part of our galaxy, which hosts the largest and densest collection of giant molecular clouds in the Milky Way. These vast, cool clouds contain enough dense gas and dust to form tens of millions of stars like the Sun. The view spans a part of the sky about 1.6 degrees across — equivalent to roughly three times the apparent size of the Moon — or about 750 light-years wide.
To make the image, the team acquired GISMO data, shown in green, in April and November 2012. They then used archival observations from the European Space Agency’s Herschel satellite to model the far-infrared glow of cold dust, which they then subtracted from the GISMO data. Next, they added, in blue, existing 850-micrometer infrared data from the SCUBA-2 instrument on the James Clerk Maxwell Telescope near the summit of Maunakea, Hawaii. Finally, they added, in red, archival longer-wavelength 19.5-centimeter radio observations from the National Science Foundation’s Karl G. Jansky Very Large Array, located near Socorro, New Mexico. The higher-resolution infrared and radio data were then processed to match the lower-resolution GISMO observations.
The resulting image essentially color codes different emission mechanisms.
Blue and cyan features reveal cold dust in molecular clouds where star formation is still in its infancy. Yellow features, such as the Arches filaments making up the candy cane’s handle and the Sagittarius B1 molecular cloud, reveal the presence of ionized gas and show well-developed star factories; this light comes from electrons that are slowed but not captured by gas ions, a process also known as free-free emission. Red and orange regions show areas where synchrotron emission occurs, such as in the prominent Radio Arc and Sagittarius A, the bright source at the galaxy’s center that hosts its supermassive black hole. | 0.875603 | 4.023472 |
Lee Billings has a fascinating article up at Aeon asking why we continue to send missions to Mars when the best chance of life existing today is in Europa’s underground ocean.
If Europa is alive, if some biology dwells within those dark waters, the implications would be even more staggering than finding life on Mars. Our gaze would turn to Jupiter’s Ganymede next, and to Callisto, along with Saturn’s Titan and Enceladus, and perhaps even the dwarf planets such as Ceres and Pluto, all of which also likely harbour substantial subsurface reservoirs, heated through some combination of tides and radioactive decay.
And if water and life could exist there, why not in the hearts of large comets, before the Sun’s planets and moons even finished forming? Our solar system might have brimmed with hidden life for nearly as long as the Sun has shined, and ice-roofed worlds might be the default abodes for biology in the Universe. Life within a roofed world could proceed swimmingly against any number of otherwise-fatal cosmic calamities, whether being slingshotted into the interstellar dark as a rogue planet, or being bathed in hard radiation from a nearby supernova or burping black hole. We could then guess why, like our solar system, the Universe at large looks so desolate to us. In this scenario, most life, even if it had eyes to see, would never glimpse sky, stars, light, or fire, and would have scant hope of ever reaching what lies above and beyond its icy shell.
I’ve highlighted what I considered to be the most mind blowing part of the article above, but I recommend the whole piece.
As Billings admits, the cost of exploring Europa is much higher than Mars. And Europa is a far harsher environment for us. But the possibility of life is much stronger. And the passage above makes me wonder if we shouldn’t be taking a closer looks at other places such as the large comets he mentions. Of course, all of this takes money.
The really mind blowing part though is the possibility that life might be much more prevalent in those types of environments. We tend to assume that Earth is typical, but there’s nothing to indicate that it is typical for life other than the Copernican principle, which although history has repeatedly validated it, it remains only a principal; past performance is no guarantee of future performance. | 0.866403 | 3.195158 |
School: GD DAV public school
City: Bhandarkola (Deoghar)
Teacher: Sameer Sachdeva
"I think Europa is the best place to return back with another spacecraft to learn about extra-terrestrial life in the solar system as life is based on liquid water solvent, a suite of "biogenic element" and a source of a free energy, which seems to present on Europa. The assumptions and some observations suggest that Europa may have been these life supporting factors.
Europa's putative subsurface the ocean suggest that the traditional view of planetary is strengthened by elucidation of the terrestrial life exists or could exist independently of surface photosynthesis, then the possibilities for extraterrestrial biosphere greatly expand. Processes at hydrothermal vents may have been important in Earth's origin of life but it remains unclear whether the entire origin of life could have been independent of sunlight driven surface conditions and photochemistry. Galileo spacecraft gravity measurements indicates that Europa has a combined ice and liquid water shell ≈80-170 km thick overlying metallic and rocky core and mantle. Models indicate sufficient geothermal and tidal heating to maintain much of the ice shell in liquid form.
It is common to assume Europa's composition to be that of a carbonaceous chondrite meteorite, in which case biogenic elements would be abundant .Little is known observationally. Spectral evidence reveal's certain organic functional groups (C—H,C≡H) on Jupiter's moons Ganymede and Calisto and hints at their presence on Europa. I think internal heat and has a thick upper atmosphere that traps most of the electromagnetic radiation would have sustain life by converting heat energy into some useful chemical form of energy . Methanogenesis at hydrothermal vents at the bottom of Europa's ≈100km deep ocean could supply similar amounts of energy to that which supports ecosystem at terrestrial vents although the potential annual biomass production would be≈10^8-10^9 times below terrestrial primary production based on photosynthesis. It is also possible that niches might exist within Europa's ice shell where transient near surface liquid water environments could permit photosynthesis or other metabolic processes.
Charged particles accelerate in the Jovian magnetosphere should simultaneously produce oxidants and simple organics at Europa's surface. A scientist suggested that these molecules ,if delivered to the liquid water layer could provide a surface of free energy sufficient to sustain a Europan ecosystem. The charged particles interactions with water ice should produce molecular oxygen, hydrogen peroxide and other oxidants. So, I think Europa sustains life." | 0.871128 | 3.86132 |
Episode of Uncertainty Principle about our host star: the sun.
One of the films on my list of science fiction movie masterpieces is the sci-fi thriller Sunshine. I would very much recommend it, but I’m not here to plug the movie. The movie takes place in a future where the lifeblood of our solar system, the sun, is dying, and a mission is sent to restart it. The sun is central to the plot, and the movie is filled with elements related to it. Not least of which is the name of the ship: Icarus.
The story of Icarus is a common Greek Myth that many of you may know: Icarus flies on wings made of wax and feathers, but he soars too close to the sun, his wings melt, and he falls to his death. Like most Greek stories, it’s purpose is not literal, but allegorical. Today we still use phrases like “flying too close to the sun” to describe over-ambition. There is a similar Chinese myth about ambition in which a giant chases the sun, and dies after getting too close. Clearly the purpose of these stories is their morals, but they raise an interesting question: how does temperature change the closer you get to the sun? Was it the thought of the Greeks and Chinese that the closer you were to the sun, the warmer it got? It would have been a fair assumption to make. The sun was obviously a source of heat, and other sources of heat, such as fire, radiate more heat to areas closer to them. But anyone who’s climbed a mountain could tell you that this is not so – at the altitude of mountain tops, it is consistently colder.
To answer our initial question, yes, things do get warmer the closer you get to the sun, but the sun is so distant that a few thousand feet closer or further ultimately doesn’t make much of a difference…in space. But we’re on Earth, where there is a difference with altitude, and not a consistently colder or warmer difference either. In this sense, the sun and the atmosphere are closely linked to maintaining the earth’s temperature. Take the moon for example. The moon is at about same distance from the sun that we are, on average, depending on it’s orbit around us. The moon also has virtually no atmosphere in comparison to earth – a hundred trillionth of the atmospheric pressure we have. The earth’s atmosphere not only keeps us warm, but also keeps us cool, and keeps our temperature steady. Granted, there are other factors, such as the length of the lunar day which is nearly a month long, but the moon’s temperatures vary from 253 degrees F (123 degrees C) during the day, and -387 degrees F (-233 degrees C) at night. Earth, obviously, has more mild temperatures, and it is very well thanks to our atmosphere.
Our atmosphere does more than just let us breathe – in fact, it has quite a few jobs, as well as many layers. The atmosphere has what is called a lapse rate: a change in temperature at different elevations, or layers. It’s hard to tell exactly where layers begin and end, so the elevations of the layers will be approximate.
The troposphere is the part of the atmosphere you live in, and begins at sea level. This is where all the weather happens, and the temperatures are fairly mild, steadily decreasing the higher up you get into the troposphere. Above the troposphere is the stratosphere, beginning at around ten to twenty kilometers above the earth’s surface. This is where airplanes fly, and where the ozone layer is located. Ozone protects us from the harmful ultraviolet radiation from the sun, so its disappearance is not ideal. Throughout the stratosphere, temperatures start to rise again, but not by much. Starting at about 50 kilometers is the mesosphere, the part of the atmosphere where meteors burn up and become “shooting stars”. Like the troposphere, things get increasingly colder as you go up the mesosphere, all the way down to -90 degrees C at the top, the coldest part of our atmosphere. At around 90 km we reach the thermosphere, which as the name suggests, is very very hot. The thermosphere absorbs lots of x-rays and ultraviolet rays, raising temperatures to anywhere from 500 to 2000 degrees celsius.
Now this is where things get kind of weird. Above the thermosphere is the exosphere, about the place where “outer space” begins. There seems to be a disagreement within the scientific community about whether or not the exosphere is actually part of earth’s atmosphere or just a part of space. Regardless, the exosphere is very very thin, it might as well be a vacuum to us. But what’s the weather like up here? It’s technically very very hot, but only technically. On earth, we measure temperature by the amount of energy being bounced around within the immediate atmosphere. The atoms and molecules of the atmosphere are vibrating in an active gaseous state, and are close enough to exchange energy with one another. At the exosphere, atoms and molecules are in an excited state to be considered very hot, but they barely ever make contact with one another to exchange energy. You would feel a different kind of temperature. It would be sort of like being on the surface of the moon. Up here, it is very hot in direct sunlight, but becomes very cold once you get into any kind of shade. Temperature is directly affected by whether or not you are in sunlight. Let’s bring the exosphere down to our level. Are you inside? You’ve immediately frozen to death. Now let’s go outside into the sun – you’re burnt alive. It’s a very hostile environment to life.
Let’s leave earth, and travel to the two planets closer to the sun than us, being Mercury, and Venus, Mercury being the closer of the two. Ultimately, things get hotter the closer you get to the sun, as you receive more solar radiation. But there’s a problem: though Mercury is closer to the sun than Venus, it is not the hotter of the two. Mercury, like our moon, has a virtual vacuum of an atmosphere. It’s surface temperatures vary from -220 degrees C to 420 degrees C. In contrast, the Venus surface temperature lies at over 460 degrees C. This is caused by its thick and carbon dioxide heavy atmosphere, which creates a tremendous greenhouse effect – a hint at what excess carbon dioxide can do to climate. But if these two planets had similar atmospheres, Mercury would likely be the warmer of the two.
Which brings us to the heart of our solar system, Helios itself. Helios is the name the ancient Greeks gave to their sun god. Perhaps if they knew what we do about the sun, they would revere it all the more. Even still we bow our heads in its blinding light. Now of course I’m not calling for the worship of our sun as a deity, but if you ever need to reference a higher power, the sun is a prime example. And as I will show, it is definitely worthy of our respect, even though it is a small, ordinary star, in our galaxy.
The sun is a phoenix. A much larger star in eons past held the material that would one day become the sun, and us. In a cataclysmic death that we don’t quite understand called a supernova, this star would have flung it’s contents across space creating a massive cloud of stellar gas and dust. It is from this dust that the sun, and its siblings, would be born. This gas and dust, mostly hydrogen and helium, would gravitationally collapse, and once the gravity became strong enough, the pressure of the star would cause fusion to occur, and a star comes to be. Similar stars – perhaps thousands more – would form in the same gas cloud, and over the millions of millennia, they would drift throughout the galaxy, never to meet again. The well known star cluster Pleiades is a prime example of this. These stars were born in the same stellar nursery, but they have not yet drifted apart. It was not until May of 2014 that the announcement of a likely sister of the sun was found. The star’s name is HD 162826, and is 110 light years distant. It is in the constellation Hercules, and is not visible to the naked eye. Siblings of the sun could aid in the search for extraterrestrial life, because of the similar chemical makeup of our solar systems, assuming they have planets.
It was over four and a half billion years ago that the sun began its monarchy over the solar system. It contains 99.86 percent of the solar system’s mass; the other 0.14 percent is the rest of the solar system, the moons, planets, and us. We are the debris of the sun’s formation. Weighing in at approximately 2×1030 kilograms, the sun is over 300,000 times the mass of the earth. In shear size, the sun is like a million earths compacted together. With a core burning at 15 million degrees celsius, the sun is a great fusion reactor that burns with a fire that would put Hell to shame. It is a source of power unlike anything we could conceive. Through it’s immense heat and density, it fuses Hydrogen together to form Helium (which get’s its from the sun god Helios). When this happens, light particles, or photons, are released, and over the course of tens to hundreds of thousands of years crawl their way to the surface, and to us. The sun releases the equivalent of 90 billion megatons of TNT per second. For perspective, the energy in one megaton of TNT could power the average american household for over a hundred thousand years. Ninety Billion times that. Every single second. In the face of that, our reluctance to convert to solar energy seems, inexcusable. There are hypotheses about hyper advanced civilizations that encompass stars in “dyson spheres” – massive super structures built to capture a great deal of the energy leaving a star. Surely our primitive civilization can spare a few solar panels per household. Searching for stars that don’t emit visible light could also aid in the search for extraterrestrial intelligence by hinting at dyson spheres. Will we ever have the ingenuity to harness such energy?
We owe our existence to the sun. The vast majority of surface life on planet earth evolved because the sun was there to provide just the right amount of energy. And just our luck we have a particularly stable star as well. If the earth is our mother, then the sun is our father. The sun inseminated the earth with the necessary tools to create life. But some of the resources came from elsewhere. The sun converts hydrogen into helium through fusion. In the early universe there was only hydrogen and maybe some helium. So where do we, other carbon based life-forms and rocky planets come from? The stellar ancestors of our sun that we mentioned earlier are the source of such elements. Much larger stars can convert light elements like hydrogen and helium into successively heavier elements. Such stars burn through their hydrogen faster, and in their explosive deaths, they shoot their elements out into space. There were no planets orbiting the first generation of stars, because such elements had not been formed, so we can thank stellar fusion for our existence.
A different death awaits our sun. As the sun runs out of hydrogen, it will grow into a red giant, engulfing the inner solar system – meaning us. This will happen in five billion years time, which to the sun is twenty turns around the galaxy. So our sun is middle aged. Hopefully, the descendants of humanity will have moved on by then.
In it’s power, and longevity, dare I say the sun is godlike, but unlike a deity, the sun does not make choices about our existence, and cannot be appeased. In July, 2012, a massive solar storm missed earth by about a week. It was one of the strongest in recorded history. Human beings themselves would have been unscathed, but as a technology dependent civilization, the impact on our infrastructure would have been great, effecting things like the internet and gps for quite some time. Recovering from such a disaster completely would take quite some time. Perhaps we should consider sun proofing our technology.
Solar storms can be stronger. In his book A Short History of Nearly Everything, Bill Bryson notes that some of the mass extinctions on planet earth remain without explanation. A possible hypothesis is super strong solar storms that could wipe out much of life itself. And more eerily, would leave not a single trace in the fossil record. My intention is not to frighten you, we’ve been around this long without such an incident, but there are dangers out there in the universe, and they are numerous. And as an intelligent civilization, we can prepare ourselves for such catastrophes.
When it’s a particularly sunny day, I encourage you to go out and enjoy the sunlight, and the uncontainable power that lies behind it. It brought you here.
Thanks for listening, and keep exploring. | 0.847992 | 3.246708 |
A telescope in South America has found tantalizing evidence of primitive galaxies born in the early universe, a find that, if confirmed, would mark the first-ever view of the so-called "dark galaxies."
Dark galaxies are small, gas-rich objects from the early universe. The existence of such galaxies, which are devoid of stars, but packed with gas, has long been predicted in galaxy formation theories, but direct proof of them has so far remained elusive.
Now, an international team of astronomers may have found dark galaxies by using the light from quasars, the brightest and most energetic objects in the universe, as a guide.
Quasars are powered by enormous black holes that give off huge amounts of energy and light as gas, dust and other material falls into their cores. The astronomers pinpointed the dark galaxies by their glow from the quasars' light.
"Our approach to the problem of detecting a dark galaxy was simply to shine a bright light on it," study co-author Simon Lilly, of ETH Zurich, an engineering and science university in Switzerland, said in a statement. "We searched for the fluorescent glow of the gas in dark galaxies when they are illuminated by the ultraviolet light from a nearby and very bright quasar. The light from the quasar makes the dark galaxies light up in a process similar to how white clothes are illuminated by ultraviolet lamps in a night club."
The quasar key
In the new study, the scientists were able to glean some preliminary characteristics of the dark galaxies. They estimate that the mass of the gas in such galaxies is roughly 1 billion times that of the sun, which is expected for gas-rich, low-mass galaxies in the early universe. [7 Surprising Things About the Universe]
The astronomers also estimate that star formation in the dark galaxies is suppressed by a factor of more than 100 compared with typical star-forming galaxies at similar stages in their cosmic histories.
In theories of galaxy formation, dark galaxies are thought to be the building blocks of the bright, star-filled galaxies we see today. Some theories state that dark galaxies may have also funneled gas to larger galaxies to form the stars that currently exist.
But dark galaxies are inherently challenging to spot, the researchers said. Since dark galaxies have no stars, they do not emit much light. Astronomers have long attempted to confirm their existence using new techniques that could reveal dark galaxies in the cosmos.
Previous studies of small absorption dips in the spectra of background light sources were thought to have hinted at dark galaxies, but this new study may be the first time that these mysterious objects have been directly detected.
Chasing dark galaxies
Using the European Southern Observatory's Very Large Telescope (VLT) in northern Chile, the researchers saw the extremely faint fluorescent glow of the dark galaxies. They used the telescope's FORS2 instrument to map a region of the sky around the bright quasar HE 0109-3518, searching for ultraviolet light that is released by hydrogen gas when it is bombarded with intense radiation.
"After several years of attempts to detect fluorescent emission from dark galaxies, our results demonstrate the potential of our method to discover and study these fascinating and previously invisible objects," study lead author Sebastiano Cantalupo, from the University of California, Santa Cruz, said in a statement.
The astronomers found almost 100 gaseous objects within a few million light-years of the brilliant quasar. They eventually narrowed the list to 12, after weeding out objects where the emission might be a product of star formation in the galaxies, rather than from the quasar's light.
According to the researchers, these objects represent the most convincing detections of dark galaxies in the early universe to date.
"Our observations with the VLT have provided evidence for the existence of compact and isolated dark clouds," Cantalupo said. "With this study, we've made a crucial step towards revealing and understanding the obscure early stages of galaxy formation and how galaxies acquired their gas." | 0.860018 | 4.097298 |
Observing the sky with the green filter of it panoramic camera, the Mars Exploration Rover Spirit came across a surprise: a streak across the sky. The streak, seen in the middle of this mosaic of images taken by the navigation and panoramic cameras, was probably the brightest object in the sky at the time. Scientists theorize that the mystery line could be either a meteorite or one of seven out-of-commission spacecraft still orbiting Mars. Because the object appeared to move 4 degrees of an arc in 15 seconds it is probably not the Russian probes Mars 2, Mars 3, Mars 5, or Phobos 2; or the American probes Mariner 9 or Viking 1. That leaves Viking 2, which has a polar orbit that would fit with the north-south orientation of the streak. In addition, only Viking 1 and 2 were left in orbits that could produce motion as fast as that seen by Spirit. Said Mark Lemmon, a rover team member from Texas A&M University, Texas, "Is this the first image of a meteor on Mars, or an image of a spacecraft sent from another world during the dawn of our robotic space exploration program? We may never know, but we are still looking for clues."The inset shows only the panoramic image of the streak. | 0.824712 | 3.257873 |
Fr.: catalogue de Caldwell
A collection of 109 impressive celestial objects compiled for amateur astronomers. These objects (→ star clusters, → nebulae, → supernova remnants, and → galaxies), selected from the → New General Catalog and the → Index Catalog, are not present in the → Messier catalog.
Named after Patrick Caldwell Moore (1923-2012), English amateur astronomer, who compiled the catalog in 1995; → catalog.
After James Clerk Maxwell (1831-1879), British outstanding physicist, who made fundamental contributions to electromagnetic theory and the kinetic theory of gases.
Fr.: pont de Maxwell
Fr.: division de Maxwell
A division in Saturn's ring in the outer part of the C ring. It is about 87500 km from Saturn's center and is 500 km wide. The gap was discovered in 1980 by Voyager 1.
Fr.: démon de Maxwell
A → thought experiment meant to raise questions about the possibility of violating the → second law of thermodynamics. A wall separates two compartments filled with gas. A little "demon" sits by a tiny trap door in the wall. He is able to sort hot (faster) molecules from cold molecules without expending energy, thus bringing about a general decrease in → entropy and violating the second law of thermodynamics. The → paradox is explained by the fact that such a demon would still need to use energy to observe and sort the molecules. Thus the total entropy of the system still increases.
Fr.: équations de Maxwell
A set of four fundamental equations that describe the electric and
magnetic fields arising from varying electric charges and magnetic fields,
electric currents, charge distributions,
and how those fields change in time. In their vector differential form,
these equations are:
→ maxwell. It should be emphasized that the equations originally published by James Clerk Maxwell in 1873 (in A Treatise on Electricity and Magnetism) were 20 in number, had 20 variables, and were in scalar form. The German physicist Heinrich Rudolf Hertz (1857-1894) reduced them to 12 scalar equations (1884). It was the English mathematician/physicist Oliver Heaviside (1850-1925) who expressed Maxwell's equations in vector form using the notations of → gradient, → divergence, and → curl of a vector, thus simplifying them to the present 4 equations (1886). Before Einstein these equations were known as Maxwell-Heaviside-Hertz equations, Einstein (1940) popularized the name "Maxwell's Equations;" → equation.
Fr.: règle de Maxwell
Every part of a deformable electric circuit tends to move in such a direction as to enclose the maximum magnetic flux.
Fr.: distribution de Maxwell-Boltzmann
The distribution law for kinetic energies (or, equivalently, speeds) of molecules of an ideal gas in equilibrium at a given temperature.
Fr.: incompatibilité entre Newton et Maxwell
The incompatibility between → Galilean relativity and Mawxell's theory of → electromagnetism. Maxwell demonstrated that electrical and magnetic fields propagate as waves in space. The propagation speed of these waves in a vacuum is given by the expression c = (ε0.μ0)-0.5, where ε0 is the electric → permittivity and μ0 is the magnetic → permeability, both → physical constants. Maxwell noticed that this value corresponds exactly to the → speed of light in vacuum. This implies, however, that the speed of light must also be a universal constant, just as are the electrical and the magnetic field constants! The problem is that → Maxwell's equations do not relate this velocity to an absolute background and specify no → reference frame against which it is measured. If we accept that the principle of relativity not only applies to mechanics, then it must also be true that Maxwell's equations apply in any → inertial frame, with the same values for the universal constants. Therefore, the speed of light should be independent of the movement of its source. This, however, contradicts the vector addition of velocities, which is a verified principle within → Newtonian mechanics. Einstein was bold enough to conclude that the principle of Newtonian relativity and Maxwell's theory of electromagnetism are incompatible! In other words, the → Galilean transformation and the → Newtonian relativity principle based on this transformation were wrong. There exists, therefore, a new relativity principle, → Einsteinian relativity, for both mechanics and electrodynamics that is based on the → Lorentz transformation.
Fr.: puit de potentiel
Region in a → field of force in which the potential decreases abruptly, and in the surrounding region of which the potential is larger.
1) xoš, xub; 2) câh
1) In a good or satisfactory manner; thoroughly, carefully, or soundly.
1) M.E., from O.E. wel(l) (cognates Du. wel, Ger. wohl).
1) Xoš "good, well, sweet, fair, lovely," probably related to hu-
"good, well," → eu-.
Xub, ultimately from Av. huuāpah-
"doing good work," → operate.
well-formed formula (wff)
disul-e xošdisé (wff)
Fr.: formule bien formée (FBF)
Fr.: ensemble bien ordonné
Fr.: puits zénithal
1) A well used in Antiquity from bottom of which the sky could be observed
during the day with a better contrast. The aperture of the well reduced the
light diffused by the sky. | 0.807755 | 3.722649 |
Scientists using the Kepler telescope pushed the number of planets discovered in the galaxy to about 1,700. Twenty years ago, astronomers had not found any planets circling stars other than the ones revolving around the sun.
“We almost doubled just today the number of planets known to humanity,” NASA planetary scientist Jack Lissauer said in a teleconference.
Astronomers used a new confirmation technique to come up with the largest single announcement of a batch of exoplanets — what planets outside our solar system are called.
Wednesday’s announcements also were about implications for life behind those big numbers.
All the new planets are in systems like ours where multiple planets circle a star. The 715 planets came from looking at just 305 stars. They were nearly all in size closer to Earth than gigantic Jupiter.
And four of those new exoplanets orbit their stars in “habitable zones” where it is not too hot or not too cold for liquid water which is crucial for life to exist.
The four new habitable zone planets are all at least twice as big as Earth so that makes them more likely to be gas planets instead of rocky ones like Earth — and less likely to harbour life.
So far Kepler has found nine exoplanets in the habitable zone, NASA said. Astronomers expect to find more when they look at all four years of data collected by the now-crippled Kepler; so far they have looked at two years.
Planets in the habitable zone are likely to be farther out from their stars because it is hot close in. And planets farther out take more time orbiting, so Kepler has to wait longer to see it again.
Another of Kepler’s latest discoveries indicates that “small planets are extremely common in our galaxy,” said MIT astronomer Sara Seagar, who wasn’t part of the discovery team. “Nature wants to make small planets.”
And, in general, smaller planets are more likely to be able to harbour life than big ones, Kaltenegger said. | 0.860163 | 3.277009 |
The Hubble Ultra Deep Field: A million-second-long exposure in one of the darkest parts of the sky reveals the first galaxies to emerge from the so-called "dark ages," the time shortly after the big bang when the first stars reheated the cold, dark universe. This view is actually two separate images taken by Hubble's Advanced Camera for Surveys and the Near Infrared Camera and Multi-object Spectrometer.
Image credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team
Wait, how many stars?!
What does the universe look like? How many galaxies, stars and planets are out there? What is the age distribution of the stars? How many habitable planets are there?
If only astronomers could send a census form to every galaxy in the universe!
Instead, figuring out what the universe looks like requires a much more indirect approach—observing objects from great distances and creating models that describe these observations. As observation techniques advance, so does our knowledge about the universe. One recent observational study led by Pieter van Dokkum (Yale) and Charlie Conroy (Harvard-Smithsonian Center for Astrophysics) indicates that there may be three times as many stars as previously thought!
In the study astronomers looked at the light coming from eight nearby galaxies in order to determine how the number of low mass stars compares to the number of high mass stars. They were looking specifically at elliptical galaxies, which look like big, smooth bulges in contrast with the disk structure of spiral galaxies. The stars in elliptical galaxies are older than those in spiral galaxies like our Milky Way, and elliptical galaxies contain less dust and gas--meaning not many new stars are forming there.
The mass of the sun is roughly 2x10^30 kg (about 333,000 times the mass of the Earth). The low mass stars that the astronomers were looking for have a mass less than1/3 that of the sun. These stars, known as red dwarfs because of their size and color, are cool, dim stars, which makes them hard to observe unless they are very close. Red dwarfs are the most common type of star in the universe.
L: This image of the elliptical galaxy NGC 1132 and its surrounding region combines data from NASA's Chandra X-ray Observatory and the Hubble Space Telescope. The blue/purple in the image is the x-ray glow from hot, diffuse gas detected by Chandra. Hubble's data reveal a giant foreground elliptical galaxy, plus numerous dwarf galaxies in its neighborhood, and many much more distant galaxies in the background.
Image credit: X-ray: NASA/CXC/Penn State/G. Garmire; Optical: NASA/ESA/STScI/M. West
R: A composite image of the spiral galaxy Messier 81 from NASA's Spitzer and Hubble space telescopes and NASA's Galaxy Evolution Explorer. It is located about 12 million light-years away in the Ursa Major constellation and is one of the brightest galaxies that can be seen from Earth through telescopes.
Image credit: NASA/JPL-Caltech/ESA/Harvard-Smithsonian CfA
Since astronomers use their observations as the basis for creating models to explain how the universe has evolved over time, a change in the input of the number and kinds of stars in each type of galaxy can have a big effect on our understanding of the history of the universe. Red dwarfs are hard to observe, so previously scientists assumed that elliptical galaxies had the same ratio of red dwarf stars to stars like the sun (100:1) as do spiral galaxies like ours. However, this new study shows that elliptical galaxies may have ten times more red dwarf stars than astronomers thought!
How did the astronomers observe the red dwarf stars?
The twin Keck telescopes take their final views of the cosmos as the sun begins to rise over Mauna Kea.
Image credit: Rick Peterson/WMKO
The observing methods astronomers use have improved enormously since Galileo Galilei turned a crude telescope to the sky 400 years ago. Today astronomers use all kinds of sophisticated tools to capture individual photons coming from the darkest patches of sky. For this study, astronomers used a specially modified spectrometer attached to one of the 10-meter, 300-ton telescopes at Keck Observatory, located on Hawaii’s Mauna Kea. A spectrometer is a device that analyzes light and outputs information about the intensity of the light at different wavelengths.
Spectrometers are often used in astronomy. When light from an object at which a telescope is pointed passes through a spectrometer, the spectrometer produces a graph of wavelength versus intensity (brightness) for the object. This is powerful information because different materials emit and reflect light of different wavelengths by different amounts. The resulting light spectrum gives unique information about the source of the light and the kinds of materials that the light passed through before entering the spectrometer.
For example, Figure 1 shows the spectrum for galaxy IRAS F00183-7111. The peaks and valleys in the graph indicate the presence of different kinds of materials, as indicated in the graph.
Like water ice and neon gas, the light coming from a red dwarf star has its own spectral signature. Although red dwarfs are dim stars, the astronomers reasoned that if there were enough of them in an elliptical galaxy, they would show up in the galaxy’s light spectrum. Then, based on the brightness, the scientists could estimate how many red dwarfs were in the galaxy. Their technique worked—and they found that instead of a ratio of approximately 100 red dwarfs to each sun-like star, there were 1,000! About one-third of the galaxies in the universe are elliptical galaxies, which means that there could be three times more stars than previously estimated.
Figure 1: The spectrum from faint galaxy IRAS F00183-7111, taken from the Spitzer Space Telescope infrared spectrograph.
Image credit: NASA/JPL-Caltech
So what?Having more accurate information about the universe enables us to make even better models. These models are extremely useful in helping us understand how the universe evolved and what is likely to happen in the future. Although humans have been studying the sky for millions of years, some BIG questions remain:
- What is dark matter?
- Is there life anywhere else in the universe?
- How many earth-like planets are there, and are they inhabitable?
The presence of these additional red dwarf stars just might have something to say about these questions. Stay tuned!
For more information, check out…
Types of Stars, Sloan Digital Sky Survey
Galaxy Classification, Sloan Digital Sky Survey
Can Life Thrive Around a Red Dwarf Star? by Michael Schirber, Astrobiology Magazine
The Universe Does Think Small(press release), Harvard-Smithsonian Center for Astrophysics
The journal article in Nature announcing these results (requires subscription or payment)
arXiv e-print of the journal article announcing these results (no cost) | 0.837081 | 4.070604 |
Quick, what’s the reddest star visible to the naked eye?
Depending on your sky conditions, your answer may well be this week’s astronomical highlight.
Mu Cephei, also known as Herschel’s Garnet Star, is a ruddy gem in the constellation Cepheus near the Cygnus/Lacerta border. A variable star ranging in brightness by a factor of about three-fold from magnitudes 5.0 to 3.7, Mu Cephei is low to the northeast for mid-northern latitude observers in July at dusk, and will be progressively higher as summer wears on.
William Herschel first came across this colorful star, and gave it its nickname while surveying the region in 1783. He noted “A very fine deep garnet color” for the star, and the name stuck. He also went on to describe Mu Cephei as “A most beautiful object, especially if we look for some time at a white star before we turn our telescope to it, such as (+2.5 magnitude) Alpha Cephei, which is near at hand.”
Herschel was referring to the color contrast that often occurs when suddenly being confronted with such a visually colorful object in what is often a grey-to-white universe. Curiously, Herschel also notes how earlier stellar cartographers missed this star, perhaps due to its variability. Mu Cephei varies on average over a span of 755 days, although periods as short as 100 days and as long as 12.8 years are also superimposed over the cycle.
Johann Bayer first noted this star with its Greek letter designation of Mu Cephei in the 1600’s, although its variable nature was not recorded until 1848 by John Russell Hind. Hind is also famous for the discovery of another ruddy jewel and star party secret weapon, Hind’s Crimson Star in the constellation Lepus.
Mu Cephei is also sometimes referred to by the Arabic name Erakis. The name brings to mind the desert world Arrakis of Dune fame, which in the fictional universe of Frank Herbert, orbits around the real world star Canopus. Where the name Erakis comes from isn’t immediately clear, although there’s conjecture that early star map compilers confused it with Mu Draconis.
According to Star Names, Their Lore & Meaning by Richard Hinckley Allen, Mu Cephei was entered by Giuseppe Piazzi as Herschel’s “Garnet Star” in his late 18th century Palermo catalog.
What color does Herschel’s Garnet Star appear to you? One thing I always like about observing colored stars is comparing and contrasting different observers’ opinions. Mu Cephei sits at the coordinates;
Right Ascension: 21 Hours 43’ 30”
Declination: +58° 46’ 48”
This can put it high overhead late on Summer evenings and progressively earlier as we head towards Fall.
Mu Cephei also sits embedded in the extensive nebulosity of IC 1396, a wonderfully rich region for astrophotographers.
The “redness” of a star is measured by the magnitude contrast that it shows when comparing its brightness when viewed with a blue,versus a green (visible light) filter. This is the B-V index of a star. In the case of Herschel’s Garnet Star, the B-V magnitude index is +2.35. This is only slightly less than La Superba at +2.5. Contrast that with the familiar orange-tinted stars of Antares (B-V +1.83) & Betelgeuse (+1.85).
Colored variable stars appear redder when near their minima. The good news is, we’re currently near a maximum in brightness for Mu Cephei. In the case of Herschel’s Garnet Star, it appears to fade from orange to red as it cycles. An optical illusion, known as the Purkinje effect, can often cause an observer to overestimate the brightness of a crimson-colored star. The longer you stare at it, the brighter it appears. Throwing the star out of focus slightly can cause this apparent change in brightness to vanish.
Burnham’s Celestial Handbook notes that Mu Cephei “Appears a deep orange-red, but on occasion takes on a peculiar purple tint.” Can you see this spurious effect? We think it’s interesting that Herschel chose the word “garnet” to describe this star, as the gemstone can vary from shades of red to orange to even green!
Stars like Mu Cephei are also great targets, as they hold up well under light-polluted suburban skies. Herschel’s Garnet Star is also the reddest of the non-carbon stars.
And that leads us to the “wow factor” of what you’re truly seeing. Mu Cephei is a class M2Ia Supergiant star, about 2,400 light years distant (estimates still vary widely). It shines with a luminosity of 600,000 times that of our own Sun, making it one of the brightest known stars in the Milky Way. Move Mu Cephei to the standard absolute magnitude distance of 32.6 light years, and it would shine at magnitude -7.6, 16x times brighter than Venus at its best.
Mu Cephei is also 19 times more massive than our Sun, and has a radius of 1,650 times larger than Sol. Place Mu Cephei in our solar system, and it would extend out to the orbit of the planet Saturn. This makes Mu Cephei one of the largest stars known in terms of volume, with only a handful of larger stars known. It also “stars” (bad pun intended) in this classic video on astronomical scale;
The surface temperature of Mu Cephei is also relatively cool among stars, if you consider 3,690 Kelvin to be cool. Astronomers also detected water vapor in the spectrum of the star as early as 1964, another rarity. Massive stars such as Mu Cephei are destined to “live fast, die young” with life spans measured in the millions of years instead of the sedate billions of year life span of stars like our own Sun. Mu Cephei will one day grace our skies with a fine supernova, an event that could be on its way tomorrow night or millions of years from now.
All food for thought as you track down this fine scarlet delight in Cepheus, just as Sir William Herschel did centuries ago. | 0.90681 | 3.798035 |
If you missed April'syou have a chance this week to catch some "shooting stars" as the remains of a famous comet burn up in the night sky. .
The Eta aquarids are expected to peak on Tuesday and Wednesday May 5-6.
Every year around this time, Earth floats through a stream of debris left by Halley's Comet. Scraps of dust, stone, and other debris heat up when they collide with our atmosphere, creating the fleeting trails and the occasional fireball visible to the naked eye.
According to NASA, the meteors appear to come from the constellation Aquarius and more precisely from the region of the constellation near one of the brightest stars, Eta Aquarii, which is how the shower gets its name.
Unfortunately, the shower has some competition this year. It falls just before the.
"Intense brilliance from one of the largest full moons of the year will reduce the number of visible meteors from the usual 40 an hour to no more than 1
But if you're looking for a reason to go outside, that's still not a bad show for a meteor shower.
Phillips says the best time to spot the Eta Aquarids is to get up early, an hour or so before sunrise when Aquarius is high in the eastern sky.
"Tuesday morning and Wednesday morning are both good. Halley & # 39; s debris flow is wide enough to spread the shower over two days. "
In general, the further south you are, the better your view of this shower will be. Good news, Australia !
Plan to see the show as close as possible around 4 or 5 am Find a location away from light pollution with a clear view of the sky Lie down, let your eyes get used to the dark and just relax. If you can orient yourself to look at Aquarius, that's great, but if you have a wide enough view of the sky, you should be able to catch meteors without locating the constellation.
Enjoy the fire in the air, preferably at least six feet away from other skywatchers. | 0.801264 | 3.088121 |
First Person: Yuri Kovalev
For decades, physicists have pursued direct evidence of black holes. In 2011, Russia launched Spektr-R, or RadioAstron, a space radio telescope, to collect the confirmational data. Yuri Kovalev, a physicist with the Lebedev Physical Institute of the Russian Academy of Sciences in Moscow, is the project scientist of the RadioAstron space interferometer, which uses the interference between two beams of light to make precise measurements of distant galaxies. Kovalev discussed his research with contributing correspondent Brian Malow, during a press tour hosted by the Moscow Institute of Physics and Technology.
What is your specific area of study within astrophysics?
I’m studying active galactic nuclei, which are galaxies like ours, but located far away, billions of light years away from us, and they have a little bit bigger supermassive black hole in their centers. The idea is, in the center of our galaxy we have a black hole, we believe, of just a few million solar masses, but it is not active. The center of our galaxy is not active in the sense that it doesn’t have a lot of matter falling into it and it doesn’t have very hot plasma, which is ejected away from the center. Active galactic nuclei, called quasars, would have a larger black hole, something like a billion solar masses, and would have a big accretion disk, a disk of dust and matter, which falls on the center. About 10 percent of this matter is ejected out in the form of very narrow relativistic jets.
These jets are like two spokes coming out perpendicular to the disk?
Yes, they are. We believe they are about perpendicular and we believe that there are two. Quite often we see only one because of relativistic effects. One of them, which faces us, looks much brighter. We believe that at some periods of time the center of our galaxy is more active than at others. There is a NASA satellite, the Fermi Gamma-ray Space Telescope, which has seen bubbles in gamma rays, which might hint at that.
What exactly are you interested in studying about active galactic nuclei?
I’m interested in what happens in the center, how these jets are formed and how they are emitted. We believe that these jets consist of very fast electrons. The electrons are accelerated somehow in the centers of these galaxies and then they go away from the center at near the speed of light. We want to know what the mechanism of their emission is. Also, there is a question of whether these truly are electrons. Some scientists are even discussing that these could be protons. If these are protons, and we can check it with our project, then it is truly a very cool thing because it is 2,000 times more complicated to accelerate them. Protons are 2,000 times heavier than electrons.
Prior to the launch of RadioAstron, how did you and your colleagues study active galactic nuclei?
I was studying them using two ground-based telescopes, both in Russia. We have the largest radio telescope in the world, the RATAN-600. It is 600 meters in diameter. Later I often used telescopes all around the world, such as in the United States and Europe. When the research community formed this huge instrument, which we’ll call the interferometer, it had to be an international project.
The idea of Very Long Baseline Interferometry (VLBI) was proposed by Russian scientists, Leonid Matveenko, Nikolai Kardashev, and Gennady Sholomitskii. VLBI uses data from multiple radio telescopes to analyze signals from astronomical radio sources, such as a quasars. It was first successfully implemented by American scientists, which is often the case, and was one of the first intercontinental experiments between the United States and Russia. American scientists approached the Lebedev Physical Institute to suggest having an experiment between a telescope in Green Bank, West Virginia, and a telescope in Pushchino, a town in the southern Moscow region. They replied that it was a great idea, but suggested that we have another telescope, which is even better, in Crimea, so you are welcome to come.
It was the middle of the Cold War, truly difficult times, and the American side just came and it was wonderful that they realized that Russians are the same as Americans in many respects. Later, it was determined that the reason why it was not supported to have an experiment between America and Pushchino is because when you do the experiment, you, as a by-product, measure a position of your telescope with an accuracy of about one centimeter. So to have a reference point with an accuracy of one centimeter, near Moscow, in the middle of the Cold War, would be absolutely impossible. The experiment had to be sent to Crimea. Even in these very difficult times astronomy or astrophysics was one of the very few topics that we were able to do together. So the roots of all that we are discussing right now come from the Cold War times many years ago.
How did your project come about?
RadioAstron, which is a radio satellite combined with observatories on the ground to create the largest telescope in history, was originally conceived during the Soviet times. The first official statement about it was made by the General Secretary of the Communist Party of the Soviet Union Leonid Ilyich Brezhnev, in the early 1980s. Apparently the project went through all the difficult times together with the Soviet Union. It was built, it was almost ready to go to space in the early 1990s, and then it collapsed together with the country. Then we had to bring it all back and rebuild it starting in 2004. We launched it from Baikonur on a Russian-Ukrainian rocket in 2011, and it has been operational since early 2012. It operates under a so-called open sky policy, so any person can apply for observing with us including our fellow American colleagues, and they do.
What was the process of loading and deploying the satellite?
We produced a flower of 27 petals, which was put together on the ground and fit nicely into the 3-meter diameter of the rocket. Then, five days later, after the launch, it was unfurled, not without problems.
After launching it, the Lavochkin Research and Production Association commanded the spacecraft, the telescope, to unfurl. The ring in the base of the telescope started to rotate and pull open these petals. Ten minutes later, the ring stopped, but we on the ground didn’t get a confirmation from the detectors that the petals had unfurled successfully. Several hours of attempts didn’t change anything. Later Lavochkin estimated and realized that it was not unfurled, just by several centimeters. This would mean the end of the mission. Just several centimeters was not enough, because we had to build a parabolic structure with an accuracy of 1 millimeter.
They realized that they probably had a temperature gradient in the base of the telescope. They rotated it so that the Sun would shine on the base of the telescope and would take care of the residual temperature gradient in the base. One day later they came back; they had another telemetry session. They commanded the telescope to unfurl again, and it unfurled successfully. We got confirmations from all the sensors. Then it was fixed and it has worked ever since.
That must have been an exciting moment. Were you there?
I was watching it on a video conference that was streamed from Lavochkin. It was a Friday, in July 2011. I’ll never forget it.
What’s the mission of RadioAstron?
We are studying different kinds of objects in the sky. Number one is actually active galactic nuclei or quasars. Number two is pulsars, dead neutron stars in our galaxy. We use them to study the interstellar medium in our galaxy and the scattering of radio waves. Number three is so-called masers. These are clouds of, for example, water vapor, which are located both in our galaxy, in regions where planets and stars are born, and also they are located in other galaxies in their disks. In addition to that, there is a very peculiar and very important object for us, which is the center of our own galaxy, and it has its own story.
We are also trying to do a little bit in gravitational astronomy, because we have a very accurate atomic clock on board the satellite. Every nine days—the time it takes to complete its elliptical orbit—the clock on the satellite goes through a different gravitational potential than the clocks that are located on the ground. Because the elapsed time differs based on the observers’ distance from a gravitational mass, the clock on our satellite advances differently. Einstein’s theory of general relativity predicts how the clocks should behave, so we can check the theory by comparing its predictions with what we actually see on the satellite.
What have you learned about active galactic nuclei?
The thing with the quasars is that we thought that we understood very well the theory of how the jets in quasars emit their very bright radiation. And the theory has predicted that cores of these quasars cannot be brighter than a certain level. For example, if you inject a blob of very hot plasma, very energetic electrons, into this jet from the central supermassive black hole and its surroundings, then it will emit very brightly. However, the electrons will very quickly lose their energy due to the process of falling to a lower state.
In what is called an inverse Compton process, electrons emit photons, and because they emit very many photons, they hit other photons. There is also a higher probability that the electrons will then hit a photon, causing the electron to lose its energy. It has been predicted that, because of these collisions, the quasar cannot appear brighter than a certain limit, a result that is called a Compton catastrophe.
We have checked this theoretical prediction and we have shown that actually it is wrong. We have observed the quasars to be at least 10 times brighter than the theory predicts. This is truly exciting because there is nothing better in the life of a scientist than to show that theories are wrong.
People sometimes don’t quite appreciate that scientists would like theories to be disproven.
Let me tell you that theorists are the first to be happy about it. That is how science works. Science works by showing that the theory is wrong. And by showing it, you allow the theory to evolve and to understand nature around you better. One of the explanations is that these are not relativistic electrons, but they are relativistic protons. Because they are 2,000 times heavier, they allow you to have a much higher limit on the brightness. In principle, if these are relativistic protons, this will solve our problem. But then there is an even bigger problem, how to accelerate them. We don’t know how to accelerate protons to become relativistic—protons that move very close to the speed of light.
Have you achieved your mission goals?
We believe that we have achieved the main scientific goals of the mission. However, we collected the last round of proposals for the mission about a month ago, and the number of proposals has gone up.
The demand is even greater than before, because our initial results have demonstrated the potential of studying the universe at this extreme resolution. RadioAstron has proven to be useful for many different applications. Therefore, the mission has been officially extended by Roscosmos, the Russian space agency, until the end of 2018.
The mission is already past its expected lifetime of five years, but it will go a little longer. What’s next for you?
We truly hope to see the center of our galaxy through the interstellar fog. That is what we haven’t achieved yet. We are working together with the Event Horizon Telescope (EHT), a ground-based telescope that has been in the works since 2012. EHT is expected to produce its first image of the center of our galaxy later this year.
Talking about the long-term future, we are currently building a mission plan for the Millimetron observatory, which will detect signals at millimeter and submillimeter wavelengths. It will be similar to the Herschel Space Observatory, which was active from 2009 to 2013. The resolution will be better than what we have with RadioAstron.
Everything will be more transparent in the universe. We will have less scattering and also less absorption. This will help us see central supermassive black holes, both in the center of our galaxy, if not already observed by that time, and in other galaxies. | 0.907882 | 3.972759 |
From: NASA HQ
Posted: Tuesday, October 29, 2013
A NASA spacecraft that will examine the upper atmosphere of Mars in unprecedented detail is undergoing final preparations for a scheduled 1:28 p.m. EST Monday, Nov. 18 launch from Cape Canaveral Air Force Station in Florida.
The Mars Atmosphere and Volatile Evolution mission (MAVEN) will examine specific processes on Mars that led to the loss of much of its atmosphere. Data and analysis could tell planetary scientists the history of climate change on the Red Planet and provide further information on the history of planetary habitability.
"The MAVEN mission is a significant step toward unraveling the planetary puzzle about Mars' past and present environments," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington. "The knowledge we gain will build on past and current missions examining Mars and will help inform future missions to send humans to Mars."
The 5,410-pound spacecraft will launch aboard a United Launch Alliance Atlas V 401 rocket on a 10-month journey to Mars. After arriving at Mars in September 2014, MAVEN will settle into its elliptical science orbit.
Over the course of its one-Earth-year primary mission, MAVEN will observe all of Mars' latitudes. Altitudes will range from 93 miles to more than 3,800 miles. During the primary mission, MAVEN will execute five deep dip maneuvers, descending to an altitude of 78 miles. This marks the lower boundary of the planet's upper atmosphere.
"Launch is an important event, but it's only a step along the way to getting the science measurements," said Bruce Jakosky, principal investigator at the University of Colorado, Boulder's Laboratory for Atmospheric and Space Physics (CU/LASP) in Boulder. "We're excited about the science we'll be doing, and are anxious now to get to Mars."
The MAVEN spacecraft will carry three instrument suites. The Particles and Fields Package, provided by the University of California at Berkeley with support from CU/LASP and NASA's Goddard Space Flight Center in Greenbelt, Md., contains six instruments to characterize the solar wind and the ionosphere of Mars. The Remote Sensing Package, built by CU/LASP, will determine global characteristics of the upper atmosphere and ionosphere. The Neutral Gas and Ion Mass Spectrometer, built by Goddard, will measure the composition of Mars' upper atmosphere.
"When we proposed and were selected to develop MAVEN back in 2008, we set our sights on Nov. 18, 2013, as our first launch opportunity," said Dave Mitchell, MAVEN project manager at Goddard. "Now we are poised to launch on that very day. That's quite an accomplishment by the team."
MAVEN's principal investigator is based at CU/LASP. The university provided science instruments and leads science operations, as well as education and public outreach, for the mission.
Goddard manages the project and provided two of the science instruments for the mission. Lockheed Martin built the spacecraft and is responsible for mission operations. The University of California at Berkeley's Space Sciences Laboratory provided science instruments for the mission. NASA's Jet Propulsion Laboratory in Pasadena, Calif., provides navigation support, Deep Space Network support, and Electra telecommunications relay hardware and operations.
For more information about the MAVEN mission, visit:
// end // | 0.872456 | 3.340617 |
Dark matter is like the hidden part of an iceberg found below the water line. The hidden part is the dominant portion of the mass and supports the structure apparent from the visible portion above. Dark matter couples to ordinary matter through the gravitational force. The ordinary visible matter, which we detect through light from galaxies and stars, is analogous to the portion of an iceberg above the water line.
Why is dark matter important? It dominates the mass-energy density of the universe during the early part of its lifetime. Just after the epoch of the cosmic microwave background (CMB) the universe is composed of mostly dark matter (dark energy comes to dominate much later, during the most recent 5 billion years). But also there is the ordinary matter, which at that time is a highly uniform gas of hydrogen and helium atoms, with slightly overdense and slightly underdense regions.
The existence of a large amount of dark matter promotes much more efficient gravitational collapse of the overdense regions. This is a self-gravitational process in which regions that are slightly denser than the critical mass density (which is also the average mass density of the universe) at a given time will collapse away from the overall expansion that continues around them. Both the dark and ordinary matter in such a region collapse together, but it is the ordinary matter that forms the first stars since it interacts via various physical processes (think friction, radiation, etc.) to a much greater degree allowing for collapse. The dark matter, interacting only via gravity and perhaps the weak nuclear force, but not through electromagnetism, remains more spread out, more diffuse. The dark matter promotes the collapse process though, through increasing the self-gravity of a given region and this results in more efficient formation of stars and galaxies. There are many more stars and galaxies formed at early times than would be the case in the absence of substantial dark matter.
From cosmological observations including the CMB and high redshift (distant) supernovae, we find dark matter is about 1/4 of the mass-energy density of the universe. Dark matter is composed of either faint ordinary matter or, more likely, exotic matter that interacts through the weak and gravitational forces only. Dark matter is clearly detected by its gravitational effects on galaxy rotation curves, and is inferred from the kinematics of clusters of galaxies and the temperature measures of X-ray emission from very hot gas between galaxies in these same clusters. Dark matter is also detected through gravitational lensing effects in our galactic halo and in very large-scale cosmological structures. The abundance of deuterium, which is produced from Big Bang nucleosynthesis, in conjunction with the universe’s now well-known expansion rate, severely constrains the density of baryons (amount of ordinary nucleonic matter, i.e. protons and neutrons) in the universe and leads to the conclusion that over 80% of matter is nonbaryonic.
The MACHO (MAssive Compact Halo Objects) alternative, which refers to potential ordinary matter, is thus limited. The WIMP (Weakly Interacting Massive Particles) contribution is dominant. Hot WIMPS (e.g. neutrinos) are ruled out because they inhibit clumpiness and galaxy formation in the early universe. Cold nonbaryonic dark matter is the best candidate, with the primary candidate being an hypothesized, undiscovered particle. Neutralinos are thought by many particle physicists to be the best candidate for this, and have an expected mass of order 50 to 250 times the mass of the proton. It must be emphasized that no neutralino or similar particles (known as supersymmetric particles) have ever been detected directly. It is hoped that the Large Hadron Collider newly operational at CERN near Geneva may do this.
There may be direct detection of an annual modulation of the WIMP wind in a large scintillation array. There is also a possible indirect detection which manifests as an excess of 1 GeV gamma rays in our galactic halo. Significantly more sensitive detectors are needed to find these elusive particles and to provide a stronger foundation for supersymmetric physics, which postulates many new and heavy particles. An important experiment AMS-02 (Alpha Magnetic Spectrometer, 2nd generation) is scheduled to be carried to the International Space Station on the last Endeavour Shuttle mission scheduled for April 19, 2011. See http://www.ams02.org and http://cosmiclog.msnbc.msn.com/_news/2011/04/04/6403905-will-space-jam-delay-shuttle-launch
The next decade should allow us to shed new light on dark matter. Whatever it is made of, without the existence of substantial amounts of dark matter, there wouldn’t be nearly as many stars and galaxies in the universe, and we very likely wouldn’t be here. | 0.811746 | 4.173509 |
July 6, 2017 – When it comes to the distant universe, even the keen vision of NASA’s Hubble Space Telescope can only go so far. Teasing out finer details requires clever thinking and a little help from a cosmic alignment with a gravitational lens.
By applying a new computational analysis to a galaxy magnified by a gravitational lens, astronomers have obtained images 10 times sharper than what Hubble could achieve on its own. The results show an edge-on disk galaxy studded with brilliant patches of newly formed stars.
“When we saw the reconstructed image we said, ‘Wow, it looks like fireworks are going off everywhere,’” said astronomer Jane Rigby of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The galaxy in question is so far away that we see it as it appeared 11 billion years ago, only 2.7 billion years after the big bang. It is one of more than 70 strongly lensed galaxies studied by the Hubble Space Telescope, following up targets selected by the Sloan Giant Arcs Survey, which discovered hundreds of strongly lensed galaxies by searching Sloan Digital Sky Survey imaging data covering one-fourth of the sky.
The gravity of a giant cluster of galaxies between the target galaxy and Earth distorts the more distant galaxy’s light, stretching it into an arc and also magnifying it almost 30 times. The team had to develop special computer code to remove the distortions caused by the gravitational lens, and reveal the disk galaxy as it would normally appear.
The resulting reconstructed image revealed two dozen clumps of newborn stars, each spanning about 200 to 300 light-years. This contradicted theories suggesting that star-forming regions in the distant, early universe were much larger, 3,000 light-years or more in size.
“There are star-forming knots as far down in size as we can see,” said doctoral student Traci Johnson of the University of Michigan, lead author of two of the three papers describing the research.
Without the magnification boost of the gravitational lens, Johnson added, the disk galaxy would appear perfectly smooth and unremarkable to Hubble. This would give astronomers a very different picture of where stars are forming.
While Hubble highlighted new stars within the lensed galaxy, NASA’s James Webb Space Telescope will uncover older, redder stars that formed even earlier in the galaxy’s history. It will also peer through any obscuring dust within the galaxy.
“With the Webb Telescope, we’ll be able to tell you what happened in this galaxy in the past, and what we missed with Hubble because of dust,” said Rigby.
These findings appear in a paper published in The Astrophysical Journal Letters and two additional papers published in The Astrophysical Journal.
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C. | 0.869843 | 3.957181 |
There's something enchanting about meteor showers.
These light shows in Earth's celestial canopy show off just how dynamic and active our universe really is, with their dazzling flashes appearing faster than any other object in the night sky, like the movement of constellations or the passing shadow of a lunar eclipse.
Bill Cooke, the lead for NASA's Meteoroid Environment Office, spoke with Space.com and offered skywatching tips and details on the major meteor showers visible this year.
"Meteor showers are an investment [of time]! Preparation is key to seeing them," Cooke said. "But it's cheap — just using your eyes will do." No telescope or binoculars are necessary, he said. "it's the simplest form of astronomy there is."
Meteor shower observing can't be done on a whim, but it's pretty straightforward: Get away from bright lights, take time to adjust your eyes to the dark night sky and avoid looking at your cellphone if you get bored. "You know, that's something about meteor observing: You let your eyes adapt to the dark, and what kills [meteor viewing for] most people nowadays is that they'll look at their phones, and that bright screen just totally trashes your night vision," Cooke said.
Give your eyes 30 to 45 minutes to adapt to the dark, he said, and take in as much of the sky as possible by lying down flat on your back. Meteors can appear anywhere in the sky, and the more sky you see, the better your chance is to spot one, he said. Each shower has a radiant, or a point in the sky where the meteors appear to originate. Knowing where the radiant is can be helpful, though the longer streaks will be visible farther away from the radiant.
Keep in mind that some sky conditions can impede successful viewing of shooting stars. Cloud coverage could block the sky, and the moon could also tarnish meteor shower viewing even on a clear night. Depending on the lunar phase, the amount of moonlight will wash out the faint meteors.
Sometimes meteor showers produce streaks that are exceptionally bright. Observers can occasionally spot fireballs, or meteors brighter than Venus, the brightest planet in the night sky. The rate of shooting stars can be higher than usual in some instances, too, when the stream of space rocks gets a gravitational "nudge" from the planet Jupiter.
Meteor showers happen when Earth passes through the debris field of a comet or asteroid as these objects make their way around the sun, shedding "crumbs" along the way. That's why a given meteor shower generally appears around the same time each calendar year. And occasionally, when the Jovian planet gets close to a stream of debris, its immense gravity perturbs the particles, nudging them slightly closer to Earth and thereby increasing the amount of meteors visible in the night sky. Occasionally, this can produce outbursts, or brief periods of intense activity in which skywatchers can see more than 1,000 meteors per hour.
Most annual meteor showers don't outburst, though, and are typically classified as strong, medium or weak showers, depending on their peak rates. This guide will feature strong and medium showers occurring in 2020, when observers have a good chance to spot a meteor streak.
Lyrid meteor shower — peaks April 21-22
The Lyrid meteor shower is a medium-strength shower, according to the American Meteor Society (AMS). It will peak on the night of April 21, displaying about 10 meteors per hour. The moon will be a thin crescent only about two days from the new moon, Cooke said, so the moonlight won't flood your observations. The Lyrids will be visible beginning at about 10:30 p.m. local time.
Where to see the Lyrids
The radiant will be between the constellations Lyra and Hercules. The bright star Vega is part of Lyra, so you can also look for it to get a good idea of where the radiant for the Lyrids will be.
Viewers should have a good view of the meteor shower for most of the night until dawn. The Lyrids have been viewed by different cultures for the past 2,700 years, according to NASA.
Astronomers think the source for all the space bits that create the Lyrid meteor shower is Comet Thatcher.
Eta Aquarid Meteor shower — peaks May 4-5
In the predawn hours of May 5, observers get the chance to spot Eta Aquarids at their peak. Shooting star rates will be about 20 per hour, according to Cooke, but can reach up to 40 per hour.
Although the moon will be in its waxing gibbous phase (approaching full moon), Earth's natural satellite will set below the horizon before dawn and thereafter won't put a damper on meteor shower viewing.
These chunks of space debris come from a celestial icon: Halley's Comet. The Eta Aquarid meteor shower is categorized as a strong shower and is best viewed from the Southern Hemisphere or close to the equator. Folks in some northern latitudes, however, can also observe them.
Where to see the Eta Aquarids
People close to the equator will have the best chance to see the Eta Aquarids. The meteors radiate from the constellation Aquarius, which dwells in the southern sky. This means that the radiant for these shooting stars will be lower on the horizon for those viewing from the Northern Hemisphere, and it will appear higher in the sky for observers in the Southern Hemisphere.
These meteors are swift and produce long trains, according to AMS, but don't usually produce fireballs.
Perseid meteor shower — peaks August 11-12
The Perseids are a strong meteor shower. They appear in the summer and produce rich and bright streaks. Cooke said that usual rates are about one per minute, or 60 per hour, and AMS estimates that the rate can increase to as many as 75 per hour.
"The Perseids are a very good meteor shower with good rates in bright meteors, and it occurs on August evenings when the temperature is more conducive to people being outdoors," Cooke said.
It's an early morning shower; the best view will happen a couple of hours before dawn, Cooke said. The best time to view these shooting stars will be the early hours of Aug. 12.
The moon will not work in your favor and will probably cut down the rate of visible Perseid meteors. It will be in its last quarter phase; generally, anything brighter than first or last quarter will impede viewing.
Where to see the Perseids
Sometimes the Perseid debris field is perturbed by Jupiter and outbursts, but that won't happen in 2020.
Orionid meteor shower — peaks October 20-21
Like the Eta Aquarids, the Orionid meteor shower is a by-product of Halley's Comet. In 2020 the Orionids will peak on the night of Oct. 20, with rates of about 10-20 meteors per hour.
The moon won't interfere because it will be in a crescent phase (about 23% full) and will dip below the horizon before the shower starts up.
This medium-strength shower can outburst and reach higher rates, but the Orionid meteor shower has produced "low to average displays" in recent years, according to AMS.
Where to see the Orionids
These meteors should begin to appear around midnight local time, Cooke said.
Orionids are named for their radiant near the constellation Orion, which is one of the easier constellations to spot with the three stars that make up it's "belt." While you're viewing Orion, check out the red star Betelgeuse — it's been dimming over the last few months, and the astronomical community has been monitoring it closely in the event the dimming is a precursor to a supernova.
Leonid meteor shower — peaks November 16-17
The Leonids will be one of the weakest showers this year but will have little interference from moonlight, since the moon will be only 5% full.
The rate of Leonid shooting stars in 2020 will be about five per hour, Cooke said, while the American Meteor Society is predicting rates of up to 15 per hour.
The moon will be a thin crescent the night of Nov. 16, when the shower peaks. Though the rate will be low in 2020, this shower does spike during certain years.
Where to see the Leonids
Leonid skygazing can be incredible, or it can be dull. It all depends on where its parent body, Comet 55P/Tempel-Tuttle, will be in its orbit and the kind of debris clumps that will be around when our planet passes through this comet's orbit.
The Leonids put on big shows in 1966, 1999 and 2001, according to AMS, when the comet was making its closest approach to the sun. A good display of Leonid activity may come in 2031 when the shower will rain down over 100 meteors an hour, according to AMS.
The Leonids' radiant is located in the sickle-shaped head of the constellation Leo, the lion.
Geminid meteor shower — peaks December 13-14
The best meteor shower of the year will be the Geminids in mid-December. "It will be the best meteor shower of 2020, no question about it," said Cooke. Though it's a chilly time in the Northern Hemisphere, the Geminids will peak at an ideal time, just one day after the new moon.
Year after year, the Geminids are the strongest meteor shower in terms of rates. Cooke said that when the shower was observed in the 1830s, rates were about 30 meteors per hour, and now, over 100 appear per hour. Some observers have estimated 140 meteors per hour, Cooke added.
Unlike the other showers on this list, the Geminids are the by-product of an asteroid. The debris that falls onto Earth's atmosphere during this meteor shower comes from asteroid Phaethon.
Where to see the Geminids
"The Geminids are great for an all-nighter because you'll see Geminid meteors throughout the night," said Cooke.
The meteor shower's radiant is located in the constellation Gemini. The shower is best viewed from the Northern Hemisphere but can be viewed from the Southern Hemisphere, although at a reduced meteor rate.
"The Geminid radiant rises around sunset, and you'll see the most Geminids around 2 a.m. local time, when Gemini is highest in your sky," Cooke said. "So you'll begin to see Geminids after sunset, and their numbers will increase up until about 2 o'clock in the morning, [when] you'll see the most Geminids," he added.
The meteor shower is not likely to produce objects with long trails, according to AMS, but the meteors will appear frequently.
- Meteor shower quiz: How well do you know 'shooting stars'?
- Meteor storms: How supersized displays of 'shooting stars' work
- The 10 must-see skywatching events to look for in 2020 | 0.800378 | 3.829567 |
S Doradus (also known as S Dor) is located 160,000 light-years away, and is one of the brightest stars in the Large Magellanic Cloud (LMC), a satellite of the Milky Way. It is a luminous blue variable and one of the most luminous stars known, but so far away that it is invisible to the naked eye.
S Doradus was noted in 1897 as an unusual and variable star, of Secchi type I with bright lines of Hα, Hβ, and Hγ. The formal recognition as a variable star came the assignment of the name S Doradus in 1904 in the Second supplement to Catalogue of Variable Stars.
S Dor was observed many times over the coming decades. In 1924, it was described as "P Cygni class" and recorded at photographic magnitude 9.5 In 1925, its absolute magnitude was estimated at −8.9. In 1933 it was listed as a 9th magnitude Beq star with bright hydrogen lines. It was the most luminous star known at that time.
In 1943, the variability was interpreted as being due to eclipses of a binary companion, orbiting with a period of 40 years. This was refuted in 1956, when the variability was described as irregular and the spectrum as A0 with P Cygni profiles and emission for many spectral lines. The brightness was observed to decline by 0.8 magnitudes from 1954 into 1955. At the same time, S Doradus was noted as being similar to the Hubble–Sandage variables, the LBVs discovered in M31 and M33. The brief 1955 minimum was followed by a deep minimum in 1964, when the spectrum was compared to Eta Carinae in strong contrast to the mid-A spectrum at normal brightness.
By 1969 the nature of S Doradus was still uncertain, considered possibly to be a pre-main-sequence star, but during the next decade the consensus settled on the S Doradus type variables and Hubble-Sandage variables being evolved massive supergiants. They were eventually given the name "luminous blue variables" in 1984, coined in part because of the similarity of the acronym LBV to the well-defined LPV class of variable stars. The classification system defined for the General Catalogue of Variable Stars pre-dated this and so the acronym SDOR is used for LBVs.
S Doradus is the brightest member of the open cluster NGC 1910, also known as the LH41 stellar association, visible in binoculars as a bright condensation within the main bar of the LMC. This is within the N119 emission nebula, which has a distinctive spiral shape. It is one of the visually brightest individual stars in the LMC, at some times the brightest. There are only a handful of other 9th magnitude stars in the LMC, such as the yellow hypergiant HD 33579.
There are several compact clusters near S Doradus, within the general NGC 1910/LH41 association. The closest is less than four arc-minutes away, contains two out of the three WO stars in the entire LMC, and the entire cluster is about the same brightness as S Doradus. A little further away is NGC 1916. Another LBV, R85, is just two arc-minutes away. This rich star-forming region also hosts a third Wolf–Rayet star, at least 10 other supergiants, and at least 10 class O stars.
S Doradus has a number of close companion stars. The Washington Double Star Catalog lists two 11th magnitude stars 5" away, which at the distance of the LMC is about four light years. A much closer companion has been found using the Hubble Space Telescope Fine Guidance Sensor, 1.7" away and four magnitudes fainter. There are other nearby stars, most notably a 12th magnitude OB supergiant at 13".
This star belongs to its own eponymous S Doradus class of variable stars, also designated as luminous blue variables or LBVs. LBVs exhibit long slow changes in brightness, punctuated by occasional outbursts. S Doradus is typically a magnitude 9 star, varying by a few tenths of a magnitude on timescales of a few months, superimposed on variations of about a magnitude taking several years. The extreme range of these variations is from about visual magnitude 8.6 – 10.4. Every few decades it shows a more dramatic decrease in brightness, to as low as magnitude 11.5. The nature of the variation is somewhat unusual for an LBV; S Doradus is typically in an outburst state, with only occasional fades to the quiescent state that is typical of most stars in the class.
The colour of S Doradus changes as its brightness varies, being bluest when the star is faintest. At the same time, the spectrum shows dramatic changes. It is typically an extreme mid A supergiant with P Cygni profiles on many lines (e.g. A5eq or A2/3Ia+e). At maximum brightness, the spectrum can become as cool as an F supergiant, with strong ionised metal lines and almost no emission components. At minimum brightness, the spectrum is dominated by emission, particularly forbidden lines of Feii but also helium and other metals. At the deep minima these features are even more pronounced, and Feiii emission also appears.
Attempts to identify regularity in the unpredictable changes of brightness suggest a period of around 100 days for the small amplitude variations near maximum brightness. At minimum brightness, these microvariations are considered to occur with periods as long as 195 days. The slower variations have been characterised with a period of 6.8 years, with an interval of 35–40 years between deep minima. The microvariations are similar to the brightness changes shown by α Cygni variables, which are less luminous hot supergiants.
The instability strip
S Doradus variables (LBVs) show distinct quiescent and outburst states. During the quiescent phase, LBVs lie along a diagonal band in the H–R diagram called the S Doradus Instability Strip, with the more luminous examples having hotter temperatures.
The standard theory is that LBV outbursts occur when the mass loss increases and an extremely dense stellar wind creates a pseudo-photosphere. The temperature drops until the wind opacity starts to decrease, meaning all LBV outbursts reach a temperature around 8,000–9,000 K. The bolometric luminosity during outbursts is considered to remain largely unchanged, but the visual luminosity increases as radiation shifts from the ultraviolet into the visual range. Detailed investigations have shown that some LBVs appear to change luminosity from minimum to maximum. S Doradus has been calculated to be less luminous at maximum brightness (minimum temperature), possibly as a result of potential energy going into expansion of a substantial portion of the star. AG Carinae and HR Carinae show similar luminosity decreases in some studies, but in the most convincing case AFGL 2298 increased its luminosity during its outbursts.
Rare larger eruptions can appear as long-lasting under-luminous supernovae, and have been termed supernova impostors. The cause of the eruptions is unknown, but the star survives and may experience multiple eruptions. Eta Carinae and P Cygni are the only known examples in the Milky Way galaxy, and S Doradus has not shown such an eruption.
The temperature of an LBV is difficult to determine because the spectra are so peculiar and the standard colour calibrations don't apply, so the luminosity changes associated with brightness variations cannot be calculated accurately. Within the margins of error, it has often been assumed that the luminosity stays constant during all LBV outbursts. This is likely if the outburst consists only of an opaque stellar wind forming a pseudo-photosphere to mimic a larger cooler star.
Better atmospheric physics and observations of luminosity changes during some LBV outbursts have cast doubt on the original models. The atmosphere of S Doradus has been modelled in detail between a normal minimum at magnitude 10.2 in 1985 and a maximum at magnitude 9.0 in 1989. The temperature was calculated to drop from 20,000 K to 9,000 K, and the luminosity dropped from 1,400,000 L☉ to 708,000 L☉. This corresponds to an increase in the radius of the visible surface of the star from 100 R☉ to 380 R☉. A simpler calculation of the variation from the deep 1965 minimum at magnitude 11.5 to the 1989 maximum gives a temperature drop from 35,000 K to 8,500 K, and the luminosity drop from 2,000,000 L☉ to 910,000 L☉. For a brief period during the maximum in late 1999, the temperature dropped further to between 7,500 K and 8,500 K, without the brightness changing noticeably. This is normal in other LBVs at maximum and is as cool as they can get, but it has not been seen in S Doradus before, or since. Observations of AG Carinae have shown that any luminosity changes between minimum and maximum may occur abruptly over a small temperature range, with the luminosity approximately constant during the rest of the light curve.
The mass of an LBV is difficult to calculate directly unless it is in a binary system. The surface gravity changes dramatically and is difficult to measure from the peculiar spectral lines, and the radius is poorly defined. LBVs are thought to be the direct predecessors of Wolf–Rayet stars, but may be either just evolved from the main sequence or post-red supergiant stars with much lower masses. In the case of S Doradus, the current mass is likely to be in the range of 20–45 M☉.
- Pickering, E. C.; Fleming, W. P. (1897). "Large Magellanic Cloud". Astrophysical Journal 6: 459. doi:10.1086/140426. Bibcode: 1897ApJ.....6..459P.
- Pickering, Edward C. (1905). "Second supplement to Catalogue of Variable Stars". Annals of Harvard College Observatory 53: 143. Bibcode: 1905AnHar..53..143P.
- Cannon, Annie J. (1924). "Peculiar Spectra in the Large Magellanic Cloud". Harvard College Observatory Bulletin 801: 1. Bibcode: 1924BHarO.801....1C.
- Shapley, Harlow; Wilson, Harvia H. (1925). "The Magellanic Clouds, IV. The Absolute Magnitudes of Nebulae, Clusters, and Peculiar Stars in the Large Cloud". Harvard College Observatory Circular 271: 1. Bibcode: 1925HarCi.271....1S.
- Merrill, Paul W.; Burwell, Cora G. (1933). "Catalogue and Bibliography of Stars of Classes B and a whose Spectra have Bright Hydrogen Lines". Astrophysical Journal 78: 87. doi:10.1086/143490. Bibcode: 1933ApJ....78...87M.
- Shapley, Harlow (1931). "Notes on the Large Magellanic Cloud, I. A Cosmographic Survey". Harvard College Observatory Bulletin 881: 1. Bibcode: 1931BHarO.881....1S.
- Lewis, Isabel M. (1926). "The Magellanic Clouds". Astronomical Society of the Pacific Leaflets 1 (7): 23. Bibcode: 1926ASPL....1...23L.
- Gaposchkin, Sergei (1943). "The Variable Star S Doradus as an Eclipsing Binary". Astrophysical Journal 97: 166. doi:10.1086/144509. Bibcode: 1943ApJ....97..166G.
- Smith, Henry J. (1957). "Spectra of Bright-Line Stars in the Large Magellanic Cloud". Publications of the Astronomical Society of the Pacific 69 (407): 137. doi:10.1086/127032. Bibcode: 1957PASP...69..137S.
- Thackeray, A. D. (1965). "Spectroscopic variations of S. Doradus". Monthly Notices of the Royal Astronomical Society 129 (2): 169–180. doi:10.1093/mnras/129.2.169. Bibcode: 1965MNRAS.129..169T.
- Martini, A. (1969). "On the interpretation of S Doradus". Astronomy and Astrophysics 3: 443. Bibcode: 1969A&A.....3..443M.
- Thackeray, A. D. (1974). "Variations of S Dor and HDE 269006". Monthly Notices of the Royal Astronomical Society 168: 221–233. doi:10.1093/mnras/168.1.221. Bibcode: 1974MNRAS.168..221T.
- Sharov, A. S. (1975). S Dor-type variables in other galaxies. 67. 275–284. doi:10.1007/978-94-010-9934-9_38. ISBN 978-90-277-0579-2. Bibcode: 1975IAUS...67..275S.
- Conti, P. S. (1984). Basic Observational Constraints on the Evolution of Massive Stars. 105. 233–254. doi:10.1007/978-94-010-9570-9_47. ISBN 978-90-277-1775-7. Bibcode: 1984IAUS..105..233C.
- Kholopov, P. N. (1981). "On the Classification of Variable Stars". Peremennye Zvezdy 21: 465. Bibcode: 1981PZ.....21..465K.
- Neugent, Kathryn F.; Massey, Philip; Morrell, Nidia (2012). "THE DISCOVERY OF A RARE WO-TYPE WOLF–RAYET STAR IN THE LARGE MAGELLANIC CLOUD". The Astronomical Journal 144 (6): 162. doi:10.1088/0004-6256/144/6/162. ISSN 0004-6256. Bibcode: 2012AJ....144..162N.
- Massey, Philip (February 2000). "An Unprecedented Change in the Spectrum of S Doradus: As Cool as It Gets". The Publications of the Astronomical Society of the Pacific 112 (768): 144–147. doi:10.1086/316515. Bibcode: 2000PASP..112..144M.
- Feast, M. W.; Thackeray, A. D.; Wesselink, A. J. (1960). "The brightest stars in the Magellanic Clouds". Monthly Notices of the Royal Astronomical Society 121 (4): 337. doi:10.1093/mnras/121.4.337. Bibcode: 1960MNRAS.121..337F.
- Neugent, Kathryn F.; Massey, Philip; Morrell, Nidia (2012). "The Discovery of a Rare WO-type Wolf-Rayet Star in the Large Magellanic Cloud". The Astronomical Journal 144 (6): 162. doi:10.1088/0004-6256/144/6/162. Bibcode: 2012AJ....144..162N.
- Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal 122 (6): 3466. doi:10.1086/323920. Bibcode: 2001AJ....122.3466M.
- Aldoretta, E. J.; Caballero-Nieves, S. M.; Gies, D. R.; Nelan, E. P.; Wallace, D. J.; Hartkopf, W. I.; Henry, T. J.; Jao, W.-C. et al. (2015). "The Multiplicity of Massive Stars: A High Angular Resolution Survey with the Guidance Sensor". The Astronomical Journal 149 (1): 26. doi:10.1088/0004-6256/149/1/26. Bibcode: 2015AJ....149...26A.
- Wolf, B.; Appenzeller, I.; Cassatella, A. (1980). "IUE and ground based observations of the LMC star S Doradus". Astronomy and Astrophysics 88: 15. Bibcode: 1980A&A....88...15W.
- Van Genderen, A. M.; Sterken, C.; De Groot, M. (1997). "New discoveries on the S DOR phenomenon based on an investigation of the photometric history of the variables AG Car, S DOR and Eta Car". Astronomy and Astrophysics 318: 81. Bibcode: 1997A&A...318...81V.
- Lamers, H. J. G. L. M. (February 6–10, 1995). "Proceedings of IAU Colloquium 155, Astrophysical applications of stellar pulsation". 83. Cape Town, South Africa: Astronomical Society of the Pacific. 176–191. Bibcode: 1995ASPC...83..176L.
- Munari, U.; Siviero, A.; Bienaymé, O.; Binney, J.; Bland-Hawthorn, J.; Campbell, R.; Freeman, K. C.; Fulbright, J. P. et al. (2009). "RAVE spectroscopy of luminous blue variables in the Large Magellanic Cloud". Astronomy and Astrophysics 503 (2): 511. doi:10.1051/0004-6361/200912398. Bibcode: 2009A&A...503..511M.
- van Genderen, A.M. (2001). "S Doradus variables in the Galaxy and the Magellanic Clouds". Astronomy & Astrophysics 366 (2): 508–531. doi:10.1051/0004-6361:20000022. Bibcode: 2001A&A...366..508V.
- Wolf, B. (1989). ""Normal" LBV Eruptions a La S Doradus". Physics of Luminous Blue Variables. Astrophysics and Space Science Library. 157. pp. 91–100. doi:10.1007/978-94-009-1031-7_10. ISBN 978-94-010-6955-7.
- Lamers, Henny J. G. L. M. (1987). "Variations in Luminous Blue Variables". Instabilities in Luminous Early Type Stars. Astrophysics and Space Science Library. 136. pp. 99–126. doi:10.1007/978-94-009-3901-1_7. ISBN 978-94-010-8232-7.
- Davidson, Kris (1987). "Giant Outbursts of the Eta Carinae – P Cygni Type". Instabilities in Luminous Early Type Stars. Astrophysics and Space Science Library. 136. pp. 127–142. doi:10.1007/978-94-009-3901-1_8. ISBN 978-94-010-8232-7.
- Humphreys, Roberta M.; Davidson, Kris (1994). "The luminous blue variables: Astrophysical geysers". Astronomical Society of the Pacific 106: 1025. doi:10.1086/133478. Bibcode: 1994PASP..106.1025H.
- Smith, Nathan; Vink, Jorick S.; De Koter, Alex (2004). "The Missing Luminous Blue Variables and the Bistability Jump". The Astrophysical Journal 615 (1): 475–484. doi:10.1086/424030. Bibcode: 2004ApJ...615..475S.
- Smith, Nathan; Tombleson, Ryan (2015). "Luminous blue variables are antisocial: Their isolation implies that they are kicked mass gainers in binary evolution". Monthly Notices of the Royal Astronomical Society 447 (1): 598–617. doi:10.1093/mnras/stu2430. Bibcode: 2015MNRAS.447..598S.
- Groh, J. H.; Hillier, D. J.; Damineli, A.; Whitelock, P. A.; Marang, F.; Rossi, C. (2009). "On the Nature of the Prototype Luminous Blue Variable Ag Carinae. I. Fundamental Parameters During Visual Minimum Phases and Changes in the Bolometric Luminosity During the S-Dor Cycle". The Astrophysical Journal 698 (2): 1698–1720. doi:10.1088/0004-637X/698/2/1698. Bibcode: 2009ApJ...698.1698G.
- Lamers, H. J. G. L. M.; Bastiaanse, M. V.; Aerts, C.; Spoon, H. W. W. (1998). "Periods, period changes and the nature of the microvariations of Luminous Blue Variables". Astronomy and Astrophysics 335: 605. Bibcode: 1998A&A...335..605L.
<ref> tag with name "GCVS" defined in
<references> is not used in prior text.
<ref> tag with name "rgcrv" defined in
<references> is not used in prior text.
<ref> tag with name "nicolet" defined in
<references> is not used in prior text.
<ref> tag with name "mk" defined in
<references> is not used in prior text.
<ref>tag with name "dr1" defined in
<references>is not used in prior text.
https://en.wikipedia.org/wiki/S Doradus was the original source. Read more. | 0.833565 | 4.00624 |
If you could look up at the night sky from the surface of Mars, what would you see?
First, there would be some slight differences in the stars' paths. All of the familiar stars and constellations would appear the same as they do from here on Earth. However, because the north and south poles on Mars are oriented a bit differently than they are on Earth, the stars would appear to wheel across the sky on somewhat different paths.
For example, the north polar axis of Mars does not point toward Earth's North Star (Polaris), but rather toward a vacant spot in the sky roughly midway between the bright star Deneb in the constellation Cygnus and the fourth-magnitude star Erakis in the constellation Cepheus. So there is no "North Star" as seen from Mars. [Moons of Mars: Phobos and Deimos in Photos]
And there is no "South Star" either, although the Martian south polar axis does point toward a spot in the constellation Vela, not far from the diamond-shaped pattern of stars known as the "False Cross" (not to be confused with Crux, the Southern Cross).
Second, Mars explorers would be treated to the unusual sky sight of two tiny moons, Phobos and Deimos, that are likely asteroids that were captured in the distant past by the Red Planet's gravity.
Both moons were discovered in August 1877 as a result of a systematic search by Asaph Hall (1829-1907) of the U.S. Naval Observatory. Hall didn't find any moons for a long while and actually became so disconsolate that he considered giving up the search, but after some encouragement from his wife, Angeline Stickney Hall, he persisted and found two satellites within several nights of each other.
Hall named the moons Phobos ("fear") and Deimos ("panic"), after the two sons of the Roman god Mars; those figures served as Mars' chariot attendants as well as his constant companions.
Phobos and Deimos are so small that even in large Earth-based telescopes they appear as mere points of light. Phobos, the larger of the two, measures 14 miles (23 kilometers) across, while Deimos is just 8 miles (13 km) wide.
Both satellites revolve around Mars in nearly circular orbits, and very nearly in the plane of the planet's equator. Phobos orbits a mere 3,700 miles (6,000 km) above the Martian surface. Astronomers have deduced that Phobos is drawing closer to Mars at the rate of 0.7 inches (1.8 centimeters) per year and conceivably could crash into the Red Planet in 40 million to 50 million years. Before that happens, however, strong tidal forces induced by Mars should break Phobos into a myriad of particles that would encircle Mars in a series of thin rings.[Mars Rover Sees Phobos and Deimos (Video)]
Deimos orbits a bit farther out, at a distance of 12,400 miles (20,000 km).
Weird moon views
Interestingly, because of the two moons' extreme closeness to their host planet, there are actually parts of Mars from which Phobos and/or Deimos would not be visible — the bulge of Mars' own curvature gets in the way! For any place on the Red Planet's surface beyond 83 degrees north or south of the equator, for example, Deimos could never be seen. Phobos could never been seen from any location beyond 70 degrees north or south of the Martian equator.
Because both Phobos and Deimos move almost exactly parallel to the Martian equator, the best views of both moons would come at the planet's equatorial region. But an astronaut standing there would see these two moons move across the night sky in quite different ways.
To understand these motions, first keep in mind that, like Earth's moon, both Deimos and Phobos move in their respective orbits from west to east.
Since the Earth rotates from west to east on its axis more than 27 times faster than the moon revolves once around its companion planet, Earthlings are accustomed to seeing the moon rise in the east, cross the sky and set in the west. This happens because the planet's citizens are all carried along by Earth's rotation toward the east; about every 25 hours, Earthlings are rotated first toward the moon, then overtake it and ultimately leave it behind (in the west).
Now consider the situation with Mars' moons. Deimos takes 30 hours and 18 minutes to make one swing around Mars, and the Red Planet makes one full turn on its axis every 24 hours and 37 minutes. So an observer on the Martian surface would see Deimos rise in the east, but the moon would then move across the Martian sky at a very slow pace. In fact, it would take about 33 hours to get directly overhead (or very nearly so), and then another 33 hours to descend and set in the west.
And then, the Martian explorer would have to wait another 66 hours before Deimos again reappeared above the eastern horizon!
In contrast, Phobos takes only 7 hours and 39 minutes to orbit Mars. So it has the distinction of being the only natural satellite in the solar system that revolves around its host planet in a time shorter than the planetary "day," running three laps around the Red Planet during each Martian day.
As a consequence, as seen from the Martian equator, Phobos would appear to move far more rapidly than Deimos. In fact, Phobos would already be moving overhead just 2 hours and 48 minutes after rising. And after another 2 hours and 48 minutes, it would already setting. An astronaut on Mars could therefore witness Phobos rising twice during a single night.
And since Phobos' west-to-east motion is much faster than Mars' rotation period, the satellite would appear to rise in the west and set in the east.
Furthermore, about every 10 hours and 18 minutes, Phobos would appear to race closely past Deimos as the two moons trekked in opposite directions. Phobos, in fact, would probably even briefly eclipse Deimos as seen from some parts of Mars on each pass.
Try picturing this: During the 66 hours that Deimos moves ponderously in the sky toward the west, Phobos whizzes rapidly in the opposite direction more than six times!
Phobos goes through its entire cycle of phases in the short time it takes to go once around Mars. If, for example, Phobos were rising in the west just as the sun were setting, it would be at its "new" phase. A little over four hours later, it would already have moved well past the overhead point to a position roughly halfway up in the east and would appear "full." When it set in the east about an hour and a half later, it would have waned to its "last quarter" phase.
As for Deimos: Because the sun moves across the sky more than twice as fast as Deimos does, this moon would appear to go through a full set of phases more than twice during the 66 hours that it is continuously above the horizon.
Unfortunately, because of the very small size of both satellites, Mars skywatchers should not expect to see the same kind of sight that Earthlings are accustomed to seeing with their own moon. Deimos, for example, would appear only about one-nineteenth the apparent width of Earth's moon. The Mars satellite would shine at its very best when at its "full" phase, but because of its very small size it would probably look more like an oversized version of Venus to the unaided eye.
Phobos, the closer and larger of the two moons, would appear noticeably bigger and brighter. It would appear about one-third as large as Earth's moon (as seen from Earth). At Phobos' peak brightness, it would shine perhaps 20 times brighter than Deimos.
But neither Martian satellite is a sphere like Earth's moon; rather, they are irregularly shaped lumps, pitted (especially in the case of Phobos) with a variety of craters. One crater on Phobos that stands out in spacecraft observations measures roughly 6 miles (10 km) across and has been named "Stickney" in honor of Asaph Hall's wife.
Some have suggested that, as seen from Mars, Phobos would resemble a shiny potato in the sky. But perhaps Isaac Asimov (1920-1992) said it best in his book, "Science, Numbers and I" (Doubleday, 1968): "The interplay of light and shadow [on Phobos] will produce a fascinating display of kaleidoscopic change that will never exhaust the fancy."
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmer's Almanac and other publications, and he is also an on-camera meteorologist for News 12 Westchester, N.Y. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com. | 0.852747 | 3.889312 |
Some features of this site are not compatible with your browser. Install Opera Mini to better experience this site.
In the black dome of night, the stars seem fixed in their patterns. They rotate through the sky over the seasons so unchangingly that most cultures have used the presence of one or another constellation to tell time. The planets, however, are different, puzzling. They glide slowly and seemingly erratically across the sky. Attempts to explain why the planets move as they do led to modern science’s understanding of gravity and motion.
“We revolve around the Sun like any other planet.” —Nicolaus Copernicus
“Of all discoveries and opinions, none may have exerted a greater effect on the human spirit than the doctrine of Copernicus. The world has scarcely become known as round and complete in itself when it was asked to waive the tremendous privilege of being the center of the universe.” —Johann Wolfgang von Goethe
The ancient Greek philosophers, whose ideas shaped the worldview of Western Civilization leading up to the Scientific Revolution in the sixteenth century, had conflicting theories about why the planets moved across the sky. One camp thought that the planets orbited around the Sun, but Aristotle, whose ideas prevailed, believed that the planets and the Sun orbited Earth. He saw no sign that the Earth was in motion: no perpetual wind blew over the surface of the Earth, and a ball thrown straight up into the air doesn’t land behind the thrower, as Aristotle assumed it would if the Earth were moving. For Aristotle, this meant that the Earth had to be stationary, and the planets, the Sun, and the fixed dome of stars rotated around Earth.
For nearly 1,000 years, Aristotle’s view of a stationary Earth at the center of a revolving universe dominated natural philosophy, the name that scholars of the time used for studies of the physical world. A geocentric worldview became engrained in Christian theology, making it a doctrine of religion as much as natural philosophy. Despite that, it was a priest who brought back the idea that the Earth moves around the Sun.
In 1515, a Polish priest named Nicolaus Copernicus proposed that the Earth was a planet like Venus or Saturn, and that all planets circled the Sun. Afraid of criticism (some scholars think Copernicus was more concerned about scientific shortcomings of his theories than he was about the Church’s disapproval), he did not publish his theory until 1543, shortly before his death. The theory gathered few followers, and for a time, some of those who did give credence to the idea faced charges of heresy. Italian scientist Giordano Bruno was burned at the stake for teaching, among other heretical ideas, Copernicus’ heliocentric view of the Universe.
But the evidence for a heliocentric solar system gradually mounted. When Galileo pointed his telescope into the night sky in 1610, he saw for the first time in human history that moons orbited Jupiter. If Aristotle were right about all things orbiting Earth, then these moons could not exist. Galileo also observed the phases of Venus, which proved that the planet orbits the Sun. While Galileo did not share Bruno’s fate, he was tried for heresy under the Roman Inquisition and placed under house arrest for life.
At about the same time, German mathematician Johannes Kepler was publishing a series of laws that describe the orbits of the planets around the Sun. Still in use today, the mathematical equations provided accurate predictions of the planets’ movement under Copernican theory. In 1687, Isaac Newton put the final nail in the coffin for the Aristotelian, geocentric view of the Universe. Building on Kepler’s laws, Newton explained why the planets moved as they did around the Sun and he gave the force that kept them in check a name: gravity.
While Copernicus rightly observed that the planets revolve around the Sun, it was Kepler who correctly defined their orbits. At the age of 27, Kepler became the assistant of a wealthy astronomer, Tycho Brahe, who asked him to define the orbit of Mars. Brahe had collected a lifetime of astronomical observations, which, on his death, passed into Kepler’s hands. (Brahe, who had his own Earth-centered model of the Universe, withheld the bulk of his observations from Kepler at least in part because he did not want Kepler to use them to prove Copernican theory correct.) Using these observations, Kepler found that the orbits of the planets followed three laws.
Like many philosophers of his era, Kepler had a mystical belief that the circle was the Universe’s perfect shape, and that as a manifestation of Divine order, the planets’ orbits must be circular. For many years, he struggled to make Brahe’s observations of the motions of Mars match up with a circular orbit.
Eventually, however, Kepler noticed that an imaginary line drawn from a planet to the Sun swept out an equal area of space in equal times, regardless of where the planet was in its orbit. If you draw a triangle out from the Sun to a planet’s position at one point in time and its position at a fixed time later—say, 5 hours, or 2 days—the area of that triangle is always the same, anywhere in the orbit. For all these triangles to have the same area, the planet must move more quickly when it is near the Sun, but more slowly when it is farthest from the Sun.
This discovery (which became Kepler’s second law of orbital motion) led to the realization of what became Kepler’s first law: that the planets move in an ellipse (a squashed circle) with the Sun at one focus point, offset from the center.
Kepler’s third law shows that there is a precise mathematical relationship between a planet’s distance from the Sun and the amount of time it takes revolve around the Sun. It was this law that inspired Newton, who came up with three laws of his own to explain why the planets move as they do.
If Kepler’s laws define the motion of the planets, Newton’s laws define motion. Thinking on Kepler’s laws, Newton realized that all motion, whether it was the orbit of the Moon around the Earth or an apple falling from a tree, followed the same basic principles. “To the same natural effects,” he wrote, “we must, as far as possible, assign the same causes.” Previous Aristotelian thinking, physicist Stephen Hawking has written, assigned different causes to different types of motion. By unifying all motion, Newton shifted the scientific perspective to a search for large, unifying patterns in nature. Newton outlined his laws in Philosophiae Naturalis Principia Mathematica (“Mathematical Principles of Natural Philosophy,”) published in 1687.
Law I. Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed theron.
In essence, a moving object won’t change speed or direction, nor will a still object start moving, unless some outside force acts on it. The law is regularly summed up in one word: inertia.
Law II. The alteration of motion is ever proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed.
Newton’s second law is most recognizable in its mathematical form, the iconic equation: F=ma. The strength of the force (F) is defined by how much it changes the motion (acceleration, a) of an object with some mass (m).
Law III. To every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.
As Newton himself described: “If you press a stone with your finger, the finger is also pressed by the stone.”
Within the pages of Principia, Newton also presented his law of universal gravitation as a case study of his laws of motion. All matter exerts a force, which he called gravity, that pulls all other matter towards its center. The strength of the force depends on the mass of the object: the Sun has more gravity than Earth, which in turn has more gravity than an apple. Also, the force weakens with distance. Objects far from the Sun won’t be influenced by its gravity.
Newton’s laws of motion and gravity explained Earth’s annual journey around the Sun. Earth would move straight forward through the universe, but the Sun exerts a constant pull on our planet. This force bends Earth’s path toward the Sun, pulling the planet into an elliptical (almost circular) orbit. His theories also made it possible to explain and predict the tides. The rise and fall of ocean water levels are created by the gravitational pull of the Moon as it orbits Earth.
The ideas outlined in Newton’s laws of motion and universal gravitation stood unchallenged for nearly 220 years until Albert Einstein presented his theory of special relativity in 1905. Newton’s theory depended on the assumption that mass, time, and distance are constant regardless of where you measure them.
The theory of relativity treats time, space, and mass as fluid things, defined by an observer’s frame of reference. All of us moving through the universe on the Earth are in a single frame of reference, but an astronaut in a fast-moving spaceship would be in a different reference frame.
Within a single frame of reference, the laws of classical physics, including Newton’s laws, hold true. But Newton’s laws can’t explain the differences in motion, mass, distance, and time that result when objects are observed from two very different frames of reference. To describe motion in these situations, scientists must rely on Einstein’s theory of relativity.
At slow speeds and at large scales, however, the differences in time, length, and mass predicted by relativity are small enough that they appear to be constant, and Newton’s laws still work. In general, few things are moving at speeds fast enough for us to notice relativity. For large, slow-moving satellites, Newton’s laws still define orbits. We can still use them to launch Earth-observing satellites and predict their motion. We can use them to reach the Moon, Mars, and other places beyond Earth. For this reason, many scientists see Einstein’s laws of general and special relativity not as a replacement of Newton’s laws of motion and universal gravitation, but as the full culmination of his idea. | 0.839137 | 3.314429 |
Leo Minor is a small, faint constellation in the northern sky, with only one star brighter than fourth magnitude.
The constellation’s name means “the smaller lion” in Latin. Leo Minor was created by the Polish astronomer Johannes Hevelius in 1687. Hevelius created the constellation from 18 stars between the larger constellations Leo and Ursa Major.
Leo Minor is located between Ursa Major to the north, Cancer to the southwest, Lynx to the west, and Leo, which represents the larger lion, to the south. Notable deep sky objects in Leo Minor include Hanny’s Voorwerp, a quasar ionization echo, and the interacting galaxies Arp 107.
FACTS, LOCATION & MAP
Leo Minor is the 64th constellation in size, occupying an area of 232 square degrees. It is located in the second quadrant of the northern hemisphere (NQ2) and can be seen at latitudes between +90° and -40°. The neighboring constellations are Cancer, Leo, Lynx and Ursa Major.
Leo Minor does not have any stars brighter than magnitude 3.00 or located within 10 parsecs (32.6 light years) of Earth. The brightest star in the constellation is 46 Leonis Minoris, also known as Praecipua, with an apparent magnitude of 3.83. The nearest star is the binary system 11 Leonis Minoris (spectral class G8V/M5V), located at a distance of 36.46 light years from Earth.
Leo Minor has three stars with known exoplanets, HD 87883 (spectral class K0V), HD 82886 (G0D), and Kelt-3 (F2D).
Leo Minor does not contain any Messier objects. The Leo Minorids are the only meteor shower associated with the constellation. It takes place from October 19 to 27 every year and is linked to the comet C/1739 K1.
Leo Minor is a relatively new constellation, and has no myths associated with it. It was first depicted in 1687 in Johannes Hevelius’ Catalogus Stellarum Fixarum. In 1845, the catalogue was revised by Francis Baily, who assigned Greek letters to stars that were brighter than magnitude 4.5, but he did not give the constellation’s brightest star the designation Alpha in his British Association Catalogue.
In 1870, the English astronomer Richard A. Proctor renamed the constellation to Leaena, or the Lioness, in an attempt to shorten constellation names in order to make them easier to manage on star charts, but the name was not widely adopted.
MAJOR STARS IN LEO MINOR
Praecipua – 46 Leonis Minoris
Praecipua is the brightest star in Leo Minor. It has an apparent magnitude of 3.83 and is 94.9 light years distant from the Sun. It has the stellar classification of K0+III-IV, which means that it is an orange star halfway between the subgiant and giant stage of evolution. The star has 1.5 solar masses, is 32 times more luminous than the Sun, and has a diameter 8.5 times solar.
46 Leonis Minoris was presumably intended to get the Alpha designation, but the English astronomer Francis Baily, who had decided to letter all the stars brighter than magnitude 4.5, omitted the designation from his catalogue.
The star’s Latin name, Praecipua, means “the chief (star of Leo Minor).”
β Leonis Minoris (Beta Leonis Minoris)
Beta Leonis Minoris is the only star in Leo Minor that has a Greek letter name. It is the second brightest star in the constellation.
Beta Leonis Minoris is a binary star. The components have stellar designations G8III-IV and F8IV, which means that they are a yellow giant-subgiant and a yellow-white subgiant. The brighter star is 36 times more luminous than the Sun and has about twice the mass. It has 7.8 times the Sun’s radius. The companion is 5.8 times more luminous and has 1.35 solar masses. It has twice the solar radius.
The stars have apparent magnitudes of 4.40 and 6.12 and are approximately 146 light years distant from the Sun
21 Leonis Minoris
21 Leonis Minoris is the third brightest star in the constellation. It has an apparent magnitude of 4.49 and is 92.1 light years distant from the solar system. It has the stellar classification os A7V, which means that it is a white dwarf.
10 Leonis Minoris
10 Leonis Minoris is a yellow giant with the stellar classification of G8III. It has an apparent magnitude of 4.60.
37 Leonis Minoris
37 Leonis Minoris is a yellow supergiant belonging to the stellar class G2.5IIa. It has an apparent magnitude of 4.69 and an absolute magnitude of -1.84. The star is approximately 580 light years distant from the solar system.
20 Leonis Minoris
20 Leonis Minoris is another binary star in Leo Minor. It has an apparent magnitude of 5.40 and is 49.1 light years distant from Earth.
The system consists of a yellow dwarf belonging to the spectral class G3 Va and an old red dwarf of the spectral type M6.5. The two stars are separated by 14.5 seconds of arc.
11 Leonis Minoris
11 Leonis Minoris is another star system in Leo Minor. The primary star is a yellow dwarf belonging to the spectral class G8V. The star is a bit more massive than the Sun, and slightly dimmer. It has an apparent magnitude of 5.41. The primary component is classified as an RS Canum Venaticorum type variable, which means that it is a close binary star with an active chromosphere which can cause large stellar spots, which in turn cause variations in brightness. The star’s luminosity varies by 0.04 magnitudes.
The companion is a red dwarf of the spectral type M5V. It has an apparent magnitude of 13.0.
11 Leonis Minoris is 36.5 light years distant from the solar system.
HD 87883 is an orange dwarf star belonging to the spectral class K0V. It has an apparent magnitude of 7.56 and is approximately 59 light years distant from the solar system. It is believed to be about 9.8 billion years old.
A planet was discovered orbiting the star on August 13, 2009. HD 87883 b, the exoplanet, is a long-period planet; it takes seven and a half years to complete an orbit around the star.
DEEP SKY OBJECTS IN LEO MINOR
Hanny’s Voorwerp and IC 2497
Hanny’s Voorwerp is a quasar ionization echo, a rare type of astronomical object that was considered an unidentified astronomical object at the time of discovery. It was first spotted by Hanny van Arkel, a Dutch school teacher, in 2007. She discovered the object while taking part in the Galaxy Zoo project as an amateur volunteer. The object’s name, Hanny’s Voorwerp, means Hanny’s object in Dutch.
Hanny’s Voorwerp is located near the spiral galaxy IC 2497 and appears as a bright blob. The object is believed to be the size of the Milky Way galaxy. It has a large central hole, approximately 16,000 light years across. Both the object and the galaxy are about 650 million light years distant from Earth.
Star formation is occurring in the region of Hanny’s Voorwerp which is facing the galaxy. It is thought to be the result of the outflow of gas from the galaxy’s core and the gas interacting with a region of the object. The youngest stars in the region are several million years old.
A theory suggests that Hanny’s Voorwerp is composed of remnants of a small galaxy revealing the impact of radiation from a quasar event that took place in the central region of IC 2497 some 100,000 years ago. The quasar event is believed to have stimulated the bright emission. A theory explaining the absence of a light source is that, because the object and the galaxy are between 45,000 and 70,000 light years apart, the voorwerp is showing a ghost image of the illumination of the quasar, or a light echo of events that occurred before those currently seen in IC 2497.
A more recent theory suggests that the illumination comes from a supermassive black hole at the centre of the galaxy, and from the light produced by the interaction of the gas surrounding the galaxy and an energetic jet from the black hole.
Arp 107 is a pair of interacting galaxies approximately 450 light years distant from Earth. The galaxies are in the process of merging. They have an apparent magnitude of 14.6.
NGC 3432, sometimes known as the Knitting Needle Galaxy, lies 3 degrees southeast of the star 38 Leonis Minoris. It appears almost edge-on and can be observed in amateur telescopes. The galaxy has an apparent magnitude of 11.67 and is about 42 million light years distant from the solar system.
NGC 3003 is a barred spiral galaxy in Leo Minor. It is 5.8 arc minutes in size and has an apparent magnitude of 12.3. It appears almost edge-on.
NGC 3344 is a spiral galaxy seen face-on. It is approximately 25 million light years distant and 7.1×6.5 arc minutes in size. It has an apparent magnitude of 10.5.
NGC 3504 is a barred spiral galaxy with an apparent magnitude of 11.67. It is a starburst galaxy, a region of massive star formation. Two supernovae were observed in the galaxy in recent years, one in 1998 and another in 2001.
NGC 3486 is a type Sb spiral galaxy, also appearing almost face-on. It has an apparent magnitude of 11.0.
NGC 3021 is a spiral galaxy with a visual magnitude of 10.88, located at an approximate distance of 100 million light years away. The galaxy occupies an area 1.6’ by 0.9’ in size. A supernova, SN 1995al, was discovered in the galaxy in 1995.
NGC 2859 is a barred lenticular galaxy about 82.2 million light years away. The galaxy has an apparent magnitude of 11.8 and an apparent size of 4.3’ by 3.8’.
The galaxy’s central supermassive black hole has an estimated mass 105 million times that of the Sun.
NGC 2859 has a strong bar and a secondary bar positioned at nearly a right angle, but is lacking in visible spiral arms. The galaxy’s outer region has a conspicuous, detached ring.
Leo Minor is also home to the Seyfert galaxies 3C 234 and 3C 223 with a quasar-like appearance, and AGC 198691, a small galaxy nicknamed Leoncino. Leoncino has the smallest known metallicity, which indicates the kind of galaxies that were first formed in the Universe. | 0.833246 | 3.789387 |
Uk.businessinsider. Dark Matter: In Reality, It Could Just Be Unique Atoms. A research paper that was published last year provides an interesting, simple and most importantly traditional answer to the mystery of dark matter.
The pair of theoretical physicists Professor Robert Scherrer and post-doc fellow Chiu Man Ho, working at the Vanderbilt University of Nashville, Tennessee, US, published a detailed analysis on the subject of anapoles on the Physics Letters B online journal. The article revolves around the elusive Majorana fermion, a common atom that posses a unique electromagnetic field shape, described as a ‘anapole’. As seen in the picture below, a Majorana fermion has magnetic field lines in a torus (donut) shape, as opposed to the standard north-south dipole of common atoms.
Because of this unique EM field, the Majorna fermion would not behave like a traditional atom experienced in everyday life. As said by Dr. Bouncing neutrons fail to find dark matter or energy. Earlier this year, researchers found the signal of inflation hidden in the cosmic microwave background—the radiative remnants of the Big Bang took a long time to reveal their secrets.
It was a big day. Cosmologists everywhere broke out the Radler, got horrendously drunk, and rioted in front of campus administration buildings. Okay, maybe not—getting drunk while drinking Radler is difficult under the best of circumstances. No, in reality, they went back to work. Even if those results hold up and inflation is as predicted, that still leaves cosmologists missing two pieces of their puzzle: dark matter and dark energy. Three forces walk into a bar. Fermi telescope detects signal that could be annihilating dark matter.
Researchers using data obtained by the orbiting Fermi Telescope may have found the first clear, direct evidence of dark matter in our own galaxy.
The signal comes in the form of an excess of gamma rays coming from an area surrounding the galactic core, and it appears to be exactly what we'd expect from a weakly interacting massive particle, or WIMP. Perhaps as significantly, however, there are no known astronomical features that can produce a signal like this. The Universe provides plenty of evidence that dark matter exists. Everything from the behavior of galaxies to the structure of galaxy clusters indicates that there's more matter present than we can detect. We have spotted instances of gravitational lensing by matter in what appears to be largely empty space. But when it comes to identifying the particles that actually comprise dark matter, we've tended to look closer to home. Galactic Mystery – Matter – On the Dark Side. Heralding a new age in the cosmos, Norwegian Kristian Birkeland predicted that the universe likely consisted of an exotic component that would later be called dark matter.
His comments about this subject matter appeared in a description of the Norwegian Aurora Polaris Expedition (1902-1903). Birkeland’s ideas about the Expedition were published in the fateful year of 1913 which would see the rise of the socialist Federal Reserve System and the Income Tax in the United States of America, two key components of the communist manifesto. Evolutionary processes were in motion throughout all fields of endeavor.
Economics, politics, science and the hearts and minds of men and women were in the balance whilst relativism not truth held sway over the modern imagination. Cosmology would suffer from the same ‘evolutionary’ mindset and Birkeland wrote as much: Simulation shows that dark energy and matter can reproduce the Universe. To the best of our ability to tell, the Universe is being shaped by things we can't directly detect: dark matter and dark energy.
That makes it somewhat challenging to determine if our understanding of these influences is roughly correct. It's simply hard to be confident that we haven't missed some other dark entity that's lurking beyond our abilities of detection. One of the ways we can have some confidence that we're not missing anything major is to run models of the Universe. If we've got the basic physics right, then you should be able to set these models loose at an early point in the Universe's history and end up with something that looks like the Universe we're living in. Dark Energy, Dark Matter. Dark Energy, Dark Matter In the early 1990s, one thing was fairly certain about the expansion of the Universe.
It might have enough energy density to stop its expansion and recollapse, it might have so little energy density that it would never stop expanding, but gravity was certain to slow the expansion as time went on. Granted, the slowing had not been observed, but, theoretically, the Universe had to slow. Dark Matter: The Cosmos' Greatest Mystery Deepens. Like Hollywood legends Audrey Hepburn and Katharine Hepburn, dark energy and dark matter are completely unrelated, even though they share a name.
Dark energy, a force that makes the universe expand faster and faster all the time, is called dark because it's mysterious. Nobody knows what it is. Dark matter, on the other hand, a type of matter that outweighs ordinary stars and galaxies 5 to 1, is called dark because it's utterly invisible. We know it's there because its gravity yanks galaxies and stars around, but it neither emits nor reflects any light. Both darks are a big deal in astronomy.
Dark-Matter Theory Questioned by Astronomers' New Findings. The theory of dark matter took decades to take hold in astronomy, and no wonder.
It's pretty tough to wrap your mind around the notion that some mysterious, invisible substance pervades the cosmos — and even tougher to accept that it outweighs ordinary matter by a factor of 6 to 1, at least. Evidence eventually trumped incredulity, though, and by the 1980s, the vast majority of scientists were on board with the idea, nutty though it might seem, and there they've remained ever since. But a new study out of the European Southern Observatory claims that this now established theory could be in trouble. Chilean astronomers took a look at the motion of 400-plus stars in the broadly defined neighborhood of the sun and concluded that the way they're all moving is inconsistent with conventional ideas about dark matter. This could indeed be a blow to dark matter — in principle, anyway. Dark matter. Tentative dark matter hits fit with shadow dark sector - physics-math - 16 April 2013.
Researcher in US bunker find 'concrete hint' of dark matter. Discovery made in lab deep inside a US mine in Minnesota Researchers say they are 99.8% sure they have traces of dark matter By Mark Prigg Published: 10:12 GMT, 16 April 2013 | Updated: 10:54 GMT, 16 April 2013 Researchers have revealed further 'concrete hints' of the elusive material called dark matter at an underground laboratory in the US.
Though it is believed to make up a quarter of our universe, dark matter has never been directly observed. However, US researchers working deep inside a mine in Minnesota using an experiment called CDMS - which stands for Cryogenic Dark Matter Search - say they now have promising results. Alpha Magnetic Spectrometer to release first results. 18 February 2013Last updated at 00:21 ET By Jonathan Amos Science correspondent, BBC News, Boston The AMS was taken up to the ISS in 2011.
Has Dark Matter Finally Been Found? Big News Soon. Have we found dark matter? Scientist leading $2bn space experiment says results set for release. Dark matter is believed to provide the gravity which binds the cosmosBut if proved to exist it would challenge the conventional view of physicsScientists have attempted to track it down with spectrometer bolted to ISSFirst set of results from the instrument to be published in two weeks By Damien Gayle Published: 10:52 GMT, 19 February 2013 | Updated: 11:39 GMT, 19 February 2013.
Astronomers release the largest 3D map of the universe ever created. Unique project will take six years to completeAlready contains details of 200 million galaxies By Mark Prigg Published: 14:56 GMT, 8 August 2012 | Updated: 07:22 GMT, 9 August 2012 Scientists today released a groundbreaking 3D flythrough of the universe, revealing massive galaxies and distant black holes. The largest map of its kind ever created, researchers hope it can help the investigation of mysterious dark matter and dark energy that make up 96 percent of the universe. Scroll down for video. Mysterious 'dark matter' is mapped at last - showing a 'cosmic web' spanning a billion light years.
Is the Sun surrounded by dark matter? New simulation tries to answer one of the universe's biggest mysteries (and the answer: probably) Dark Matter Filament Between Galaxy Clusters Found. This story was updated at 9:32 a.m. EDT on July 5. A giant string of invisible dark matter has been discovered across the universe between a pair of galaxy clusters. The filament forms a bridge between two huge clusters called Abell 222 and Abell 223, which lie 2.7 billion light-years away. The universe is thought to be filled with such strings of dark matter, a mysterious substance that cannot be seen, only sensed through its gravitational pull.
Scientists have made previous attempts to find dark matter filaments, which are predicted by theories that suggest galaxy clusters form at the intersections of filaments. "This is the first time [a dark matter filament] has been convincingly detected from its gravitational lensing effect," said astronomer Jörg Dietrich of the University Observatory Munich, in Germany. "The standard wisdom is that the gravitational lensing of filaments is too weak to be detected with current telescopes," Dietrich told SPACE.com. Dark Matter Filaments Detected In Abell 222 And Abel 223 Supercluster. | 0.816159 | 3.793212 |
Texas Astronomers Unravel 20-Year Dark Matter Mystery with New Computer Models
10 September 2013
AUSTIN — Astronomers at The University of Texas at Austin believe they have discovered the answer to a 20-year debate over how the mysterious cosmic “dark matter” is distributed in small galaxies. Graduate student John Jardel and his advisor Karl Gebhardt found that the distribution, on average, follows a simple law of decreasing density from the galaxy’s center, although the exact distribution often varies from galaxy to galaxy. The findings are published today in The Astrophysical Journal Letters.
Dark matter is matter that gives off no light, but that astronomers detect by seeing its gravitational tug on other objects (like stars). Theories abound on what dark matter might be made of — unseen particles, dead stars, and more — but nobody knows for sure. Though mysterious, understanding the nature of dark matter is important, because it makes up most of the matter in the universe. The only way to understand how the cosmos evolved to its present state is to decode dark matter’s role.
For that reason, astronomers study the distribution of dark matter within galaxies and on even larger scales. Dwarf galaxies, in particular, make great laboratories to study dark matter, Jardel says, because they contain up to 1,000 times more dark matter than normal matter. Normal galaxies like the Milky Way, on the other hand, contain only 10 times more dark matter than normal matter.
For the past 20 years, observational astronomers and theorists have debated how dark matter is distributed in galaxies. Observational astronomers, through their studies of telescope data, have argued that galaxies have a fairly uniform distribution of dark matter throughout. Theorists, backed by computer simulations from the 1990s, have argued that dark matter density decreases steadily from a galaxy’s core to its hinterlands. The disagreement is known as the “core/cusp debate.”
Jardel’s work set out to study the question using both data from telescopes and newly developed computer modeling. The project started out “not assuming core or cusp theory is right,” he says, “but just asking ‘what is it?.’ These new models allowed us to take this approach.”
Jardel used telescope observations of several of the satellite galaxies orbiting the Milky Way, including the Carina, Draco, Fornax, Sculptor, and Sextans dwarf galaxies. The work involved running many supercomputer models for each galaxy to determine the distribution of dark matter within it, using the university’s Texas Advanced Computing Center (TACC).
He found that in some of the galaxies, the dark matter density decreased steadily from the center. In others, the density held constant. And some galaxies fell in between. However, when all the galaxies’ distributions were analyzed together, the results showed that on average, the theorists were right.
“When you look at individual galaxies,” Jardel says, “some of them look wildly different from expectations. However, when you average several galaxies together, these differences tend to cancel each other out.” This seems to suggest that the theory behind dark matter in galaxies is correct on the whole, but that “each galaxy develops slightly differently.”
The results do “pose more questions — questions about dark matter itself, and how normal matter interacted with dark matter” to form the types of galaxies seen today, Jardel says.
Possible next steps in this research include getting more telescope observations of these galaxies, both their centers and their extreme outlying regions, to understand the distribution of dark matter within them even better. More theory is also needed to explain the details of why certain galaxies’ dark matter halos deviate from the norm.
This work was partially funded by a grant from the National Science Foundation.
— END —
Graduate student, Dept. of Astronomy
The University of Texas at Austin
Dr. Karl Gebhardt
Herman and Joan Suit Professor in Astronomy
The University of Texas at Austin | 0.870776 | 3.940893 |
Thanks to gravitational wave astronomy, we are getting a better understanding of what happens when black holes collide. But the closely orbiting black holes only generate ripples in space-time strong enough to be detected from just before they smash. What happens before then? We can only extrapolate.
But a new discovery could change all that. In a galaxy just over 2.5 billion light-years away, astronomers have spotted two supermassive black holes destined for a colossal smash-up.
Don’t get too excited. They’re still pretty far apart, and astronomers estimate that it could take another 2.5 billion years for them to meet. But there’s still a lot we can learn from them, even if we won’t be around to see the fireworks.
The biggest promise of this discovery is getting us closer to discerning the gravitational wave background, a hypothetical hum of low-frequency gravitational waves from sources like supermassive black holes just about to merge.
We are yet to detect this noise – it’s outside the range of our current instruments. But now that we have an actual pair of supermassive black holes in our sights, their characteristics provide astronomers with an estimate of how many such pairs could be out there, potentially making this gravitational wave background noise.
“It’s a bit like a chaotic chorus of crickets chirping in the night,” said astrophysicist Andy Goulding of Princeton University. “You can’t discern one cricket from another, but the volume of the noise helps you estimate how many crickets are out there.”
Having a grasp on this noise could eventually help us figure out whether supermassive black holes even merge at all.
So far, our black hole collision detections have been of much less dramatic stellar-mass black holes; the most powerful gravitational wave detection to date was a collision between black holes 50 and 34 times the mass of the Sun, respectively.
Supermassive black holes are another category altogether. Each one in this newly discovered pair is estimated to be 400 million times the mass of the Sun; and each is the nucleus of a galaxy, the two coming together in a galactic collision.
What will the nucleus of that final galaxy look like? Will it be one giant supermassive black hole 800 billion times the mass of the Sun, or, as they draw closer together, will the two black holes become stuck in a perpetual orbit with each other?
“It’s a major embarrassment for astronomy that we don’t know if supermassive black holes merge,” said astrophysicist Jenny Greene of Princeton University. “For everyone in black hole physics, observationally this is a long-standing puzzle that we need to solve.”
According to theoretical modelling, when two galaxies merge, their black holes are inexorably drawn together, transferring their orbital energy to the gas and stars around them, and thus orbiting in a tighter and tighter spiral.
We know that pairs of stellar-mass black holes will eventually come together and form a single object, but with supermassive black holes, there’s a problem.
As their orbit shrinks, so too does the region of space to which they can transfer energy. By the time they’re one parsec apart (around 3.2 light-years), theoretically this region of space is no longer large enough to support further orbital decay, so they remain in a stable binary orbit – potentially for billions of years. This is called the final parsec problem.
If we could see a binary galactic nucleus, we could resolve that problem, but at a distance of one parsec, colliding black holes would be way too close to each other to tell apart (although one candidate has been spotted)… and, well, you know how hard it is to see a black hole at all.
This newly discovered pair is still around 430 parsecs (1,400 light-years) apart, so they won’t directly solve the final parsec problem – but they are still useful as they have given researchers a better estimate of how long it takes before such a collision would start producing detectable gravitational waves.
We’re not there yet. But by analysing this newly discovered black hole pair in the context of a hypothetical gravitational wave background, the team was able to arrive at an estimate of around 112 merging supermassive black holes within detection distance of Earth.
That’s a good-enough quantity close to us that we might have the first gravitational wave background detection in a few years.
If the gravitational wave background is full of noise from supermassive black hole pairs, then somehow, they do indeed manage to close that final parsec between them.
And, if we don’t detect that noise, maybe that parsec really does remain insurmountable.
The research has been published in The Astrophysical Journal Letters. | 0.870381 | 4.05286 |
Orion Nebula from Hubble
This dramatic image offers a peek inside a cavern of roiling dust and gas where thousands of stars are forming. The image, taken by the Advanced Camera for Surveys (ACS) aboard NASA's Hubble Space Telescope, represents the sharpest view ever taken of this region, called the Orion Nebula. More than 3,000 stars of various sizes appear in this image. Some of them have never been seen in visible light. These stars reside in a dramatic dust-and-gas landscape of plateaus, mountains, and valleys that are reminiscent of the Grand Canyon.
The Orion Nebula is a picture book of star formation, from the massive, young stars that are shaping the nebula to the pillars of dense gas that may be the homes of budding stars. The bright central region is the home of the four heftiest stars in the nebula. The stars are called the Trapezium because they appear in a trapezoid pattern. Ultraviolet light unleashed by these stars is carving a cavity in the nebula and potentially disrupting the growth of hundreds of smaller stars. Located near the Trapezium stars are stars still young enough to have disks of material encircling them. These disks are called protoplanetary disks or "proplyds" and are too small to see clearly in this image. The disks are the building blocks of solar systems.
The bright glow at upper left is from M43, a small region being shaped by a massive, young star's ultraviolet light. Astronomers call the region a miniature Orion Nebula because only one star is sculpting the landscape. The Orion Nebula has four such stars. Next to M43 are dense, dark pillars of dust and gas that point toward the Trapezium. These pillars are resisting erosion from the Trapezium's intense ultraviolet light. The glowing region on the right reveals arcs and bubbles formed when stellar winds - streams of charged particles ejected from the Trapezium stars - collide with material.
The faint red stars near the bottom are the myriad brown dwarfs that Hubble spied for the first time in the nebula in visible light. Sometimes called "failed stars," brown dwarfs are cool objects that are too small to be ordinary stars because they cannot sustain nuclear fusion in their cores the way our Sun does. The dark red column, below, left, shows an illuminated edge of the cavity wall.
The Orion Nebula is 1,400 light-years away, one of the nearest star-forming regions to Earth. Astronomers used 520 Hubble images, taken in five colors, to make this picture. They also added ground-based photos to fill out the nebula. The ACS mosaic covers approximately the apparent angular size of the full moon.
The Orion observations were taken between 2004 and 2005.
For More Information
Please give credit for this item to:
NASA, ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team | 0.806639 | 3.847741 |
Jan 19, 2015
Io’s caldera continue to puzzle scientists.
Previous Pictures of the Day discuss several confirmed predictions about electrical activity on Io, notably, the intense electric arcing between the moon and its parent body, Jupiter. Images of Io verify that Io ought to be considered from an electric discharge hypothesis, rather than the commonly accepted view. The majority of planetary scientists think that Io is being “kneaded” by tidal forces in Jupiter’s gravity field.
According to a recent press release, volcanoes (as those planetary scientists believe) are erupting on Io with larger and brighter plumes that ever before. Imke de Pater, from the University of California at Berkeley said:
“We typically expect one huge outburst every one or two years, and they’re usually not this bright. Here we had three extremely bright outbursts, which suggest that if we looked more frequently we might see many more of them on Io.”
Since Io is electrically connected to Jupiter, such variability is not unexpected in an Electric Universe. The most active regions are found along the edges of so-called “lava lakes,” while the remainder of the dark umbras surrounding them are extremely cold. No volcanic vents are seen. “Plumes” of erupting gas and dust move across Io, as illustrated by the Prometheus hot spot. However, that spot moved more than 80 kilometers since it was first imaged by Voyager 2. Galileo mission specialists were shocked when they realized that Io’s volcanic plumes also emit ultraviolet light, characteristic of electric arcs.
“The remarkable filamentary structure in the Tvashtar plume is similar to details glimpsed faintly in 1979 Voyager images of a similar plume produced by Io’s volcano Pele. However, no previous image by any spacecraft has shown these mysterious structures so clearly.”
Most of Io’s hot spots appear to be located between 30 degrees and 60 degrees farther east than models of its internal heat profile predict, a recent article announced. Christopher Hamilton from the University of Maryland said:
“The unexpected eastward offset of the volcano locations is a clue that something is missing in our understanding of Io. In a way, that’s our most important result. Our understanding of tidal heat production and its relationship to surface volcanism is incomplete.”
From a conventional perspective, the filamentary structure of Io’s plumes will never be adequately explained. Nor will the anomalous movement of the caldera across its surface. Since Io and Jupiter are immersed in an electric field, and the induced charge flow between them dissipates more than 2 trillion watts, the electrical circuit on Io is concentrating the intense bombardment from Jupiter into several “plasma guns,” or dense plasma foci.
NASA scientists acknowledge the electrical activity in the Jovian system, but fail to draw the logical conclusion. As noted plasma physicist Anthony Peratt observed:
“The apparent filamentary penumbra on Io may be the first direct verification of the plasma gun mechanism at work in the solar system.”
The variability in the so-called volcanic eruptions is most likely another indication of the electrical connection between Jupiter and its moons. | 0.901666 | 3.823837 |
On the Edge: Exoplanets with Orbital Periods Shorter Than a Peter Jackson Movie
Brian Jackson, Boise State Univeristy
From wispy gas giants to tiny rocky bodies, exoplanets with orbital periods of several days and less challenge theories of planet formation and evolution. Recent searches have found small rocky planets with orbits reaching almost down to their host stars’ surfaces, including an iron-rich Mars-sized body with an orbital period of only four hours. So close to their host stars that some of them are actively disintegrating, these objects’ origins remain unclear, and even formation models that allow significant migration have trouble accounting for their very short periods. Some are members of multi-planet system and may have been driven inward via secular excitation and tidal damping by their sibling planets. Others may be the fossil cores of former gas giants whose atmospheres were stripped by tides.
In this presentation, I’ll discuss the work of our Short-Period Planets Group (SuPerPiG), focused on finding and understanding this surprising new class of exoplanets. We are sifting data from the reincarnated Kepler Mission, K2, to search for additional short-period planets and have found several new candidates. We are also modeling the tidal decay and disruption of close-in gaseous planets to determine how we could identify their remnants, and preliminary results suggest the cores have a distinctive mass-period relationship that may be apparent in the observed population. Whatever their origins, short-period planets are particularly amenable to discovery and detailed follow-up by ongoing and future surveys, including the TESS mission.
New Tools for Galactic Archaeology from the Milky Way
Gail Zasowski, John Hopkins University
One of the critical components for understanding galaxy evolution is understanding the Milky Way Galaxy itself — its detailed structure and chemodynamical properties, as well as fundamental stellar physics, which we can only study in great detail locally. This field is currently undergoing a dramatic expansion towards the kinds of large-scale statistical analyses long used by the extragalactic and other communities, thanks in part to an enormous influx of data from space- and ground-based surveys. I will describe the Milky Way and Local Group in the context of general galaxy evolution and highlight some recent developments in Galactic astrophysics that take advantage of these big data sets and analysis techniques. In particular, I will focus on two diverse approaches: one to characterize the distribution and dynamics of the carbon-rich, dusty diffuse ISM, and one to map the resolved bulk stellar properties of the inner disk and bulge. The rapid progress in these areas promises to continue, with the arrival of data sets from missions like SDSS, Gaia, LSST, and WFIRST.
Characterization of Biosignatures within Geologic Samples Analyzed using a Suite of in situ Techniques
Kyle Uckert, NMSU
I investigated the biosignature detection capabilities of several in situ techniques to evaluate their potential to
detect the presence of extant or extinct life on other planetary surfaces. These instruments included: a laser desorption
time-of- flight mass spectrometer (LD-TOF-MS), an acousto-optic tunable filter (AOTF) infrared (IR) point spectrometer, a
laser-induced breakdown spectrometer (LIBS), X-ray diffraction (XRD)/X-ray fluorescence (XRF), and scanning electron
microscopy (SEM)/energy dispersive X-Ray spectroscopy (EDS). I measured the IR reflectance spectra of several speleothems
in caves in situ to detect the presence of biomineralization. Microorganisms (such as those that may exist on other solar
system bodies) mediate redox reactions to obtain energy for growth and reproduction, producing minerals such as
carbonates, metal oxides, and sulfates as waste products. Microbes occasionally become entombed in their mineral
excrement, essentially acting as a nucleation site for further crystal growth. This process produces minerals with a
crystal lattice distinct from geologic precipitation, detectable with IR reflectance spectroscopy. Using a suite of
samples collected from three subterranean environments, along with statistical analyses including principal component
analysis, I measured subsurface biosignatures associated with these biomineralization effects, including the presence of
trace elements, morphological characteristics, organic molecules, and amorphous crystal structures.
I also explored the optimization of a two-step LD-TOF-MS (L2MS) for the detection of organic molecules and other
biosignatures. I focused my efforts on characterizing the L2MS desorption IR laser wavelength dependence on organic
detection sensitivity in an effort to optimize the detection of high mass (≤100 Da) organic peaks. I analyzed samples
with an IR reflectance spectrometer and an L2MS with a tunable desorption IR laser whose wavelength range (2.7 – 3.45
microns) overlaps that of our IR spectrometer (1.6 – 3.6 microns), and discovered a IR resonance enhancement effect. A
correlation between the maximum IR absorption of organic functional group and mineral vibrational transitions – inferred
from the IR spectrum – and the optimal IR laser configuration for organic detection using L2MS indicates that IR
spectroscopy may be used to inform the optimal L2MS IR laser wavelength for organic detection. This work suggests that a
suite of instruments, particularly LD-TOF-MS and AOTF IR spectroscopy, has strong biosignature detection potential on a
future robotic platform for investigations of other planetary surfaces or subsurfaces.
Observations of Solar System Bodies with the VLA and ALMA
Dr. Bryan Butler, NRAO
Observations of solar system bodies at wavelengths from submm to meter wavelengths provide important and unique information about those bodies. Such observations probe to depths unreachable at other wavelengths – typically of order 10-20 wavelengths for bodies with solid surfaces, and as deep as tens of bars for those with thick atmospheres (the giant planets). In the past five years, two instruments have been commissioned which have revolutionized the ability to make very sensitive, high-resolution observations at these wavelengths: the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/Submillimeter Array (ALMA). I will present a discussion of results over the past five years from observations from both the VLA and ALMA. These include observations of the atmospheres of all of the giant planets, the rings of Saturn, and the surfaces of many icy bodies in the outer solar system. I will also present plans for the Next Generation Very Large Array (ngVLA), the next step for millimeter to centimeter wavelength interferometry.
Cosmology from the Moon: The Dark Ages Radio Explorer (DARE)
Dr. Jack Burns, University of Colorado Boulder
In the New Worlds, New Horizons in Astronomy & Astrophysics Decadal Survey, Cosmic Dawn was singled out as one of the top astrophysics priorities for this decade. Specifically, the Decadal report asked “when and how did the first galaxies form out of cold clumps of hydrogen gas and start to shine—when was our cosmic dawn?” It proposed “astronomers must now search the sky for these infant galaxies and find out how they behaved and interacted with their surroundings.” This is the science objective of DARE – to search for the first stars, galaxies, and black holes via their impact on the intergalactic medium (IGM) as measured by the highly redshifted 21-cm hyperfine transition of neutral hydrogen (HI). DARE will probe redshifts of 11-35 (Dark Ages to Cosmic Dawn) with observed HI frequencies of 40-120 MHz. DARE will observe expected spectral features in the global signal of HI that correspond to stellar ignition (Lyman-α from the first stars coupling with the HI hyperfine transition), X-ray heating/ionization of the IGM from the first accreting black holes, and the beginning of reionization (signal dominated by IGM ionization fraction). These observations will complement those expected from JWST, ALMA, and HERA. We propose to observe these spectral features with a broad-beam dipole antenna along with a wide-band receiver and digital spectrometer. We will place DARE in lunar orbit and take data only above the farside, a location known to be free of human-generated RFI and with a negligible ionosphere. In this talk, I will present the mission concept including initial results from an engineering prototypes which are designed to perform end-to-end validation of the instrument and our calibration techniques. I will also describe our signal extraction tool, using a Markov Chain Monte Carlo technique, which measures the parameterized spectral features in the presence of substantial Galactic and solar system foregrounds.
Giant Planet Shielding of the Inner Solar System Revisited: Blending Celestial Mechanics with Advanced Computation
Dr. William Newman, UCLA
The Earth has sustained during the last billion years as many as five catastrophic collisions with asteroids and comets which led to widespread species extinctions. Our own atmosphere was literally blown away 4.5 billion years ago by a collision with a Mars-sized impactor. However, collisions with comets originating in the outer solar system accreted much of the present-day atmosphere. Relatively advanced life on our planet is the beneficiary of a number of impact events during Earth’s history which built our atmosphere without destroying a large fraction of terrestrial life. Using very high precision Monte Carlo integration methods to explore the orbital evolution over hundreds of millions of years followed by the application of celestial mechanical techniques, the presentation will explain directly how Earth was shielded by the combined influence of Jupiter and Saturn, assuring that only 1 in 100,000 potential collisions with the Earth will materialize.
Solving the Puzzles of the Moon
Shun Karato, Yale University
After 50 years from the first landing of men on the Moon, about 380 kg of samples were collected by the Apollo mission. Chemical analyses of these samples together with a theory of planetary formation led to a “giant impact” paradigm (in mid 1970s). In this paradigm, the Moon was formed in the later stage of Earth formation (not the very late stage, though), when the proto-Earth was hit by an impactor with a modest size (~ Mars size) at an oblique angle. Such an impact is a natural consequence of planetary formation from a proto-planetary nebula. This collision may have kicked out mantle materials from the proto-Earth to form the Moon. This model explains mostly rocky composition of the Moon and the large angular momentum of the Earth-Moon system. High temperatures caused by an impact likely removed much of the volatile components such as water.
However, two recent geochemical observations cast doubt about the validity of such a paradigm. They include (i) not-so-dry Moon suggested from the analysis of basaltic inclusions in olivine, and (ii) the high degree of similarities in many isotopes. The first observation is obviously counter-intuitive, but the second one is also hard to reconcile with the standard model of a giant impact, because many models show that a giant impact produces the Moon mostly from the impactor. In this presentation, I will show how one can solve these puzzles by a combination of physics/chemistry of materials with some basic physics of a giant impact.
Simulating Planetesimal Formation in the Kuiper Belt and Beyond
Rixin Li, University of Arizona
A critical step in planet formation is to build super-km-sized planetesimals in protoplanetary disks. The origin and demographics of planetesimals are crucial to understanding the Solar System, circumstellar disks, and exoplanets. I will overview the current status of planetesimal formation theory. Specifically, I will present our recent simulations of planetesimal formation by the streaming instability, a mechanism to aerodynamically concentrate pebbles in protoplanetary disks. I will then discuss the connections between our numerical models and recent astronomical observations and Solar System explorations. I will explain why all planetesimals likely formed as binaries. | 0.929711 | 3.956266 |
How can a planet be “hotter than hot?” The answer is when heavy metals are detected escaping from the planet’s atmosphere, instead of condensing into clouds.
Observations by NASA’s Hubble Space Telescope reveal magnesium and iron gas streaming from the strange world outside our solar system known as WASP-121b. The observations represent the first time that so-called “heavy metals” — elements heavier than hydrogen and helium — have been spotted escaping from a hot Jupiter, a large, gaseous exoplanet very close to its star.
Normally, hot Jupiter-sized planets are still cool enough inside to condense heavier elements such as magnesium and iron into clouds.
But that’s not the case with WASP-121b, which is orbiting so dangerously close to its star that its upper atmosphere reaches a blazing 4,600 degrees Fahrenheit. The temperature in WASP-121b’s upper atmosphere is about 10 times greater than that of any known planetary atmosphere. The WASP-121 system resides about 900 light-years from Earth.
“Heavy metals have been seen in other hot Jupiters before, but only in the lower atmosphere,” explained lead researcher David Sing of the Johns Hopkins University in Baltimore, Maryland. “So you don’t know if they are escaping or not. With WASP-121b, we see magnesium and iron gas so far away from the planet that they’re not gravitationally bound.”
Ultraviolet light from the host star, which is brighter and hotter than the Sun, heats the upper atmosphere and helps lead to its escape. In addition, the escaping magnesium and iron gas may contribute to the temperature spike, Sing said. “These metals will make the atmosphere more opaque in the ultraviolet, which could be contributing to the heating of the upper atmosphere,” he explained.
The sizzling planet is so close to its star that it is on the cusp of being ripped apart by the star’s gravity. This hugging distance means that the planet is football shaped due to gravitational tidal forces.
“We picked this planet because it is so extreme,” Sing said. “We thought we had a chance of seeing heavier elements escaping. It’s so hot and so favorable to observe, it’s the best shot at finding the presence of heavy metals. We were mainly looking for magnesium, but there have been hints of iron in the atmospheres of other exoplanets. It was a surprise, though, to see it so clearly in the data and at such great altitudes so far away from the planet. The heavy metals are escaping partly because the planet is so big and puffy that its gravity is relatively weak. This is a planet being actively stripped of its atmosphere.”
The researchers used the observatory’s Space Telescope Imaging Spectrograph to search in ultraviolet light for the spectral signatures of magnesium and iron imprinted on starlight filtering through WASP-121b’s atmosphere as the planet passed in front of, or transited, the face of its home star.
This exoplanet is also a perfect target for NASA’s upcoming James Webb Space Telescope to search in infrared light for water and carbon dioxide, which can be detected at longer, redder wavelengths. The combination of Hubble and Webb observations would give astronomers a more complete inventory of the chemical elements that make up the planet’s atmosphere.
The WASP-121b study is part of the Panchromatic Comparative Exoplanet Treasury (PanCET) survey, a Hubble program to look at 20 exoplanets, ranging in size from super-Earths (several times Earth’s mass) to Jupiters (which are over 100 times Earth’s mass), in the first large-scale ultraviolet, visible, and infrared comparative study of distant worlds.
The observations of WASP-121b add to the developing story of how planets lose their primordial atmospheres. When planets form, they gather an atmosphere containing gas from the disk in which the planet and star formed. These atmospheres consist mostly of the primordial, lighter-weight gases hydrogen and helium, the most plentiful elements in the universe. This atmosphere dissipates as a planet moves closer to its star.
“The hot Jupiters are mostly made of hydrogen, and Hubble is very sensitive to hydrogen, so we know these planets can lose the gas relatively easily,” Sing said. “But in the case of WASP-121b, the hydrogen and helium gas is outflowing, almost like a river, and is dragging these metals with them. It’s a very efficient mechanism for mass loss.”
The results will appear online today in The Astronomical Journal.
The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C. | 0.852742 | 4.055913 |
China's Chang'e-4 lander and rover are scheduled to launch in December this year to perform the first ever soft-landing on the far side of the Moon, but the mission's side quests are already performing impressive feats.
One of two microsatellites launched along with a required communications relay satellite in May has quietly been allowing radio operators to download images from the spacecraft taken along its elliptical lunar orbit.
Longjiang-2, aka DSLWP-B, was developed by students at the Harbin Institute of Technology (HIT) in Heilongjiang Province, northeast China. Despite having a mass of just 47 kg, the tiny satellite managed to use its own propulsion to slow down and enter lunar orbit while the relay satellite continued past the Moon to its special destination.
During its time in orbit Longjiang-2 has used a student-developed camera to take images of the Moon, Mars, the Sun and other objects. UHF tests have seen data transmitted by Longjiang-2 and received and decoded by radio operators on Earth.
Data has been downloaded from radio and satellite tracking enthusiasts around the world, including Florida, Brazil, China, the Netherlands, Italy and more.
The 50x50x40-cm sat also carries a radio astronomy payload, while also having been built to cope with the radiation environment of deep space.
Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, told SpaceNews in June that the Longjiang/DSLWP probes signal the beginning of ambitious plans for small deep space probes, with the even smaller NASA MarCO probes currently on their way to Mars.
“I think in the decade to come, we’ll continue to see ambitious, large planetary probes, like the European-Japanese Bepi-Colombo and China’s Chang’e-4 which are both preparing for launch, but we’ll also see the flourishing of these small, simple and highly focused probes,” McDowell said.
Unfortunately its partner, Longjaing-1/DSLWP-A, was lost shortly after trans-lunar injection, and likely remains in distant Earth orbit after a lunar flyby.
The student team at HIT also operate the LilacSat-1, a 2-unit CubeSat launched as part of the European QB50 initiative, and LilacSat-2, a technology test satellite launched on the first Long March 6 rocket in 2015.
The Longjiang satellites piggybacked on a launch necessary for the the Chang'e-4 lunar landing and roving mission late this year.
As the far side of the Moon never faces the Earth, a special relay satellite was launched in May and sent to orbit around a special point in space known as the second Earth-Moon Lagrange point from which it will facilitate communications between the ground and spacecraft.
Known as Queqiao, the 450 kg satellite also carries a Netherlands-China Low-Frequency Explorer (NCLE) instrument to carry out low frequency astronomy which is not possible on Earth due to its atmosphere, and provide a window into the cosmic 'dark ages'.
Also aboard Longjiang-2 is a small optical imager developed by the King Abdulaziz City for Science and Technology (KACST) of Saudi Arabia, one of four international partners in the Chang'e-4 mission.
That camera returned amazing images of the Earth and Moon together, as well as the lunar surface. The images were shared following a China National Space Administration event hosted with its Saudi Arabian partners, and further images have not been released.
The Chang'e-4 landing and roving mission will launch in December carrying a number of cameras and science payloads with which to analyze the South Pole-Aitken Basin, a fascinating, large and ancient impact basin on the lunar far side.
The lander and rover were manufactured as backups to the successful Chang'e-3 landing on Mare Imbrium on the near side of the Moon in 2013, but have been repurposed for a more complex mission.
By Andrew Jones, GBTimes | 0.849821 | 3.075606 |
The Sahara Desert is one of the harshest, most inhospitable places on the planet, covering much of North Africa in some 3.6 million square miles of rock and windswept dunes. But it wasn’t always so desolate and parched. Primitive rock paintings and fossils excavated from the region suggest that the Sahara was once a relatively verdant oasis, where human settlements and a diversity of plants and animals thrived.
This January 2, 2019 essay by Jennifer Chu, of Massachusetts Institute of Technology does encapsulate climate evolution through time, and not its undeniable change.
Study shows the Sahara swung between lush and desert conditions every 20,000 years, in sync with monsoon activity
A new analysis of African dust reveals the Sahara swung between green and desert conditions every 20,000 years, in sync with changes in the Earth’s tilt. Credit: Massachusetts Institute of Technology
Now researchers at MIT have analyzed dust deposited off the coast of west Africa over the last 240,000 years, and found that the Sahara, and North Africa in general, has swung between wet and dry climates every 20,000 years. They say that this climatic pendulum is mainly driven by changes to the Earth’s axis as the planet orbits the sun, which in turn affect the distribution of sunlight between seasons—every 20,000 years, the Earth swings from more sunlight in summer to less, and back again.
For North Africa, it is likely that, when the Earth is tilted to receive maximum summer sunlight with each orbit around the sun, this increased solar flux intensifies the region’s monsoon activity, which in turn makes for a wetter, “greener” Sahara. When the planet’s axis swings toward an angle that reduces the amount of incoming summer sunlight, monsoon activity weakens, producing a drier climate similar to what we see today.
“Our results suggest the story of North African climate is dominantly this 20,000-year beat, going back and forth between a green and dry Sahara,” says David McGee, an associate professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “We feel this is a useful time series to examine in order to understand the history of the Sahara desert and what times could have been good for humans to settle the Sahara desert and cross it to disperse out of Africa, versus times that would be inhospitable like today.”
McGee and his colleagues have published their results today in Science Advances.
A puzzling pattern
Each year, winds from the northeast sweep up hundreds of millions of tons of Saharan dust, depositing much of this sediment into the Atlantic Ocean, off the coast of West Africa. Layers of this dust, built up over hundreds of thousands of years, can serve as a geologic chronicle of North Africa’s climate history: Layers thick with dust may indicate arid periods, whereas those containing less dust may signal wetter eras.
Scientists have analyzed sediment cores dug up from the ocean bottom off the coast of West Africa, for clues to the Sahara’s climate history. These cores contain layers of ancient sediment deposited over millions of years. Each layer can contain traces of Saharan dust as well as the remains of life forms, such as the tiny shells of plankton.
Past analyses of these sediment cores have unearthed a puzzling pattern: It would appear that the Sahara shifts between wet and dry periods every 100,000 years—a geologic beat that scientists have linked to the Earth’s ice age cycles, which seem to also come and go every 100,000 years. Layers with a larger fraction of dust seem to coincide with periods when the Earth is covered in ice, whereas less dusty layers appear during interglacial periods, such as today, when ice has largely receded.
But McGee says this interpretation of the sediment cores chafes against climate models, which show that Saharan climate should be driven by the region’s monsoon season, the strength of which is determined by the tilt of the Earth’s axis and the amount of sunlight that can fuel monsoons in the summer.
“We were puzzled by the fact that this 20,000-year beat of local summer insolation seems like it should be the dominant thing controlling monsoon strength, and yet in dust records you see ice age cycles of 100,000 years,” McGee says.
Beats in sync
To get to the bottom of this contradiction, the researchers used their own techniques to analyze a sediment core obtained off the coast of West Africa by colleagues from the University of Bordeaux—which was drilled only a few kilometers from cores in which others had previously identified a 100,000-year pattern.
The researchers, led by first author Charlotte Skonieczny, a former MIT postdoc and now a professor at Paris-Sud University, examined layers of sediment deposited over the last 240,000 years. They analyzed each layer for traces of dust and measured the concentrations of a rare isotope of thorium, to determine how rapidly dust was accumulating on the seafloor.
Thorium is produced at a constant rate in the ocean by very small amounts of radioactive uranium dissolved in seawater, and it quickly attaches itself to sinking sediments. As a result, scientists can use the concentration of thorium in the sediments to determine how quickly dust and other sediments were accumulating on the seafloor in the past: During times of slow accumulation, thorium is more concentrated, while at times of rapid accumulation, thorium is diluted. The pattern that emerged was very different from what others had found in the same sediment cores.
“What we found was that some of the peaks of dust in the cores were due to increases in dust deposition in the ocean, but other peaks were simply because of carbonate dissolution and the fact that during ice ages, in this region of the ocean, the ocean was more acidic and corrosive to calcium carbonate,” McGee says. “It might look like there’s more dust deposited in the ocean, when really, there isn’t.”
Once the researchers removed this confounding effect, they found that what emerged was primarily a new “beat,” in which the Sahara vacillated between wet and dry climates every 20,000 years, in sync with the region’s monsoon activity and the periodic tilting of the Earth.
“We can now produce a record that sees through the biases of these older records, and so doing, tells a different story,” McGee says. “We’ve assumed that ice ages have been the key thing in making the Sahara dry versus wet. Now we show that it’s primarily these cyclic changes in Earth’s orbit that have driven wet versus dry periods. It seems like such an impenetrable, inhospitable landscape, and yet it’s come and gone many times, and shifted between grasslands and a much wetter environment, and back to dry climates, even over the last quarter million years.”
More information: “Monsoon-driven Saharan dust variability over the past 240,000 years” Science Advances (2019). advances.sciencemag.org/content/5/1/eaav1887 | 0.864551 | 3.556018 |
UPDATE (Thursday, 07 May 2020): A possible naked-eye outburst of Comet SWAN! Despite of bright moonlight and thin clouds, Comet C/2020 F8 (SWAN) is still visible from Brunei just before nautical twilight today, May 07, 2020 at 0520. The greenish coma is due to molecules of Cyanogen and Carbon gas ejected from the comet nucleus. In the following days, the comet is located very low on the Eastern horizon in early morning twilight, before it fades in full daylight next week.
Another comet observer, Abdul Waliyuddin, a member of Brunei Darussalam Astronomical Society (PABD), managed to capture the beautiful Comet Swan as it makes its way through our solar system. Waliyuddin said “The pre-dawn skies of Seria gave way to a clear view of the celestial ceiling this morning. It was spewing a tail of gas and dust that can extend up to hundreds of millions of kilometres away from its epicenter from Seria, Belait, Brunei Darussalam”
Comet SWAN was only discovered two months ago. There is much to be understood and learned from our skies. Whatever science tells us about the biology of our fingers will always be lesser than the true reality of the wonders of our finger. Likewise, whatever we know about our skies will always be lesser than the actual existential reality of the grandeur of space.
Wednesday, 06 May 2020: A green glowing fuzzy ball of Comet C/2020 F8 SWAN is unexpectedly bright with obvious tail at dawn today, May 06, 2020, from Brunei Darussalam. Currently in the constellation Pisces, the comet is visible in the twilight Eastern horizon from Brunei Darussalam until mid-May. Comet C/2020 F8 SWAN is at magnitude 6 (just visible to the unaided eye) under dark sky conditions, which is an easy target for digital camera and binoculars.
Friday, May 1, 2020, Bandar Seri Begawan – As Comet ATLAS disintegrates, Comet SWAN arrives. This was a single 8-second exposure photograph of Comet SWAN through a small refractor telescope taken on Friday, May 01, 2020 at 5:12 a.m. under cloudy condition from Tutong, Brunei Darussalam.
At the moment, naked eyes can see the comet only as a green fuzzball, with developing mini-tail, in the constellation Cetus and located above the East-Southeast horizon at predawn. By comparing the surrounding stars in the sky chart, the Comet is approximately at magnitude less than 6 which is just bright enough to be spotted by the human eye under dark sky or through a binocular for light polluted sky.
Much about Comet SWAN remains unknown. It was discovered just a few weeks ago, on April 11, 2020, when a sudden gases dump by the comet has made it show up in data from the spacecraft’s hydrogen-detecting instrument known as the Solar Wind Anistropies (SWAN).
Astronomers expect comet SWAN continues to become brighter as it moves towards the Sun (perihelion – on May 27, 2020 at 0.43 Astronomical Units); and more visible as it approaches closest to Earth on May 13, 2020 at 0.57 Astronomical Units, or 85,065,197 km.
Cometary luminosity is very hard to predict and no guarantees, as seen by what’s happened to Comet Atlas. But if the comet vaporizes well by sunlight and produces enough ejected gas and dust particles of tails, it would put the comet bright enough to be seen with the naked eyes.
How to spot comet SWAN from Brunei?
All eyes on the pre dawn sky for the brightening comet this coming weeks from early May until mid-May from Brunei. It will be best view at around 4.30 am when the comet rises on the Eastern horizon, but you’ll need an unobstructed horizon to observe the icy cosmic body. Use the sky chart below to locate the position of the comet in the sky. Wishing you clear skies and wide eyes.
For more update of this comet: https://theskylive.com/c2020f8-info and http://aerith.net/comet/catalog/2020F8/2020F8.html. Use the ephemeris of the
Comet for Brunei Darussalam from May 01 until June 30, 2020, to locate the comet below: | 0.803394 | 3.415942 |
On August 13, 1596, German theologian and astronomer David Fabricius discovered the first known periodic variable star, which he called Mira Ceti (The ‘Wonder’ in the stellar constellation ‘Whale’).
David Fabricius – Early Years
David Fabricius was born in Esens, Lower Saxony and received a pretty good education, learning mostly Latin. In Braunschweig, he first gained a few experiences in astronomy. His teacher introduced him to astronomy as well as mathematics before he attended University (most probably the University of Helmstedt) and became a protestant pastor. In the following years, he spent a lot time studying the heavens and the stars. Fabricius also started communicating with contemporary scientists about the movements of planets, about northern lights as well as comets. One of these scientists was Tycho Brahe, and another Johannes Kepler. Between 1601 and 1609 he exchanged forty letters with the latter, mainly about the planet Mars. He undertook numerous journeys and became acquainted with important contemporaries. When Tycho Brahe was in Wandsbek from 1597 to 1599, David Fabricius was one of his visitors.
The Discovery of Mira Ceti
On August 13, 1596 (Gregorian calendar), Fabricius noticed the alterability of the star Omikron at Cetus. This star changes about every 331 days its luminosity. Due to this weird ability, Fabricius named this star ‘res mira‘ (strange thing), since Johannes Hevelius it is simply called Mira, the “Wondrous”. Cetus is a very large but often hard to notice constellation between Fish and the Eridanus. It contains next to Mira another variable star, Tau Ceti. Mira became the eponym of a whole class of long-period variable stars. David Fabricius’ discovery was very important to contemporary scientists. Many believed that the constellations of the zodiac were unalterable and eternal, which he disproved.
Focussing on Meteorology
After his amazing success, Fabricius began focusing on meteorology, researching the influence of celestial bodies on the air circulation on earth. His manuscripts on the topic were well preserved and exist up to this day. In his last period, David Fabricius worked together with his son, Johann. In 1611 his son Johann (the eldest of seven sons) returned from his studies in Leiden and brought a telescope with him. Observing the sun in February 1611, he noticed dark spots. Father and son Fabricius made joint observations and were able to establish their existence without any doubt. David Fabricius determined the rotation time of the sun from the movement of the spots on the visible solar disk. Although Galileo Galilei in Pisa and Thomas Harriot in London had already noticed spots on the sun in 1610, Johann Fabricius and Christoph Scheiner in Ingolstadt were the first to write and publish a scientific treatise on the subject.
Further Projects and Mysterious End
In addition to astronomy, Fabricius also investigated a possible influence of the stars on the movements of the Earth’s air circuit. In 1589 he produced the first East Frisian map printed in East Frisia under the title “Never and warhafftige Beschriinge des Ostfreslandes“. David Fabricius’ ending is a bit strange and mysterious. He is said to have delivered a sermon shortly before his death in which he claimed he knew a goose and chicken thief, but did not want to reveal his name. A self-made horoscope predicted disaster for May 7, 1617 and Fabricius spent the day in his house. In the evening he thought the danger was over and set out for a walk. On the way, a farmer, Frerik Hoyer, killed him with a peat spade. Hoyer obviously felt embarrassed as a thief and was angry about it. He was whacked to death for what he did.
At yovisto academic video search, you may enjoy a video lecture by Carolin Crawford on the Sounds of the Universe.
References and Further Reading:
- Fabricius at The Biographical Encyclopedia of Astronomers [PDF]
- Fabricius at the Galileo Project
- David Fabricius at Wikidata
- Tycho Brahe – The Man with the Golden Nose, SciHi Blog
- And Kepler Has His Own Opera – Kepler’s 3rd Planetary Law, SciHi Blog
- Johannes Hevelius and his Selenographia, SciHi Blog
- Johannes Fabricius and the Sunspots, SciHi Blog
- Timeline of 16th century astronomers, via Wikidata | 0.918008 | 3.457471 |
Description of the payload
The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne mission to measure the polarization of the cosmic microwave background (CMB) in search of the signature of primordial gravity waves excited by an inflationary epoch in the early universe.
It is composed by two identical telescopes cooled to 1.5 K within a large (3 meter tall, 3500-liter capacity) liquid helium bucket dewar. There are no windows between the LHe-cooled telescope and the ambient environment: PIPER uses the efflux of boiloff helium gas to prevent the atmosphere at balloon altitudes from condensing on the optics. This technique was first applied in a previous balloon-borne instrument denominated ARCADE. The unusual cryogenic design provides mapping speed a factor of 10 better than any other CMB instrument, allowing PIPER to achieve sensitivities with overnight balloon flights that would otherwise require 10-day flights from other places like Antarctica.
Each of PIPER's twin telescopes illuminates a pair of 32x40 element transition-edge superconducting detector arrays for a total of 5120 detectors. A Variable-Delay Polarization Modulator (VPM) injects a time-dependent phase delay between orthogonal linear polarizations to cleanly separate polarized from unpolarized radiation. The combination of background-limited detectors with fast polarization modulation allows PIPER to rapidly scan large areas of the sky.
Details of the balloon flight and scientific outcome
Launch site: Scientific Flight Balloon Facility, Fort Sumner, (NM), US
Balloon launched by: Columbia Scientific Balloon Facility (CSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon Raven - 11.820.000 cuft
Flight identification number: 681N
The balloon was launched at 16:12 utc on October 13th, 2017 using the dynamic method, assisted by the Big Bill launch vehicle. Climb to altitude was nominal and ceiling of 98.000 ft was reached about 19:30 utc while flying E of Tucumcari, new Mexico. The balloon moved during the entire flight in a NE direction more or less along along the New Mexico / Texas border, as can be seen in the map at left.
The flight was terminated and the payload separated from the balloon at 3:00 utc on October 14th, while flying over Union County in NE New Mexico. The landing of the payload was a little rough as it toched ground with a sideways speed around 40 miles/hour and did a cartwheel, landing on the bottom, then on the top, and then on the bottom again. However, the instrument resisted very well the ride and emerged in good shape at all.
Total flight time from launch to landing was 11 hours and 30 minutes.
External references and bibliographical sources | 0.85165 | 3.485512 |
Moons Of All The Planets
Know all 219 known moons of all the planets in our solar system? Well here they are! Every so often new moons are discovered for Saturn and the dwarf planets. (m = apparent magnitude)
☿ Mercury Moons = 0
Mercury is too close to the Sun to hold on to a moon.
♀ Venus Moons = 0
Venus may have had a moon in the distant past, which collided with another object and then impacted Venus.
♁ Earth Moons = 1
Earth also has several quasi-satellites - asteroids 2020 CD3 and 2020 HO3 being the closest with the most stable temporary orbits.
♂ Mars Moons = 2
Both moons of Mars may be captured asteroids, and can be viewed in small (4-inch) telescopes.
- ASTEROID BELT REGION -
⚳ Dwarf Ceres Moons = 0
Ceres is the only dwarf planet located in the asteroid belt and has no moons surprisingly. A number of smaller asteroids (also called minor planets) do have moons, but they are all too faint to see in any amateur telescope. Notable asteroids with moons include:
Sylvia with 2 moons Romulus & Remus; Eugenia with 2 moons Petit-Prince & S\2004; Daphne with moon Peneius, Kalliope with moon Linus; Minerva with 2 moons Aegis & Gorgoneion; Kleopatra with 2 moons Alexhelios & Cleoselene; and Ida with moon Dactyl.
- OUTER SYSTEM REGION -
♃ Jupiter Moons = 79
Moons of Jupiter are listed in order of size. The first 4 moons listed, the Galilean moons, are viewable naked eye under dark skies, while Amalthea can be be viewed in a 8-10-inch telescope.
♄ Saturn Moons = 82
Moons of Saturn are listed in order of size. The first four moons are viewable with good binoculars and the next four moons with a 4- to 8-inch telescope. Saturn also has hundreds to thousands of moonlets embedded in its ring system.
S/2006 S 1
S/2006 S 3
♅ Uranus Moons = 27
Moons of Uranus are listed in order of size. The first 4 moons can be viewed in medium-sized (8- to 10-inch) telescopes.
♆ Neptune Moons = 14
Moons of Neptune are listed in order of size. Triton is viewable using a medium-sized (8-10 inch) telescope. Triton is believed to be a dwarf planet from the Kuiper Belt captured by Neptune.
- KUIPER BELT REGION -
♇ Dwarf Pluto Moons = 5
Moons of Pluto are listed in order of size. Pluto and Charon are considered a binary dwarf planet system. None of the moons are visible in any amateur telescope. Pluto however, at current magnitude 14, is viewable in 10-inch and larger telescopes.
Dwarf Orcus Moons = 1
Dwarf Salacia Moons = 1
Dwarf Haumea Moons = 2
Dwarf Quaoar Moons = 1
Dwarf Makemake Moons = 1
Dwarf Varda Moons = 1
Dwarf Gonggong Moons = 1
Dwarf Eris Moons = 1
- INNER OORT CLOUD REGION -
Planets here are in very elongated orbits that go from the Kuiper Belt out to the inner edge of the Oort Cloud. Several dwarf planets out there are believed to be perturbed by Planet 9, thought to be a mini-Neptune planet at 10X Earth mass. It's existence is highly probable but not yet confirmed. | 0.839055 | 3.215686 |
Awarded Euclid’s exploration track
2020 May 11
The mosaic of the regions that will have been covered by Euclid after its six years of expected lifetime, on a Mollweide projection of the celestial sphere in ecliptic coordinates. Credits: Euclid Consortium/ECSURVThe team at IA that is part of the Euclid consortium survey group: Ismael Tereno, Joćo Dinis, C. Sofia Carvalho, António da Silva.Structural and thermal model of the Euclid Satellite. Credits: ESA–S. CorvajaEuclid STAR 2020 prize. Credits: Vincenzo Cardone (INAF/OAR)
The international role of Instituto de Astrofísica e Ciências do Espaço (IA1
) was once more acknowledged, now within one of the major European Space Agency (ESA
) missions. The consortium of the Euclid2
mission, a space telescope that will probe the dark Universe and is scheduled to be launched in 2022, awarded the Euclid STAR 2020
prize in the Team category to one of the consortium groups with a strong Portuguese and IA participation.
The Euclid Survey Group (ECSURV) is responsible for producing the calendar of the sky mapping to be undertaken by Euclid, with its roughly 40,000 observations. It establishes what region of the sky the telescope will be looking at for each moment of the mission’s lifetime of more than six years3
. The group sees thus recognized their exceptional contribution to the success of the Euclid mission4
. Created in 2012 and with a Portuguese participation since the beginning, it currently includes four IA members, in addition to nine other members from Italy and France.
The planning produced by ECSURV is a fundamental piece for all the science and instrumentation of the telescope, and touches nearly all the components of the mission, states Ismael Tereno
, a researcher of IA and of Faculdade de Ciências da Universidade de Lisboa (Ciências Ulisboa
), and coordinator of the Portuguese team of ECSURV. “Scientists centred on the focus of the mission want to know the progress of the observations and what will be available at each data release,
” Ismael Tereno explains. “Those who will explore the other scientific sides need to know if the surveys will enable those scientific cases. Thus, it is a product with great visibility in the Euclid community.
is responsible for the development of the computer programme that builds the reference survey. Researcher of IA and Ciências Ulisboa and a member of ECSURV, he jumped into this task in 2013, in a team work that at first also involved C. Sofia Carvalho
, researcher of IA and also member of the group. João Dinis says that it has been challenging. “There are a myriad of constrains that the satellite must obey and which limit the observations plan: its movements and turns are limited, and each calibration field must be observed in a specific way. It’s great to have now the recognition of a work that is well done. It gives you a new encouragement.
“The Euclid project is the most ambitious human effort to map the cosmos from space, and will be a reference for many years to come,
” stresses Jarle Brinchmann
, researcher and member of IA’s Executive Board, and coordinator of the Scientific Legacy at the Euclid consortium. “This map will combine data from large surveys already made with ground-based telescopes with exquisite data obtained with Euclid. We will rely on the excellent work done by the surveys team to coordinate and calibrate it all.
The work of the group continues and a new important phase is approaching. In October, they will submit the surveys and calibrations plan to a review by ESA, a special moment, in face of the proximity of the launch date, scheduled for August 2022.
The group was nominated to the Euclid STAR 2020 – Team award by the Euclid consortium community
itself, which gathers more than 1500 members from 14 European countries, United States and Canada. “We have a small participation when compared to those of the main countries, and it is very satisfactory to see that, besides that, it is having a great impact and visibility,
” says Ismael Tereno.
Launched in 2017, these awards, of symbolic nature, acknowledge annually the exceptional contributions to the mission made by members and groups of the consortium. The prizes were announced on 6 May and were also awarded in the categories Student, Junior Engineer, Junior Scientist, Senior Member and Coordination.
“It is with great pride on the whole national team that I see this award happening,
” says António da Silva
, researcher of IA and Ciências ULisboa, member of the Euclid Consortium Board and also member of the surveys group. “For this kind of participation in an European mission, it was essential the support of our institutions and of the funding agencies, FCT and, more recently, PT SPACE.
Contacts Ismael Tereno
- The Instituto de Astrofísica e Ciências do Espaço (Institute of Astrophysics and Space Sciences – IA) is the reference Portuguese research unit in this field, integrating researchers from the University of Lisbon and the University of Porto, and encompasses most of the field’s national scientific output. It was evaluated as "Excellent" in the last evaluation of research and development units undertaken by Fundação para a Ciência e Tecnologia (FCT). IA's activity is funded by national and international funds, including FCT/MCES (UID/FIS/04434/2019).
- The Euclid mission main purpose is to understand why the Universe is expanding at an accelerated pace. Data gathered with this mission will enable the shedding of light on the nature of Dark Energy and Dark Matter.
- The Euclid telescope will complete two types of surveys throughout six years. A wide survey will cover most dark regions in the sky, free of the contamination by light from the Solar System and our galaxy. The study of dark energy will be centred on the analysis of these regions. The deep fields survey, narrower and focused on three smaller and very dark celestial regions, will enable the calibration of the instruments, but also the extension of the mission goals to the study of very distant galaxies.
- In recognition of this award, the Portuguese team of ECSURV express their thanks, in particular, to Yannick Mellier (Euclid Consortium Lead) for his support and for having proposed, in 2011, that the IA team could have the responsibility of implementing the mission surveys, to Roberto Scaramella (Euclid Science Team and ECSURV group leader) and the group colleagues for the coordination and strong collaboration spirit, to David Oliveira (ECSURV ex-member) for his important work in the development of the software during the first year of activity of the Portuguese team, and to Mário João Monteiro (Portuguese delegate at ESA's Science Programme Committee and researcher at IA) and Jarle Brinchmann for their support to the participation of Portugal in the Euclid Consortium.
João DinisAntónio da SilvaC. Sofia CarvalhoJarle Brinchmann Science Communication Group Sérgio Pereira
Ricardo Cardoso Reis João Retrê
(Coordination, Lisboa)Daniel Folha | 0.876097 | 3.009902 |
Rotation of Planets Influences Habitability
There are currently almost 2,000 extrasolar planets known to us, but most are inhospitable gas giants. Thanks to NASA’s Kepler mission, a handful of smaller, rockier planets have been discovered within the habitable zones of their stars that could provide a niche for alien life.
The habitable zone of a star is typically defined as the range from a star where temperatures would allow liquid water to exist on the surface of a planet. At the inner edge of this zone, the star’s blistering heat vaporizes the planet’s water into the atmosphere in a runaway greenhouse effect. At the outer edge of the habitable zone, temperatures are so cold that clouds of carbon dioxide form and the little solar energy that does arrive bounces off the clouds, turning the planet into a frozen wasteland.
However, this concept is rather simple. In reality, many other factors come into play that could affect a planet’s habitability. New research has revealed that the rate at which a planet spins is instrumental in its ability to support life. Not only does rotation control the length of day and night, it can also tug on the winds that blow through the atmosphere and ultimately influence cloud formation.
The paper has been accepted to Astrophysical Journal Letters and a preprint is available online at Arxiv.
Air circulation and rotation rates
The radiation that the Earth receives from the Sun is strongest at the equator. The air in this region is heated until it rises up through the atmosphere and heads towards the poles of the planet where it subsequently cools. This cool air falls through the atmosphere and is ushered back towards the equator. This process of atmospheric circulation is known as a Hadley cell.
If a planet is rotating rapidly, the Hadley cells are confined to low latitudes and they are arranged into different bands that encircle the planet. Clouds become prominent at tropical regions, which are important for reflecting a proportion of the light back into space. However, for a planet in a tighter orbit around its star, the radiation received from the star is much more extreme.
This will decrease the temperature difference between the equator and the poles and ultimately weaken the Hadley cells. The result is fewer clouds at the tropical regions available to protect the planet from the intense heat, and the planet becomes uninhabitable.
If, on the other hand, the planet is a slow rotator, then the Hadley cells can expand to encompass the entire world. This is because the atmospheric circulation is enhanced due to the difference in temperature between the day and night side of the planet. The days and nights are very long, so that the half of the planet that is bathed in light from the star has plenty of time to soak up the Sun. In contrast, the night side of the planet is much cooler, as it has been shaded from the star for some time.
This difference in temperature is large enough to cause the warm air from the day side to flow to the night side, in a similar manner as opening a door on a cold day results in warm air fleeing from a room. The increased circulation causes more clouds to build up over the substellar point, which is the point on the planet where the star would be seen directly overhead, and where radiation is most intense. The clouds over the substellar point then create a shield for the ground below as most of the harmful radiation is reflected away.
The high albedo clouds can allow a planet to remain habitable even at levels of radiation that were previously thought to be too high, so that the inner edge of the habitable zone is pushed much closer to the star.
“Rotation can have a huge effect, and lots of planets that we previously thought were definitely not habitable now can be considered as candidates,” says Dorian Abbot of the University of Chicago, and a co-author on the paper.
Earth in Venus’ orbit
The study used computer simulations to show that a slowly rotating planet with the same atmospheric composition, mass, and radius of the Earth could potentially be habitable even at Venus’ distance from the Sun. Under the typical boundaries of a habitable zone, Venus is situated closer to the Sun than the inner edge of the zone. In the study, the simulated planet received almost twice as much radiation as the actual Earth did, and yet the surface temperature was cool enough for life to thrive due to the shielding clouds.
Despite the slow rotation, Venus itself is actually a scorching hot planet with a atmosphere so dense that it would crush a person on the surface in seconds. This goes to show that just because a planet is rotating slowly does not automatically mean that it is habitable, rather it has the potential to be habitable if the right conditions exist.
For instance, it is possible that Venus used to spin much faster, giving shorter days than it has now. Venus’ atmosphere is enriched with deuterium, which indicates that an ocean might have once been present. Such a rapid rotation rate on a planet so close to the Sun would have led to a runaway greenhouse effect and the loss of the oceans. By the time the rotation of the planet slowed to its current rate the damage was irreversible.
Finding the slow rotators
While it is difficult to measure planetary rotation rates, future observations by the James Webb Space Telescope might be able to measure rotation if the right conditions were present. The James Webb Space Telescope is an infrared telescope due to launch in 2018, and it is capable of measuring the level of heat emitted by exoplanets.
The telescope would be able to measure the heat emitted from any high albedo clouds that are formed over the substellar point. An unusually low temperature at what is expected to be the hottest location on the planet could indicate that the planet is a potentially habitable slow rotator.
“From space, Earth looks like it is between -70 and -50 degrees Celsius over large regions of the western tropical Pacific because of high clouds there, even though the surface is more like 30 degrees Celsius,” says Abbot.
It is also known than many planets that orbit cool M dwarf stars are either tidally locked, meaning that the same side of the planet faces the star all the time, or they are slow rotators.
This research emphasises the importance of looking beyond the traditional habitable zone for planets that could host life, and it turns out that planets we once thought were too hot might actually be just right for life. | 0.84942 | 3.829562 |
There’s no geological artist quite like Earth’s plate tectonics. Thanks to this ongoing operation, we have mountains and oceans, terrifying earthquakes, incandescent volcanic eruptions, and new land being born every single second.
But nothing lasts forever.
Eventually, the mantle will cool to such an extent that this planetwide conveyor belt will grind to a halt. At that point, you can say farewell to the carbon cycle, as well as the constant reshaping and reshuffling of landmasses that have been big drivers of evolution over eons.
Quiming Cheng, a mathematical geoscientist and president of the International Union of Geological Sciences, is the latest to take on the prophetic role of predicting when this bleak day may arrive. He calculates that the shutdown will arrive in about 1.45 billion years. That’s well before the sun is expected to swell into a red giant and consume us in its death throes roughly 5.4 billion years from now. (Here’s why tardigrades may be the only life-forms that survive until the world’s end.)
The study, published this month in Gondwana Research, has provoked controversy, and some experts argue that we can never accurately predict the end of plate tectonics. But scientists largely agree that such an end will arrive one day, putting Earth on a path to a geologic standstill.
So, what will our home world be like when those major planetary processes give up the ghost?
Figuring that out means first understanding how plate tectonics work. Earth was born 4.54 billion years ago in the pyres of the early solar system. Once entirely molten, the heat generated by its formation and radioactive materials in the rock began to escape. As the planet cooled, Earth settled into its current layered structure, with a dense inner iron core, a liquid outer core, and a brittle upper mantle and crust sandwiching the hot, plastic-like rock of the lower mantle.
Anywhere between 600 million and 3.5 billion years ago, slabs made of the crust and upper mantle–collectively known as the lithosphere–became cold and dense enough to be able to sink into the lower mantle, kicking off the era of plate tectonics. The lithosphere became divided into a jigsaw puzzle of plates that are constantly jostling across the planet’s surface, driving geological action above and below the oceans. (Meet the next supercontinent, Pangaea Proxima.)
At mid-ocean ridges, mantle material rises, decompresses, and triggers profuse melting, creating oceanic lithosphere. The colder and denser edges of the slabs help pull this lithospheric plate away from these ridges and down into the depths. They usually dive beneath a less dense oceanic or continental plate in a process known as subduction. This activity generates explosive volcanoes and fresh crust at the surface.
When two continental slabs collide, they buckle, and mountain ranges like the Alps or the Himalaya form. Upwelling mantle plumes can sometimes appear beneath continental or oceanic slabs, and this ever-moving center of melting creates chains of volcanoes.
At some point, though, the mantle will cool to such an extent that the slabs can no longer sink into it, and several studies have attempted to predict when this will transpire.
Cheng’s new paper uses mathematical models to estimate how fast the mantle is cooling, based on what we know about the intensity of the planet’s magmatic activity from three billion years ago to now. That, he says, gives us a first-order estimate of when plate tectonics will end.
On the Path to Stillness
Regardless of the precision of this figure, plate tectonics will inevitably perish, says Ken Hudnut, a research geophysicist working with the United States Geological Survey. When that day arrives, it “may well be the end of the world as we know it.”
Earth would likely enter a single lid regime, a completed jigsaw of titanic slabs that will no longer drift or sink. Mountain building will stop, but Earth will still have an atmosphere, so erosion by wind and waves will shave down the mighty peaks to hilly plateaus. Eventually, much of the flattened continents will be underwater.
Subduction zones will no longer exist, so while earthquakes will still happen every now and then, truly earthshattering events above magnitude 7 or so will be consigned to history. At the same time, much of the world’s explosive volcanism would be extinguished—although volcanoes would not be entirely snuffed out.
Mars, a world of failed plate tectonics, did manage to forge some impressive volcanic features, including Olympus Mons, the largest volcano in the solar system. Without moving plates, a long-lived upwelling mantle plume focused plenty of crustal melting on that one single spot.
While the mantle of future Earth remains warm enough to convect and partially melt, we would get similar but scattered stationary hot spots of plume-driven volcanism. We would never get anything as large as Olympus Mons on Earth, as our gravitational field is too strong, and anything that massive and tall would simply sink into the crust. Instead, our voluminous volcanoes would be flatter and far more spread out.
And as happens today, parts of the lower lithosphere would continue to peel off and fall into particularly hot parts of the mantle. This would cause mantle material to rise in its place, pushing up the crust and forming isolated mountain ranges and associated basins. This activity would cause minor earthquakes and maybe even additional pockets of volcanism.
“These are the processes that shape Venus' surface,” says Robert Stern, a plate tectonics expert at the University of Texas at Dallas, referring to another world without fully-functioning plate tectonics. But eventually, as cooling continues, those mechanisms will also cease to be, and the planet’s final volcanic lights will be snuffed out. The mantle will be relatively frigid, and Earth will “become a dead planet, like Mercury,” he says.
Perhaps just before it does, Earth’s liquid core will cool enough to end convection, causing the planet’s protective magnetic field to fail. The sun’s stream of energetic particles will strip away our atmosphere, and its expansion will boil away the oceans.
“There is not a lot to look forward to after plate tectonics’ demise,” Hudnut says. The planet will just keep getting flatter and more boring, he predicts, until “Earth splashes into what’s left of the sun.”
Prophets of Plate Tectonics
Other researchers have come up with different plate tectonic death dates. One 2016 study used extremely detailed but simplified computer simulations to put the end date at five billion years, roughly around the time of the sun’s demise.
Another 2008 paper used evidence of past plate tectonic activity to suggest that plate tectonics are intermittent. Its authors predict that the next major pause will take place 350 million years from now, when the Pacific Ocean closes and its many subduction zones deactivate.
“The question is a good one, and yes, it will end eventually,” says Stern. However, he fundamentally disagrees with the new study’s reasoning. “I don't believe any estimated time of death for plate tectonics,” he says.
Christopher Scotese, an emeritus plate tectonics specialist at the University of Texas at Arlington, suggests that the paper shouldn’t have focused on mantle cooling. Instead, it should have based its efforts on the slab pull mechanism, because “slab pull rules.”
Instead of a gradual slowdown, Scotese predicts that plate tectonics will be invigorated during the next one to two billion years, before the conveyor belt ends. He reasons that as the mantle heat flow diminishes, the slabs will become extremely cool and dense, allowing them to subduct faster.
Hudnut notes that predicting any future geophysical events is, even in the short term, “challenging beyond current human capabilities.” Despite this, he emphasizes that it’s good to think ahead. And while none of the predictive papers are perfect, they do highlight the complexity of the subject matter and where there are intriguing gaps in our knowledge of how our own home planet operates.
The wildly differing models “help clarify our ideas about why plate tectonics happen in the first place,” Scotese says. “There may be things we figure out about the future that can be applied to the past.” | 0.840147 | 3.121885 |
[an error occurred while processing this directive]
Planetary scientist Dr Andrew Prentice can't wait to find out what NASA's New Horizons spacecraft will tell us about Pluto.
As NASA's New Horizons spacecraft speeds towards humanity's historic first encounter with the frozen world of Pluto, over three billion kilometres away planetary scientist Dr Andrew Prentice sits quietly in his office dreaming of the upcoming encounter.
"It's still more than two years away, but it will provide us with such a wealth of new data to examine," says Prentice.
The 60-something lecturer who is now semi-retired after clocking up over 40 years on the job, was recently awarded the Vice Chancellors' Medal for Teaching Excellence at Melbourne's Monash University.
But that doesn't mean he's slowing down.
The Oxford University trained astronomer is still actively researching and sees New Horizons as more than a vehicle for exploring far-off worlds.
"It's a tool that will allow us to test predictions relating to ideas about how the solar system formed," says Prentice, who has made several predictions about our solar system that have been proven correct by NASA missions.
Launched in 2006, New Horizons is now 3.4 billion kilometres away and flying towards the orbit of Neptune, the most distant planet in the solar system.
But it still has another 1.3 billion kilometres to go before reaching Pluto and the Kuiper belt, a place of dark frozen worlds, cometary bodies and icy debris left over from the formation of the solar system 4.6 billion years ago.
^ to top
New Horizons is one of the fastest spacecraft ever built, travelling at over 55,000 kilometres an hour, to reach Pluto before the plutonian winter.
Its historic voyage has already taken it beyond the red deserts of Mars, over the stormy cloud tops of Jupiter, around its moons, and past the orbits of Saturn and Uranus.
It's a neighbourhood Prentice knows well, having successfully predicted the location of a family of new moons in orbit around Neptune in 1989.
"That was possibly my biggest triumph," says Prentice.
"We did the calculations and they showed up right on cue where they should be."
His calculations about the ringed world of Saturn and it's many moons have also proven remarkably accurate.
"Titan is huge, it's bigger than the planet Mercury and my data indicates it would have originally formed independently as a planet only to be later captured by Saturn's gravity," says Prentice.
If his hypothesis is correct, Prentice says Titan should have a slightly oblate structure.
"Well, Titan did turn out to be oblate, and that could only happen if it formed in a free orbit as I predicted," says Prentice.
"I don't want you to think we have all the answers, we still have a lot of work to do which is why New Horizons will be so important."
^ to top
When it reaches Pluto in 2015, New Horizons will spend five months exploring the dwarf planet and its five-known moons.
It will make its closest approach to Pluto and its largest moon Charon, on 14 July, undertaking hundreds of scientific observations with its onboard instruments, shedding new light on these distant worlds.
According to calculations Prentice made 20 years ago, Pluto and Charon were once a single rocky body covered in a mix of water ice, dry ice and methane ice. But this proto-Pluto object may have spun so fast that the rock and ice separated, flinging the icy outer mantle into orbit to create Charon.
"Charon today, is thus predicted to be a layered ball of dry ice, water ice and methane ices," says Prentice.
He predicts that both Charon and Pluto — which has a rock-graphite core and icy mantle — will be "quite smooth and nearly crater-free, consistent with worlds that once had deep outer liquid mantles."
On the other hand, the four distant moonlets — thought to be icy asteroids that were captured by the Pluto-Charon system — will be craggy, heavily cratered and irregular in shape, he says.
"In addition, Pluto and Charon are expected to be brighter in appearance than the outer moons, whose surfaces are rendered grey and dull through their graphitic component."
While waiting to see if his predictions are correct, Prentice is keeping busy.
"I've been lucky enough to have teamed up with NASA and been involved with many of their planetary missions," he says.
"It's not good to have too many irons in the fire at one time."
"But last year I was working on Cassini with Titan, Mercury which is being visited by Messenger, and the asteroid Vesta which was being studied by the Dawn spacecraft and is now on its way to another asteroid Ceres".
"Then there's all the exciting new data that will be coming out of Mars from the new rover Curiosity," say Prentice
"And the new discoveries lurking at the edge of the solar system, all these new Kuiper Belt objects and what's caused them."
"There's a lot still to do."
Dr Andrew Prentice is a planetary mathematician at Monash University. He is regarded as one of the world's experts on the formation of our solar system. He has made several accurate predictions about our solar system that have been confirmed by NASA. He spoke to Stuart Gary.
^ to top
Published 03 December 2012[an error occurred while processing this directive] | 0.89425 | 3.60323 |
Space tourism will be a reality within the next 20 years -- or sooner. Passenger spaceships will take you on a trip to the moon, around the Earth's orbit -- or beyond. But getting there is only half the fun, according to a company called Orbital Outfitters. Founded by ex-NASA surgeon Jonathan Clark and businessman Rick Tumlinson, O.O. has invented the most extreme sport ever, as well as the first ever space sport: space diving. This will entail skydiving from high above the Earth's atmosphere all the way back down to the surface.
The company is working to develop the necessary equipment that would make a planetary dive possible (and also safe), aiming for an open-for-business date of ten years from now. The company's first major hurdle (which they had hoped to demonstrate in 2009) is to break the current world skydiving record -- 108,200 feet (31,333 meters) by Col. Joe Kittinger in 1960 -- with a dive of 120,000 feet (36,576 meters). Their next big goal would be to attempt a 60-mile (96.5-kilometer), suborbital dive; but their ultimate aim is a dive from orbit.
Here's how it would work: A space-diver launches into space, harnessed into a holding area on the open deck of a passenger rocket wearing a state-of-the-art spacesuit. Normally, skydivers undo their harnesses and hurl themselves out of an open plane at around 30,000 feet (9,144 meters). The space-diver would hurtle into the dark expanse of space at an altitude of 150 miles (241.4 kilometers). For comparison's sake, that's like jumping from Los Angeles and ending up in San Diego.
For the next seven minutes, the diver free-falls at speeds of up to 2,500 miles per hour (4,023 kilometers per hour). Once that threshold is reached, the diver's specially designed suit discharges a drogue chute (a parachute designed to slow the thing that's falling) in order to stabilize descent and fight the vacuum-like effects of space upon re-entry into the Earth's atmosphere. At about 3,000 feet (914.4 meters) above the ground, when the inner atmosphere is reached, the falling speed drops to a relatively slow 120 miles per hour (193.1 kilometers per hour). Then, a conventional parachute opens, and the space traveler safely floats down to the ground.
In other words, the space diver is like a meteor hurtling through space and into Earth's atmosphere, except that most meteors burn up and break apart upon entry. That happening to a human being would be a major deterrent against the sport, but Jonathan Clark theorizes that it might not be a concern. He believes that proper protection, such as thermal coatings, a decent oxygen supply and an aerodynamic heat shield, would protect the diver. He also believes that the human body is too small to bust apart on re-entry, as a meteor would [source: Popsci]. | 0.869782 | 3.248132 |
Earth-like planets may be common in the universe, a new University of California, Los Angeles (UCLA) study implies. The team of astrophysicists and geochemists presents new evidence that the Earth is not unique.
The scientists, led by Alexandra Doyle, a UCLA graduate student of geochemistry and astrochemistry, developed a new method to analyse in detail the geochemistry of planets outside of our solar system.
Doyle did so by analysing the elements in rocks from asteroids or rocky planet fragments that orbited six white dwarf stars.
Edward Young, UCLA professor of geochemistry and cosmochemistry, added, "We have just raised the probability that many rocky planets are like the Earth, and there’s a very large number of rocky planets in the universe."
White dwarf stars are dense, burned-out remnants of normal stars. Their strong gravitational pull causes heavy elements like carbon, oxygen and nitrogen to sink rapidly into their interiors, where the heavy elements cannot be detected by telescopes.
The closest white dwarf star Doyle studied is about 200 light years from Earth and the farthest is 665 light years away.
Doyle expanded on the importance of this, saying, "By observing these white dwarfs and the elements present in their atmosphere, we are observing the elements that are in the body that orbited the white dwarf."
The white dwarf’s large gravitational pull shreds the asteroid or planet fragment that is orbiting it, and the material falls onto the white dwarf, she said.
"Observing a white dwarf is like doing an autopsy on the contents of what it has gobbled in its solar system," Doyle added.
When iron is oxidised, it shares its electrons with oxygen, forming a chemical bond between them, Young said.
"This is called oxidation, and you can see it when metal turns into rust," he said. "Oxygen steals electrons from iron, producing iron oxide rather than iron metal. We measured the amount of iron that got oxidised in these rocks that hit the white dwarf. We studied how much the metal rusts."
Rocks from the Earth, Mars and elsewhere in our solar system are similar in their chemical composition and contain a surprisingly high level of oxidised iron, Young said.
The researchers said the oxidation of a rocky planet has a significant effect on its atmosphere, its core and the kind of rocks it makes on its surface.
Until now, scientists have not known in any detail whether the chemistry of rocky exoplanets is similar to or very different from that of the Earth.
How similar are the rocks the UCLA team analysed to rocks from the Earth and Mars?
The researchers studied the six most common elements in rock: iron, oxygen, silicon, magnesium, calcium and aluminium. They used mathematical calculations and formulas because scientists are unable to study actual rocks from white dwarfs.
"We can determine the geochemistry of these rocks mathematically and compare these calculations with rocks that we do have from Earth and Mars," said Doyle, whose background is in geology and mathematics.
Receive the latest developments and updates on Australia’s space industry direct to your inbox. Subscribe today to Space Connect here. | 0.857832 | 3.900816 |
Popular Science Monthly/Volume 66/February 1905/Galileo II
U. S. MILITARY ACADEMY, WEST POINT, N. Y.
Galileo in the Sidereus Nuncius (1610) gives this account of the invention of the telescope:
On the title page of his book the telescope is described as 'lately invented by him.' This claim Galileo does not make, but in subsequent years it was charged by his enemies that he claimed credit not his due, and the charge perpetually reappears. The amazing discoveries of this memorable year are enumerated on the title page in question.
The surface of the moon was covered with brilliant and dark areas as the peacock's tail with spots. Perhaps the moon has an atmosphere, he says. The heights of lunar mountains can be fixed by measuring their shadows. The ashy-light of the moon ('old moon in the new moon's arms') is perhaps caused by a lunar twilight. He gives Leonardo da Vinci's explanation also—the true one—that it is caused by earth-light reflected to the moon and back to us. The stars appear as points of light, the planets as small discs. The telescope brings countless new stars to light. In the belt and sword of Orion he sees eighty stars where only seven were known before; in the Pleiades forty instead of six or seven. The Milky Way is a multitude of faint stars clustered together. The nebulæ of Orion and Praesepe are formed of stars. His discovery of the moons of Jupiter dates from January 7, 1610, when three of them were seen. They describe circular orbits about their planet. Jupiter, like each of the planets, has an atmosphere, he says. His telescope was not perfect enough to show this. It is a deduction from analogy.
New discoveries soon followed in respect to Saturn (Dec., 1610) and Venus (Jan., 1611), and they were announced in anagrams as follows:
Altissimvm planetam tergeminvm observavi.
(I have observed the highest planet—Saturn—to be tri-form.)
Hæc immatura à me jam feustra leguntur, O. Y.
Cynthia figuras aemulatur mater amorum.
(The mother of the loves—Venus—emulates the figure of Cynthia—the Moon.)
The latter discovery was of capital importance. If the planet Venus revolved about the sun as Copernicus had said, it must show phases like the moon. The phases, invisible to Copernicus, were revealed by the telescope. They occurred at the precise times required to demonstrate the truth of his theory. It was now no longer a theory. It was proved. From this moment no competent witness could doubt the truth of the Copernican system—Galileo less than any one.
An opportunity unique in the history of the world was presented to Galileo and he utilized it to the full. He went from triumph to triumph. The phases of Venus, the mountains of the moon, the constitution of the Milky Way, the tricorporate figure of Saturn, the solar spots, the moons of Jupiter, were death-blows to the systems of Aristotle and of Ptolemy, and were skilfully utilized to establish the system of Copernicus. That system rests, for us, not on the telescopic discoveries of Galileo, but on the working out of its details by Kepler and Newton. To the Italians of Galileo's day Kepler was all but unknown; it is even doubtful whether Galileo appreciated Kepler's splendid discoveries; it is, at any rate, certain that he never publicly mentioned them with praise.
The mere fact that the number of planets and satellites was increased by Galileo's telescope from seven to eleven was another blow to ancient superstitions. Seven was a mystic and magical number. It had relations even to Christianity, so his contemporaries thought. The seven golden candlesticks of Revelations were the seven planets. We can form some idea of the hold of certain magical numbers on the imaginations of our ancestors by remembering that when Huyghens discovered a satellite to Saturn—thus raising the number of celestial bodies to twelve—he looked no more, ‘because twelve was universally admitted to be a perfect number.’ There were six planets and six satellites and he ventured to predict that no more would be discovered. Huyghens died in the year 1695. He was the foremost man of science on the continent of Europe.
In 1610 Galileo had seen Saturn ‘tricorporate’—in December, 1612, he writes:
The explanation of the disappearance of the ansæ of Saturn's ring was not given until 1656 (by Huyghens). Galileo's telescope was not sufficiently perfect and he died without solving what was a mere riddle to him.
The spots on the sun were first seen by Galileo, though they were first described by others (Fabritius, Schemer). In April, 1611, Galileo exhibited them at Rome to an audience of notabilities. His own observations had convinced him, he says, that the spots were real; that they were not fixed at one part of the solar globe; that they had motions; he sees no reason to doubt that they are attached to the surface of the sun; he believes that they form at the sun's surface, are dissipated and may reappear. By August, 1612, he made other observations which confirmed his earlier conjectures. Their motions prove that the sun is spherical and that it turns on an axis. He notes also that the spots all lie within certain special zones of latitude. He observes the sun by projection—by receiving its image on a sheet of cardboard. Certain large spots can be seen by the naked eye, but by an inveterate prejudice that the heavenly bodies are incorruptible, they have not been remarked; to the shame of astronomers, he says, such appearances have previously been taken for Mercury in transit over the solar disc.
Galileo's discoveries were received with incredulity by the wisest men of Italy. The warm-hearted Kepler (April, 1610) was the first to recognize ‘the divinity of his genius.’ Little by little they made their way as Galileo demonstrated them triumphantly to friends and enemies. Arguments of all sorts were brought against them and against the heliocentric theory which they supported.
Since it can be certainly gathered from Scripture that the heavens move above the earth, and since a circular motion requires something fixed around which to move. . . the earth is at the center of the universe. (Polocco, 1644.)
If the earth is a planet, and only one among several planets, it can not be that any such great things have been done especially for it as the Christian doctrine teaches. If there are other planets, since God makes nothing in vain, they must be inhabited; but how can their inhabitants be descended from Adam? How can they trace back their origin to Noah's ark? How can they have been redeemed by the Savior?
The last paragraph is probably an answer to Galileo's opinion (December, 1612) that the moon and planets may be inhabited, though by creatures different from ourselves. Galileo writes to Kepler (August, 1610):
While Galileo was teaching the elements of Euclid at Padua his colleague, Cremonini, was expounding Aristotle's de Cœlo. It was Cremonini who refused to look at the newly discovered satellites of Jupiter through the telescope, alleging as a reason that their existence was quite contrary to Aristotle's philosophy. It was the same Cremonini who, in 1619, with a dignity and firmness that must be sincerely admired, flatly refused to change the substance of his university lectures at the demand of the Grand Inquisitor of Padua. His duty was to expound the words of Aristotle as he found them, he said; he declined to teach as Aristotle's any doctrine that he did not sincerely believe to be the master's. Let this manly stand be counted off against his refusal to be convinced against authority. He is reputed to have been the last scholastic. When he died, in 1631, there was no one to take his place. The times had changed. We are accustomed to attribute all the merit of the change to Galileo, whose career so brilliantly represents what was best in the new scientific spirit. It is impossible to declare what the movement of the world would have been had Galileo never lived. It would, perhaps, have been much the same. A company of less brilliant men would, perhaps, have done Galileo's work, taking a century for the task. Scholasticism was already moribund; the telescope was invented; the time was ripe; Kepler had already discovered his great laws of planetary motion; who can doubt that scholars would have arisen to fill the opening opportunity?
Gradually the fame of Galileo rose to a great height. He became the best known man in Europe. His lecture rooms were crowded. At Easter, 1610, he showed the Medicean stars to Cosmo II in Florence, and in May he writes a letter describing the work that he has projected—treatises on the constitution of the world, on mechanical motion, on sound, color, vision, tides, fortification, tactics, artillery, sieges, surveying, etc. This letter soon brought an offer from the Grand Duke to appoint Galileo first philosopher and mathematician at the University of Pisa at a salary of 1,000 scudi. He is not to be obliged to reside at Pisa—and in fact his duties were usually performed by substitutes.
In July, 1610, Galileo left the service of Venice for that of Florence. It was a sad exchange for him. Venice was the only state in Italy that dared to stand up against the power of Rome. There were weighty reasons of state why the Duke of Florence could not do so. The Jesuits had been banished from the soil of Venice (1606) ‘for ever.’ They were all powerful in Rome and in Florence. It is evident from letters of this time that Galileo's desertion of Padua produced an unfavorable impression of self-seeking even among his friends.
Galileo's visit to Rome in March, 1611, was a veritable triumph for him. His expenses were paid by the court, he was lodged with the Tuscan ambassador, and received with the greatest honor by the Pope (Paul V.) and the cardinals, including Cardinal Barberini, the future Pope Urban VIII. To them he showed his discoveries. They were convinced and interested. At the request of Cardinal Robert Bellarmine, four learned men of the Roman College (Clavius among them) reported on what they had seen through the telescope and fully confirmed his observations. This report is of great importance, since it was, in effect, a sanction by the Church itself. Galileo was received a member of the Accademia dei Lincei, and its president, Prince Cesi, became his lifelong friend. The Cardinal del Monte writes to the Grand Duke of Florence (May 31, 1611) that Galileo had given great satisfaction: ‘Were we still living under the ancient republic of Rome I verily believe there would have been a column on the capitol erected in his honor.’ Galileo was at the top of the wave of fortune to all appearance. At this very moment, however, Cremonini's trial was going on before the Roman Inquisition and on the records is an inquiry whether Cremonini and Galileo were in any relation with each other. He was already suspected of heresy. His friendship would, even then, have been prejudicial. By 1613 Galileo was aware that there was a league of his Florentine enemies against him. In a letter to Prince Cesi he makes light of it. ‘I laugh at it,’ he says, but it was none the less serious. It was based on religious scruples, but stirred to action by bitter personal animosities.
Brilliant successes, like those of Galileo, raise up an army of enemies. He was haughty with his own. Sure of his talents, his fortune and his powerful patrons in church and state, he had no managements for any one. ‘The wind is fair: now is the time to take in sail,’ is a maxim that he would have scorned. Of Aristotle's virtues he practised magnificence, not prudence. His colleagues in the universities were mostly Aristotelians. The heretical and Arab Aristotle had been banished; the Greek Aristotle reigned supreme. Galileo handled his opponents harshly. He was proud; he had a right to be. He was haughty; it led to his fall. When certain chosen astronomers of Italy were asked in 1615 by the Holy Office to report on his system, the report was adverse. Science and pseudo-science were in conflict and the latter won. The Aristotelianism of the universities was bound closely to that of the church. In attacking the orthodox Aristotle, Galileo attacked—or was supposed to have attacked—orthodoxy itself. His enemies were vanquished in philosophy; they dragged in texts of scripture to support the weakness of their science. Galileo met them on this ground also, which was a fatal error. He was no more competent to discuss texts of scripture than they to decide upon points of science.
Father Castelli, an ardent friend of Galileo's, had been appointed to be professor of mathematics at Pisa (1613). At a dinner at the Ducal Palace (December, 1613) the conversation turned on astronomical matters. Did the Medicean stars really exist? asked the Dowager Duchess Christine. The professor of physics in the university reluctantly admitted that they did—that he had seen them. Castelli then praised Galileo's splendid discovery. The professor whispered something to the duchess to insinuate that while the discoveries might be true, the conclusion in favor of the Copernican theory was certainly contrary to scripture. Castelli was called upon to reply and made a brilliant answer. The Grand Duke and most of those present were convinced. Castelli reports all this to Galileo, and Galileo writes in reply (December 21, 1613) a long and eloquent letter on the subject. The original of this letter was never found, although the Inquisition made diligent search for it. Many authentic copies were circulated, however. The question of the place of the Bible in scientific questions is discussed. Galileo is a good Catholic; the scriptures can not lie or err, he says. But the expositors are fallible. They will fall into error, nay into heresy, if they interpret Holy Writ literally. Both scriptures and external nature owe their origin to the Divine Word.
This noble declaration of the independence of man's reason, written in 1613, marks the highest insight yet reached by the human spirit in this regard. It is the greatest product of Galileo's philosophical genius. It was written in haste, he says, yet its form is perfect and convincing. It is the weighty expression of convictions felt, pondered over and matured. It precisely expresses the attitude of the generations that followed Darwin. No considerable body of men ever held it before that day. It delighted Castelli and a few of the more enlightened of Galileo's circle. His enemies received it with breathless, uncomprehending rage. They sought for flaws in the argument and, unhappily, they had not far to seek. For, not content with these general principles, Galileo went on to explain certain passages of scripture in a fashion that, at the best, was weak and unconvincing, almost disingenuous. The famous passage in Joshua, ‘The sun stood still in the midst of heaven (and hasted not to go down about a whole day)’ is expounded by first suppressing the words in parentheses, next by a wire-drawn argument to prove that Joshua's command was given when the sun was near setting (which disagrees with the words purposely omitted) and that ‘the midst of heaven’ does not mean the place of the sun near noon, but its central place in space among the planets. Hence, says Galileo, this passage actually demonstrates that the sun occupies the center of the world, and refutes Ptolemy. The plain meaning of the verse was distorted by a wilful suppression. It is said in the XIX. Psalm ‘The sun's going forth is from the end of the heaven and his circuit unto the ends of it.’ Galileo explained this to mean that the sun is the nuptial bed, and the bridegroom coming out of his chamber rejoicing is the light of the sun—his rays—not the sun himself. There is not a shade of reason for this arbitrary interpretation. It is not convincing to us; it was abhorrent to his adversaries. Is it any wonder that they loudly proclaimed their intention to protect the words of the Bible from the profane interpretations of laymen? Into the quicksand of theological interpretation Galileo had no call to enter. He should have declined the controversy thrust upon him by his enemies on the simple ground that he was no more fitted to deal with theology than his adversaries with science. This was, however, not his belief, and he accepted their challenge. By so doing he quite nullified the effect of his noble stand upon general principles. Radical and bold as this stand was, he could have maintained it as Cremonini had maintained his own upon a similar issue. At this critical point in his career two roads were open. He recklessly, even presumptuously, chose the wrong one. All his tribulations are the result of this choice. In two letters of February 16 and March 28, 1615, Galileo, writing to Mgr. Dini, regrets that he has been forced to defend his system against religious scruples. In his letter to the Grand Duchess Christine he had said ‘the professors of theology should not assume authority on subjects which they have not studied.’ It never so much as crossed his mind that his own interpretations of the texts of Joshua and the Psalms were like assumptions of authority. In all that follows it must not be forgotten that Galileo had the free choice of leaving the scriptural interpretations alone and of confining himself to science and to philosophical considerations of a general nature. He chose to enter the lists, and there is every reason to believe that he felt sure of winning.
Galileo's case recalls that of Roger Bacon, nearly four centuries earlier. The science of both these men of genius was, in the main and essentially, illuminating and correct. It was, for both of them, opposed by ignorant men who feared that which they could not understand. Both of them went out of the province in which alone they had authority, to enter another in which their contemporaries and fellows were at least as well able to judge as they. Both of them overbore and offended their colleagues by harshness. When they were brought to trial those very colleagues were, in turn, accusers, jurors and judges. A like fate befell both.
The history of Jordano Bruno does not fall within the scope of this article and need be considered only so far as it affected the contemporaries of Galileo, and Galileo himself. The following paragraphs from Draper's ‘Intellectual Development of Europe’ give the views of a writer who is inclined to present Bruno's history in the most favorable light. The foot notes are my own.
In 1612 Galileo writes to Kepler that epicycles and eccentrics are not chimerical; ‘not only are there many motions in eccentrics and epicycles, but there are no other motions.’ This, written three years after Kepler had sent him his Theory of Mars containing the proof of elliptic motion, shows that Galileo had not yet appreciated Kepler's revolutionary discoveries. It is doubtful if he ever did so. He makes no effective use of them in his arguments in favor of the Copernican doctrines.
In the meantime busy enemies were stirring up trouble. The letter to Castelli gave great offense. The Bishop of Fiesole became enraged at Copernicus and was much surprised to learn that he had been dead for eighty years. A Dominican friar, P. Caccini, preached a violent sermon against Galileo (1614) on the text Viri Galilæi quid statis aspicientes in cœlum? Ye men of Galilee, why stand ye gazing up into Heaven? Castelli was advised by the archbishop of Pisa, ‘for his welfare,’ ‘if he wished to escape ruin,’ to abandon the Copernican opinion, because that opinion, besides being an absurdity, was perilous, scandalous, rash, heretical and contrary to scripture.
Another Dominican friar, Lorini, addressed to Cardinal Mellini, president of the Congregation of the Index, a denunciation of ‘the Galileists,’ who hold the doctrine of Copernicus. The congregation accordingly (February, 1619) opened a secret inquiry. A copy of Galileo's letter to Castelli was examined by the consultator of the Holy Office, who pronounced that some phrases of it looked ill at first sight, but that they were capable of interpretation in a good sense, and did not deviate from Catholic doctrine. Caccini was summoned to Rome as a witness and gave evidence, most of which was found to be baseless (November, 1615) and was disregarded.
Early in the same year Galileo had sent copies of the letter to Castelli to friends in Rome. It was greatly admired; but his friends, one and all, strenuously advised him to keep to philosophy and to avoid religious discussion. Prince Cesi expressly warns him to avoid all mention of the Copernican theory, for Cardinal Bellarmine—a good, great and powerful prince of the Church—had told him that in his opinion the theory was heretical and contrary to scripture. Cardinals Barberini, Del Monte and Bellarmine assured Galileo's Roman friends that so long as he confined himself to scientific questions and did not enter into theological interpretations of the Bible he had nothing to fear (August, 1615). All these cardinals were very friendly to Galileo personally, and their friendship stood him in good stead. Their attitude was representative of that of the church. So long as religion was not attacked science was to be free. Any assault on doctrine was to be repelled with vigor, and at all costs. Theological interpretation was not to be permitted to laymen. That was a business reserved by the church.
A Carmelite monk, Foscarini, printed in 1615 a letter on ‘the opinion of the Pythagoreans and of Copernicus of the mobility of the earth and the stability of the sun,’ which was widely read and quickly came to a second edition. The Inquisition was at this time considering Foscarini's book also. Galileo felt that his presence at Rome would be advantageous, and in December, 1615, he set out provided with letters of introduction from the Grand Duke to dignitaries, including the Tuscan ambassador, Guicciardini. He was received with honor as a celebrity. With no great effort he freed himself from all personal difficulties and was able to report (February 6, 1616) that the monk Caccini had made him a formal visit to ask his pardon. On the same day he writes to the Tuscan Secretary of State, Piechena: “My business, so far as it relates to myself, is completed. All the exalted personages who have been conducting it have told me so plainly and in a most obliging manner. . . . So far as this point is concerned, therefore, I might return home without delay.”
He goes on to say that it is proposed to pass judgment upon the Copernician doctrine, and that it is his conviction that he may be of use in the investigation of the matter, on account of his scientific knowledge. Accordingly he proposes to stay. He had been personally vindicated. It was his ardent desire to convert the Romans to the heliocentric theory. This he attempted by giving private lectures in many of the great houses of Rome. His lectures began by stating all the arguments in favor of Ptolemy's system and then went on to demolish them one by one, leaving nothing standing. The lectures were admired by many great folk, and Galileo gained a great personal success for the time. His very success made his well-wishers uneasy and unquiet.
Before Galileo's visit, Fra Paolo Sarpi, professor of philosophy in Venice, distinguished as a champion of free thought and as a friend of Galileo had written: “I hear that Galileo is going to Rome, where he is invited by several Cardinals to explain his new discoveries in the heavens. I fear much that, in such a case, he may develop the reasons that lead him to prefer the doctrine of Copernicus, which will be far from pleasing to the Jesuits and other monks. They have changed what was only a question of physics and astronomy into a theological question, and I foresee, with great vexation, that Galileo, in order to live in peace, and not labeled as heretic and excommunicate, will be constrained to abjure his real sentiments on this matter. A day will come, of that I am almost sure, when enlightened men will deplore the misfortune of Galileo and the injustice done to so great a man. But, pending that day, he must suffer, and he must not complain otherwise than secretly.”
The Tuscan ambassador at Rome was anxious to be rid of Galileo, and in many letters reports that it were well he returned home. He hints that Galileo's course may even bring dangers to Tuscany; he can not ‘approve that we should expose ourselves to such annoyances and dangers without very good reason.’ He insinuates that Cardinal Carlo de Medici may be compromised (March 4, 1616). “Galileo seems disposed to emulate the monks in obstinacy, and to contend with personages who can not be attacked without ruining yourself; we shall soon hear at Florence that he has madly tumbled into some abyss or other.” “The moment is badly chosen to promulgate a philosophical idea.” The Grand Duke, from friendliness to Galileo and in fear of untoward complications, gave instructions for his recall, which were conveyed in a dispatch from the ducal secretary: “You have had enough of monkish persecutions. . . . His Highness fears that your longer tarrying at Rome might involve you in difficulties, and would therefore be glad, as you have so far come honorably out of the affair, if you would not tease the sleeping dog any more, and would return here as soon as possible. For there are rumors flying about which we do not like, and the monks are all powerful.” Galileo set out for Florence on the fourth of April, 1616.
Let us stop for a moment to inquire what the course of affairs would have been if Galileo, whose personal affairs were honorably concluded on February 6, had thereupon returned to Florence. He had renewed old friendships; he had formed new ones; he was esteemed and regarded by the Pope and the most influential of the Cardinals. His enemies in Florence were utterly silenced. His accuser, Caccini, had made the humblest apologies. The Grand Duke and most of the court were his admiring friends. He had every freedom for research if only he would leave the interpretation of scripture to theological experts. ‘Write freely, but keep outside the sacristy’ his friends advised. Why did he remain in Rome? To convert the Congregation of the Index to Copernicanism? This would have been a triumph for science, and a personal triumph as well. The Roman Curia had absolutely no interest in science as such. They were determined that religion should not suffer. Galileo's brilliant lectures were not conceived in the spirit that convinces. He silenced opposition by sarcasm. A second crisis in Galileo's affairs dates from this period (February, March, 1615).
Before this date momentous action had been taken by the Inquisition. On February 19 the Qualificators of the Holy Office had been summoned to give their opinion on two propositions based on Galileo's treatise on the Solar Spots:
I. That the sun is the center of the world and immovable from its place.
II. That the earth is not the center of the world, nor immovable, but moves, and also with a diurnal motion.
The Qualificators were to give their opinion as theological and philosophical experts, and gave it four days afterwards. The astronomer Riccioli declares that the opinions of astronomical experts were also obtained and that the judgment of the Holy Office was based upon them (Delambre: Histoire de l'Astronomie Moderne, i., 680). There is no reason to doubt the assertion. It is exceedingly important as showing that the Inquisition took the best expert advice known to them before action. This significant fact is not mentioned in any of the Warfare-of-Science books, nor even by so careful an historian as Gebler.
The scientific value of the expert astronomical opinion was, of course, exactly nil. It was given, probably, by Aristotelians, personally inimical to Galileo, and fully committed to the Ptolemaic system. It was, equally of course, adverse to Galileo. They may well have quoted the dictum of Tycho Brahe that the system of Copernicus was ‘absurd and contrary to Holy Writ’ since the judgment recites these very words. On March 5, 1616, the ‘De Revolutionibus’ of Copernicus and another work by Diego di Zuniga were suspended by the Congregation of the Index ‘until they be corrected,’ and Foscarini's book was ‘altogether prohibited and condemned’ as well as ‘all other works’ in which the Copernican opinion is taught. On February 25 the Pope directed ‘Cardinal Bellarmine to summon before him the said Galileo and to admonish him to abandon the said opinion; and, in case of his refusal to obey, that the Commissary is to intimate to him, before a notary and witnesses, a command to abstain altogether from teaching or defending this opinion and doctrine, and even from discussing it; and if he do not acquiesce therein, that he is to be imprisoned.’ This document is followed in the Vatican MS. by another: “Friday, the 26th (February, 1616). At the Palace, the usual residence of the Lord Cardinal Bellarmine, the said Galileo, having been summoned and brought before the said Lord Cardinal, was in the presence of the Most Rev'd Michael Angelo Segnezzio, . . . Commissary-General of the Holy Office, by the said Cardinal warned of the error of the aforesaid opinion and admonished to abandon it; and immediately thereafter, before me and before witnesses, the Lord Cardinal Bellarmine being still present, the said Galileo was by the said Commissary commanded and enjoined . . . to relinquish altogether the said opinion . . .; nor henceforth to hold, teach or defend it in any way whatsoever, verbally or in writing; otherwise proceedings would be taken against him in the Holy Office; which injunction the said Galileo acquiesced in and promised to obey. Done at Rome in the place above said, in presence of (two persons named) witnesses.” This annotation was long supposed to have been fabricated in 1632 to meet new conditions then arising. It is, however, entirely genuine. (Gebler's ‘Galileo,’ Appendix III.)
The exact wording is to be noted. Upon this admonition the subsequent fate of Galileo hangs.
(To be continued.)
- Galileo uses the words perspicillum, occhiale, etc., for the instrument. The word telescope was invented to describe the new instrument by Demiscianus at the request of Prince Cesi, president of the Accademia dei Lincei about 1612. The telescope itself was invented by Hans Lippershey.
- Compare the letter of Leonardo da Vinci to the Duke of Milan reciting the labors that he was ready to undertake in his service.
- The letter was subsequently expanded and addressed in its new form to the Grand Duchess Christine (1614).
- Bruno was twice disciplined for ‘open and avowed’ heresy during the thirteen years of his cloister life (1563-1576). He denied the personality of Christ for one thing.
- Toulouse, Paris (1579 and 1585), Oxford (1583), Wittenburg (1587), Prague (1588), Helmstadt (1589), Frankfort (1590), Marburg (1586), Venice (1592), Rome (1593). These dates correct some errors of the text.
- One of them; his pantheistic ideas were, perhaps, his worst heresies in the eyes of his judges. His doctrine that space is infinite filled the pious Kepler, as well as Bruno's Roman judges, with ‘horror.’ Bruno's works were full of opinions that were abhorrent to all religious people of his time. He was inclined to pronounce in favor of polygamy, and he advocated a species of socialism. Religion he made essentially synonymous with intellectual culture, neglecting moral discipline and spiritual feeling.
- Gebler records, however the action of Cardinal Gaetano who, in 1616, applied to Thomas Campanella, a learned Dominican and a friend of Galileo's, for an opinion upon the relation of the Copernican theory of Holy Scripture. Campanella's ‘Apology’ for Galileo was all in his favor and reconciled, in form at least, Copernican science with the Bible. It was overweighed by other reports. It is worth recording that Campanella was not permitted to publish this ‘Apology’ in Italy and was obliged to disavow an edition which appeared at Frankfort. | 0.86991 | 3.305591 |
Dubai: It was 30 years ago today (April 25, 1990), when the Hubble Space Telescope was launched.
Over the last three decades, this eye in the sky has covered more than 6 billion kilometres.
In the proces, the orbiting observatory gave us some of the most amazing photos. But more than the stunning pictures, it has also greatly expand our knowledge of the universe.
So what makes this instrument special? Here's all you need to know about the Hubble Space Telescope.
1: What is it?
As the name suggests, the Hubble Space Telescope is a telescope in orbit. An astronomical tool in the sky. It’s also a spacecraft that can be controlled from the ground.
2: Why is this day special for the Hubble space telescope?
Today, April 25, 2020, the Hubble Space Telescope celebrates 30 years since its launch.
3: How did the idea start?
Hubble's history started from the first proposal of a space telescope by Lyman Spitzer in 1946, During the 1970s, the US National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) began planning for such a project.
Hubble saw five servicing missions in the 1990s and 2000s. During its years in orbit, it made many significant observations and discoveries Hubble.
4: What’s the advantage of using a space-based telescope?
It’s deemed necessary so astronomers could transcend the blurring effects of the earth’s atmosphere and take clearer images of the Universe, the likes of which man has never seen or done before.
Hubble's orbit above the Earth means scientists are able to avoid the distorting atmosphere to make the very high-resolution observations essential in understanding planets, stars and galaxies. Hubble was designed as a high-standard flagship mission and has paved the way for other space-based observatories. Notably it can access the otherwise invisible ultraviolet part of the spectrum, and also has access to areas of the infrared not visible from the ground.
5: How did the Hubble Space Telescope add to our knowledge of the universe?
This telescope-spacecraft, has delved deeper into the early years of the Universe than was ever thought possible.
- It has played a critical part in the discovery that the expansion of the Universe is accelerating.
- It has probed the atmospheres of planets around distant stars.
- It’s been one of the most successful scientific collaborations.
- It's a massive success, with long-term impact on engineering, science and culture.
It has played a critical part in the discovery that the expansion of the Universe is accelerating.
6: Where did it get its name from?
The Hubble Space Telescope is named after Edwin Powell Hubble (1889-1953), one of the great pioneers of modern astronomy.
7: What's in this flying telescope?
At the heart of Hubble are a 2.4-meter primary mirror.
It also has a collection of five science instruments that work across the entire optical spectrum — from infrared, through the visible, to ultraviolet light.
Hubble is equipped with cameras, spectrographs and fine guidance sensors.
8: Can astronauts fix it when something wrong happens?
The observatory was designed to be serviced in space, allowing outdated instruments to be replaced.
This is because the telescope was placed into a low-Earth orbit and uses modular components so that it can be recovered on subsequent missions.
That way, faulty or outdated parts are more easily replaced before being re-released into orbit.
9: How many times has it been serviced?
Five. While the US Space Shuttle program was still active, five missions have repaired, upgraded, and replaced systems on the telescope, including all five of the main instruments.
10: What problems were sorted on the Hubble Space Telescope?
Following its launch however, astronomers quickly realized it wasn’t working correctly. A defect in the mirror resulted in blurry images of object. Astronauts repaired the telescope in 1993 by adding an instrument to correct for the lens aberration — essentially eyeglasses for Hubble.
That was the first of five service missions. Others added new cameras, repaired gyroscopes, and replaced the batteries. The last Hubble service mission was in 2009, prior to the end of Shuttle flights in 2011. Hubble has long outlived its original life span, and it’s due for replacement soon.
11: Where does it get its power from?
The computers and scientific instruments onboard are powered by two 2.45m x 7.56m solar panels.
12: Does it have on-board batteries?
The power generated by the solar panels is also used to charge six nickel-hydrogen batteries that provide power to the spacecraft for about 25 minutes per orbit while the Hubble flies through the Earth's shadow.
13: How do scientists control or manoeuvre it?
The telescope uses an elaborate system of direction controls to improve its stability during observations.
A set of reaction wheels manoeuvres the telescope into place and its position in space is monitored by gyroscopes.
14: How does it “lock” on stars or celestial objects?
The spacecraft uses Fine Guidance Sensors (FGS) to lock onto guide stars. This ensures the extremely high pointing accuracy needed to make very accurate observations.
15: Does the Hubble have any rockets or rocket fuel on board (to control its orientation, or correct its altitude)?
The telescope does not have any rockets on board. Boosting the spacecraft’s orbit can only be done during servicing missions, when the telescope is attached to the Space Shuttle.
But since the Space Shuttle program was discontinued, the Hubble Space Telescope has been on its own.
16: How big is the Hubble Space Telescope?
- Dimensions: Length: 13.2 meters, diameter: 4.2 meters
- Mass: 11,110 kg (at the time of launch)
- In addition, it also has two solar panels, each measuring 2.45 x 7.56 m.
17: How much did it cost to build and launch it?
From its original total cost estimate of about $400 million, the telescope cost about $4.7 billion by the time of its launch.
Hubble's cumulative costs were estimated to be about $10 billion in 2010, 20 years after launch.
$10bEstimated cumulative cost of the Hubble Space Telescope
18: What are the instruments on board the space telescope?
- The Advanced Camera for Surveys (ACS)
- The Wide Field Camera 3 (WFC3)
- The Cosmic Origins Spectrograph (COS)
- The Space Telescope Imaging Spectrograph (STIS)
- The Near Infrared Camera and Multi-Object Spectrometer (NICMOS)
- Fine Guidance Sensors (FGS)
19: How high is it above the sky? What is its orbit?
It hovers over the Earth at approximately 570 km above the ground, inclined at 28.5 degrees to the Equator.
The spacecraft whirls around our planet at 28,000 kilometres an hour and takes 96 minutes to complete one orbit.
20: How many kilometers did it cover so far?
As of spring 2018, the telescope had made more than 163,500 trips around our planet. Those trips correspond to about 6.4 billion kilometres. This April 2020, it would have completed 175,175 trips around the Earth, corresponding to 6.86 billion kilometres.
21: How many gigabytes of data does it generate?
It’s designed as an observatory in space, and gathers data through its various instruments.
The orbiting observatory generates more than 80 gigabytes of data each month.
As of spring 2018, the Hubble Space Telescope has made over 1.5 million observations of more than 43,500 celestial objects.
This year, 30 years’ worth of observations has produced more than 154.93 terabytes of data.
22: What’s the scientific value of the Hubble Space Telescope?
Astronomers using Hubble data have published more than 15,500 scientific papers, making it one of the most productive scientific instruments ever built.
23: Why is it important to look out into space? How far can it see?
It’s important to look out into space, because it allows us to look back into time, close to the moment of the "Big Bang".
24: How does this time-space thing work?
Looking into deep space, billions of lightyears away, gives us insights into the beginning of time and creation, as we know it.
For a simple illustration of how it works, let’s consider the Sun. It is the nearest star to us, about 93 million miles away. Given that distance, it takes about 8.4 minutes for the light of the Sun to reach the earth.
Another example: Proxima Centauri. It’s a small, low-mass star located 4.24 light-years away from the Sun in the southern constellation of Centaurus (from its Latin name means the "nearest [star] of Centaurus". This object was discovered in 1915 by Robert Innes and is the nearest-known star to the Sun.
As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one year (365.25 days). It's a unit of distance, not a unit of time.
The light-year is most often used when expressing distances to stars and other distances on a galactic scale, especially in non-specialist and popular science publications. The unit most commonly used in professional astrometry is the parsec (symbol: pc, about 3.26 light-years; the distance at which one astronomical unit subtends an angle of one second of arc).
25: So what you see is not always what you get?
In astronomical terms, yes.
It means the light we see emitted by Proxima Centauri the moment we look at it on a cloudless night was actually emitted 4.24 years ago. So at that same moment, this star could have moved to another place in the sky, and is no longer where your eyes actually found it.
This is distance tricking the eye.
Here’s a simple video of how Hubble’s ability to look into “deep space” allows us to understand the universe better:
Kilometres per minute: 1,080,000,000
26: What is the farthest star ever seen by Hubble?
Icarus is the farthest star known to man, spotted by Hubble Telescope. Icarus, whose official name is MACS J1149+2223 Lensed Star 1, is the farthest individual star ever seen. It is only visible because it is being magnified by the gravity of a massive galaxy cluster, located about 5 billion light-years from Earth.
As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one year (365.25 days).
The term light-year should not be misinterpreted as a unit of time. Rather, the light-year is most often used when expressing distances to stars and other distances on a galactic scale, especially in non-specialist and popular science publications.
The unit most commonly used in professional astrometry is the parsec ("pc", about 3.26 light-years; the distance at which one astronomical unit subtends an angle of one second of arc).
27: From where is the Hubble being controlled?
The science operations are co-ordinated and conducted by the Space Telescope Science Institute (STScI) in Baltimore and at NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Maryland, USA.
The European Space Agency maintains staff at STScI.
28: So what really makes the Hubble Space Telescope special?
Since its deployment on April 25, 1990, from the payload bay of Space Shuttle Discovery (STS-31), it has been repaired five times. Astronauts had to train on earth for months to do their repair mission in space. When it was launched, astronomers soon found a serious, though not fatal, flaw.
If the Hubble was like all other astronomical instruments lofted into orbit on rockets, it would have had to live out its operational life with that flaw, working at a fraction of peak efficiency. But not Hubble. It’s not like any other space telescope. It was designed to be serviced by astronauts visiting it on the Space Shuttle missions. That’s one reason why it was placed in a low earth orbit, so it could be accessible by the spacewalkers.
29: What’s next after the Hubble Space Telescope, what will replace it?
Its planned successor is the James Webb Space Telescope (JWST) which is scheduled to be launched next year, in March 2021.
30: Would the Hubble be retired eventually?
Probably, but not too soon. It may remain active for years to come.
Keeping Hubble operational would serve two purposes. First, it’s a hedge against potential issues with the Webb Telescope, due for launch in 2021.
Unlike Hubble, Webb will be positioned far away from Earth at the L2 Lagrange point.
That’s a stable orbital location that keeps the Earth between the telescope and the sun. It will be too far away to service effectively, so making sure the Hubble works as a backup could be smart. There will also be limited time on the Webb Telescope for astronomers, so keeping some observations on Hubble could free up time for studies that can only be completed by the more powerful Webb Telescope.
The James Webb Space Telescope (JWST) will launch on an Ariane 5 rocket from French Guiana, then take 30 days to fly a million miles to its permanent home: a Lagrange point, or a gravitationally stable location in space. It will orbit around L2, a spot in space near Earth that lies opposite from the sun.
The Webb telescope will actually orbit the Sun, 1.5 million kilometers (1 million miles) away from the Earth at what is called the second Lagrange point or L2.
By way of comparison, Hubble orbits 550 kilometres (340 mi) above Earth's surface, and the Moon is roughly 400,000 kilometres (250,000 mi) from Earth.
BONUS: If something goes wrong with the Hubble Space Telescope, could it be fixed again?
It's possible. The Hubble is a byproduct of the US Space Shuttle program, which was retired in 2011.
Now, there’s another planned service mission. It’s still in the early stages, but officials think that a private space company could have a vehicle capable of going on a Hubble refurbishment mission.
(Sources: NASA, ESA) | 0.829644 | 3.630683 |
Decades ago when he was in grade school, Christopher Walker stepped outside with his father to see the NASA all-aluminized Echo balloon cross the nighttime sky in Earth’s orbit. That early space spectacle stuck with him, he explains, and unknowingly, was a reflection on his future.
Fast forward several decades. Today, Walker is a professor of Astronomy and an associate professor of Optical Sciences and Electrical Engineering at the University of Arizona in Tucson. Walker’s winning NASA Innovative Advanced Concept (NIAC) Phase II proposal in 2014 investigated the prospect for a 33-foot – suborbital large balloon reflector, or LBR for short.
Scanning the universe
Looking up from a height of some 120,000 feet above the Earth, the sensor-laden LBR can serve as a telescope. Walker’s telescope would consist of an inflatable, half-aluminized spherical reflector deployed within a much larger, carrier stratospheric balloon, about the size of a football field. The outer balloon would double as a protective structure or radome once it is positioned.
Looking down and out, the LBR’s mission could involve Earth remote sensing by carrying out precision looks at the outer edge – or limb – of our planet and studying the atmosphere and greenhouse gases, Walker says. LBR has the capacity to become a hub to support telecommunication activities too, he adds.
But the looking up can clearly provide an astronomical plus. That is, by combining suborbital balloon and telescope technologies, this 33-foot class telescope would be free of roughly 99 percent of the Earth’s atmospheric absorption – perfect for scanning the universe in the far-infrared.
Addressing key unknowns
Walker is a supporter of NIAC and its mission to nurture visionary ideas that could transform future NASA missions with the creation of breakthroughs-radically better or entirely new aerospace concepts-while engaging America’s innovators and entrepreneurs as partners.
“There was no place other than NIAC within NASA to get this off the ground,” Walker admits. “To be honest, at first I was afraid to share the idea with colleagues because it may have sounded so crazy. You need a program within NASA that will actually look at the insane stuff…and NIAC is it.”
Walker’s early NIAC work centered on bringing the LBR concept to a technology readiness level of at least 2 or 3 in maturity, as well as addressing key unknowns, assumptions, risks, and paths forward.
Walker is now hard at work parlaying his NIAC Phase II research into development of a “space-based” version of LBR.
This space-based adaptation is dubbed the TeraHertz Space Telescope (TST). If deployed, the TST would be a telescope for probing the formation and evolution of galaxies over cosmic time.
TST would operate at wavelengths longer than the James Webb Space Telescope (JWST), but due to its size, will have the same or better angular resolution and sensitivity.
The orbital version would shed the outer balloon, just leaving an inflated sphere. “You’re not fighting gravity to make it spherical. It makes it structurally easier to achieve very high tolerance of ‘sphere-isity,'” Walker adds. “In space the sphere can be radiatively cooled to very low temperatures, allowing a better view of the distant universe.”
While buoyed by the TST idea and other possible applications, Walker is quick to add that technology readiness levels remain to be grappled with. Furthermore, he’s fully aware that dollar resources are precious.
“This concept is different from the more traditional, costly approaches of building a telescope for space. It’s a tough road ahead, but we’ll keep pushing forward,” Walker says. “I’m hopeful I can get people motivated and excited about the concept…to think outside the box,” he explains.
Source: Space Daily – spacedaily.com | 0.838092 | 3.198478 |
According to a new study, scientists were able to identify a part of the ancient interstellar dust from which the Solar System, including the Earth, has formed with billions of years ago. This finding is “surviving pre-solar interstellar dust that formed the very building blocks of planets and stars,” as it was described by Hope Ishii of the University of Hawaii at Manoa, the leading author of this study, who hopes to find more about the planetary formation processes.
The dust was collected from the Earth’s upper atmosphere where it was deposited by the comets which whizzed near Earth, over the time. As these comets flew next to our Sun, the dust they released in they fly reached Earth and stocked up in the upper atmosphere from where the scientists collected it and examined it using electron microscopes.
“These interplanetary dust particles survived from the time before the formation of the planetary bodies in the solar system, and provide insight into the chemistry of those ancient building blocks,” explained James Cliston, the study’s co-author.
This ancient interstellar dust might help scientists better understand the planetary formation processes
The dust is actually composed of nanoparticles called GEMS (Glass Embedded with Metal and Sulfides), small glassy materials that do not exceed 1/100th the thickness of a human hair, as reported by USA Today.
According to Hope Ishii, now that the scientists have found the building blocks of the planets in our Solar System, including Earth, they can learn more about the planetary formation processes and about the processes that influenced the evolution of the planets.
Ethan Siegel, a renowned astrophysicist, commented on the importance of the recent discovery stating that this is “an enormous discovery and if the conclusions stand the test of time, we may have just revolutionized our understanding of how all planetary systems come into being.”
The scientists involved in discovering this ancient interstellar dust in the Earth’s atmosphere have published yesterday an initial report on this finding but they will further study the dust to learn more about the planetary formation processes. | 0.858355 | 3.591567 |
In cosmic terms, it was a close call.
A large asteroid capable of wreaking widespread damage if it collided with Earth passed within half a million miles last month, the closest approach of such an object in 50 years, astronomers said today.
The asteroid, a collection of rock and dust half a mile or more in diameter, crossed Earth's orbit undetected March 23 at a distance equal to twice that between Earth and the Moon. Object Will Return
Scientists later calculated that the asteroid, traveling at 46,000 miles an hour, is orbiting the Sun once a year on an elliptical path that regularly brings it back toward Earth.
''It can come this close or closer in the future,'' said Dr. Henry Holt, the Northern Arizona University astrogeologist and astronomer who discovered the object in photographs taken March 31 using the 18-inch Schmidt telescope at the Mount Palomar Observatory in California. ''We'd like to know more about it and when it's coming.''
''Sooner or later, it should collide with the Earth, the Moon or Mars,'' he said in a telephone interview.
Dr. Bevan French, an advanced program scientist with the National Aeronautics and Space Administration, said that if an asteroid this size hit Earth, the impact would be equivalent to the explosion of 20,000 one-megaton hydrogen bombs. A megaton is the explosive power of one million tons of TNT.
Dr. French, an expert on large space objects in the agency's Solar System Exploration Division, said in an interview that such an impact would create a crater between 5 miles and 10 miles wide and perhaps a mile deep.
''Landing in the ocean could be even more destructive,'' he said. ''Depending upon the depth of the water, angle of entry and size and speed of the object, it could create huge waves several hundred meters high.''
Waves that large could sweep over coastal areas, causing widespread destruction, Dr. French said.
Experts say the geological record of Earth shows evidence of more than 100 large objects hitting the planet. Theory About Dinosaurs
Collisions with larger objects are suspected of causing dramatic disturbances in the solar system, although there is no evidence of planets being knocked out of orbit. Uranus rotates on its side, with its equator perpendicular to the plane of its orbit, and scientists believe it is the result of the planet's being tipped off its original axis in a violent collision with another body.
A new theory to explain the origin of Earth's Moon invokes a collision between early Earth and a body the size of Mars, with debris flying out into space and clumping together to form the Moon.
Scientists believe that less massive objects hitting a planet could tip the planet's axis of rotation, causing great disturbances in seasonal weather, but the asteroid observed last month is too small to cause such problems.
A widely discussed theory, supported by geochemical evidence in sediments worldwide, holds that an asteroid or comet about six miles in diameter struck Earth 65 million years ago. The debris and gases from the impact presumably plunged the world into months of darkness, which could account for the mass extinctions of life at that time. The most prominent victims of the hypothetical collision were the dinosaurs.
Most of the solar system's asteroids are orbiting the Sun in a large belt between Mars and Jupiter. It is widely agreed that this belt originally consisted of 50 or so large bodies that eventually crashed into each other and broke up.
The largest asteroid, 620 miles in diameter, is believed to be one of the few survivors of this original group. The remaining fragments show periodic changes in brightness, indicating to astronomers that they are tumbling, irregularly shaped objects.
According to Eugene M. Shoemaker of the United States Geological Survey in Flagstaff, Ariz., one of of the world's leading experts on asteroids, calculations of asteroid orbits and cratering evidence on the Moon indicate that an asteroid whose diameter was greater than 1 kilometer, or 0.6 of a mile, will hit Earth once every 40 million years. Smaller asteroids will hit Earth much more often. Use of Nuclear Warhead
In 1968 the asteroid Icarus came within four million miles of Earth, and this spurred discussions about possibly defending Earth against a collision, said Dr. French. If there were enough warning, he said, people who have studied the issue conclude it might be possible to fire a missile with a nuclear warhead at the asteroid in hopes of deflecting it from Earth.
''This would not be easy,'' Dr. French said, ''but it's possible.
''If something is headed directly toward you on a collision course, it would be very hard to locate, since you wouldn't detect its motion until it was right on you. It would probably appear to be a faint star until it was too late.''
A scientific conference in Colorado in 1982 studied the question of using nuclear weapons against asteroids and concluded that diverting a one-kilometer-wide asteroid would require only half the explosive power of the atomic bomb dropped on Hiroshima.
The recently detected asteroid, designated 1989FC, is one of about 40 fast-moving bodies called Apollo objects whose orbits have been discovered to cross that of Earth.
Dr. George W. Wetherill of the Carnegie Institution of Washington said the objects could be the solid remains of depleted comets, the source of the smaller, but similar, meteors that constantly bombard Earth. It is also possible, he said, that the objects are debris from collisions within the asteroid belt.
The passage of 1989FC was the closest to Earth since 1937, when a slightly larger asteroid called Hermes passed at about the same distance, said Dr. Brian Marsden of the Smithsonian Astrophysical Observatory in Cambridge, Mass. Dr. Marsden catalogues and calculates the orbits of astral objects.
Based on photographs taken by Dr. Holt and a colleague, Norman G. Thomas, and other data, Dr. Marsden calculated that 1989FC takes about a year to go around the Sun and has an orbit that extends past the orbit of Mars and inward past the path of Venus. | 0.834963 | 3.355325 |
PASADENA, Calif. (April 16th, 2003) New distance measurements from faraway galaxies further strengthen the view that the strongest burst of star formation in the universe occurred about two billion years after the Big Bang.
Reporting in the April 17 issue of the journal Nature, California Institute of Technology astronomers Scott Chapman and Andrew Blain, along with their United Kingdom colleagues Ian Smail and Rob Ivison, provide the redshifts of 10 extremely distant galaxies which strongly suggest that the most luminous galaxies ever detected were produced over a rather short period of time. Astronomers have long known that certain galaxies can be seen about a billion years after the Big Bang, but a relatively recent discovery of a type of extremely luminous galaxy—one that is very faint in visible light, but much brighter at longer wavelengths—is the key to the new results.
This type of galaxy was first found in 1997 using a new and much more sensitive camera for observing at submillimeter wavelengths (longer than the wavelengths of visible light that allows us to see, but somewhat shorter than radio waves). The camera was attached to the James Clerk Maxwell Telescope (JCMT), on Mauna Kea in Hawaii.
Submillimeter radiation is produced by warm galactic “dust”—micron-sized solid particles similar to diesel soot that are interspersed between the stars in galaxies. Based on their unusual spectra, experts have thought it possible that these “submillimeter galaxies” could be found even closer in time to the Big Bang.
Because the JCMT cannot see details of the sky that are as fine as details seen by telescopes operating at visible and radio wavelengths, and because the submillimeter galaxies are very faint, researchers have had a hard time determining the precise locations of the submillimeter galaxies and measuring their distances. Without an accurate distance, it is difficult to tell how much energy such galaxies produce; and with no idea of how powerful they are, it is uncertain how important such galaxies are in the universe.
The new results combine the work of several instruments, including the Very Large Array in New Mexico (the world’s most sensitive radio telescope), and one of the 10-meter telescopes at the W. M. Keck Observatory on Mauna Kea, which are the world’s largest optical telescopes. These instruments first pinpointed the position of the submillimeter galaxies, and then measured their distances. Today’s article in Nature reports the first 10 distances obtained.
The Keck telescope found the faint spectral signature of radiation that is emitted, at a single ultraviolet wavelength of 0.1215 micrometers, by hydrogen gas excited by either a large number of hot, young stars or by the energy released as matter spirals into a black hole at the core of a galaxy. The radiation is detected at a longer, redder wavelength, having been Doppler shifted by the rapid expansion of the universe while the light has been traveling to Earth.
All 10 of the submillimeter galaxies that were detected emitted the light that we see today when the universe was less than half its present age. The most distant produced its light only two billion years after the Big Bang (12 billion years ago). Thus, the submillimeter
galaxies are now confirmed to be the most luminous type of galaxies in the universe, several hundred times more luminous than our Milky Way, and 10 trillion times more luminous than the sun.
It is likely that the formation of such extreme objects had to wait for a certain size of a galaxy to grow from an initially almost uniform universe and to become enriched with carbon, silicon, and oxygen from the first stars. The time when the submillimeter galaxies shone brightly can also provide information about how the sizes and makeup of galaxies developed at earlier times.
By detecting these galaxies, the Caltech astronomers have provided an accurate census of the most extreme galaxies in the universe at the peak of their activity and witnessed the most dramatic period of star buildup yet seen in the Milky Way and nearby galaxies. Now that their distances are known accurately, other measurements can be made to investigate the details of their power source, and to find out what galaxies will result when their intense bursts of activity come to an end. | 0.8454 | 4.124891 |
The CHARA (Center for High Angular Resolution Astronomy) array is an optical interferometer, located on Mount Wilson, California. The array consists of six 1-metre (40 in) telescopes operating as an astronomical interferometer. Construction was completed in 2003. CHARA is owned by Georgia State University (GSU).
|Organization||Georgia State University|
|Telescope style||optical telescope|
CHARA’s six telescopes each have a one-meter diameter mirror to reflect light. They are spread across Mount Wilson to increase the angular resolution of the array. Each of the six telescopes provides a different image, to combine it into one image the light from each telescope is transported through vacuum tubes and fed into a single beam, where they are matched up to within one micron. This process is called interferometry, and allows the array to have the same resolving power as a telescope with a 330-meter mirror, and an angular resolution of 200 micro-arcseconds.
In 1984 CHARA was founded, and with financial support from the National Science Foundation (NSF), in 1985 planning for the array began. Construction for the array started on July 13, 1996, and with $6.3 million awarded to GSU by the NSF, and the same amount matched by GSU, going towards the effort. In July 1998, GSU was awarded another $1.5 million by W.M. Keck Foundation, which allowed for a sixth telescope to be added to the previously planned five. With a final gift of $574,000 from David and Lucile Packard Foundation, the funding for the array was completed in October 1998.
After another five years of construction, the CHARA array was completed in 2003. In April of the same year, CHARA was awarded a 3-year grant to support scientific programs at the center, which was renewed in 2006. In 2013 another grant from the NSF worth 3.6 million was given to the Center.
Observatories throughout the world have come to CHARA to test beam combining technology.
On January 15, 2007, the diameter of an exoplanet was measured directly, using CHARA. This was achieved by using the observed angular diameter of the star that the planet orbited, and the already known distance of the star from Earth, to get the diameter of the star. With this they could calculate the diameter of the exoplanet when comparing its size to the star when it passed in front of it. This was the first time the diameter of an exoplanet was directly measured, and returned a value slightly different than that obtained from indirect, more conventional methods.
In 2013 CHARA was used to capture images showing the starspots on Zeta Andromedae, a star 181 light years away. This was the first time that images of starspots on stars other than our Sun has been taken.
CHARA directly observed binary stars, such as Beta Lyrae and Algol. CHARA directly imaged multiple stars, such as Regulus, Rasalhague, Altair, Alderamin and Beta Cassiopeiae to measure the flattened shape of these rapidly rotating stars. Because the equator is further from the center of the star, it will appear cooler than the poles, an effect called gravity darkening.
CHARA holds annual science meetings where recent advancements in science and technologies relevant to the array are discussed. The center also gives access to the array to the astronomical community using the National Optical Astronomy Observatory peer review system for around 50 nights per year. They also have periodic community workshops.
- "About". www.chara.gsu.edu. Retrieved 2017-10-26.
- Hand, Eric (2010-04-07). "Telescope arrays give fine view of stars". Nature News. 464 (7290): 820–821. Bibcode:2010Natur.464..820H. doi:10.1038/464820a. PMID 20376117.
- Baron, Fabien. "History of CHARA". www.chara.gsu.edu. Retrieved 2017-10-26.
- "CHARA Array awarded $3.9 million to provide telescope access to scientists across the nation". EurekAlert!. Retrieved 2017-10-26.
- Leverington, David (2016-11-24). Observatories and Telescopes of Modern Times: Ground-Based Optical and Radio Astronomy Facilities since 1945. Cambridge University Press. ISBN 9781316841815.
- "CHARA measures an exoplanet". Astronomy.com. Retrieved 2017-10-26.
- "'Starspot' Images that Give Insight into Early Sun Captured by University's CHARA Telescope Array - News Hub -". News Hub. 2016-05-04. Retrieved 2017-10-26.
- "Seeing Stars | DiscoverMagazine.com". Discover Magazine. Retrieved 2017-10-26.
- Zhao, M.; Gies, D.; Monnier, J. D.; Thureau, N.; Pedretti, E.; Baron, F.; Merand, A.; ten Brummelaar, T.; McAlister, H.; Ridgway, S. T.; Turner, N. (September 2008). "First Resolved Images of the Eclipsing and Interacting Binary β Lyrae". ApJL. 684 (2): L95. arXiv:0808.0932. Bibcode:2008ApJ...684L..95Z. doi:10.1086/592146. ISSN 0004-637X.
- Baron, F.; Monnier, J. D.; Pedretti, E.; Zhao, M.; Schaefer, G.; Parks, R.; Che, X.; Thureau, N.; ten Brummelaar, T. A.; McAlister, H. A.; Ridgway, S. T. (June 2012). "Imaging the Algol Triple System in the H Band with the CHARA Interferometer". ApJ. 752 (1): 20. Bibcode:2012ApJ...752...20B. doi:10.1088/0004-637X/752/1/20. hdl:2027.42/98563. ISSN 0004-637X.
- "CHARA - Rapid Rotators". chara.gsu.edu. Retrieved 2020-01-24.
- "CHARA - Be Stars". chara.gsu.edu. Retrieved 2020-01-24. | 0.801874 | 3.195769 |
By the time New Horizons travels the remaining 80 million miles and reaches Ultima Thule on January 1, it will be more than 1 billion miles beyond Pluto. “It’s really a puzzle”, New Horizons principal investigator Alan Stern, of the Southwest Research Institute in Boulder, Colorado, said.
NASA’s New Horizons probe is exploring the furthest regions of our Solar System and will be making a very special visit on New Year’s Day 2019, when it will buzz an object unofficially called Ultima Thule, also known as Kuiper Belt object 2014 MU69. Ultima Thule, as we already know, is not spherically shaped. The probe will pass Ultima Thule in a week’s time at 12:33 a. m. EST on January 1, 2019.
When we see those high-resolution images, we’ll know the answer to Ultima’s vexing, first puzzle. Known as 2003 SD220, the massive space rock will pass Earth on December 22nd.
New Horizons will come within about 2,200 miles of Ultima Thule. Onboard the spacecraft, it’s three years older. Scientists have found a mysterious, distant object sitting at the edge of our solar system. The new object appears to suggest that is the case: it has an orbit that seems to suggest there is a Super-Earth wobbling it from afar. The newly discovered object is called 2015 TG387, is probably a small dwarf planet at just 300 km across, and is incredibly far away. But there could be many more of them than we have ever realised, the researchers said.
Now, if Sedna’s orbit was the result of capture during the Solar system’s youth, one might expect other objects to have shared the same fate. The extended observations show TG387’s orbit is even more extreme than Sedna’s. Instead,’ Oumuamua looked like an inactive, dark-red, solid chunk. The observation took a lot of time – it was the longest observation performed by the European Space Agency’s XMM – Newton space telescope, over 20 days in two sessions.
What will be the outcome no-one can say. And the find reinforces the idea that there are likely many more objects like it in our solar system orbiting out of sight. ( This article and its images were originally posted on ScienceAlert August 15, 2018 at 02:25AM. )
While most of these moons orbit Saturn and Jupiter, which are outside the Sun’s habitable zone, that may not be the case in other solar systems, said Stephen Kane, an associate professor of planetary astrophysics and a member of the University of California Riverside’s Alternative Earths Astrobiology Center.
“The image field is extremely rich with background stars, which makes it difficult to detect faint objects”, Hal Weaver, a New Horizons project scientist and LORRI principal investigator, said in a statement. But Dr Kipping said: “Both bodies, however, are considered to be gaseous and therefore unsuitable for life as we know it” .
As such, the existence of Planet Nine has always remained questionable. A new study gives credence to the theory and suggests that a ninth planet might actually exist. However, this too has been deemed impossible, since such an event should have taken place within the past 10 million years, which the scientist say is highly unlikely. It takes the planet 233 days to complete a single orbit around its cool red sun. It is so close that the next generation of telescopes may be able to image it directly, the researchers said. The new discovery of a single, much smaller planet orbiting Barnard’s star is based on a different observational technique called radial velocity. Even so, the size of the newly found planet is just on the edge of what current instruments can detect.
Two other planets had previously been found orbiting Gliese 876, a small red star known as an M dwarf, the most common type of star in the galaxy, but those were Jupiter-size gas giants. The research team believes that the largest near-earth asteroid, 1036. The cloud of dust will be about five million-billion kilograms in mass and about 1600 miles wide.
Image Credit: NASA/Johns Hopkins APL/Steve Gribben | 0.900541 | 3.677073 |
Researchers used the Submillimeter Array at the Harvard-Smithsonian Center for Astrophysics to view star cluster W49A, revealing an intricate network of filaments feeding star-building material inward at speeds of about 4,500 miles per hour (2 km/sec).
Cambridge, Massachusetts – W49A might be one of the best-kept secrets in our galaxy. This star-forming region shines 100 times brighter than the Orion nebula, but is so obscured by dust that very little visible or infrared light escapes.
The Smithsonian’s Submillimeter Array (SMA) has peered through the dusty fog to provide the first clear view of this stellar nursery. The SMA revealed an active site of star formation being fed by streamers of infalling gas.
“We were amazed by all the features we saw in the SMA images,” says lead author Roberto Galván-Madrid, who conducted this research at the Harvard-Smithsonian Center for Astrophysics (CfA) and the European Southern Observatory (ESO).
W49A is located about 36,000 light-years from Earth, on the opposite side of the Milky Way. It represents a nearby example of the sort of vigorous star formation seen in so-called “starburst” galaxies, where stars form 100 times faster than in our galaxy.
The heart of W49A holds a giant yet surprisingly compact star cluster. About 100,000 stars already exist within a space only 10 light-years on a side. In contrast, fewer than 10 stars lie within 10 light-years of our Sun. In a few million years, the giant star cluster in W49A will be almost as crowded as a globular cluster.
The SMA also revealed an intricate network of filaments feeding gas into the center, much like tributaries feed water into mighty rivers on Earth. The gaseous filaments in W49A form three big streamers, which funnel star-building material inward at speeds of about 4,500 miles per hour (2 km/sec).
“Move over, Mississippi!” quips co-author Qizhou Zhang of the CfA.
Being denser than average will help the W49A star cluster to survive. Most star clusters in the galactic disk dissolve rapidly, their stars migrating away from each other under the influence of gravitational tides. This is why none of the Sun’s sibling stars remain nearby. Since it is so compact, the cluster in W49A might remain intact for billions of years.
The Submillimeter Array mapped the molecular gas within W49A in exquisite detail. It showed that central 30 light-years of W49A is several hundred times denser than the average molecular cloud in the Milky Way. In total, the nebula contains about 1 million suns’ worth of gas, mostly molecular hydrogen.
“We suspect that the organized architecture seen in W49A is rather common in massive stellar cluster-formation,” adds co-author Hauyu Baobab Liu of the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan.
The team expects to continue analyzing the SMA data for some time to come.
“It’s a mine of information,” says Galván-Madrid.
Headquartered in Cambridge, Massachusetts, the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.
Publication: R. Galván-Madrid, et al., “MUSCLE W49: A Multi-Scale Continuum and Line Exploration of the Most Luminous Star Formation Region in the Milky Way. I. Data and the Mass Structure of the Giant Molecular Cloud,” 2013, ApJ, 779, 121; doi:10.1088/0004-637X/779/2/121
PDF Copy of the Study: MUSCLE W49 : A Multi-Scale Continuum and Line Exploration of the Most Luminous Star Formation Region in the Milky Way. I. Data and The Mass Structure of the Giant Molecular Cloud
Image: Roberto Galván-Madrid (ESO), Hauyu Baobab Liu (ASIAA, Taiwan), Tzu-Cheng Peng (ESO) | 0.879238 | 3.903673 |
Today I want to talk about electron configuration because I think it is one of the biggest failings of the education system. It is widely accepted in schools that we cannot be taught the full truth about things from day one – and I accept this in full. However what I do not accept is when in order to teach something a misleading version is taught first because the issue with this is if that student does not go on to further studies then they spend the rest of their life in the dark. This in my view is what happens with electron configurations, something I will outline in this post.
You are first taught that electrons orbit in a planetary model in a configuration that goes 2 in the first shell, then 8 in the shell after that and so on and so forth. What I am going to explain now is a simplified version of reality – the version of reality I just explained is beyond even considering how simplified it is. I will however explain towards the end why despite being terribly oversimplified it does work in terms of allowing you to do some Chemistry – this is why it had you so fooled all this time.
The single most important notion when you try to comprehend an electron configuration is the quantum number – there are two which we are going to concern ourselves with in order to understand the configuration and these two are used by both Physicists and Chemists widely. The last two we will state but not explain.
The principle quantum number is the number which is most familiar two you – it is the shell (or orbital) numberings of the electrons orbiting the nucleus which can range from 1 until theoretically infinity – but clearly there are natural limits in terms of the orbitals of the heaviest known elements. So the shell numbering in itself is quite easy – it goes 1 for hydrogen and helium, two for lithium, beryllium, boron carbon… 4 for potassium… 5 for tin… notice anything? Take a look at the periodic table.
What you should see is that the principle quantum number corresponds to the period number. So if you have a periodic table you can very easily tell me the principle quantum number for any element – very good so far. Now when you have you principle quantum number that also allows you do construct quite easily the number of electrons that can be found in that level. The relationship is easy – if we denote the principle quantum number n then the number of electrons that can be found at that particular given level is 2n². So for level 1 we have 2 – which is fine we had that before. And then for level 2 we have 2 x 4 so great the same as before again we have 8. But what about level 3? We have 18. That isn’t 2 and it isn’t 8… it is 18. As we start to go up and up the number starts to get bigger and bigger. Much bigger. So what is going on?
This is where we need our second quantum number. If you only looked at the principle quantum number then trust me the world would not make very much sense because electrons do not occupy shells in the order of 1 then 2 then three. It turns out, within each of these shells are subshells. In fact the number of subshells at each level is very easy to work out too – the number of subshells is equal to the principal quantum number. So shell 1 has no subshells (1 subshell is just the shell itself). Number two has two subshells and so on and so forth. Before we delve any further it is worth quickly stopping and saying what we really mean when we say “shells”.
You may well be familiar with the uncertainty principle? Well if you are not all it basically says is you cannot determine an electrons exact location and velocity at the same time. The basic issue that falls out of this is I cannot tell you exactly where my electrons are. What I can tell you is where they might be. Actually I can do better than this, I can tell you where they will probably be. So what I can show you is a probability distribution of where my electron is most likely to be and it looks a little bit like this.
The above graph is for one given subshell – so what we find is that the probability of finding the electron is greatest at a certain distance from the nucleus. Then we define the space that this subshell occupies as the region where there is a 95% chance of finding my electron – i.e. the region where it probably is. So when people say that electron shells are more like fuzzy clouds this is why – the electrons could in theory be anywhere – the graph is a asymptotic to the x axis, it is just they tend to move within the confines of a certain area of space.
Hopefully none of this is too taxing so far – personally I think it isn’t too difficult to visualise. What we need to consider next is the single most important part. What makes an electron a member of one shell, and not a different shell? Any two electrons have the same negative charge and the same mass and within a given atom are influenced by the same nucleus. So what should make an electron favour certain locations in one subshell but different locations in another? The answer to all of this is energy levels. Each subsell represents a different energy level. Remember that electrons are attracted to the nucleus – they favour positions which are closer to the nucleus with lower energy levels. The only reason that they do not all go into the first subshell is that they cannot fit (this makes sense if you think about it – the subshell occupies a certain amount of space, and each electron is negatively charged so you can only fit a certain number of particles that repel each other into a given region of space.
Okay, I think we are ready to tie this all together. We have the principle quantum number. This is the shell number. For any given shell n, there are n subshells all representing orbitals of different energy levels. Now we give these subshells a quantum number – the azimuthal quantum number. If you are a chemist you will know these as s, p, d, f, g, h etc in that order – and these we will stick with for now. Often in Physics we use different notation but it is actually harder to type on a keyboard. Now if this azimuthal quantum number is ℓ, then the relationship of how many electrons can be in each subshell is;
2(2ℓ + 1)
So it is easy – s can have 2, p can have 6, d can have 14 etc. So you might think the logical order is 1s,2s,2p,3s,3p,3d etc but this is wrong and the reason for that is that electrons prefer naturally the lowest energy levels – and actually 3d is a higher energy level that that which is found with 4s. So the result is that the 4s subshell is formed first. There is a way for simple subshell configurations you can work out the final shell from the periodic table and work backwards – but for now just take this as fact:
So we have the 4s filled here before the 3d and so on and so forth. Are you starting to understand a little bit now why the electrons are viewed more as fuzzy clouds that as strict orbital rings? It really does make much more sense. When you know the number of electrons in an atom (fairly easy to work out) you can write out the electron configuration which looks like this, for the element oxygen:
Now if you remember anything from Chemistry you will remember that this configuration isn’t fully “stable”… what we really mean by this is it isn’t the desired state for oxygen is to complete its outer shell – the p shell which holds up to 6. Now remember I said I would explain why the old 2,8,8 model often works? It is because for the majority of elements the Chemistry is dominated by the outer shells – the p and s shells which together have 8 electrons as a maximum. So when you were saying you needed to complete the 8 electrons, you were in a way flirting with the truth. But because the understanding is too simplistic you cannot fully appreciate what happens with more complex electrons.
Understanding the electron configuration is really everything – there is nothing much more to Chemistry. Why is Oxygen found as O2? Well because it needs two electrons to complete its outermost p-shell and in order to do this it can “share” two electrons (i.e. they can occupy a region of common space) and complete the shells. This is a pure covalent bond with no polar element.
Couple of closing remarks:
- The spin forms another quantum number and is very important in physics. The first subshell of 2 must have electrons of opposite spin.
- There is a further quantum number that determines the magnetism which along with the azimuthal quantum number determines the shape of the orbital.
The shape of the orbital I have displayed below for interest only. How do we know this? VERY HARD vector mathematics which I do not profess to understand. Maybe I will update you with more information when I have taken my final year quantum mechanics module. None the less the shapes are quite beautiful functions in three dimensional space. This is for 1s, 2p, 3d, 4f.
Thanks for reading and being patient with me this month – let’s just say it has been a busy one! | 0.853859 | 3.006037 |
A black hole is a region of spacetime exhibiting gravitational acceleration so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of the region from which no escape is possible is called the event horizon. Although the event horizon has an enormous effect on the fate and circumstances of an object crossing it, no locally detectable features appear to be observed. In many ways, a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, making it essentially impossible to observe.
Only once since I began a twenty year fascination with Einstein's time/light theory have I heard from anyone connected to NASA who dared to address this fact to a sublimely ignorant public. He was hushed up in the slow lane with indifference and a public that couldn't tell you how the world can make it through the next decade without imploding. With a list of almost infinite problems how can we think of getting people out that far, much less plan for the return of our astronauts after 4000 generations of time. Imagine, a frigid, distant shadow-region in the far suburbs of our Solar System, where a myriad of twirling icy objects--some large, some small--orbit our Sun in a mysterious, mesmerizing phantom-like ballet within this eerie and strange swath of darkness. Here, where our Sun is so far away that it hangs suspended in an alien sky of perpetual twilight, looking just like a particularly large star traveling through a sea of smaller stars, is the Kuiper Belt--a mysterious, distant deep-freeze that astronomers are only now first beginning to explore. Makemake is a denizen of this remote region, a dwarf planet that is one of the largest known objects inhabiting the Kuiper Belt, sporting a diameter that is about two-thirds the size of Pluto. In April 2016, a team of astronomers announced that, while peering into the outer limits of our Solar System, NASA's Hubble Space Telescope (HST) discovered a tiny, dark moon orbiting Makemake, which is the second brightest icy dwarf planet--after Pluto--in the Kuiper Belt. The GRAIL mission determined the internal structure of the Moon in great detail for nine months during 2012. Armed with this the new information, GRAIL astronomers were able to redefine the sizes of the largest impact basins on the lunar surface. | 0.879994 | 4.065949 |
A Moon Made Of Lightweight Fluff! Methone is small and oval--and unlike other tiny objects, composed of rock and ice, that scurry around our Solar System. Methone, which was observed up close for the very first time in 2012, is not pockmarked by impacts like other worldlets of its kind. Instead, this strange little moon, is very smooth--it shows not a hill nor an impact crater anywhere on its weirdly smooth surface. This shiny, white, icy egg in Space, residing in a peaceful nest of ice crystals, is an enigma wrapped in a bewildering mystery that some astronomers may have solved. The answer to the bewitching riddle of Methone? It is composed of lightweight fluff! The Ocean Worlds Of Our Solar System. There are more than 100 moons in our Solar System that do their mysterious gravitational dance around the eight major planets belonging to our Sun's family. Most of them are icy and small, containing only tiny quantities of rocky material, and they circle around the quartet of giant gaseous planets that dwell in the outer regions of our Solar System. The four majestic, giant denizens of the outer limits--Jupiter, Saturn, Uranus, and Neptune--are cloaked in blankets of gas, and they are orbited by sparkling, icy moons and moonlets. Of the quartet of relatively small, rocky terrestrial planets--Mercury, Venus, Earth, and Mars--Mercury and Venus are moonless, and Mars is circled by a pathetic duo of tiny and somewhat deformed moons (Phobos and Deimos). The two little moons of Mars are interesting objects, frequently considered to be asteroids that escaped from the Main Asteroid Belt between Mars and Jupiter, only to be snared by the Red Planet's gravitational pull when our Solar System was young. Earth's own beautiful, beguiling, bewitching Moon is the only large one inhabiting the inner kingdom of our Solar System. Titan: Titan, the tormented, hydrocarbon-slashed largest moon of Saturn--and the second largest moon in our Solar System, after Ganymede--could possess a subsurface, salty ocean that may well be as salty as the Dead Sea on Earth. The salty water could begin approximately 31 to 62 miles beneath Titan's icy shell, according to recent estimates. Meanwhile, on Titan's smog enshrouded surface, "life as we do not know it" could swim in alien lakes and rivers that flow with liquid methane and ethane hydrocarbons--instead of water. | 0.80932 | 3.589002 |
Asteroids and comets are often thought of as distinct types of small bodies, but astronomers have discovered an increasing number of “crossovers.” These objects initially appear to be asteroids, and later develop activity, such as tails, that are typical of comets.
The University of Hawaiʻi Asteroid Terrestrial-impact Last Alert System (ATLAS) is now behind the discovery of the first known Jupiter Trojan asteroid to have sprouted a comet-like tail. The Minor Planet Center (MPC) designated the new discovery as 2019 LD2, found near the orbit of Jupiter.
The MPC is the single worldwide location for receipt and distribution of positional measurements of minor planets, comets and outer irregular natural satellites of the major planets. ATLAS is a NASA-funded project using wide-field telescopes to rapidly scan the sky for asteroids that might pose an impact threat to Earth.
Early in June 2019, ATLAS reported what seemed to be a faint asteroid near the orbit of Jupiter. Inspection of ATLAS images taken by collaborators Alan Fitzsimmons and David Young at Queen’s University Belfast revealed its probable cometary nature. Follow-up observations by UH astronomer J.D. Armstrong and student Sidney Moss on June 11 and 13 using the Las Cumbres Observatory global telescope network confirmed the cometary nature of this body.
In July, new ATLAS images caught 2019 LD2 again—now truly looking like a comet, with a faint tail made of dust or gas. The asteroid reappeared in April 2020 during routine ATLAS observations that confirmed it still looked like a comet. Those observations showed that 2019 LD2 has probably been continuously active for almost a year.
Why this asteroid is considered rare
ATLAS has discovered more than 40 comets but what researchers find extraordinary is 2019 LD2’s orbit. The early indication that it was an asteroid near Jupiter’s orbit has now been confirmed through precise measurements from many different observatories. 2019 LD2 is a special kind of asteroid called a Jupiter Trojan, and no object of this type has ever before been seen to spew out dust and gas like a comet. | 0.835718 | 3.672873 |
A group of scientists from Harvard University has shown that it is likely that the size of exoplanets, which are between two and four times the size of the Earth, is due to the fact that water is its main component. This finding would be an important step in the search for life beyond the Solar System as it augurs well for the possible formation of Earth-like planets with water.
This finding is important because, although water has previously been implicit in individual exoplanets, this work concludes that water-rich planets are common.
This work, which will be presented at the Goldschmidt conference in Boston, is a further step in the study of exoplanets, discovered in 1992 and which aroused interest in understanding their composition to determine, among other things, if they are suitable for the development of life.
Professor Sara Seager, a planetary scientist at the Massachusetts Institute of Technology and deputy science director of the mission, said, “It’s amazing to think that the enigmatic medium-sized exoplanets could be water worlds with large amounts of water.
Now, a new evaluation of the data of the exoplanets by the Kepler Space Telescope and the Gaia mission indicates that many of the known planets could contain up to 50% of water, which is much more than 0.02% of the content of water on Earth.
“It was a great surprise to realize that there must be a large number of aquatic worlds,” said Harvard University Senior Researcher Dr. Li Zeng.
Scientists realized that many of the 4,000 confirmed exoplanets or candidates that have been discovered so far can be divided into two categories: those with an average planetary radius of 1.5 with respect to the Earth and those that measure on average 2.5 times the radius of the Earth.
In this sense, a group of international scientists has developed a model of their internal structure after analyzing the exoplanets through measurements of the Gaia satellite of its mass and its radius.
“We have analyzed how mass is related to radium and we have developed a model that could explain the relationship,” Li Zeng explains.
“The model indicates that those exoplanets that have a radius of about 1.5 times the radius of the Earth, tend to be rocky planets (five times the mass of the Earth), while those with a radius of x2.5 the Earth’s radius (with a mass about ten times that of Earth) are probably water worlds, ” continues the doctor.
“This is water, but not a common water like we can find on Earth”
“This is water, but not a common water like we can find on Earth,” says Zeng. ” The surface temperature is expected to be in the range of 200 to 500 degrees Celsius, its surface may be enveloped in an atmosphere dominated by water vapor, with a layer of liquid water underneath.” Going deeper, one would expect to find that This water is transformed into ice due to the high pressure before reaching the solid rocky core. The beauty of the model is that it explains how the composition relates to the known facts about these planets, “the doctor asserted.
Also, the study indicates that about 35% of all known exoplanets that are larger than Earth should be rich in water. Thus, these water worlds were probably formed in a similar way to giant planetary nuclei such as Jupiter, Saturn, Uranus or Neptune, which are found in the Solar System.
The recently launched TESS (Transiting Exoplanet Survey Satellite) mission will find many more exoplanets thanks to terrestrial spectroscopic tracking. The new generation of space telescopes, the so-called James Webb Space Telescope, will be able to characterize the environment of some of the exoplanets, according to Zeng.
In addition, Professor of Planetary Sciences at the Massachusetts Institute of Technology and Deputy Scientific Director of the TESS mission, Sara Seager, explains that it is “incredible” to think that the “enigmatic” exoplanets can contain large amounts of water and that the observations of The atmosphere in the future – of thick vapor atmospheres – can “support or refute the new findings”. | 0.906255 | 3.89259 |
‘Crazy, dynamic, unpredictable’ comet ISON still glowing, but is it still alive?
The unpredictable behavior of the ancient ISON comet has scientists scratching their heads, as the world’s space agencies had to quickly backtrack from their earlier claim that it had been destroyed in its encounter with the sun.
29 November, 2013
The 2km-wide relic has been traveling to meet our star for over a million years. But the “dinosaur bone of solar system formation,” as senior research scientist at Johns Hopkins University, Carey Lisse, dubbed it, did not shine as bright after its slingshot encounter around the sun on Thursday, forcing scientists and stargazers to conclude the celestial body had lost its tail and nucleus.
Karl Battams of NASA wrote on the space agency’s dedicated ISON blog about the confusion that the celestial body has caused.
“After impressing us yesterday, comet ISON faded dramatically overnight and left us with a comet with no apparent nucleus,” Battams said, also mentioning the deluge of calls he and the team had received from reporters, despite not being able to provide them with 100 percent clarity.
“As the comet plunged through the solar atmosphere, and failed to put on a show… we understandably concluded that ISON had succumbed to its passage and died a fiery death. Except it didn't! Well, maybe...,” he continued.
There were conflicting theories about the comet’s fate, but what emerged later in the photographic evidence forced everyone to backtrack.
The assumptions were dictated by the fact that traveling just over a million kilometers above our star’s surface would have melted all the comet’s ice at temperatures of over 2,000 degrees Celsius, while the sun’s magnetic field would have strongly influenced its behavior as well.
But claims of the ISON’s demise were later challenged with photographic evidence, as scientists saw a faint, but still bright glow of what they believe to be a piece of the comet.
Battams then went on to describe “a faint smudge of dust” visible in the images taken after the comet’s apparent exit from behind our star, which showed the faint glow traveling along ISON’s orbit. Admitting this could simply be a speck of dust, hopes were not high. However, the glow did not disappear.
“Now, in the latest LASCO C3 images, we are seeing something beginning to gradually brighten up again. One could almost be forgiven for thinking that there's a comet in the images!”
“We have a whole new set of unknowns, and this ridiculous, crazy, dynamic and unpredictable object continues to amaze, astound and confuse us no end,” Battams finished, asking everyone to be patient with further guess work. He added that if the glow is indeed the comet, we will be seeing it in the night sky in a matter of days.
NASA was not alone in retracting its earlier assessments: the European Space Agency stepped back from its earlier claims of ISON’s end as well.
However, scientists do not wish to make any further predictions as to its future at this point, because the comet could still just as easily stop releasing material and die out, if it indeed has not burned up after encountering the sun’s corona.
- ISON stands for International Scientific Optical Network
- Discovered September 2012 by two amateur Russian astronomers
- Originated in the Oort Cloud, about halfway from the sun to the next star
- Its age is about 4.5 billion years, like our solar system, where it originated
- Studying the comet should help our understanding of planet formation: when comets are destroyed from brushing close to the sun, the resulting vapors give clues of their chemical composition | 0.83167 | 3.066482 |
The Cassini spacecraft perished in a literal blaze of glory on September 15, 2017, when it ended its 13-year study of Saturn by intentionally plunging into the gas giant’s swirling atmosphere. The crash came after a last few months of furious study, during which Cassini performed the Grand Finale — a sensational, death-defying dance that saw the spacecraft dive between the planet and its rings 22 times.
As new perspectives often do, this one revealed a surprise. Previously, planetary scientists had assumed that Saturn’s rings were as old as the solar system itself—about 4.5 billion years old. But cosmic clues hidden deep within the rings caused some Cassini scientists to massively revise this figure. The rings aren’t as old as the solar system, they argued in a paper published this summer in the journal Science. They emerged no more than 100 million years ago, back when dinosaurs roamed Earth.
An explosion of media coverage linking the rings to the age of dinosaurs helped to quickly solidify the new findings in the public’s eye. If you enter the search phrase “how old are Saturn’s rings,” Google returns the answer “100.1 million years.”
Aurélien Crida, a planetary scientist at the Côte d’Azur Observatory, was incredulous at this definitive declaration. “I was a bit pissed off by how it was assessed, that the rings are young and it’s over,” he said.
He and other skeptics have pointed out that there are a lot of potential problems with the argument, from the physics of the ring pollution to the origins of the rings themselves. “The rings look young, but that doesn’t mean they really are young,” said Ryuki Hyodo, a planetary scientist at the Japanese Aerospace Exploration Agency. “There are still some processes that we are not considering.”
In response to the hypothesis, Crida coauthored a commentary for Nature Astronomy, published in September, that presented a litany of uncertainties. The dinosaurian age of the rings is an eye-catching claim, said Crida, but it circumvents an uncomfortable reality: Too many uncertainties exist to permit any firm estimate of the age of the rings. Despite Cassini’s heroics, “we’re not really far ahead of where we were almost 40 years ago,” back when the Voyager probes first took a good look at Saturn, said Luke Dones, a planetary scientist at the Southwest Research Institute in Boulder, Colorado.
Proponents of the younger age stand by their work. “Every new exciting result gets challenged,” said Burkhard Militzer, a planetary scientist at the University of California, Berkeley, and a coauthor of the Science paper. “It’s the natural way to proceed.”
The debate is about more than the narrow question of the rings’ age. The age of Saturn’s rings will influence how we understand many of Saturn’s moons, including the potentially life-supporting world Enceladus, with its frozen ocean. And it will also push us closer to answering the ultimate question about Saturn’s rings, one that humans have wondered about since Galileo first marveled at them over 400 years ago: Where did they come from in the first place?
We know the age of the Earth because we can use the decay of radioactive matter in rocks to work out how old they are. Planetary geologists have done the same for rocks from the moon and Mars.
Saturn’s rings, predominantly composed of ice fragments with trace amounts of rocky matter, don’t lend themselves to this kind of analysis, said Matthew Hedman, a planetary scientist at the University of Idaho. That means age estimates have to be based on circumstantial evidence. | 0.915941 | 3.755368 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.