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This could well be another post that illustrates my ignorance, more than anything else, but maybe I’ll learn something from it, even if noone else does. I have been assuming that it was generally agreed/accepted that periods of major climate change were forced rather than unforced. It’s possible that I’m using these terms incorrectly, so what I mean by forced is that the changes are driven by some kind of external influence. Unforced being internal variability. [Addendum : I had initially used the term natural/internal variability but, as Kevin points out in the comments there can be natural external forcings, so I’m trying to stick with internal – to the climate system – variability when referring to unforced changes].
Examples of forced variability would be volcanic outgassing – hundreds of millions of years ago – allowing greenhouse gases to accumulate in the atmosphere, warming the planet and driving us out of a snowball earth. Asteroid impacts have been associated with other periods of climate change. Orbital variations (Milankovitch cycles) are thought to be the driver for climate variability in the last 500000 years. Variations in solar intensity and variations in volcanic activity (in this case associated with aerosols) have been linked with the Medieval Warm Anomaly (MWA) and with the Little Ice Age (LIA). Today, the driver of climate change today is thought (known?) to be anthropogenic emissions of CO2.
A few recent discussions have, however, made me wonder about the issue of forced versus unforced variability. From discussions on this post it seems that even though millenial reconstructions can tell us a lot about our past climate history, there is much we still don’t know and much more (in particular about forcings) that they could still tell us. From discussion on this post it seems that even though the timings of the orbital variations (Milankovitch cycles) coincide with variations in our climate, we still haven’t shown definitively that they are indeed linked. Science of Doom has an interesting recent post that discusses this issue.
So, could this uncertainty about our past climate history indicate that some past climate changes could have been unforced, rather than forced? Our climate is clearly very complex and can be chaotic (on short timescales at least). It certainly seems plausible that some kind of internal variability could change – for example – a major ocean current, send warm water to the poles, melt polar ice, change the planet’s albedo, and produce a phase of warming that could then be amplified by the release of greenhouse gases. It’s my understanding, though, that there’s no actual evidence for this – at this stage at least. Also, although it may be true that we haven’t definitively shown, for example, that Milankovitch cycle are the drivers for major climate change in the last 500000 years, the timings seem so similar that it, at least, seems plausible that this is the driver, even if we haven’t definitively shown how it actually operated. Maybe not, of course, but I’m not aware of a plausible alternative.
So, I guess the two issues are : is there any evidence for unforced variability (long-term rather than short-term at least), and – in terms of global warming/climate change today – does it matter? I’m well aware that many “sceptics” argue that global warming/climate change today could be due to internal variability (unforced). So, if one could find evidence for unforced variability in our past climate, that would – I suspect – lead some to argue that we can’t rule out a significant unforced influence to climate change today. The problem with that is that we “know” that there is a significant external forcing (from anthropogenic greenhouse gasses). If you want global warming/climate change today to be unforced, you then need to show how the anthropogenic forcings have been cancelled while, independently, internal variations have produced a warming that is consistent with that expected from this external forcing. Anything’s possible – I guess – but some things are just very unlikely.
So, as I said at the beginning, maybe this post is more indicative of my ignorance than anything else. An earlier comment by Arthur Smith partly motivated this post and makes me think that – at least – I’m not alone in wondering about this. If others have thoughts or views on this, feel free to make them through the comments (although taking the new Comments Policy into account would be appreciated).
[Addendum : I’ve edited this slightly to try and better illustrate that unforced means internal variability, while forced applies to external influences, some of which can still be natural.] | 0.833939 | 3.367982 |
NASA has announced the passing of two objects passing by Earth’s orbit. One of it is a comet but it’s not clear whether the second object is a comet or an asteroid.
The first object is a rare comet and is known as C/2016 U1 NEOWISE, which was discovered by the NEOWISE, NASA’s asteroid-hunting mission. It reached the closest point to the Earth on December 13, 2016 and will get the closest to The Mercury’s orbit which will be the closest to the Sun on January 14, 2017.
The comet is expected to be bright enough to be seen on January 14. Due to the unpredictable brightness of a comet it may or may not be visible through a good pair of binoculars. It would be best observed from the Northern Hemisphere just before dawn in the Southern sky. It will be moving south every day until January 14 when it is closest to the Sun. This is the first time according to astronomers that it has come this close to Earth.
Very little is known about C/2016 U1 NEOWISE because this is the first time it has be observed ad it is believed that its orbital might be millions of years. So it might be that it would be another million years before seen again.
The second object which is known as 2016 WF9 is still a mystery to the NASA scientists. The object which seems to be about 1 kilometer across is hard to identify as either a comet or asteroid. The reason is due to its lack of trail of icy debris unlike comets. It does, however, have the reflective properties and body structure of a comet. Scientists are observing its approach to confirm if it is a comet. It will closest to Earth on February 25, at a distance of about 32 million miles. Although this may seem like a long distance this is, in fact, the closest on the astronomical scale.
Comets heat up and shed material as the approach the Sun. The orbital period of 2016 WF9 is 5 years and is therefore seen more frequently. It is believed to have ‘cometary origins’ and may have lost majority of the volatiles that are on or under the surface. | 0.805318 | 3.246057 |
The role Australia played in relaying the first television images of astronaut Neil Armstrong’s historic walk on the Moon 50 years ago this July features in the popular movie The Dish.
But that only tells part of the story (with some fictionalisation as well).
What really happened is just as dramatic as the movie, and needed two Australian dishes. Australia actually played host to more NASA tracking stations than any other country outside the United States.
How big is the Moon? Let me compare …
Right place, right time
Our geographical location was ideal as US spacecraft would pass over Australia during their first orbit, soon after launch. Tracking facilities in Australia could confirm and refine their orbits at the earliest possible opportunity for the mission teams.
To maintain continuous coverage of spacecraft in space as the Earth turned, NASA required a network of at least three tracking stations, spaced 120 degrees apart in longitude. Since the first was established in the US at Goldstone, California, Australia was in exactly the right longitude for another tracking station. The third station was near Madrid in Spain.
Australia’s world-leading place in radio astronomy was another factor, having played a key role in founding the science after the second world war. Consequently, Australian engineers and scientists developed great expertise in designing and building sensitive radio receivers and antennas.
While these were great at discovering pulsars and other stars, they also excelled at tracking spacecraft. When the CSIRO Parkes radio telescope opened in 1961 it was the most advanced and sensitive dish in the world. It became the model for NASA’s large tracking antennas.
The Commonwealth Rocket Range at Woomera, South Australia, also allowed Australians to gain experience in tracking missiles and other advanced systems.
The dish you need is at Honeysuckle Creek
NASA invested a considerable amount in its Australian tracking facilities, all staffed and operated by Australians under a nation-to-nation treaty signed in February 1960.
For human spaceflight, the main tracking station was at Honeysuckle Creek, near Canberra. Its 26-metre dish was designed as NASA’s prime antenna in Australia for supporting astronauts on the Moon.
NASA’s nearby Deep Space Network station at Tidbinbilla also had a 26-metre antenna but with a more sensitive radio receiver. It was called on to act as a wing station to Honeysuckle Creek, enhancing its capabilities, and ultimately tracked the orbiting command module during Apollo 11.
Over in Western Australia, Carnarvon’s smaller 9-metre antenna was used to track the Apollo spacecraft when initially in Earth orbit, as well as to receive signals from the lunar surface experiments.
To augment the receiving capabilities of these stations, the 64-metre Parkes radio telescope was asked to support Apollo 11 while astronauts were on the lunar surface. The observatory’s director, John Bolton, was prepared to accept a one-line contract:
The Radiophysics Division would agree to support the Apollo 11 mission.
The original plan
The decision to broadcast the first moonwalk was almost an afterthought.
Originally, the tracking stations were to receive only voice communications and spacecraft and biomedical telemetry. What mattered most to mission control was the vital telemetry on the status of the astronauts and the lunar module systems.
Since Parkes was an astronomical telescope, it could only receive the signals, not transmit. It was regarded as a support station to Honeysuckle Creek, which was also tasked with receiving the signals from the lunar module, Eagle.
When the decision was made to broadcast the moonwalk, Parkes came into its own. The large collecting area of its dish provided extra gain in signal strength, making it ideal for receiving a weak TV signal transmitted 384,000km from the Moon, using the same power output as two LED lights today.
One giant leap
On Monday, July 21 1969, at 6.17am (AEST), astronauts Neil Armstrong and Buzz Aldrin landed the Eagle lunar module on the Sea of Tranquillity.
It occurred during the coverage period of the Goldstone station, while the Moon was still almost seven hours from rising in Australia.
The flight plan had the astronauts sleeping for six hours before preparing to exit the lunar module. Parkes was all set to become the prime receiving station for the TV broadcast.
This changed when Armstrong exercised his option for an immediate walk – five hours before the Moon was to rise at Parkes. With this change of plan, it seemed the moonwalk would be over before the Moon even rose in Australia.
But as the hours passed, it became evident that the process of donning the spacesuits took much more time than anticipated. The astronauts were being deliberately careful in their preparations. They also had some difficulty in depressurising the cabin of the lunar module.
Meanwhile, moonrise was creeping closer in Australia. Staff at Honeysuckle Creek and Parkes began to hope they might get to track the moonwalk after all – at least as a backup to Goldstone in the US.
Bad weather hits
The weather at Parkes on the day of the landing was miserable. It was a typical July winter’s day – grey overcast skies with rain and high winds. During the flight to the Moon and the days in lunar orbit, the weather at Parkes had been perfect, but this day, of all days, a violent squall hit the telescope.
Still, the giant dish of the Parkes radio telescope was fully tipped down to its 30-degree elevation limit (the telescope’s horizon is 30 degrees above the true horizon), waiting for the Moon to rise in the north-east.
As the Moon slowly crept up to the telescope’s horizon, dust was seen racing across the country from the south. The dish, being fully tipped over, was at its most vulnerable, acting like a huge sail.
The winds picked up and two sharp gusts exceeding 110km/h struck the large surface, slamming it back against the zenith angle drive pinions that controlled the telescope’s up and down motion. The control tower shuddered and swayed from this battering, creating concern in all present.
The atmosphere in the control room was tense, with the wind alarm ringing and the 1,000-ton telescope ominously rumbling overhead.
Parkes had two radio receivers installed in the focus cabin of the telescope. The main receiver was on the focus position and a second, less sensitive receiver was offset a very short distance away, which gave it a view just below the main receiver.
Fortunately, as the winds abated, the Moon rose into the field-of-view of the telescope’s offset receiver, just as Aldrin activated the TV at 12.54pm (AEST). It was a remarkable piece of timing.
The 64m antenna at Goldstone, the 26m antenna at Honeysuckle Creek and the 64m dish at Parkes all received the signal simultaneously.
At first, NASA switched between the signals from Goldstone and Honeysuckle Creek, searching for the best-quality TV picture.
After finding Goldstone’s image initially upside down and then of poor quality, Houston selected Honeysuckle’s incoming signal as the one used to broadcast Armstrong’s “one giant leap” to the world.
Eight minutes into the broadcast, at 1.02pm (AEST), the Moon finally rose high enough to be received by Parkes’ main, on-focus receiver. The TV quality improved, so Houston switched to Parkes and stayed with it for the remainder of the two-and-a-half hours of the moonwalk, never switching away.
Honeysuckle continued to concentrate on their main task of communications with the astronauts and receiving that vital telemetry data.
Throughout the moonwalk, the weather remained bad at Parkes. The telescope operated well outside safety limits for the entire duration. It even hailed toward the end, but there was no degradation in the TV signal.
The moonwalk lasted a total of 2 hours, 31 minutes and 40 seconds, from the time the Eagle’s hatch opened to the time the hatch closed.
Australians saw it first
In Australia, the Apollo 11 feed was split. One feed was sent to NASA mission control for broadcast around the world. The other went directly to the ABC’s Gore Hill studios, in Sydney, for distribution to Australian TV networks.
As a result Australians watched the moonwalk, and Armstrong’s first step through Honeysuckle, just 300 milliseconds before the rest of the world.
An estimated 600 million people, one-sixth of the world’s population at the time, watched the historic Apollo 11 moonwalk live on TV. At the time it was the greatest television audience in history. As a proportion of the world’s population, it has not been exceeded since.
The success of the Apollo 11 mission was due to the combined effort, dedication and professionalism of hundreds of thousands of people in the United States and around the planet.
Australians from Canberra to Parkes, remote Western Australia to central Sydney played a critical role in helping broadcast that historic moment to an awestruck world.
You can hear more about the Moon landing in our special podcast series, To the Moon and beyond. | 0.852704 | 3.03722 |
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along the edge. Though apparently so small, its dimensions most be enormous. If no farther from the earth than 61 Cygni, the diameter would be 2,000,000,000 miles. It is probably immensely further distant.
The spiral or " whirlpool nebulse" are exceedingly curious in their appearance. The most remarkable one is that in Canes Venatici. It consists of brilliant spirals sweeping outward from a central nucleus, and all overspread with a multitude of stars. One is lost in attempting to imagine the distance of such a mass, and the forces which produce such a "tremendous hurricane of matter—perhaps of suns."
Planetary nebtdce, by their circular form and pale uniform light, resemble the disks of the most distant planets of our system. Their edges are generally well denned, though sometimes slightly furred. Threefourths of them are in the southern hemisphere. Several have a blue tinge. There is one in Ursa Major, which if located at the distance named before—that of 61 Cygni— would fill a space equal to
... PLANETARY NBBULA.
three times the entire orbit of Neptune. About twenty-five of these "island universes" have been found scattered through the ocean of space. Columbus discovered a new continent, and so immortalized his name; what shall we say of the astronomer who discovers a universe of worlds?
Irregular nebula, are those which have no definite form. Many of them present all the irregularities of clouds torn and rent by the tempest. Some of the likenesses which may be traced by the fancy are strangely fantastic: for example, the "dumb-bell nebula" in the constellation Vulpecula, and the "crab nebula" near the southern horn of Taurus.
There is also one known as " the great nebula in the sword-handle of Orion," in which may be seen a faint resemblance to the wings of a bird.
Nebulous stars are so called because they are enveloped by a faint nebula, usually of a circular form. The star is generally seen at the centre, although some which are elliptical surround two stars, one in each focus. It is thought that these may be suns possessing immense atmospheres, which are rendered visible somewhat as that of our sun is in the zodiacal light; and that in like manner our sun
itself to those in space presents the appearance of a nebulous star. The luminous atmosphere of the star in Cygnus, if located at the distance of <* Centauri, is of an extent equal to "fifteen times the distance of Neptune from the sun."
Variable nebuke.—Certain changes take place among the nebnlre which can be accounted for only under the supposition that they, like some of the stars, are variable. Mr. Hind tells us of one in Taurus which • was distinctly visible with a good telescope in 1852, but in 1862 it had vanished entirely out of the reach of a much more powerful instrument. It seems to have disappeared altogether. The great nebula in Axgo, when observed by Herschel in 1838, had in the centre a vacant space containing a star of the first magnitude completely enshrouded by nebulous matter. In 1863, the nebulous matter had disappeared, and the star was only of the sixth magnitude. These facts as yet defy explanation. They only illustrate the vast and wonderful changes constantly taking place in the heavens.
Double nebuke.—There seems to be a physical connection existing between some of the nebulse, similar to that already noticed in respect to certain stars. In the case of the latter, this inter-relation has been proved, since their movements even at their distances can yet be traced in the lapse of years. "But owing to the almost infinite depths in the abyss of the heavens at which these nebulsB exist, thousands of years, perhaps thousands of centuries, would be necessary to reveal any movement." (Guillemin.)
Magellanic Clouds.—Not far from the southern pole of the heavens there are two cloud-like masses, distinctly visible to the naked eye, known to navigators as " Cape Clouds." Sir John Herschel describes them as consisting of swarms of stars, clusters, and nebulse, seemingly grouped together in the wildest | 0.822317 | 3.674649 |
NASA spacecraft, Messenger (The Mercury Surface, Space ENvironment, GEochemistry, and Ranging), is set to crash land into Mercury’s surface on April 30th.
It will be the final act of the probe which has been orbiting Mercury for the last four years. Scientists managed to keep the spacecraft circling the innermost planet of the solar system for three years longer than planned.
The final use of the probe will be to crash into the surface of Mercury, to gather scientific data. It will help with a better understanding of the planet’s atmosphere, magnetic fields, craters and the nature of its surface.
Its final descent will allow Messenger to peek into craters at the planet’s pole; where the sun never shines, looking for water and chemical building blocks of life.
Out of fuel and losing altitude, Messenger is expected to make a high-speed crash near the planet’s north pole at around 3:25 EDT (1925 GMT) on April 30, flight controllers told reporters during a webcast news conference.
The impact at 8,724 miles per hour (14,040 km per hour) will leave a fresh crater, roughly 52 feet (16 meters) in diameter, that should serve as an interesting reference point for a follow-on European spacecraft called BepiColombo, which is due to arrive in 2024.
The crater may help scientists learn more about the planet’s unexpectedly fast weathering processes, one of dozens of Messenger’s finding.
Topping the lead scientist’s list of Messenger discoveries is the detection of elements such as potassium and sulfur on the planet’s surface, volatiles that should have evaporated under the presumably scorching conditions 36 million miles (58 million km) from the sun where Mercury formed and orbits today. Earth, by comparison, is about 93 million miles (150 million km) from the sun.
Messenger also confirmed the existence of ices and other materials, possibly even carbon-based organics, on the floors of craters where sunlight never shines.
As it makes its final descent toward the planet’s surface, Messenger will attempt to peer directly inside targeted craters, said lead scientist Sean Solomon, with Columbia University’s Lamont-Doherty Earth Observatory in New York.
It also will look for magnetized crust in an effort to flesh out the odd story of why such a tiny planet has such a strong, and recently discovered asymmetrical, magnetic field.
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All things considered, outer space is a pretty terrifying place. It’s utterly silent, unfathomably vast, and it experiences weather extremes that make Earth’s seem mild in comparison.
And then there’s the radiation. We’re pretty much protected from hazardous levels galactic cosmic rays (GCRs) by our planet’s magnetic field but, just past low orbit, high-energy protons and charged particles can cause serious health and cognition problems.
But new NASA-funded research out of the University of California, San Fransisco and Brookhaven National Laboratory in New York suggests that not everyone’s brain is impacted by cosmic rays. In fact, the brains of female astronauts may be completely immune. In a paper published earlier this month in the journal Brain, Behavior, and Immunity, the researchers showed that female mice are immune to the cognitive damage that results from simulated space radiation. The study may pave the way toward treating this hazardous consequence of space travel.
“These results demonstrate that female mice are protected from the deleterious consequences of deep space exposure,” Susanna Rosi, a neuroscientist at UCSF and one of the study’s lead authors, told Digital Trends. “More in detail, we found that male mice develop a large range of cognitive deficits that are not present in females after exposure to galactic cosmic ray simulation.”
These cognitive deficits included changes in sociability, social memory, anxiety-like behaviors, and memory.
“When we look carefully in the brain we found fundamental differences between male and female,” Rosi said. Only male brains had an increase in inflammatory cells and a loss of neural synapses. “These results are compelling because they show fundamental sex differences.”
GCRs are not an immediate concern for today’s astronauts. The International Space Station is still within low-Earth orbit and no human has made it beyond the planet’s magnetic field since the Apollo missions. But with the way the new space race is shaping up, we may soon be headed back to the moon and Mars, where protection from cosmic rays is a top priority.
Rosi and her lab, including postdoctoral researcher and first author of the study, Karen Krukowski, have put forward the hypothesis that inflammatory cells called microglia account for the disparity between female and male mice by protecting female but not male brains. However, it’s unclear if or why this is the case.
The researchers note that this is just the beginning of what is likely to be a long investigation into safety measures for future space missions. They will continue to test more complex combinations of simulated space radiation and research ways to modify microglia to potentially treat these cognitive deficits. | 0.846493 | 3.489266 |
Quick Facts About The Sun Studying SOHO Spacecraft
Earth’s Eye On The Sun!
The SOHO (SOlar Heliospheric Observatory) spacecraft is a joint project between the European Space Agency (ESA) and NASA designed as a space-based observatory, viewing and investigating the Sun from its halo orbit around the Earth – Sun L1 point which is 1.5 million kilometres from Earth. From the Sun’s core through to its outer atmosphere the corona (the source of the solar winds) and beyond.
Fast Summary Facts About SOHO!
- Type: L1 Orbiter
- Destination: Earth – Sun L1 point
- Status: Active
- Launch Location: Cape Canaveral, Florida
- Launch Date: December 2nd 1995
- Arrival Date: December 14th 1995
- Mission Duration: 3 years planned life, 23 years in total (with extensions)
Fun Facts About The SOHO Mission!
- The name SOHO is an acronym that stands for Solar Heliospheric Observatory.
- The spacecraft was designed to study the internal structure of our the Sun, its boiling outer layers and atmosphere which are the origin of the solar winds (the ionized gases which blow outwards throughout the Solar System) which interact with Earth’s magnetosphere and upper atmosphere.
- The SOHO spacecraft operates from a permanent vantage point 1.5 million kilometres from Earth, towards the Sun, orbiting in what is called a halo orbit around the Lagrangian point L1 every 6 month.
- Several other space-based observatories (notably the DSCOVR spacecraft) orbit the L1 point and monitor space weather in Earth’s vicinity in real-time.
- At launch, SOHO weighed approximately 1,850 kilograms (4,080 lbs) (which included its station-keeping propellant) and was launched aboard an Atlas II rocket.
- The probe utilizes solar panels for power generation (generating 1,500 Watts).
- SOHO main spacecraft body measures 3.65 m x 3.65 m (12 x 12 feet) with its solar panels extending 9.5 m (31 feet).
- SOHO gave scientist their first long-term uninterrupted view of the Sun.
- This uninterrupted view of the Sun has enabled SOHO to become a prolific comet spotter, having discovered over 3,000 comets!
- In 1998 SOHO suffered a malfunction and disappeared for 4 months before scientist could resurrect the spacecraft back to fully operational status.
- The initial science mission lasted 2 years, with further extensions totalling 21 years of in-orbit investigations – amazing!
- Communications with Earth is via the NASA run Deep Space Network.
- The SOHO mission has cost a total of around 1 billion Euros! WOW, space exploration can be really expensive! | 0.865109 | 3.586692 |
Satellite observations have shown that the Earth’s cloud cover is strongly correlated with the galactic cosmic ray flux. While this correlation is indicative of a possible physical connection, there is currently no confirmation that a physical mechanism exists. We are therefore setting up an experiment in order to investigate the underlying microphysical processes. The results of this experiment will help to understand whether ionization from cosmic rays, and by implication the related processes in the universe, has a direct influence on Earth’s atmosphere and climate. Since any physical mechanism linking cosmic rays to clouds and climate is currently speculative, there have been various suggestions of the role atmospheric ions may play; these involve any one of a number of processes from the nucleation of aerosols up to the collection processes of cloud droplets. We have chosen to start our investigation at the smallest scales, namely the role of cosmic ray produced ions on atmospheric aerosol nucleation and growth processes. Aerosol theory suggests that this is one of the most promising areas to search for an effect. However, guided by the nature of our initial results, it will be possible to develop the experiment to cover additional processes involved in the route to cloud droplet formation. The experiment will be conducted at the Danish National Space Center where a clean room facility has been provided. It comprises a 7 m3 reaction chamber across which an electric field is applied to control the number of ions present. This will enable experiments to be performed both with and without the presence of ions, thus providing information as to the potential role of ions in aerosol processes.
|Publication status||Published - 2006|
|Event||7th Informal Conference on Atmospheric and Molecular Science - Helsingør, Denmark|
Duration: 9 Jun 2006 → 11 Jun 2006
Conference number: 7
|Conference||7th Informal Conference on Atmospheric and Molecular Science|
|Period||09/06/2006 → 11/06/2006| | 0.825032 | 3.595454 |
The Internet as it stands today is the greatest revolution in the world of communications. It’s a technical marvel, enabling us to do many things that even up to a couple decades ago were firmly in the realms of science fiction. Indeed the incredible acceleration of technical innovation that we’ve experienced in recent history can be attributed to the wide reaching web that enables anyone to transmit information across the globe . So with the human race on the verge of a space revolution that could see a human presence reaching far out into our solar system a question burns away in the minds of those who’d venture forth.
How would we take the Internet with us?
As it stands currently the Internet is extremely unsuitable for inter-planetary communications, at least with our current level of technology. Primarily this is because the Internet is based off the back of the TCP/IP protocols which abstract away a lot of the messy parts of sending data across the globe. Unfortunately however due to the way these protocols are designed the transmission of data is somewhat unreliable as neither of the TCP/IP protocols make guarantees about when or how data will arrive at its destination. Here on Earth that’s not much of a problem since if there are any issues we can just simply request the data be sent again which can be done in fractions of a second. In space however the trade-offs that are made by the foundations of the Internet could cause immense problems, even at short distances like say from here to Mars.
Transmissions from Mars take approximately 3 minutes and 20 seconds to reach Earth since they travel at the speed of light. Such a delay is quite workable for scientific craft but for large data transfers it represents some very unique problems. For starters requesting that data be resent means that whatever system was relying on that data must wait a total of almost 7 minutes to continue what it was doing. This means unreliable protocols like the TCP/IP stack simply can not be used over distances like these when re-transmission of data is so costly and thus the Internet as it exists now can’t really reach any further than it already does. There is the possibility for something more radical, however.
For most space missions now the communication method of choice is usually a combination of proprietary protocols coupled with directed microwave communication. For most missions this works quite well, especially when you consider examples like Voyager which are 16 light hours from earth, however these systems don’t generalize very well since they’re usually designed with a specific mission in mind. Whilst an intrasolar internet would have to rely microwaves for its primary transmission method I believe that a network of satellites set up as anAldrin Cycler between the planets of our solar system could provide the needed infrastructure to make such a communications network possible.
In essence such satellites would be akin to the routers that power the Internet currently, with the main differences being that each satellite would verify the data in its entirety before forwarding it onto the next hop. Their primary function would also change depending on which part of the cycle they were in, with satellites close to a planet functioning as a downlink with the others functioning as relays. You could increase reliability by adding more satellites and they could easily be upgraded in orbit as part of missions that were heading to their destination planet, especially if they also housed a small space station. Such a network would also only have to operate between a planet and its two closest neighbors making it easy to expand to the outer reaches of the solar system.
The base stations on other planets and heavenly bodies would have to have massive caches that held a sizable portion of the Earth Internet to make it more usable. Whilst you couldn’t have real time updates like we’re used to here you could still get most of the utility of the Internet with nightly data uploads of the most updated content. You could even do bulk data uploads and downloads to the satellites when they were close to the other planets using higher bandwidth, shorter range communications that were then trickle fed over the link as the satellite made its way back to the other part of its cycle. This would be akin to bundling a whole bunch of tapes in a station wagon and sending it down the highway which could provide extremely high bandwidth, albeit at a huge latency.
Such a network would not do away with the transmission delay problems but it would provide a reliable, Internet like link between Earth and other planets. I’m not the first to toy with this kind of idea either, NASA tested their Disruption Tolerant Networking back in 2008 which was a protocol that was designed with the troubles of space in mind. Their focus was primarily on augmenting future, potentially data intensive missions but it could be easily be extended to cover more generalized forms of communication. The simple fact that agencies like NASA are already well on their way to testing this idea means we’re already on our way to extending the Internet beyond its earthly confines, and it’s only a matter of time before it becomes a reality. | 0.851321 | 3.095089 |
“Aliens have reached Earth, say researchers from the University of Edinburgh’s School of Physics and Astronomy, basing their dramatic findings on a new study of fast-moving extraterrestrial dust that constantly rains down on our atmosphere. These particles serve as tiny ‘spaceships’ for microorganisms from alien worlds that traverse the vastness of interstellar space for eons before reaching Earth. This dusty downpour could also collide with biological particles in Earth’s atmosphere with enough energy to send them careening into space, and conceivably onwards to other planets in other solar systems.
Astrobiologists earlier found evidence of microorganisms reaching the planet in air samples taken at extreme altitudes, and from the discovery in 1984 of fossilised worms in a meteorite from Mars. Exciting data from the 1976 Viking space probes, which actually confirmed the presence of Martian microorganisms but were overlooked for 25 years by careless scientists, back these findings. In 2006, researchers from Columbia University discovered traces of amino acids – the building blocks of life – on meteorites that landed in Australia and the US less than a hundred years ago.
Some scientists argue that these extraterrestrial amino acids mixed with moisture in Earth’s ancient atmosphere to produce an acidic “soup” that then nourished the planet’s first organisms. This ties in with the panspermia theory, which says that outer space seeded Earth with comet-borne primitive life forms over four billion years ago. Panspermia never found favour with modern-day scientists till the 1970s, when the late Fred Hoyle and Chandra Wickramesinghe came across “traces of life” in interstellar dust. When cultured, two species of bacteria and a microfungus found in space rocks turned out to be similar to terrestrial organisms – just as panspermia had predicted. Hoyle and Wickramasinghe believed that a torrent of such “life-altering stuff from space” reaches Earth in cycles related to solar activity and has affected the evolution of terrestrial life. If this is indeed the reality, the ‘miracle’ of life could happen anywhere, and our microbial ancestors, or more evolved cousins, are scattered like chaff throughout the universe” , by ON | 0.881658 | 3.377063 |
New views from NASA's Spitzer Space Telescope show blooming stars in our Milky Way galaxy's more barren territories, far from its crowded core.
The images are part of the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (Glimpse 360) project, which is mapping the celestial topography of our galaxy. The map and a full, 360-degree view of the Milky Way plane will be available later this year. Anyone with a computer may view the Glimpse images and help catalog features.
We live in a spiral collection of stars that is mostly flat, like a vinyl record, but it has a slight warp. Our solar system is located about two-thirds of the way out from the Milky Way's center, in the Orion Spur, an offshoot of the Perseus spiral arm. Spitzer's infrared observations are allowing researchers to map the shape of the galaxy and its warp with the most precision yet.
While Spitzer and other telescopes have created mosaics of the galaxy's plane looking in the direction of its center before, the region behind us, with its sparse stars and dark skies, is less charted. (read more) | 0.833969 | 3.02072 |
The North Magnetic Pole is on the run – and scientists might finally know why.
It’s easy to think of Earth’s geomagnetic poles as features that are set in stone (or ice), but both poles are not stationary and remain in a permanent state of flux. Since it was first documented by scientists in the 1830s, the North Magnetic Pole has wandered some 2,250 kilometers (1,400 miles) across the upper stretches of the Northern Hemisphere from Canada towards Siberia. Between 1990 and 2005, the rate of this movement accelerated from less than 15 kilometers per year to around 50 to 60 kilometers per year.
A new study, published this week in the journal Nature Geoscience, argues the changes could be explained by the to-ing and fro-ing between two magnetic "blobs" of molten material in the planet's interior, causing a titanic shift of its magnetic field.
The North Magnetic Pole is the point at which Earth's magnetic field points vertically downwards, dictated by molten iron that’s sloshing around Earth’s interior through convection currents. The recent shift towards Siberia, it seems, is caused by a blip in the pattern of flow in Earth's interior that occurred between 1970 and 1999. The change resulted in the Canadian blob becoming elongated and losing its influence on the magnetosphere, causing the pole to zoom towards Siberia.
“What we’ve discovered is that the North Magnetic Pole’s position is controlled by two patches of magnetic field – one underneath Canada and one underneath Siberia – and they act as a tug of war effect controlling the location of the pole,” Dr Phil Livermore, lead study author from the School of Earth and Environment at the University of Leeds in the UK, explained to BBC Radio 4’s Today program.
“Now historically, the Canadian patch has been winning the war and that’s why the pole has been centered over Canada but in the last few decades, the Canadian patch has weakened and the Siberian patch has strengthened slightly," he added.
“That explains why the pole has suddenly accelerated away from its historical position.”
The researchers reached this conclusion using data gathered by the European Space Agency's (ESA) Swarm satellites. This trio of satellites orbit Earth and precisely measure the magnetic signals that stem from our planet’s core, mantle, crust, and oceans, as well as from the ionosphere and magnetosphere. Keeping an eye on Earth’s magnetic field isn’t just important for abstract scientific studies; the magnetic field serves as a shield of geomagnetic energy that protects Earth from destructive solar radiation. It is also imperative for many navigation systems, from the humble compass to GPS. | 0.819144 | 3.682288 |
Dy, Er, and Yb isotope compositions of meteorites and their components: Constraints on presolar carriers of the rare earth elementsOPEN ACCESS
Quinn R. Shollenberger, Gregory A. Brennecka
Earth and Planetary Science Letters
Volume 529, 1 January 2020, 115866
• We present new methods to measure Dy isotopes by MC-ICPMS.
• Bulk meteorites can have Dy, Er, and Yb isotope anomalies due to neutron capture.
• Dy and Er isotope variations in Murchison leachates follow s-process mixing.
• Isotopic decoupling shows Yb is carried in a different presolar phase from other REEs.
• SiC may be the primary phase responsible for bulk meteorite isotope variations.”
“One way to study the original building blocks of the Solar System is to investigate primitive meteorites and their components. Specifically, isolating these meteorites’ individual components via sequential acid leaching can reveal isotopically diverse material present in the early Solar System, which can provide new insights into the mixing and transport processes that eventually led to planet formation. Such isotopic differences in the components are likely to be found in heavy rare earth elements, such as dysprosium (Dy), erbium (Er), and ytterbium (Yb), because their isotopes have different nucleosynthetic production pathways and the elements have significant differences in volatility; however, these specific elements have yet to be thoroughly investigated in the field of cosmochemistry. As such, we present the first combined Dy, Er, and Yb isotope compositions of sequential acid leachates from the Murchison meteorite, along with multiple bulk meteorites from different taxonomic classes. This work also presents a new method to separate, purify, and accurately measure Dy isotopes. Here we show that resolved Dy, Er, and Yb isotope variations in most bulk meteorites are due to neutron capture processes. However, Dy and Er isotopic compositions of bulk Murchison and Murchison leachates stem from the additions or depletions of a nucleosynthetic component formed by the s-process, most likely mainstream silicon carbide (SiC) grains. In contrast, the Yb isotope compositions of bulk Murchison and Murchison leachates display either unresolved or relatively small isotope anomalies. The disparate isotopic behavior between Dy-Er and Yb likely reflects their differing volatilities, with Dy and Er condensing/incorporating into the mainstream SiC grains, whereas the less refractory Yb remains in the gas phase during SiC formation. This work suggests that Yb is hosted in a non-SiC presolar carrier phase and, furthermore, that mainstream SiC grains may be the primary source of isotopic variation in bulk meteorites.” | 0.800104 | 3.356645 |
New radio telescope will listen to the Universe on the FM-band
(PhysOrg.com) -- The first major radio telescope to be built in Britain for many decades will 'listen' to the sky at FM frequencies, providing vast quantities of data to a supercomputer in Holland, paving the way for unexpected new discoveries.
Astronomers, including scientists at the University of Southampton, hope to detect when the first stars were formed and will observe some of the most distant galaxies, revealing more about how the Universe evolved.
The telescope is being constructed this week (June 7-11) by a band of university volunteers in a field at the Chilbolton Observatory, near Andover in Hampshire, which is part of the Science and Technology Facilities Council (STFC).
Students, lecturers and researchers mainly from the universities of Southampton, Portsmouth and Oxford are helping scientists at Chilbolton to install 96 radio antennae, which are part of the European LOFAR project (Low Frequency Array). When completed, LOFAR will consist of over 5,000 separate antennae spread in 'stations' all over Europe. Stations have already been completed in the Netherlands and Germany and others are planned in France, Sweden and Poland.
Professor Rob Fender, of the University of Southampton, who is leading the LOFAR-UK project, says: "LOFAR is an amazingly simple concept because the antennae are made from everyday components, but it is also immensely complex because of the huge amounts of radio data that these antennae produce."
The antennae will work at the lowest frequencies accessible from the Earth and will be connected using sophisticated computing and high speed internet. A supercomputer based in the Netherlands will use digital electronics to combine the signals from the antennae across Europe to make images of the entire radio sky.
All the data-streams will be combined to make the world's largest and most sensitive radio telescope. Astronomers shift and multiply these streams together to improve the signal from them all and 'digitally steer' the telescope to different parts of the sky.
Rob adds: "At the Chilbolton site, seven petabytes of raw data will be produced each year, which must be transferred in real-time to Holland. That's like streaming 100 high definition TV channels for every second of every day for the next five years."
Professor Bob Nichol, of the University of Portsmouth's Institute of Cosmology and Gravitation and LOFAR-UK, says: "The LOFAR telescope will produce an enormous volume of data which in turn will enable a significant amount of science; from monitoring the sun's activity - 'space weather' to scientists - to potentially searching for alien intelligence - maybe answering the age-old question 'Are we alone?'." | 0.802944 | 3.160855 |
The sun's galactic neighborhood just became a bit more significant. New research reveals that the sun's branch of the Milky Way may be several times longer than previously measured, which would make it a significant contender in the structure of the galaxy.
Spiral galaxies like the Milky Way contain several massive structures known as arms, which unwind from the galaxy's center. The sun's neighborhood is called the Orion Arm, though scientists often refer to it as the Local Arm. Despite its name, it is classified as a spur — a collection of dust and gas that lies between the more massive arms.
"Our study reveals that the Local Arm is not only a tiny spur of the Milky Way. In includes a prominent major arm nearly extending to the Perseus Arm and a long spur branching between the Local and Sagittarius Arms," astronomer Ye Xu of the Chinese Academy of Sciences told Space.com by email. Xu led a team that identified eight new features in the Orion Arm and determined that it is much longer than scientists have previously estimated, Xu said. [Our Milky Way Galaxy: A Traveler's Guide (Infographic)]
According to Xu, characteristics of the Local Arm "are comparable to those of the Galaxy's major spiral arms such as Sagittarius and Perseus."
Mapping from within
With their gently unfurling arms and ongoing star formation, spiral galaxies are some of the most beautiful star collections in the universe. But it is far easier to calculate the characteristics of distant galaxies than it is to understand the features of our own Milky Way.
"Determining the structure of the Milky Way has been a long-standing problem for astronomers because we are inside of it," Xu said. "While astronomers agree that our galaxy has a spiral structure, there are disagreements on how many arms it has and on their specific location."
Mark Reid, a researcher at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts who was not involved in the study, compares the Milky Way to a dinner plate with an interesting design on its face. While the pattern is easy to spot from above, it can be difficult to interpret when the plate is edge-on.
"All of the structures are projected on top of each other, and without accurate distances to these structures, it is impossible to infer the design," Reid told Space.com by email.
To measure how far parts of the arm sit from the sun, scientists search for telltale signals in star-forming regions. As gas enters galactic arms, gravitational forces squeeze the gas to produce newborn stars. In other galaxies, blobs of bluish light that are produced by the birth of stars trace out spiral arms.
In the Milky Way, star-forming regions are more challenging to map. As part of the new research, the scientists identified bright spots of radio emission known as masers, whose shift in light researchers can measure to identify their movement and distance from Earth. Masers can be made up of clouds of gas that contain trace amounts of molecules such as water and methyl alcohol.
Reid compared the microwave emissions produced by masers to the spots of red light streaming from a hand-held laser.
"All they need is a source of energy — analogous to the battery in a laser pointer — and long path-lengths to amplify the emission," Reid said. "In star-forming regions, the more massive and very young stars provide the energy."
Using the National Radio Astronomy Observatory's Very Long Baseline Array (VLBA), a suite of 10 telescopes operating in Socorro, New Mexico, the scientists identified and measured eight new masers in the Orion Arm, setting its new length at about 25,000 light-years long. (A light-year is the distance light travels in a year.) Although measurements of the arm vary, Xu’s team set the distance as being just over 16,000 light-years in 2013.
"This characterization of the Local Arm will change the image of the Milky Way," Xu said.
The new research, which was published in the journal Science Advances in September, reveals the Milky Way as more complex than scientists have previously estimated. The galaxy is typically classified as a grand-design spiral, which Reid said is often very symmetrical, often boasting only two arms.
"The Milky Way, while probably a 'pretty galaxy,' has significant irregularities," Reid said. "Based on our observations, it is clear that there are four major spiral arms and some non-symmetric structures like the Local Arm."
Further studies are needed to determine how irregular the Milky Way might be: "Without a complete map of the Milky Way, however, it is not clear how symmetric the four arms are," Reid said.
Instruments like the VLBA, located in the northern hemisphere, are limited in their ability to study the Milky Way. According to Reid, they can only map a bit more than half of the galaxy.
"We need more observations, particularly from the Southern Hemisphere, so that we can map the entire Milky Way," Reid said. | 0.807598 | 3.797497 |
Brace yourself. You can finally see how a black hole looks like. Up until today, no one really knew how a black hole looked like.
Finally, the day has come but it was no easy task.
The newly released image of a black hole (below) is a watershed moment for physics. Finally, we can put some of Einstein’s most famous predictions from a century ago to the test, but it was not as easy as pointing a big lens at the M87 galaxy and pressing a button. It took years of work and the collaboration of more than 200 scientists to make it happen. It also required about half a ton of hard drives.
What’s interesting about how the snapshot of the black hole was the length of time it took to put it together. It took years and a network of telescopes from around the world to capture the first real image of the black hole.
Data collection for the historic black hole image began in 2017 with a coordinated effort called the Event Horizon Telescope (EHT). That isn’t a single instrument but rather a collection of seven radio telescopes from around the world. The EHT used a principle called interferometry to combine the capacity of all those telescopes, creating a “virtual” telescope the size of the Earth.
The EHT had to collect a huge volume of data to deliver us this one image. Dan Marrone, Associate Professor of Astronomy at the University of Arizona says the EHT team had to install specialized super-fast data recorders on the various radio telescopes to handle the influx of measurements.
The now-famous image of a black hole comes from data collected over a period of seven days. At the end of that observation, the EHT didn’t have an image — it had a mountain of data.
The data collected was just too massive for the internet to handle. The hard drives had to be flown by plane.
According to Marrone, 5 petabytes is equal to 5,000 years of MP3 audio. There’s simply no way to send that much data efficiently over the internet. It’s faster to actually ship the hard drives to collaborators around the world. That’s why MIT has 1,000 pounds of hard drives sitting in its Haystack Observatory labs.
Thanks to the EHT project, black holes are no longer just illustrations on text books. They are real.
The historic black hole snapshot not only puts to test Einstein’s predictions. It also sheds a new light on the general relativity of black holes.
Another interesting thing about the historic snapshot of the black hole is that it took half a ton of hard drives to store the data collected from the network of telescopes. The role of a hard drive is pretty significant in putting together the first image of the black hole.
What the internet can’t handle, the hard drive can. There’s just no doubt about the importance of hard drives in massive data storage.
That’s why it makes a lot of sense to say that hard drives will always be important in this data era. Considering how important and significant they are in this day and age; they’re still not built to last forever.
Hard drives can crash. When they do, they take the data with them. Data can either be corrupted or deleted.
There are indications that your hard drive is about to crash. Watch out for such indications. For example, is your hard drive making a clicking noise? If it is, then it’s time to seek for some https://www.harddrivefailurerecovery.net/hard-drive-failure-solutions/.
Hard drives will always be synonymous to data storage. If you value your data, you should only rely on the experts to get them back in case your hard drives fail.
The Black Hole Becomes Visible With Half A Ton Of Hard Drives Find more on: The Hard Drive Recovery Associates Blog | 0.804305 | 3.755431 |
The Moon and Mars will share the same right ascension, with the Moon passing 3°11' to the north of Mars. The Moon will be 27 days old.
From Fairfield, the pair will be visible in the dawn sky, rising at 03:26 (EDT) – 3 hours and 17 minutes before the Sun – and reaching an altitude of 29° above the south-eastern horizon before fading from view as dawn breaks around 06:23.
The Moon will be at mag -10.3, and Mars at mag 1.8, both in the constellation Virgo.
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 Mars 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 39° from the Sun, which is in Libra at this time of year.
|The sky on 14 November 2017|
26 days old
All times shown in EST.
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.
|07 Oct 2017||– Mars at aphelion|
|27 Jul 2018||– Mars at opposition|
|31 Jul 2018||– Mars at perigee|
|16 Sep 2018||– Mars at perihelion| | 0.878248 | 3.31887 |
What's in the Sky — September 2018
September nights are full of wonderful treats for amateur astronomers to enjoy with binoculars and telescopes. See some of our top September stargazing suggestions below:
The fall stargazing season kicks off in September with wonderfully placed spiral galaxies M31 in Andromeda, M33 in Triangulum, and M74 in Pisces. Use a big telescope to see these distant galaxies.
The Northern Milky Way
Early in the month, around 9 PM, the "Summer Triangle" of three bright stars Vega, Deneb and Altair will be nearly overhead. In the northernmost portion of the Summer Triangle, you'll see a bright portion of the northern Milky Way. Point a telescope there and you'll discover that the fuzzy outlines of the Milky Way will resolve into vast fields of stars to explore.
For the best conditions to see the galaxies and clusters described above, plan a stargazing session for the night of September 9th, when the New Moon will provide dark skies. This is the best night of the month to observe the night sky, since light from stars and faint deep sky objects won't have to compete with bright moonlight.
Three Globular Star Clusters
Off the western side of the constellation Pegasus, three globular star clusters almost line up in a row from north to south in September skies. These globular clusters are, from north to south, M15 in Pegasus, M2 in Aquarius and M30 in Capricorn. From a dark sky site you can easily find all of them in 50mm or larger binoculars.
Planetary Nebulas in the Summer Triangle
Use a star chart and see how many of these planetary nebulas you can find in September: the famous Ring Nebula (M57) in the constellation Lyra; the Dumbbell Nebula (M27) in Vulpecula; and the "Blinking Planetary," NGC 6826 in Cygnus. Not far outside the western boundary of the Summer Triangle is a small, but intensely colorful planetary nebula, NGC 6572. All these can be seen in a 6" or larger telescope. Enhance your views of these distant clouds of dust and gas with an Oxygen-III filter.
The Galaxy Next Door
In early September, lurking low in the northeast sky is another galaxy, separate from our Milky Way - the Great Andromeda Galaxy (M31). From a very dark area without a lot of light pollution, the core of M31 is visible with the unaided eye as a slightly fuzzy spot in the sky. A pair of 7x50, 9x63 or larger binoculars will give you a much better view and any telescope will help reveal some of the neighboring galaxy's subtle dust lanes.
Dip into the Whirlpool
If you haven't tracked down "The Whirlpool Galaxy," M51, just off the handle of the easily recognizable Big Dipper asterism, do it now while you still can! It will be too low for most to get a good view after September and you'll need to wait until late winter or next spring to catch a good view of this truly picturesque galaxy. An 8" or larger telescope will help you see faint details of M51 more clearly.
A Brilliant Open Star Cluster
Off the western end of the constellation Cassiopeia is the beautiful Open Star Cluster M52. You can find it with 50mm or larger binoculars from a dark sky site, but the view is definitely better in a telescope. With an 8" or larger scope, and with the aid of an Orion UltraBlock or Oxygen-III eyepiece filter, you may even be able to catch views of faint nebulosity surrounding M52.
Don't Miss the Double Cluster
If you enjoyed observing M52, you'll love the popular favorite "Double Cluster in Perseus." Lying between constellations Cassiopeia and Perseus is a bright, fuzzy spot in the Milky Way, and a binocular will reveal two, bright open star clusters close to one another. For a real treat, use a telescope equipped with a wide-angle eyepiece to explore these sparkling clusters. In early September the "Double Cluster" appears low in northeastern skies around 9 PM, but it becomes a real showpiece later in the evening as it climbs higher in the sky.
Viewing planets is always rewarding and September will provide ample opportunities. Mars and Saturn are still visible until late in the night (early in the morning). Jupiter is still up in the early evenings, but will set fairly soon after dark. Go out and enjoy!
September Challenge Object — A Thinly Veiled Challenge
A challenging object to see in September is the supernova remnant called the Veil Nebula, located in the constellation Cygnus which is nearly overhead as soon as it gets dark. With the help of a star chart, aim your telescope at the naked eye star 52 Cygni. One branch of the Veil crosses over this star and to the east are brighter segments of this roughly circular nebula. While the Veil Nebula can be seen in big binoculars by expert observers under very dark skies, you will likely need at least a 5" aperture telescope and an Orion Oxygen-III eyepiece filter if you are anywhere near city lights.
All objects described above can easily be seen with the suggested equipment from a dark sky site, a viewing location some distance away from city lights where light pollution and when bright moonlight does not overpower the stars. | 0.899295 | 3.50762 |
My sunset chart hypothesis presents a unique and bold idea of astrology. The sunset chart is the foundation by which all charts are carefully thought about, especially the birth chart because the time-of-birth chart lies within the scope of the 24-hour period between sunsets. Most importantly, the time a baby chooses to be born presents a clear picture of his lifestyle when compared between the birth chart and the sunset chart positions of the planets. This process can be seen as a type of synastry chart between the baby at birth and the world at sunset. Additionally, the 24-hour, sunset to sunset, period represents seventy-two years of life.
Early Chaldean observations were made without the aid of our modern astrological trappings such as references to Sidereal time or Greenwich Mean Time. Their initial starting time was Local Solar Time, or more likely, from sunset to sunset. During the 24-hour time frame the star patterns and planetary placement were observed and may have marked a point of departure. My proposal suggests the time of sunset pre-sets the birth as an indicator, a matrix where planetary positions create the standard for the next 24-hour period (sunset to sunset); monthly period (lunar return) or "goal" year (pertaining to relationships between the planets and the Sun).
In a bi-wheel fashion, we rotate the inner chart and as the chart rotates, all planets will aspect their own sunset position as well as the other planets during the following 24-hour period. Consequently, during a lifetime, the timing, quality and influence of major events are based on the planets' (its own synodic) distance described by the Sun’s solar arc and position of the birth chart in relation to the sunset chart.
The charts will be erected using the equal house system in a bi-wheel fashion thereby giving us two charts to work with by comparison.
It is important for you to remember that you must erect your chart for sunset either on the SAME DATE if you were born BEFORE midnight or on the PREVIOUS date if you were born AFTER midnight.
Make a duplicate chart using the equal house system and cast two bi-wheel charts. Print them. Cut out the smaller chart out of one copy so you can turn it within the larger wheel. Each "equal house" is equal to thirty degrees and represents six years therefore, five degrees is equal to one year of life.
The Sun is used as the "focal" point or indicator. Starting from the seventh house, the idea is to simply rotate the smaller chart clockwise through the houses. By the time you have reached the cusp of the sixth house you have reached the age of six years old. If there are any planets in the sixth house that the sun has “conjoined,” note the age of the events that had taken place. Look for other aspects from/to other planets as well.
We always read the aspects between the two charts. If you have done this correctly, the Sun will "square the sunset position on the eighteenth year of life (the Sun in the small chart will be "on" the fourth house cusp). I call this aging method the "rogression."
Sunset marks the beginning of all events, and during the following 24-hour period, an individual's time of birth allows astrologers to distinguish between the character traits of the native and all the other individuals born on the same day. It is much the same as the rising sign fine-tunes the nuances of the whole Sun sign. In short, the birth chart is to the sunset chart what the Ascendant is to the Sun sign.
Unless you or your client was born at sunset, each birth chart makes some aspect to the sunset chart. The type of aspect by synastry creates a standard by the planets and quality of life.
The quality I speak of is represented by the angle between the sunset and birth chart. If someone is born with the Sun in the third or eleventh house, the aspect between the two charts, the sunset position to birth, is a trine. Planets in transit will have an easy, more positive occurrence than someone born with the birth chart in square or opposition to the sunset chart in which case the transits are more caustic.
By adjusting ancient ideas to today's concepts, we can compare a birth chart to its local sunset position and by rogression find that our entire life is encapsulated within the 24-hour period in which we were born! | 0.847258 | 3.093309 |
Spectroscopy Observing Program Coordinator:
By the end of 5th grade school children know when light passes through a prism it is broken into its component colors ranging from red to violet. Many of us are excited when we see a rainbow’s colors of ROYGBV. In 1802, the English chemist William Hyde Wollaston was the first person to note the appearance of a number of dark features in the solar spectrum. In 1814, Joseph von Fraunhofer independently rediscovered the lines and began a systematic study and careful measurement of the wavelengths of these features. Today we recognize that the colors and lines are part of an area of knowledge known as spectroscopy, the branch of science concerned with the investigation and measurement of spectra produced when matter interacts with or emits electromagnetic radiation. Spectroscopy makes use of an instrument called a spectrograph to produce the colors (spectra). A spectrum can be analyzed to produce a spectrogram, a visual representation of the spectrum of frequencies as they vary in intensity.
Most of what we know in astronomy is a result of spectroscopy: It can reveal the temperature, spectral class, and composition of an object as well as be used to infer mass, distance, luminosity, relative motion using Doppler shift and many other pieces of information. Spectroscopy is done at all wavelengths of the electromagnetic spectrum, from radio waves to gamma rays, but this program will focus on visible light. The radio frequencies are addressed in the Astronomical Leagues’ Radio Astronomy Observing Program. Through the work of Indian astronomer Meghnad Saha and others, it was realized that a primary difference between stars was their temperature, and so the classification scheme was organized into “OBAFGKM” based on temperature, from the hot O stars that cause most of the surface Hydrogen to be ionized to the cool M stars that are unable to excite Hydrogen’s electrons at all. Thus, we see different features for different classes of stars as shown in the tables below:
* - The number of observations will vary depending on which projects you choose.
The recording of astronomical spectra requires imaging and as such visual observation is not an option for this Observing Program.
The award for successfully completing the Spectroscopy Observing Program is a pin and a certificate.
Rules and Regulations
To qualify for the AL's Spectroscopy Observing Program certificate and pin, you need only be a member of the Astronomical League, either through an affiliated club, as a Member-at-Large, or as an International Member-at Large, and complete the required activities defined in the program.
Note: Remote telescopes may not be used in the Spectroscopy Observing Program. Remote Telescopes are defined on this Astronomical League web page: https://www.astroleague.org/content/terms-common-usage-observing.
To complete this Observing Program, you will need a spectroscope, camera, associated optics, mount, and drive. Special software will be needed to process the spectra.
It may be possible to construct a DIY (do it yourself) working spectroscope. Commercial models range from about two hundred dollars to thousands of dollars. The Links section below contains links to DIY pages with possible solutions.
A DSLR, CCD, or CMOS camera is needed to capture the spectra. Literature suggests a monochrome is preferred, but color will be satisfactory for this program. If using a DSLR it is important to have one with an interchangeable lens system to maximize the size of the spectra.
The optics you use will depend on the spectroscope and camera. Solutions will range from a moderate 200mm telephoto lens to a large telescope.
A go-to tracking mount is suggested to make finding and imaging the stars easier.
A variety of commercial and free software can be found on the Internet to analyze spectra. The Astronomical League makes no specific recommendations, but links can be found in the Links section below that lead to a number of helpful resources.
Determining Stellar Type:
The stellar type of a star can be determined in two ways. This Observing Program will make use of the star’s spectra to calculate its surface temperature. Based on the spectrogram’s shape, prominent features, and surface temperature, the star’s stellar type will be determined. This method will be limited to class F, G, & K type stars because the maximum wavelengths of other classes fall outside the visible range that can be detected by most cameras. Means to capture data in the UV and IR ranges exist but are beyond the scope of this Observing Program and the abilities of most amateur astronomers.
A second method performs photometry of images taken with photometric filters, usually B and V. The table below shows B – V values for various stellar classifications. While this method can be used to determine a wider range of classes, the cost of photometric B and V filters places this method beyond the scope of this program.
Note: The free program Stellarium when set to display all information displays B – V (color index) about the selected stars.
Program Activities (Three Parts)
Part I: Characterizing Star Types
The stars you choose should come from the following Stellar Evolution’s groups:
3. For each of the spectra make a spectrogram. Label prominent lines and bands. For example:
4. Making use of your spectrograms and the picture below attempt, to the best of your ability, to classify the stellar types (OBAFGKM).
Note: O, B, A, & M stars are excluded here because the maximum wavelengths fall outside the visual and normal imaging sensor ranges.
Note: Considerable variation in the data is found on the Internet. Your prediction should be considered approximate.
Look up the apparent magnitude of your stars in the Stellar Evolution’s object list. Using the absolute magnitude for the stars type found in the Spectral Type Characteristics Table, calculate the distance the star is from the Earth by the spectroscopic parallax method.
Note: There is considerable variation between internet sources for the data in the table below. Your results should be considered as an estimated distance to the stars.
You now have created the HR diagram for the stars you have studied.
Required Information to be Submitted:
- Star name,
- Date and time of the imaging (local or UT),
- Latitude and longitude of your imaging location,
- Seeing and transparency,
- Filters used (if any),
- Telescope/optics used including aperture and focal ratio,
- Camera/CCD/CMOS information including:
- exposure times,
- number of images,
- other information relevant to the image production should also be provided.
- Type of spectrograph used (include a picture if DIY),
- Spectral analysis software used,
- Spectrogram with prominent features labeled (significant lines, etc.)
- Wavelength of maximum transmission,
- Temperature of the star’s surface,
- Estimated stellar type,
- Distance to the star,
- Graph of Absolute Magnitude (y) vs. Surface Temperature (x) for all stars measured.
- Additional notes or observations related to the star. (This might include perceived visual color, imaging difficulty related to poor seeing, placement close to the horizon (airmass concerns), etc.)
Part II: Spectroscopic Binary Stars
Many double stars have separations that are much too small to see for even the best telescopes. We know they are doubles because their spectra changes repeatably over time. Your task is to verify five spectroscopic eclipsing binary stars.
To help pick spectroscopic eclipsing binary stars to verify go to the “TIDAK - TIming DAtabase at Krakow“ web site (http://www.as.up.krakow.pl/ephem/) and/or the "Ephemerides of Variable Stars" (http://www.motl.cz/dmotl/predpovedi/). You will use these databases to pick the stars you wish to verify because it will give you predictions of the best times for your observations. Select a constellation and look through the list noting the magnitudes and periods. Select eclipsing binaries that have magnitudes that are possible with your equipment based on your experience collecting data for the stars you choose in Part I. Eclipsing binaries with short periods can be done in one evening. Click an eclipsing binary and note that the new page gives a number of primary and secondary minima times for the next few days or weeks. A primary minimum is when the primary star (the brightest of the pair) blocks the light from the secondary star (the dimmer of the pair). A secondary minimum is the opposite. You should image the eclipsing binary near these two times. If the primary and secondary stars are different stellar types, it may be possible to note a change in the spectra. By clicking on the Simbad link on the page it is possible to see the Spectral Type. Select your five eclipsing binary stars so they have different spectral types as far apart as possible. Since you won’t have to note the maximum wavelength any star type can be used. While not specifically required Algol (beta Per), TX UMa, and U Cep are good examples. Negative observations are permitted since this is dependant on the resolution of your spectrometer.
Additional information other than the minima times can be found in the AAVSO’s VSX (https://www.aavso.org/vsx/).
Imaging the star every few minutes for an hour on either side of the predicted minimum should give you enough data to ensure that you can tell that the eclipse actually happened.
For the five eclipsing binary stars report imaging data as above, the two spectra, the two spectrograms, and estimated stellar types for each member in the pair.
Note: The ability to successfully complete some of the projects will depend on the resolution of your spectrograph.
Project 1: Spectra of Extended Deep Sky Objects
Capture and analyze the spectra of ten extended deep sky objects found within the Milky Way (planetary nebulae, open clusters, globular clusters, reflection and diffuse nebulae). Some types will give better results than others. Can you guess this in advance? Identify elements found in the spectra. Might your results suggest possible filters to aid in imaging these objects?
Project 2: Detect the Methane Atmosphere in Neptune and Uranus
Capture and analyze the spectra of Neptune and Uranus. Label the methane bands in their spectrograms.
Project 3 Spectra of Comets
Capture, analyze, and report any elements found in the spectra of two comets.
Project 4 Measure the red shift of galaxies
Capture and analyze the spectra of two galaxies. Galaxies with small, bright cores will work the best. Compare the spectra to an A class star to see how much the Hydrogen-alpha line has been shifted in wavelength. From the shift calculate z describing the galaxy’s red shift.
Project 5 Spectra of RR Lyra type variable stars over a night
Capture and analyze the spectra of RR Lyra or other RR Lyra type variable star over the course of one night. Note any changes in the spectrum.
Note: RR Lyra is the brightest and easiest of the type with a magnitude range of 7.17-8.14 over a .567 day period.
Project 6 User Submitted
Got an idea of something you’d like to try? Email the Observing Program’s coordinator to discuss the topic. Possible ideas could include (but are not limited to):
- the change in spectra of a carbon star throughout its period,
- a study of Wolf-Rayet stars,
- the change in a supernova over time as it dims,
- high resolution solar spectrum showing Fraunhofer lines,
- using spectra to differentiate between eclipsing binary stars and exoplanets,
- solar spectra and the sun’s rotation, or
- explore stellar class classification by the B – V method outlined above.
Submitting for Certification
To receive your Spectroscopy Observing Program certificate and pin, send a copy of your log or report including a copy of all relevant data, graphs, and contact information to the Coordinator via email or mail for verification. Submissions will not be returned. I prefer to verify the observations myself since I really love to see what other observers have done. However, if mailing the observations seems impractical and there is another member in your club who has already received the Spectroscopy Observing Program certification, I will accept an email recommendation from that person or your club's Awards Coordinator after they have reviewed and approved your work. If there are any questions or problems, please contact the Coordinator.
Upon verification of your observations, your electronic certificate and pin will be forwarded either to you or your society's Awards Coordinator, whomever you choose.
Please send your submission to:
Spectroscopy Observing Program Coordinator:
Thanks to Mark Simonson of the Everett Astronomical Society and the Hydrogen Alpha Solar Observing Program Coordinator for his efforts in assisting the development of this Observing Program and for creating the design for both the Certificate and Pin.
- Basic Astronomical Spectroscopy Software: BASS (free) - https://uk.groups.yahoo.com/neo/groups/astrobodger/info (The dowload is available from their links section, but you must join their group.)
- ISIS (free) - http://www.astrosurf.com/buil/isis-software.html
- Rspec $ - https://www.rspec-astro.com
- SBIG’s viewer for their STI Spectrograph - http://diffractionlimited.com/product/st-i-spectrograph/ (Note: this product is discontinued.)
- V-Spec free - http://astrosurf.com/vdesnoux/
- V-Spec Professional $ - http://www.rcubedsw.com/vspec---vspec-pro.html
- and there are others...
Additional Useful Links:
- Christian Buil’s page: http://www.astrosurf.com/buil/index.html
- David Haworth’s Observational Astronomy Spectroscopy Index: http://www.stargazing.net/david/spectroscopy/index.html
- Richard Walker’s page and on line books:
- Spectral Types Characteristics Table: https://sites.uni.edu/morgans/astro/course/Notes/section2/spectraltemps.html
- Robin Leadbeater’s Three Hills Observatory’s spectrograph pages: http://www.threehillsobservatory.co.uk/astro/spectroscopy.htm
- CloudyNight Disscusion about a DIY solution: https://www.cloudynights.com/topic/487663-how-to-make-your-own-star-analyser/ | 0.824286 | 3.919431 |
The spring equinox of Mars this year is a particularly auspicious time for scientists who study the red planet’s surface.
On July 4th, both the planet’s north and south poles were exposed to sunlight, allowing us to capture images from all over Mars. It was also a time when Earth and Mars came closest to each other in the current 26-month cycle, lining up in a straight-line formation on one side of the sun. Because of this (relatively) close encounter, the Mars Renaissance Orbiter (MRO), the spacecraft that collects data from the planet, could send information back to Earth at its peak data transfer rate. This allowed scientists to create more abundant and clearer images of Mars’ uncharted territories than in any other month of the orbit.
The results are the images created by the High Resolution Imaging Science Experiment (HiRISE) camera, the highest resolution instrument equipped on the MRO. The images were released on Aug. 3 on the project’s public catalog.
The images don’t reflect the natural colors of Mars. “The dust in the atmosphere affects everything we see, and we try to process the images to normalize that,” says Alfred McEwen, lead scientist of the HiRISE project and planetary geologist at the University of Arizona.”We stretch these images digitally taking the minimum values and maximum values to show the features.”
Similar to satellite images created in “false colors,” the HiRISE images show what naked eye cannot see: instead of showing dull, reddish dust in the Martian atmosphere, the processed images have enhanced contrasts to highlight territorial features, represented with ranges of synthetic reds, blues and whites.
Red indicates areas covered by dust settling from the atmosphere, blue represents rocky and sandy regions, and white is a sign of frosty surfaces of both water and dry ice. Analyzing these synthetic colors, shapes, and forms can help scientists better understand what we are really seeing on Mars.
These images are valuable for identifying future landing spots for rovers, says McEwen, and would help future landers to avoid small hazards like boulders. They are also helpful for studying basically everything on the surface of Mars: geological history, migrating sand dunes, dry ice jets and other geological processes. | 0.847439 | 3.662742 |
Climate change, periodic modification of Earth’s climate brought about as a result of changes in the atmosphere as well as interactions between the atmosphere and various other geologic, chemical, biological, and geographic factors within the Earth system.
The atmosphere is a dynamic fluid that is continually in motion. Both its physical properties and its rate and direction of motion are influenced by a variety of factors, including solar radiation, the geographic position of continents, ocean currents, the location and orientation of mountain ranges, atmospheric chemistry, and vegetation growing on the land surface. All these factors change through time. Some factors, such as the distribution of heat within the oceans, atmospheric chemistry, and surface vegetation, change at very short timescales. Others, such as the position of continents and the location and height of mountain ranges, change over very long timescales. Therefore, climate, which results from the physical properties and motion of the atmosphere, varies at every conceivable timescale.
Climate is often defined loosely as the average weather at a particular place, incorporating such features as temperature, precipitation, humidity, and windiness. A more specific definition would state that climate is the mean state and variability of these features over some extended time period. Both definitions acknowledge that the weather is always changing, owing to instabilities in the atmosphere. And as weather varies from day to day, so too does climate vary, from daily day-and-night cycles up to periods of geologic time hundreds of millions of years long. In a very real sense, climate variation is a redundant expression—climate is always varying. No two years are exactly alike, nor are any two decades, any two centuries, or any two millennia (see also Climate Change Throughout History).
This article addresses the concept of climatic variation and change within the set of integrated natural features and processes known as the Earth system. The nature of the evidence for climate change is explained, as are the principal mechanisms that have caused climate change throughout the history of Earth. For a detailed description of the development of Earth’s atmosphere, see the article atmosphere, evolution of. For full treatment of the most critical issue of climate change in the contemporary world, see global warming.
The Earth system
The atmosphere is influenced by and linked to other features of Earth, including oceans, ice masses (glaciers and sea ice), land surfaces, and vegetation. Together, they make up an integrated Earth system, in which all components interact with and influence one another in often complex ways. For instance, climate influences the distribution of vegetation on Earth’s surface (e.g., deserts exist in arid regions, forests in humid regions), but vegetation in turn influences climate by reflecting radiant energy back into the atmosphere, transferring water (and latent heat) from soil to the atmosphere, and influencing the horizontal movement of air across the land surface.
Earth scientists and atmospheric scientists are still seeking a full understanding of the complex feedbacks and interactions among the various components of the Earth system. This effort is being facilitated by the development of an interdisciplinary science called Earth system science. Earth system science is composed of a wide range of disciplines, including climatology (the study of the atmosphere), geology (the study of Earth’s surface and underground processes), ecology (the study of how Earth’s organisms relate to one another and their environment), oceanography (the study of Earth’s oceans), glaciology (the study of Earth’s ice masses), and even the social sciences (the study of human behaviour in its social and cultural aspects).
A full understanding of the Earth system requires knowledge of how the system and its components have changed through time. The pursuit of this understanding has led to development of Earth system history, an interdisciplinary science that includes not only the contributions of Earth system scientists but also paleontologists (who study the life of past geologic periods), paleoclimatologists (who study past climates), paleoecologists (who study past environments and ecosystems), paleoceanographers (who study the history of the oceans), and other scientists concerned with Earth history. Because different components of the Earth system change at different rates and are relevant at different timescales, Earth system history is a diverse and complex science. Students of Earth system history are not just concerned with documenting what has happened; they also view the past as a series of experiments in which solar radiation, ocean currents, continental configurations, atmospheric chemistry, and other important features have varied. These experiments provide opportunities to learn the relative influences of and interactions between various components of the Earth system. Studies of Earth system history also specify the full array of states the system has experienced in the past and those the system is capable of experiencing in the future.
Undoubtedly, people have always been aware of climatic variation at the relatively short timescales of seasons, years, and decades. Biblical scripture and other early documents refer to droughts, floods, periods of severe cold, and other climatic events. Nevertheless, a full appreciation of the nature and magnitude of climatic change did not come about until the late 18th and early 19th centuries, a time when the widespread recognition of the deep antiquity of Earth occurred. Naturalists of this time, including Scottish geologist Charles Lyell, Swiss-born naturalist and geologist Louis Agassiz, English naturalist Charles Darwin, American botanist Asa Gray, and Welsh naturalist Alfred Russel Wallace, came to recognize geologic and biogeographic evidence that made sense only in the light of past climates radically different from those prevailing today.
Geologists and paleontologists in the 19th and early 20th centuries uncovered evidence of massive climatic changes taking place before the Pleistocene—that is, before some 2.6 million years ago. For example, red beds indicated aridity in regions that are now humid (e.g., England and New England), whereas fossils of coal-swamp plants and reef corals indicated that tropical climates once occurred at present-day high latitudes in both Europe and North America. Since the late 20th century the development of advanced technologies for dating rocks, together with geochemical techniques and other analytical tools, have revolutionized the understanding of early Earth system history.
The occurrence of multiple epochs in recent Earth history during which continental glaciers, developed at high latitudes, penetrated into northern Europe and eastern North America was recognized by scientists by the late 19th century. Scottish geologist James Croll proposed that recurring variations in orbital eccentricity (the deviation of Earth’s orbit from a perfectly circular path) were responsible for alternating glacial and interglacial periods. Croll’s controversial idea was taken up by Serbian mathematician and astronomer Milutin Milankovitch in the early 20th century. Milankovitch proposed that the mechanism that brought about periods of glaciation was driven by cyclic changes in eccentricity as well as two other orbital parameters: precession (a change in the directional focus of Earth’s axis of rotation) and axial tilt (a change in the inclination of Earth’s axis with respect to the plane of its orbit around the Sun). Orbital variation is now recognized as an important driver of climatic variation throughout Earth’s history (see below Orbital [Milankovitch] variations).
Evidence for climate change
All historical sciences share a problem: As they probe farther back in time, they become more reliant on fragmentary and indirect evidence. Earth system history is no exception. High-quality instrumental records spanning the past century exist for most parts of the world, but the records become sparse in the 19th century, and few records predate the late 18th century. Other historical documents, including ship’s logs, diaries, court and church records, and tax rolls, can sometimes be used. Within strict geographic contexts, these sources can provide information on frosts, droughts, floods, sea ice, the dates of monsoons, and other climatic features—in some cases up to several hundred years ago.
Fortunately, climatic change also leaves a variety of signatures in the natural world. Climate influences the growth of trees and corals, the abundance and geographic distribution of plant and animal species, the chemistry of oceans and lakes, the accumulation of ice in cold regions, and the erosion and deposition of materials on Earth’s surface. Paleoclimatologists study the traces of these effects, devising clever and subtle ways to obtain information about past climates. Most of the evidence of past climatic change is circumstantial, so paleoclimatology involves a great deal of investigative work. Wherever possible, paleoclimatologists try to use multiple lines of evidence to cross-check their conclusions. They are frequently confronted with conflicting evidence, but this, as in other sciences, usually leads to an enhanced understanding of the Earth system and its complex history. New sources of data, analytical tools, and instruments are becoming available, and the field is moving quickly. Revolutionary changes in the understanding of Earth’s climate history have occurred since the 1990s, and coming decades will bring many new insights and interpretations.
Ongoing climatic changes are being monitored by networks of sensors in space, on the land surface, and both on and below the surface of the world’s oceans. Climatic changes of the past 200–300 years, especially since the early 1900s, are documented by instrumental records and other archives. These written documents and records provide information about climate change in some locations for the past few hundred years. Some very rare records date back over 1,000 years. Researchers studying climatic changes predating the instrumental record rely increasingly on natural archives, which are biological or geologic processes that record some aspect of past climate. These natural archives, often referred to as proxy evidence, are extraordinarily diverse; they include, but are not limited to, fossil records of past plant and animal distributions, sedimentary and geochemical indicators of former conditions of oceans and continents, and land surface features characteristic of past climates. Paleoclimatologists study these natural archives by collecting cores, or cylindrical samples, of sediments from lakes, bogs, and oceans; by studying surface features and geological strata; by examining tree ring patterns from cores or sections of living and dead trees; by drilling into marine corals and cave stalagmites; by drilling into the ice sheets of Antarctica and Greenland and the high-elevation glaciers of the Plateau of Tibet, the Andes, and other montane regions; and by a wide variety of other means. Techniques for extracting paleoclimatic information are continually being developed and refined, and new kinds of natural archives are being recognized and exploited.
Causes of climate change
It is much easier to document the evidence of climate variability and past climate change than it is to determine their underlying mechanisms. Climate is influenced by a multitude of factors that operate at timescales ranging from hours to hundreds of millions of years. Many of the causes of climate change are external to the Earth system. Others are part of the Earth system but external to the atmosphere. Still others involve interactions between the atmosphere and other components of the Earth system and are collectively described as feedbacks within the Earth system. Feedbacks are among the most recently discovered and challenging causal factors to study. Nevertheless, these factors are increasingly recognized as playing fundamental roles in climate variation. The most important mechanisms are described in this section.
The luminosity, or brightness, of the Sun has been increasing steadily since its formation. This phenomenon is important to Earth’s climate, because the Sun provides the energy to drive atmospheric circulation and constitutes the input for Earth’s heat budget. Low solar luminosity during Precambrian time underlies the faint young Sun paradox, described in the article Climate Change Throughout History.
Radiative energy from the Sun is variable at very small timescales, owing to solar storms and other disturbances, but variations in solar activity, particularly the frequency of sunspots, are also documented at decadal to millennial timescales and probably occur at longer timescales as well. The “Maunder minimum,” a period of drastically reduced sunspot activity between AD 1645 and 1715, has been suggested as a contributing factor to the Little Ice Age.
Volcanic activity can influence climate in a number of ways at different timescales. Individual volcanic eruptions can release large quantities of sulfur dioxide and other aerosols into the stratosphere, reducing atmospheric transparency and thus the amount of solar radiation reaching Earth’s surface and troposphere. A recent example is the 1991 eruption in the Philippines of Mount Pinatubo, which had measurable influences on atmospheric circulation and heat budgets. The 1815 eruption of Mount Tambora on the island of Sumbawa had more dramatic consequences, as the spring and summer of the following year (1816, known as “the year without a summer”) were unusually cold over much of the world. New England and Europe experienced snowfalls and frosts throughout the summer of 1816.
Volcanoes and related phenomena, such as ocean rifting and subduction, release carbon dioxide into both the oceans and the atmosphere. Emissions are low; even a massive volcanic eruption such as Mount Pinatubo releases only a fraction of the carbon dioxide emitted by fossil-fuel combustion in a year. At geologic timescales, however, release of this greenhouse gas can have important effects. Variations in carbon dioxide release by volcanoes and ocean rifts over millions of years can alter the chemistry of the atmosphere. Such changeability in carbon dioxide concentrations probably accounts for much of the climatic variation that has taken place during the Phanerozoic Eon.
Tectonic movements of Earth’s crust have had profound effects on climate at timescales of millions to tens of millions of years. These movements have changed the shape, size, position, and elevation of the continental masses as well as the bathymetry of the oceans. Topographic and bathymetric changes in turn have had strong effects on the circulation of both the atmosphere and the oceans. For example, the uplift of the Tibetan Plateau during the Cenozoic Era affected atmospheric circulation patterns, creating the South Asian monsoon and influencing climate over much of the rest of Asia and neighbouring regions.
Tectonic activity also influences atmospheric chemistry, particularly carbon dioxide concentrations. Carbon dioxide is emitted from volcanoes and vents in rift zones and subduction zones. Variations in the rate of spreading in rift zones and the degree of volcanic activity near plate margins have influenced atmospheric carbon dioxide concentrations throughout Earth’s history. Even the chemical weathering of rock constitutes an important sink for carbon dioxide. (A carbon sink is any process that removes carbon dioxide from the atmosphere by the chemical conversion of CO2 to organic or inorganic carbon compounds.) Carbonic acid, formed from carbon dioxide and water, is a reactant in dissolution of silicates and other minerals. Weathering rates are related to the mass, elevation, and exposure of bedrock. Tectonic uplift can increase all these factors and thus lead to increased weathering and carbon dioxide absorption. For example, the chemical weathering of the rising Tibetan Plateau may have played an important role in depleting the atmosphere of carbon dioxide during a global cooling period in the late Cenozoic Era.
Orbital (Milankovich) variations
The orbital geometry of Earth is affected in predictable ways by the gravitational influences of other planets in the solar system. Three primary features of Earth’s orbit are affected, each in a cyclic, or regularly recurring, manner. First, the shape of Earth’s orbit around the Sun, varies from nearly circular to elliptical (eccentric), with periodicities of 100,000 and 413,000 years. Second, the tilt of Earth’s axis with respect to the Sun, which is primarily responsible for Earth’s seasonal climates, varies between 22.1° and 24.5° from the plane of Earth’s rotation around the Sun. This variation occurs on a cycle of 41,000 years. In general, the greater the tilt, the greater the solar radiation received by hemispheres in summer and the less received in winter. The third cyclic change to Earth’s orbital geometry results from two combined phenomena: (1) Earth’s axis of rotation wobbles, changing the direction of the axis with respect to the Sun, and (2) the orientation of Earth’s orbital ellipse rotates slowly. These two processes create a 26,000-year cycle, called precession of the equinoxes, in which the position of Earth at the equinoxes and solstices changes. Today Earth is closest to the Sun (perihelion) near the December solstice, whereas 9,000 years ago perihelion occurred near the June solstice.
These orbital variations cause changes in the latitudinal and seasonal distribution of solar radiation, which in turn drive a number of climate variations. Orbital variations play major roles in pacing glacial-interglacial and monsoonal patterns. Their influences have been identified in climatic changes over much of the Phanerozoic. For example, cyclothems—which are interbedded marine, fluvial, and coal beds characteristic of the Pennsylvanian Subperiod (318.1 million to 299 million years ago)—appear to represent Milankovitch-driven changes in mean sea level.
Greenhouse gases are gas molecules that have the property of absorbing infrared radiation (net heat energy) emitted from Earth’s surface and reradiating it back to Earth’s surface, thus contributing to the phenomenon known as the greenhouse effect. Carbon dioxide, methane, and water vapour are the most important greenhouse gases, and they have a profound effect on the energy budget of the Earth system despite making up only a fraction of all atmospheric gases. Concentrations of greenhouse gases have varied substantially during Earth’s history, and these variations have driven substantial climate changes at a wide range of timescales. In general, greenhouse gas concentrations have been particularly high during warm periods and low during cold phases. A number of processes influence greenhouse gas concentrations. Some, such as tectonic activities, operate at timescales of millions of years, whereas others, such as vegetation, soil, wetland, and ocean sources and sinks, operate at timescales of hundreds to thousands of years. Human activities—especially fossil-fuel combustion since the Industrial Revolution—are responsible for steady increases in atmospheric concentrations of various greenhouse gases, especially carbon dioxide, methane, ozone, and chlorofluorocarbons (CFCs).
Perhaps the most intensively discussed and researched topic in climate variability is the role of interactions and feedbacks among the various components of the Earth system. The feedbacks involve different components that operate at different rates and timescales. Ice sheets, sea ice, terrestrial vegetation, ocean temperatures, weathering rates, ocean circulation, and greenhouse gas concentrations are all influenced either directly or indirectly by the atmosphere; however, they also all feed back into the atmosphere, thereby influencing it in important ways. For example, different forms and densities of vegetation on the land surface influence the albedo, or reflectivity, of Earth’s surface, thus affecting the overall radiation budget at local to regional scales. At the same time, the transfer of water molecules from soil to the atmosphere is mediated by vegetation, both directly (from transpiration through plant stomata) and indirectly (from shading and temperature influences on direct evaporation from soil). This regulation of latent heat flux by vegetation can influence climate at local to global scales. As a result, changes in vegetation, which are partially controlled by climate, can in turn influence the climate system. Vegetation also influences greenhouse gas concentrations; living plants constitute an important sink for atmospheric carbon dioxide, whereas they act as sources of carbon dioxide when they are burned by wildfires or undergo decomposition. These and other feedbacks among the various components of the Earth system are critical for both understanding past climate changes and predicting future ones.
Recognition of global climate change as an environmental issue has drawn attention to the climatic impact of human activities. Most of this attention has focused on carbon dioxide emission via fossil-fuel combustion and deforestation. Human activities also yield releases of other greenhouse gases, such as methane (from rice cultivation, livestock, landfills, and other sources) and chlorofluorocarbons (from industrial sources). There is little doubt among climatologists that these greenhouse gases affect the radiation budget of Earth; the nature and magnitude of the climatic response are a subject of intense research activity. Paleoclimate records from tree rings, coral, and ice cores indicate a clear warming trend spanning the entire 20th century and the first decade of the 21st century. In fact, the 20th century was the warmest of the past 10 centuries, and the decade 2001–10 was the warmest decade since the beginning of modern instrumental record keeping. Many climatologists have pointed to this warming pattern as clear evidence of human-induced climate change resulting from the production of greenhouse gases.
A second type of human impact, the conversion of vegetation by deforestation, afforestation, and agriculture, is receiving mounting attention as a further source of climate change. It is becoming increasingly clear that human impacts on vegetation cover can have local, regional, and even global effects on climate, due to changes in the sensible and latent heat flux to the atmosphere and the distribution of energy within the climate system. The extent to which these factors contribute to recent and ongoing climate change is an important, emerging area of study.
Written by Stephen T. Jackson, Professor Emeritus of Botany, University of Wyoming.
Top image credits: ©jzehnder/Fotolia | 0.804694 | 3.341172 |
The configuration of our solar system is remarkably ordered — the eight planets orbit the sun in tight circles within the same sprawling plane. Most of the exoplanets that have been discovered so far follow orbits that are much more erratic.
But, now, the first exoplanetary system with regularly aligned orbits similar to those in our solar system has been discovered. It’s located 10,000 light years away, and at its center is Kepler-30, a star as bright and massive as the sun.
“After analyzing data from NASA’s Kepler space telescope, the MIT scientists and their colleagues discovered that the star — much like the sun — rotates around a vertical axis and its three planets have orbits that are all in the same plane,” the MIT news release states.
“In our solar system, the trajectory of the planets is parallel to the rotation of the sun, which shows they probably formed from a spinning disc,” says Roberto Sanchis-Ojeda, a physics graduate student at MIT who led the research effort. “In this system, we show that the same thing happens.”
The findings, just published in the journal Nature, may help to explain the origins of “certain far-flung systems while shedding light on our own planetary neighborhood.”
“It’s telling me that the solar system isn’t some fluke,” says Josh Winn, an associate professor of physics at MIT and a co-author on the paper. “The fact that the sun’s rotation is lined up with the planets’ orbits, that’s probably not some freak coincidence.”
“Winn says the team’s discovery may back a recent theory of how hot Jupiters form. These giant bodies are named for their extremely close proximity to their white-hot stars, completing an orbit in mere hours or days. Hot Jupiters’ orbits are typically off-kilter, and scientists have thought that such misalignments might be a clue to their origins: Their orbits may have been knocked askew in the very early, volatile period of a planetary system’s formation, when several giant planets may have come close enough to scatter some planets out of the system while bringing others closer to their stars.”
“Recently, scientists have identified a number of hot Jupiter systems, all of which have tilted orbits. But to really prove this ‘planetary scattering’ theory, Winn says researchers have to identify a non-hot Jupiter system, one with planets circling farther from their star. If the system were aligned like our solar system, with no orbital tilt, it would provide evidence that only hot Jupiter systems are misaligned, formed as a result of planetary scattering.”
“… In order to resolve the puzzle, Sanchis-Ojeda looked through data from the Kepler space telescope, an instrument that monitors 150,000 stars for signs of distant planets. He narrowed in on Kepler-30, a non-hot Jupiter system with three planets, all with much longer orbits than a typical hot Jupiter. To measure the alignment of the star, Sanchis-Ojeda tracked its sunspots, dark splotches on the surface of bright stars like the sun.”
“These little black blotches march across the star as it rotates,” Winn says. “If we could make an image, that’d be great, because you’d see exactly how the star is oriented just by tracking these spots.”
“But stars like Kepler-30 are extremely far away, so capturing an image of them is almost impossible: The only way to document such stars is by measuring the small amount of light they give off. So the team looked for ways to track sunspots using the light of these stars. Each time a planet transits — or crosses in front of — such a star, it blocks a bit of starlight, which astronomers see as a dip in light intensity. If a planet crosses a dark sunspot, the amount of light blocked decreases, creating a blip in the data dip.”
“If you get a blip of a sunspot, then the next time the planet comes around, the same spot might have moved over here, and you’d see the blip not here but there,” Winn says. “So the timing of these blips is what we use to determine the alignment of the star.”
“From the data blips, Sanchis-Ojeda concluded that Kepler-30 rotates along an axis perpendicular to the orbital plane of its largest planet. The researchers then determined the alignment of the planets’ orbits by studying the gravitational effects of one planet on another. By measuring the timing variations of planets as they transit the star, the team derived their respective orbital configurations, and found that all three planets are aligned along the same plane. The overall planetary structure, Sanchis-Ojeda found, looks much like our solar system.”
“James Lloyd, an assistant professor of astronomy at Cornell University who was not involved in this research, says that studying planetary orbits may shed light on how life evolved in the universe — since in order to have a stable climate suitable for life, a planet needs to be in a stable orbit.”
“In order to understand how common life is in the universe, ultimately we will need to understand how common stable planetary systems are,” Lloyd says. “We may find clues in extrasolar planetary systems to help understand the puzzles of the solar system, and vice versa.”
“The findings from this first study of the alignment of a non-hot Jupiter system suggest that hot Jupiter systems may indeed form via planetary scattering. To know for sure, Winn says he and his colleagues plan to measure the orbits of other far-off solar systems.”
“We’ve been hungry for one like this, where it’s not exactly like the solar system, but at least it’s more normal, where the planets and the star are aligned with each other,” Winn says. “It’s the first case where we can say that, besides the solar system.” | 0.912284 | 3.998057 |
A major ‘catastrophic’ collision may have killed life on Mars (the Red Planet) four billion years ago, scientists say. According to them, this event resulted in the death of an entire alien race. The scientists were constructing their findings on data returned by the Curiosity rover.
NASA scientists believe that the massive collision perhaps caused by volcanic eruptions or a devastating crash with a Pluto-sized planet, caused the air to shrink and strip away and kill any forms life on the planet.
Dr. Chris Webster at NASA’s Jet Propulsion Laboratory in Pasadena, lead author on the study, said,
“As Mars became a planet and its magma ocean solidified, catastrophic outgassing occurred while volatiles were delivered by impact of comets and other smaller bodies. Solar wind and the possible impact by a Pluto-sized body is thought to have stripped much of the initial early atmosphere from the planet, and since then the atmosphere has developed as a balance between volcanic injection and loss to space.”
Life on Mars existed billions of years ago, scientists believe, before a catastrophic collision killed it.
The study of the Curiosity rover’s data has found that the atmosphere on Mars at one time was denser and wetter, leading scientists to believe that it contained oxygen long before the atmosphere on Earth did.
A sample drilled from a Martian sedimentary bedrock was found to contain clay minerals, sulfate minerals, and other chemicals. Minerals, including hydrogen, carbon and oxygen, were also found in rocks picked up by the Curiosity. These are the building blocks of life, NASA scientists say.
Researchers, analyzing the chemicals in the rocks, were able to conclude that the water that helped form these rocks were of a relatively neutral pH. Scientists said the finding could represent another step forward to proving the existence of conditions that could support life on Mars.
“A fundamental question for this mission is whether Mars could have supported a habitable environment,” said Michael Meyer, lead scientist for NASA’s Mars Exploration Program. “From what we know now, the answer is yes.”
NASA scientists were also probing the Martian atmosphere for methane after a telescope on Earth had detected an unexpected and mysterious amount of the gas in western hemisphere of the Red Planet. On Earth, methane is mainly a by-product of life, from animal digestion and decaying plants. The gas can also be produced by non-biological processes.
According to scientists the presence of methane could have suggested there was some form of life still lingering on the planet. However, the Curiosity rover did not find any methane. This has disappointed scientists who believe microbes may still exist on the planet.
NASA says the new results from Curiosity will make it possible for scientists to replicate the evolution of the Martian climate over time. It will also allow them to determine whether the planet was warm and wet once upon a time and if it might have had the right conditions for life.
NASA’s Dr. Paul Mahaffy and a lead scientist in the study said:
“A fundamental question regarding the habitability of early Mars is how long liquid water, in the form of lakes, or even oceans, might have persisted on the surface to support microbial life that may have been present.”
John Grunsfeld, an official at NASA said the finding makes him “feel giddy.”
He added that the new data adds to the image of Mars containing a possible freshwater lake and a snow-capped Mount Sharp before a catastrophic collision on the Red Planet killed life.
Curiosity, a six-wheeled robot was sent Mars on a two year mission. It made a dramatic landing last August on Mars equator.
By Perviz Walji | 0.803397 | 3.087867 |
A never-before-seen meteor shower expected to make a dazzling debut early Saturday morning instead fizzled over a nearly moonless sky.
A few meteors did streak by — but they were far fewer than astronomers had hoped to see.
“Predicting the strength of a meteor shower is far from an exact science,” John Scholl, president of the Pontchartrain Astronomy Society, said in an email. “So it is not unusual for one to fall below expectations.”
For would-be stargazers watching the spectacle from a bar in the French Quarter, the city’s bright lights most likely drowned out much of the show, according to Christopher Kersey, a manager at Highland Road Park Observatory in Baton Rouge.
The meteors originated from a comet called Camelopardalids after the giraffe constellation Camelopardalis. They are tiny remnants from when the comet passed through this orbit in the 18th and 19th centuries. It will pass 5 million miles from Earth on May 29, Mr. Kersey said.
Astronomers were not sure if the display would be dazzling or a dud — but, like Mr. Kersey, most were optimistic. Some astronomers said the shower might shoot as many as 800 to 1,000 meteors across the sky every hour.
If that had happened, Mr. Kersey had said, it would have looked like Earth was “plowing through a snow globe.”
Merrill Hess, president of the Baton Rouge Astronomical Society, likened comets to dirty snowballs that leave behind a trail of debris as they fly through their orbit. The tiny bits of comet dust zoomed through space at 40 miles per second until they hit the earth’s atmosphere and ignited in a bright flash fed by a rush of air as the specks hurtled down. This is what we call shooting stars.
The night’s dim crescent moon made the meteors that people did see more visible than they would have been through the light pollution that typically obscures the sky. Astronomers said we would likely see this shower only once.
Some who watched the meteor shower early Saturday said they found it hard to see through a bank of clouds, and they did not see as many shooting stars as they had hoped.
“This was the first time the earth was going to pass through the path of the comet,” Jack Huerkamp, a member of the Pontchartrain Astronomy Society, said in an email. “The big unknown was how much debris was in the path. Obviously not much!”
Though it wasn’t as spectacular as predicted, those who did catch a glimpse of the Camelopardalids shower saw something special, according to Peter Jenniskens, a NASA meteorite hunter at the SETI Institute, a nonprofit for scientific research in California. Mr. Jenniskens believes he was the first to discover the potential of the meteorite shower back in 2004.
“If you see some of these, then you are the very first person to ever see this particular meteor shower,” he said before the event. “This one hasn’t happened before, and it won’t happen again.”
Astronomers had high hopes for Camelopardalids because no one had seen it before. Even better, it was coming around on the kind of dark night perfect for viewing shooting stars, even in a well-lit place like New Orleans.
Like many urban areas, Mr. Kersey said, the city has many streetlights that illuminate tiny reflecting particles in the sky, creating a glowing haze. The stronger the haze, the fewer stars that can be seen.
A campaign to reduce nighttime illumination — called the the “dark sky” movement — has gained strength in recent years, in large part because of efforts from groups like the Arizona-based International Dark-Sky Association, which organizes a seven-day event annually to get people to help reduce light pollution.
Mr. Kersey said light fixtures were a big part of the problem in New Orleans. Many of the city’s street lamps are not capped and allow light to shine in all directions, rather than just down. That unchecked light blots constellations from a city’s night sky or dims brilliant meteor showers, unless stargazers seek out an unlit area.
“I don’t think people should have to waste gas money and vacation time to see the Milky Way,” he said. | 0.887131 | 3.413524 |
Many locations along the UK, US and Australian coasts will experience their highest tides for tens of years around September 29 or 30. Coastal roads in Miami, for instance, have already been closed in anticipation of exceptional tides.
These high tides may bring water levels uncomfortably close to the tops of harbour walks and flood defences, emphasising the threat of rising sea levels. In the UK they are unlikely to be a major problem on their own unless they coincide with storms (a strong storm surge has a greater impact than even the most exotic of tides). However in other areas, like in parts of America and the Pacific, no storms are necessary: these high tides on their own can lead to nuisance flooding.
Why do we expect such extreme tides?
Tides are controlled by changes in the position and alignment of the moon and sun relative to Earth. Every fortnight – at new moon or full moon – the Earth, sun and moon are in an approximately straight line as seen from space and the additional gravitational pull of the sun causes stronger tides, known as spring tides.
Yet each month one set of spring tides is higher than the other. This is because tidal forces are strengthened when the moon is at “perigee” and its elliptical orbit takes it closest to Earth. Tide-generating forces are also enhanced when the moon is directly overhead at the equator, part of a cycle lasting 27.2 days – a so-called “draconic month”.
Tides can differ over the course of a year, as the Earth moves from its closest (perihelion) to furthest (aphelion) point from the sun and back. More important is the variation in the sun’s position north or south of the equator, which causes the seasons. The tide-generating forces are greatest at the equinoxes in March and September when the sun is directly overhead at the equator. Spring tides are always higher at these times of year.
A perfect tide?
Over periods longer than a year, very large spring tides occur when all the astronomical factors we have mentioned earlier coincide.
Two longer-term motions of the moon’s orbit around the Earth are important. These motions (astronomers call them precessions) are the reason we are seeing unusually large spring tides this year.
The first precession is known as the cycle of lunar perigee, and influences tides about every four to five years. The elliptical orbit of the moon around the Earth slowly moves in relation to the sun, completing a full circuit every 8.8 years. This means at either the March or September equinox approximately every 4.5 years the moon is both at its closest point to the Earth, and is also overhead at the equator.
The second precession is known as the lunar nodal cycle and is due to a very slow change in the moon’s orbit. Imagine the Earth’s orbit around the sun took place on an enormous sheet of glass – what astronomers call the ecliptic plane. The moon’s orbit cuts this surface at an angle of approximately 5 degrees. Over 18.6 years the moon’s orbit slowly rotates around so it cuts through the ecliptic plane in a different place.
One effect of this is to change how far above or below the equator the moon can reach in its orbit. In 2015 the moon is at the point where it deviates the least from the equator. This slightly increases the chances of the moon being directly overhead at the equator at any given point, and thus coinciding with the other factors that contribute to extreme tidal forces.
A lot of things have to fall in place at once to generate record-breaking tides and this year the cycle of lunar perigee and the lunar nodal cycle nearly perfectly coincide, resulting in some of the highest spring tides for decades.
The authors help run the SurgeWatch website and would welcome any photos of high tides during this period.
Image by Javi Sánchez de la viña under Creative Commons licence. | 0.804497 | 3.785393 |
NASA’s New Horizons spacecraft successfully flew past the most distant world ever explored by humans on New Year’s Day. Now, a clearer picture of the 22-mile-long object known as Ultima Thule is beginning to take shape — and it has scientists baffled.
“We’ve never seen anything like this,” said Alan Stern, principal investigator for the New Horizons mission. “It’s a mystery.”
The New Horizons spacecraft zoomed past Ultima Thule on Jan.1 at a speed of 32,000 mph, furiously collecting data as it went. At the moment of closest approach it was about 2,200 miles from the small world’s surface, or roughly the distance from Los Angeles to Washington, D.C.
Ultima Thule is so small and far from the sun that before New Horizons hurdled past it, scientists had little idea what it might look like. The spacecraft revealed that it is what is known as a contact binary object, which means it is made of two distinct lobes that fused together long ago.
“It looks like two things stuck together, which is exactly what a contact binary is,” Stern said.
The first images sent back by New Horizons suggested that it resembled a snowman, but as more data have trickled in from the spacecraft, that initial impression has shifted.
The New Horizons team now thinks that Ultima Thule looks more like a snowman that has been tipped on its side and smushed. Imagine if a kid made two balls out of clay, stuck them next to each other and then pressed them both down with the palm of her hand.
“These are three dimensional bodies, but they are not spheres,” said William McKinnon, a New Horizons investigator from Washington University in St. Louis. “And they are stuck together in a very specific way — end to end.”
The researchers have also determined that the larger lobe known as Ultima is significantly flatter than the smaller lobe — Thule.
“We still don’t know the answer why, but we are working on it,” McKinnon said.
Part of what makes Ultima Thule so fascinating to scientists is its pristine condition. It is 4.1 billion miles from Earth and receives so little light and warmth from the sun that its chemistry and structure have remained frozen in time since it formed 4.5 billion years ago, Stern said.
In addition, it is part of the slow-moving, sparsely populated region of the solar system known as the Kuiper Belt, where impacts are infrequent and gentle when they do happen.
That low-frequency, low-intensity environment has helped ensure that Ultima Thule has remained intact and essentially unchanged for billions of years.
“It provides a treasure trove of information about the birth of the planets,” Stern said.
The geographical features of Ultima Thule, including the lack of stress fractures on its surface, indicate that the two lobes were initially in orbit around each other and came together gently at a speed of no more than 7 mph, scientists said.
They believe the two objects were once in orbit around each other, but that orbit shrank and shrank until the two distinct bodies merged into one.
Both Ultima and Thule have lumpy-looking surfaces that resemble monkey bread. In fact, the New Horizons team thinks the two may have formed in a similar way with individual space rocks sticking together, just like how you put individual balls of dough next to each other in a pan to form one loaf of the sweet bread.
Scientists have also determined that Ultima Thule’s surface is extremely dark and very red. The darkest areas reflect just 7% of the dim sunlight it receives while the brightest areas reflect about 14% of that light.
It appears to be composed of water ice, organic compounds and methanol, and its topography includes rolling hills, troughs and pits.
“It’s a small world with mouthwatering geology,” said Kirby Runyon, a New Horizons science team member from the Johns Hopkins Applied Physics Laboratory in Laurel, Md.
The New Horizons spacecraft will continue to send data from its Ultima Thule close encounter for at least another year. Scientists are hoping that somewhere in that data they will find evidence of a satellite around Ultima Thule, which would help them resolve the object’s density.
“We know that 35% of cold classical Kuiper Belt objects have satellites,” Stern said. “We haven’t seen one yet, but we have more sky around this object to explore.”
In the meantime, the mission team is already thinking about what New Horizons might explore next.
“We will be in the Kuiper Belt until the late 2020s, so we have almost a decade to search for another object and hopefully find something,” Stern said. “In that happens we will be probing accretion not 4 billion, but 5, 6 or 7 billion miles from the sun.”
MORE IN SCIENCE | 0.806187 | 3.611544 |
Most isolated young star discovered launching jets of material into surrounding gas and dust
Space news (astrophysics: massive, young stars in star-forming regions; unusual, isolated young star baffles astronomers) – approximately 27,000 light-years from Earth in an isolated region of the bulge of the Milky Way –
Astronomers surveying the universe looking for unusual celestial objects to study to add to human knowledge and understanding have found something they haven’t seen before. Unusual celestial object CX 330 was first noticed in data obtained during a survey of the bulge of the Milky Way in 2009 by NASA’s Chandra X-ray Observatory as a source of X-ray light. Additional observations of the source showed it also emitted light in optical wavelengths, but with so few clues to go on, astronomers had no idea what they were looking at.
During more recent observations of CX 330 during August of 2015, astronomers discovered it had recently been active, launching jets of material into gas and dust surrounding it. During a period from 2007 to 2010, it had increased in brightness by hundreds of times, which made scientists curious to examine previous data obtained from the same region of the bulge.
Looking at data obtained by NASA’s Wide-field Infrared Survey Explorer (WISE) in 2010, they realized the surrounding gas and dust was heated to the point of ionization. Comparing this data to observations taken with NASA’s Spitzer Space Telescope in 2007, astronomers determined they were looking at a young star in an outburst phase, forming in an isolated region of the cosmos.
“We tried various interpretations for it, and the only one that makes sense is that this rapidly growing young star is forming in the middle of nowhere,” said Chris Britta postdoctoral researcher at Texas Tech University in Lubbock, and lead author of a study on CX330 recently published in the Monthly Notices of the Royal Astronomical Society.
By combining this data with observations taken by a variety of both ground and space-based telescopes they were able to get an even clearer picture of CX330. An object very similar to FU Orionis, but likely more massive, compact, and hotter, and lying in a less populated region of space. Launched faster jets of outflow that heated a surrounding disk of gas and dust to the point of ionization, and increased the flow of material falling onto the star.
“The disk has probably heated to the point where the gas in the disk has become ionized, leading to a rapid increase in how fast the material falls onto the star,” said Thomas Maccarone, study co-author and associate professor at Texas Tech.
The fact CX 330 lies in an isolated region of space, unlike the previous nine examples of this type of star observed during the human journey to the beginning of space and time, tweaks the interest of astronomers. The other nine examples all lie in star-forming regions of the Milky Way galaxy with ample material for new stars to form from, but the closest star-forming region to this young star is over 1,000 light-years away.
“CX330 is both more intense and more isolated than any of these young outbursting objects that we’ve ever seen,” said Joel Green, study co-author and researcher at the Space Telescope Science Institute in Baltimore. “This could be the tip of the iceberg — these objects may be everywhere.”
We really know nothing about CX 330. More observations are required to determine more. It’s possible all young stars go through a similar outburst period as observed in the case of CX 330. The periods are just too brief in cosmological time for astronomers to observe with current technology. The real clue’s the isolation of this example as compared to previous models.
How did CX 330 become so isolated? One idea often floated is the possibility it formed in a star-forming region, before being ejected to a more isolated region of space. This seems unlikely considering astronomers believe this young star’s only about a million years old. Even if this age’s wrong, this star’s still consuming its surrounding disk of dust and gas and must have formed near its current location. It just couldn’t have traveled the required distance from a star-forming region to its current location, without completely stripping away its surrounding disk of gas and dust.
Astronomers are learning more about the formation of stars studying CX 330, that’s for sure. Using two competing ideas, called “hierarchical” and “competitive” models, scientists search for answers to unanswered questions concerning CX 330. At this point, they favor the chaotic and turbulent environment of the “hierarchical” model, as a better fit for the theoretical formation of a lone star.
It’s still possible material exists nearby CX 330, such as intermediate to low-mass stars, that astronomers haven’t observed, yet. When last viewed in August 2015, this young star was still in an outburst phase. During future observations planned with new telescopes in different wavelengths, we could get a better picture of events surrounding this unusual celestial object. Stay tuned to this channel for more information.
For people wondering if planets could form around this young star? Some astronomers are hoping planets will form from the disk of CX 330, they’ll be able to examine closer for the chemical signature of the scars left by the outbursts observed. Unfortunately, at the rate this star’s consuming its surrounding disk of gas and dust, having enough left over for the formation of planets seems unlikely.
“You said you like it hot, right!” If CX 330’s a really massive star, which seems likely. It’s short, violent lifespan would be a truly hot time for any planet and inhabitants.
Read about Japan’s new X-ray satellite Hitomi.
For more information on the travel plans to CX 330, contact NASA.
Learn more about NASA’s Wide-field Infrared Survey Explorer (WISE) here.
Discover NASA’s Chandra X-ray Observatory.
For more information of NASA’s Spitzer Space Telescope visit.
Learn more about the work being done by NASA’s Jet Propulsion Laboratory.
Discover astronomy at Texas Tech University.
Discover the Space Telescope Science Institute. | 0.871831 | 3.815063 |
The search for extraterrestrial life is fairly synonymous with the search for life as we know it. We’re just not that imaginative—when looking for other planets that could host life, we don’t know what to look for, exactly, if not Earth-like conditions. Everything we know about life comes from life on Earth.
But conditions that clearly favor life here—liquid water, surface oxygen, ozone in the stratosphere, possibly a magnetic field—may not necessarily be prerequisites for its development elsewhere. Conversely, their presence does not guarantee life, either. So what can we look for that’s an indication of life?
Skip the dwarfs
Most (about seventy percent) of the stars in our Galaxy are M dwarf stars, and many of them have associated planets. The search for signs of life has largely focused on these planets, primarily because there are so many of them. However, the environments do not seem to be especially welcoming. Because M dwarf stars are dim, the hospitable zones around them are very close to the star. As a result, the planets get stuck in a gravitational lock: their orbital period and their rotational period are the same. This means that (just like our moon) these planets always have the same hemisphere facing their sun.
In addition to light, this perpetual-day side is constantly barraged with X-rays and extreme ultraviolet radiation, and the whole planet is subject to forces that would drive off its atmosphere. Could life thrive, or even ever get a toehold, in this type of environment? “The long-term evolutionary consequences of such conditions are topics of active debate,” writes astronomy PhD candidate Paul Dalba in a recent Perspective piece in Nature Astronomy.
Instead of looking for life among the many Earth-size planets orbiting M dwarfs, Dalba suggests we look at the Earth-size planets orbiting Sun-like (G-type) stars. There are only about 10 percent as many of these, but he thinks they might be better bets. And instead of looking for conditions that might support life, Dalba suggests looking for biosignatures. Specifically, atomic O+ ions at about 300km up.
The atmospheres of Earth and other planets contain neutral gas molecules, but also the ions and free electrons that result when these neutral gases absorb photons from the Sun. Many of those ions accumulate in (surprise!) the ionosphere. Earth’s ionosphere—and crucially, within the Solar System, only Earth’s ionosphere—has these atomic O+ ions. Like a lot of them, they account for over 90 percent of the ionic species up there.
Oxygen and life
Like Earth, Venus and Mars are small rocky planets; they have permanent atmospheres like Earth, and their atmospheres are exposed to the same solar radiation as Earth’s. Data from the Pioneer Venus Orbiter and the Viking descent probe on Mars show that they have very similar ionospheres to each other—which don’t contain a lot of atomic O+ ions. Know what else Venus and Mars are missing? Photosynthesis.
Dalba’s contention is that photosynthesis on a planet’s surface, which generates a surfeit of molecular oxygen, is the only thing that can account for these atomic O+ ions in a planet’s ionosphere. The mere existence of life throws a planet’s atmosphere out of chemical balance. O+would be a neat biomarker because there isn’t a numerical cutoff required—just the dominance of O+ among the ionic species in the upper atmosphere would indicate “thriving global biological activity” on the planet below.
Dalba claims that Venus and Mars act as negative controls, demonstrating that planets like Earth but lacking life don’t have this O+ layer. Some may think that continuous volcanic activity on the surface could also generate enough oxygen, but Dalba doesn’t. Chemistry involving water and UV light can also release oxygen. But the amount of water on Earth is insufficient to account for the requisite oxygen content, so he thinks that the presence of water on other planets wouldn’t make enough oxygen there either.
Alas, at this point we don’t yet have the technology to assess the ionosphere of exoplanets for such a biosignature. Dalba concludes his piece with a plea to “the optical and the radio remote sensing communities” to get to work on inventing the detectors that might be up to the task. | 0.860196 | 3.961378 |
Scientists from MIPT, the University of Oxford, and the Lebedev Physical Institute of the Russian Academy of Sciences estimated the number of stars disrupted by solitary supermassive black holes in galactic centers formed due to mergers of galaxies containing supermassive black holes. The astrophysicists found out whether gravitational effects arising as two black holes draw closer to one another can explain why we observe fewer stars being captured by black holes than basic theoretical models predict. In their study published in The Astrophysical Journal, the researchers looked into the interplay of various dynamic mechanisms affecting the number of stars in a galaxy that are captured per unit time (tidal disruption rate). (Spoiler Alert! An advanced theoretical model yielded results that are even more inconsistent with observations, leading the team to hypothesize that the disruption of stars in galactic nuclei may occur without our knowledge.)
Disruption of stars
Tidal disruption events, or TDEs, are the only available source of information from inactive galactic nuclei. There is at least one supermassive black hole in the center of most galaxies. Surrounded by dense central star clusters, black holes occupy regions known as galactic nuclei. As their name suggests, black holes do not emit any light. However, when matter falls onto the central massive object, it gets heated to extreme temperatures and can be observed with a telescope. Active galaxies have gas clouds that feed the black hole thus making it visible. However, most of the galaxies--approximately 90 percent of them--remain "silent" because there are no gas clouds in them and so there is no matter for the black hole to feed on, except for stars that occasionally stray too close to it. When this happens, the star is pulled apart by tidal forces, experiencing what is known as spaghettification, and astronomers detect a tidal disruption event (TDE). So far, around 50 flares of radiation linked to TDEs have been observed. It is reckoned that the average rate of stellar disruption amounts to one star per 10,000 to 100,000 years per galaxy. Based on this data, the scientists are trying to develop a reliable model of what goes on in inactive galactic nuclei.
Stellar disruption simulation: https:/
Assume a spherical galaxy in a vacuum...
The simplest theoretical model involves a galaxy whose nucleus is spherical in shape and has a supermassive black hole at its center. The black hole is orbited by stars that change the direction of their motion as they pass by one another, the way billiard balls bounce off one another when they collide on the table. However, whereas a billiard ball needs to be moving straight toward the hole to fall into it, a star has more options: It is enough for its velocity vector to be in the so-called loss cone, to ensure that the star will eventually be captured and disrupted by the black hole's gravity. According to this very simple model, an average of one star per galaxy should be captured every 1,000 to 10,000 years, i.e., more frequently than observed. Although the model can be improved by taking a number of other factors into account (e.g., the difference in the mass of stars), this would only further increase the predicted tidal disruption rates.
The slingshot effect
At present, there is only one mechanism discussed in published sources that could be responsible for the fact that fewer stars are captured than expected. Curiously, it requires that most of the low-angular-momentum stars vanish, so to speak. But let us first examine an analogous case involving gas diffusion. Suppose there are gas molecules in random motion contained inside a vessel whose walls can absorb the molecules. Now imagine the molecules closest to the walls have been removed. The obvious consequence of this would be less molecules absorbed per unit time, since the remaining molecules have yet to travel a certain distance before they can come in contact with a wall. Similarly, if stars are removed from the center of the galaxy, the stellar disruption rate will fall. Naturally, the stars cannot simply vanish into thin air; but if the galaxy hosts a binary black hole, then individual stars can be ejected from the galaxy by means of a so-called gravitational slingshot, a maneuver also known as a gravity assist when man-made spacecraft are involved.
The law of conservation of energy implies that when a star is accelerated (i.e., receives additional kinetic energy), the energy of the binary black hole must be reduced. As a result, the two black holes draw closer to one another and begin to merge. Eventually, when the merger is almost complete, some of the energy is radiated outward in the form of gravitational waves, as demonstrated by this recent sensational discovery.
A nonspherical galaxy in a vacuum
Although a galaxy merger can be accompanied by a decrease in the rate of star disruption, the opposite effect has also been observed. It has to do with the fact that any galactic nucleus which is a product of a merger is slightly nonspherical in shape. In a nonspherical nucleus, stars are more thoroughly intermixed; hence, there are more stars whose orbits lie close to the black hole. This means that more stars are available to be captured and the TDE rate goes up, in spite of the slingshot effect. To find out how the interplay of these two opposing factors impacts the rate of stellar disruption, Kirill Lezhnin and Eugene Vasiliev--both MIPT graduates--performed the necessary calculations and investigated the influence that black hole mass, nuclear star cluster geometry, and initial conditions have on disruption rates.
Even more destruction
It turned out that the effect of the removal of stars from the center of the galaxy by means of the gravitational slingshot was negligible in all cases except for the spherical-galaxy-in-a-vacuum scenario. It should be noted, however, that the shape of a galaxy formed in a merger is never a perfect sphere. As far as the results of calculations are concerned, the bottom line is that an average of one star per 10,000 years per galaxy should be disrupted. And while this number is in good agreement with prior theoretical predictions, it also begs the question: Why is it the case that fewer TDEs are observed than theoretical models would have us expect?
Kirill Lezhnin, one of the authors of the study and a researcher at MIPT's Laboratory of Astrophysics and Physics of Nonlinear Processes, explains the significance of the research findings: "We showed that the observed low disruption rates cannot be accounted for by the slingshot effect. Therefore, another mechanism needs to be found which lies outside the realm of stellar dynamics studies. Alternatively, the TDE rates we arrived at could in fact be accurate. We then need to find an explanation as to why they are not observed." | 0.837407 | 4.093012 |
From the precipice of “Perseverance Valley” NASA’s teenaged Red Planet robot Opportunity has begun the historic first ever descent of an ancient Martian gully – that’s simultaneously visually and scientifically “tantalizing” – on an expedition to discern ‘How was it carved?’; by water or other means, Jim Green, NASA’s Planetary Sciences Chief tells Universe Today.
Since water is an indispensable ingredient for life as we know it, the ‘opportunity’ for Opportunity to study a “possibly water-cut” gully on Mars for the first time since they were discovered over four decades ago by NASA orbiters offers a potential scientific bonanza.
“Gullies on Mars have always been of intense interest since first observed by our orbiters,” Jim Green, NASA’s Planetary Sciences Chief explained to Universe Today.
“How were they carved? muses Green. “Water is a natural explanation but this is another planet. Now we have a chance to find out for real!”
Their origin and nature has been intensely debated by researchers for decades. But until now the ability to gather real ‘ground truth’ science by robotic or human explorers has remained elusive.
“This will be the first time we will acquire ground truth on a gully system that just might be formed by fluvial processes,” Ray Arvidson, Opportunity Deputy Principal Investigator of Washington University in St. Louis, told Universe Today.
“Perseverance Valley” is located along the eroded western rim of gigantic Endeavour crater – as illustrated by our exclusive photo mosaics herein created by the imaging team of Ken Kremer and Marco Di Lorenzo.
After arriving at the upper entryway to “Perseverance Valley” the six wheeled rover drove back and forth to gather high resolution imagery of the inner slope for engineers to create a 3D elevation map and plot a safe driving path down – as illustrated in our lead mosaic showing the valley and extensive wheel tracks at left, center and right.
Having just this week notched an astounding 4800 Sols roving the Red Planet, NASA’s resilient Opportunity rover has started driving down from the top of “Perseverance Valley” from the spillway overlooking the upper end of the ancient fluid-carved Martian valley into the unimaginably vast eeriness of alien Endeavour crater.
Water, ice or wind may have flowed over the crater rim and into the crater from the spillway.
“It is a tantalizing scene,” said Opportunity Deputy Principal Investigator Ray Arvidson of Washington University in St. Louis, in a statement. “You can see what appear to be channels lined by boulders, and the putative spillway at the top of Perseverance Valley. We have not ruled out any of the possibilities of water, ice or wind being responsible.”
“With the latest drive on sol 4782, Opportunity began the long drive down the floor of Perseverance Valley here on Endeavour crater, says Larry Crumpler, a rover science team member from the New Mexico Museum of Natural History & Science.
“This is rather historic in that it represents the first time that a rover has driven down an apparent water-cut valley on Mars. Over the next few months Opportunity will explore the floor and sides of the valley for evidence of the scale and timing of the fluvial activity, if that is what is represents.”
NASA’s unbelievably long lived Martian robot reached a “spillway” at the top of “Perseverance Valley” in May after driving southwards for weeks from the prior science campaign at a crater rim segment called “Cape Tribulation.”
“Investigations in the coming weeks will “endeavor” to determine whether this valley was eroded by water or some other dry process like debris flows,” explains Crumpler.
“It certainly looks like a water cut valley. But looks aren’t good enough. We need additional evidence to test that idea.”
The valley slices downward from the crest line through the rim from west to east at a breathtaking slope of about 15 to 17 degrees – and measures about two football fields in length!
Huge Endeavour crater spans some 22 kilometers (14 miles) in diameter on the Red Planet. Perseverance Valley slices eastwards at approximately the 8 o’clock position of the circular shaped crater. It sits just north of a rim segment called “Cape Byron.”
Why go and explore the gully at Perseverance Valley?
“Opportunity will traverse to the head of the gully system [at Perseverance] and head downhill into one or more of the gullies to characterize the morphology and search for evidence of deposits,” Arvidson elaborated to Universe Today.
“Hopefully test among dry mass movements, debris flow, and fluvial processes for gully formation. The importance is that this will be the first time we will acquire ground truth on a gully system that just might be formed by fluvial processes. Will search for cross bedding, gravel beds, fining or coarsening upward sequences, etc., to test among hypotheses.”
Exploring the ancient valley is the main science destination of the current two-year extended mission (EM #10) for the teenaged robot, that officially began Oct. 1, 2016. It’s just the latest in a series of extensions going back to the end of Opportunity’s prime mission in April 2004.
Before starting the gully descent, Opportunity conducted a walkabout at the top of the Perseverance Valley in the spillway to learn more about the region before driving down.
“The walkabout is designed to look at what’s just above Perseverance Valley,” said Opportunity Deputy Principal Investigator Ray Arvidson of Washington University in St. Louis, in a statwemwent. “We see a pattern of striations running east-west outside the crest of the rim.”
“We want to determine whether these are in-place rocks or transported rocks,” Arvidson said. “One possibility is that this site was the end of a catchment where a lake was perched against the outside of the crater rim. A flood might have brought in the rocks, breached the rim and overflowed into the crater, carving the valley down the inner side of the rim. Another possibility is that the area was fractured by the impact that created Endeavour Crater, then rock dikes filled the fractures, and we’re seeing effects of wind erosion on those filled fractures.”
Having begun the long awaited gully descent, further movements are temporarily on hold since the start of the solar conjunction period which blocks communications between Mars and Earth for about the next two weeks, since Mars is directly behind the sun.
In the meantime, Opportunity will still collect very useful panoramic images and science data while standing still.
The solar conjunction moratorium on commanding extends from July 22 to Aug. 1, 2017.
As of today, July 27, 2017, long lived Opportunity has survived over 4800 Sols (or Martian days) roving the harsh environment of the Red Planet.
Opportunity has taken over 221,625 images and traversed over 27.95 miles (44.97 kilometers.- more than a marathon.
See our updated route map below. It shows the context of the rovers over 13 year long traverse spanning more than the 26 mile distance of a Marathon runners race.
The rover surpassed the 27 mile mark milestone on November 6, 2016 (Sol 4546) and will soon surpass the 28 mile mark.
As of Sol 4793 (July 18, 2017) the power output from solar array energy production is currently 332 watt-hours with an atmospheric opacity (Tau) of 0.774 and a solar array dust factor of 0.534, before heading into another southern hemisphere Martian winter later in 2017. It will count as Opportunity’s 8th winter on Mars.
Meanwhile Opportunity’s younger sister rover Curiosity traverses up the lower sedimentary layers at the base of Mount Sharp.
And NASA continues building the next two robotic missions due to touch down in 2018 and 2020.
NASA as well is focusing its human spaceflight efforts on sending humans on a ‘Journey to Mars’ in the 2030s with the Space Launch System (SLS) mega rocket and Orion deep space crew capsule.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news. | 0.829488 | 3.362096 |
Titan is a constant point of interest and scientists find out more fascinating things about this moon of Saturn almost every week. By analyzing images from NASA’s Cassini Radar instrument, a Brigham Young University professor helped discover and analyze mountains on Saturn’s largest moon, additional evidence that it has some of the most earthlike processes of any celestial body in the solar system.
It has already been found out that in resembles our planet in a number of ways but this was a bit surprising as the mountains are made of water ice which means they erode fast. This has an impact over their height which is not impressive to say the least; they have at most 2 km (1.25 mi) from the base to the peak.
Planetary scientist Jani Radebaugh is lead author of the discovery paper in the December issue of the astronomy journal Icarus. The discovery of mountains on Titan grew out of Radebaugh’s collaboration with a research team that recently found sand dunes and methane lakes on Titan.
“Dr. Radebaugh’s work represents an important advance in our understanding of that icy moon and the Earth,” said Dr. Jason Barnes, a research scientist at the NASA Ames Research Center. “Her discovery tells us about the mountain-building process in general and about Titan’s crust in particular.”
Studying Titan can give us some clues about our planet and we could use it as a huge laboratory in which results from the two places could be compared and this would be a huge leap forward in understanding how we evolved and how life itself evolved here.
“We still don’t understand exactly how life began on Earth, so if we can understand how the fundamentals of these processes may be starting in some laboratory like Titan, it will help us understand the Earth a lot better,” Radebaugh said. | 0.905977 | 3.432386 |
This image, captured by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 (WFC3), shows a galaxy named UGC 6093. As can be easily seen, UGC 6093 is something known as a barred spiral galaxy — it has beautiful arms that swirl outwards from a bar slicing through the galaxy’s center. It is classified as an active galaxy, which means that it hosts an active galactic nucleus, or AGN: a compact region at a galaxy’s centre within which material is dragged towards a supermassive black hole. As this black hole devours the surrounding matter it emits intense radiation, causing it to shine brightly.
But UGC 6093 is more exotic still. The galaxy essentially acts as a giant astronomical laser that spews out light at microwave, not visible, wavelengths — this type of object is dubbed a megamaser (maser being the term for a microwave laser). Megamasers such as UGC 6093 can be some 100 million times brighter than masers found in galaxies like the Milky Way.
Hubble’s WFC3 observes light spanning a range wavelengths — from the near-infrared, through the visible range, to the near-ultraviolet. It has two channels that detect and process different light, allowing astronomers to study a remarkable range of astrophysical phenomena; for example, the UV-visible channel can study galaxies undergoing massive star formation, while the near-infrared channel can study redshifted light from galaxies in the distant Universe. Such multi-band imaging makes Hubble invaluable in studying megamaser galaxies, as it is able to untangle their intriguing complexity.
Credit: ESA/Hubble & NASA | 0.83874 | 3.952403 |
One of the open questions in planetary dynamics that most puzzle specialists is the origin of Mercury, the smallest planet in our solar system. Its relatively minuscule mass, almost 20 times smaller than that of Earth, and its unique orbit around the Sun, the most elongated and tilted of all the planets in the system, cannot be explained by most of the models of planetary formation. Until the mid 1990s, the most accepted explanation was that all of the planets in our solar system formed at more or less the same position in which they are currently located. With the confirmed discovery, over the last 20 years, of almost 3,000 planets orbiting other stars, known as exoplanets, forming systems different from ours, Mercury’s unique situation increasingly appears to be an exception in the galaxy—and new explanations for its orbit have been attempted.
A recent study published by planetary scientists Fernando Roig and Sandro Ricardo de Souza, of the National Observatory (NO) in Rio de Janeiro, and the Czech researcher David Nesvorný, of the Southwest Research Institute in Colorado, defends a new hypothesis to justify the strange location of Mercury, whose orbit is tilted 7 degrees with respect to the average orbital plane of the other planets. Based on computer simulations of the dynamics of our solar system more than 4 billion years ago, the researchers suggest that the planet’s orbit became so elongated and tilted because of an extreme event. At some time during the first 500 million years of our solar system, the gravitational interaction between a hypothetical giant gas planet of the size of Uranus, and Jupiter—also a gas giant—could have altered local conditions. Per this hypothesis, the unknown planet would have been ejected from the system and caused Jupiter to be suddenly displaced towards the Sun. Jupiter’s jump would have pushed Mercury into its current position (see infographic).
This hypothetical event is known as Jumping Jupiter. In accordance with this theory, Jupiter’s displacement could have given rise to Mercury’s current orbit, and also ensured the stability of the trajectory of all of the rocky planets, including Earth, around the Sun. “It seems counter-intuitive,” says Roig, “but everything indicates that the giant gas planets had to have passed through an unstable phase in order to stabilize the rocky planets.” In the simulations, the jump in Jupiter’s orbit caused by the expulsion of a hypothetical planet resulted in almost no changes in the orbits of the rocky planets, except for Mercury. Roig explains that, if Jupiter had moved slower, instead of jumping towards the Sun, Mercury’s orbit could have become even more elongated and tilted than it is today. If this had happened, Mercury could have been ejected from the solar system or collided with its neighbor, Venus. According to the astrophysicist, this encounter could have provoked a domino effect that would have destroyed all of the rocky planets. Jupiter needed to have jumped in order to ensure the survival of the rocky planets,” suggests Roig.
A little over 20 years ago, most researchers believed that the planets in the solar system formed in approximately the same positions they occupy currently, through a slow, smooth process of accumulation of gas and dust. These models predicted that other stars should give rise to planetary systems similar to ours, with two distinct types of planets: the rocky planets, with sizes similar to that of Earth, near the star; and the gas giants, such as Jupiter or Saturn, farther away. “The discovery of exoplanets radically changed this idea,” explains Roig. “We saw that there is a variety of planetary configurations very different from our solar system.”
Statistical analyses of the characteristics of all exoplanet systems discovered up until now suggest that stars similar to the Sun tend to have very different planetary systems. Many of them contain rocky planets two to three times larger than Earth, with orbits closer to their suns than Mercury is to the Sun. Jupiter’s orbit, which is almost circular and far from the Sun, also diverges from what we observe in many exoplanetary systems.
A primordial cloud of gas and dust
Astronomers agree that the Sun and its planets began to form 4.6 billion years ago, when a gigantic cloud of gas and dust in interstellar space collapsed due to the gravitational force of its own mass. At that time there was a spherical core of gas that gave rise to the Sun, surrounded by a disk of material from which the planets took shape. The first worlds to form are believed to have been the gas giants — Jupiter, Saturn, Uranus and Neptune — and a few tens of millions of years later the rocky planets Mercury, Venus, Earth and Mars. Some researchers speculate that Mercury could have originated from the fragments of a first generation of larger rocky planets, with masses comparable to that of Earth, closer to the Sun than Mercury is currently.
The gas giant formation process is believed to have lasted less than 10 million years. At that time, in the space between the planets, there was still a reasonable quantity of gas remaining from the material in the disk from which they originated. The drag from the gas led the planets to migrate to locations closer to the Sun. At some point, however, the mutual gravitational attraction between Jupiter and Saturn could have inverted the direction in which the two gas giants were migrating, leading them away from the Sun. This back-and-forth movement of the gas giants is called the grand tack by the researchers, an allusion to the maneuvering of sailboats when sailing into the wind. Shortly after the grand tack, the current rocky planets were supposedly already formed or close to forming more or less in their present positions.
The orbits of the gas giants should be very different. Jupiter should be further from the Sun than it is, while the others should be much closer to Jupiter and to each other. The gas giants might have remained in this more compact configuration for up to 500 million years. When very close together, however, they must have been constantly affected by their mutual gravitational forces. Additionally, the orbits of these planets could also have been altered by the presence of many nearby smaller bodies, known as planetesimals.
The giants shook off these planetesimals slowly, pushing them to the outer limits of the solar system, where the Kuiper Belt—whose most famous body is Pluto—and the Oort cloud are located. In 2005, astronomers Hal Levison, Alessandro Morbidelli, Kleomentis Tsiganis and Rodney Gomes, the latter also a researcher at the National Observatory, presented computer simulations showing how, starting with this initial unstable situation, the gas giants could have slowly drawn away from each other, migrating to their current positions over millions of years.
Known as the Nice model, because it was developed while the researchers worked together at the Nice Observatory, in the French city, it stood out because it explained the current layout of the gas planets. However, in 2009 the Dutch astronomer Ramon Brasser noted that the slow migration of the gas giants predicted in the Nice model would have had a large probability of causing a series of planetary collisions. The hypothetical movement of the gas giants could have resulted in the expulsion of one of them—most likely Uranus—from the solar system.
In an attempt to reconcile this inconsistency, astronomer David Nesvorný, of the Southwest Research Institute, who presently collaborates with Roig as a visiting researcher at the National Observatory, proposed, in 2011, that the solar system could have had a fifth giant gas planet, with a size similar to that of Uranus or Neptune. Nesvorný calculated that the ejection of this hypothetical planet would have caused the distance of Jupiter’s orbit around the Sun to change from 5.5 times the distance between the Earth and the Sun to 5.2 times this value over a period of less than 100,000 years. “On the timescale of the formation of the solar system, this change in orbit would have occurred quickly. This is why we describe it as Jupiter’s jump,” explains Roig. “The Nice model works well to explain the gas giants, but one soon notices that the smooth migration of the gas giants predicted by this theory would have made the formation of the rocky planets difficult,” justifies astronomer Othon Winter, a specialist in planetary dynamics at São Paulo State University (Unesp), Guaratinguetá. “So far, Jumping Jupiter is the only known solution to this problem.”
Together with other researchers, including astronomer Valerio Carruba, from Unesp, Roig and Nesvorný recently argued that the Jumping Jupiter scenario would also explain some characteristics of the asteroid belt between Mars and Jupiter. The result of simulations published in March 2016 in the journal Icarus offers an explanation for why the astronomers were unable to observe any evidence in the belt of large collisions prior to 4 billion years ago between asteroids. In the article, the authors state that the presence of the hypothetical fifth gas giant, and its later expulsion from the system, would have reshuffled the orbits of the asteroids to the extent that any evidence of these collisions would be lost.
The idea that one giant gas planet escaped the solar system and its star is not as crazy at it may seem. Roig reminds us that astronomers have already observed the effect of a gravitational lens on the light of stars that could be attributed to the passage of giant planets wandering through interstellar space. Some researchers estimate that there are thousands of wandering worlds in the Milky Way. “These bodies have no way of forming far from stars,” explains Roig. “They must have formed in a planetary system and were then ejected.”
Secular families (nº 2014/06762-2); Grant Mechanism Regular Research Project; Principal Investigator Valerio Carruba (Unesp); Investment R$31,200.00.
ROIG, F. et al. Jumping Jupiter can explain Mercury’s orbit. Astrophysical Journal Letters. V. 820, No. 2, March 24, 2016.
BRASIL, P. I. O. et al. Dynamical dispersal of primordial asteroid families. Icarus. V. 266, p. 142-151, March 1, 2016.
ROIG, F. & NESVORNÝ, D. The evolution of asteroids in the jumping-Jupiter migration model. The Astrophysical Journal. V. 150, No. 6. December 1, 2015. | 0.921917 | 3.98874 |
HD 189733b is a boiling gas giant similar to Jupiter and Saturn in our Solar System. If HD 189733b -- 63 light years away -- is anything to go by, planets that support life are exceedingly rare. Think about it -- just Earth supporting life in the vast and desert space of 63 light years! So what makes the earth special?
We live on a blue planet. Seventy percent of the surface is covered in water, and many life forms have similar high water proportions in their tissues. Water itself has some unusual qualities. It is one of the lightest in gaseous phase, very dense in liquid form, and the cohesiveness of water molecules means the compound has an unexpectedly high boiling point and unexpectedly high freezing point.
4°C appears to be a magical value for H2O. Whether water is heated or cooled, it expands at this temperature. As such, an entire body of fresh water needs to be the same temperature to achieve the density of ice (rather than just a surface layer). Freezing occurs from the top down, which means biological life lower down is insulated.
But in the broad strokes of the planet, it is the heat capacity of our oceans that stabilise what would otherwise be vigorous and destructive temperature flux manifesting in dust and gas storms as we see on many other planets, including one of our closest neighbours, Venus. Ocean temperatures fluctuate only a third as much as land temperatures.
There are other anomalies besides, including water's crystalline structure in solid phase, its low viscosity, and that water is easily supercooled but not easily glassified. Similarly the Mpemba effect predicts that -- under specialised circumstances - warm water freezes faster than cold water.
All of these features add up to an exception substance with unique flexibilities and intolerances beneficial to life -- and this substance covers the surface of our planet.
Mars differs from Earth in two respects. Mars is an ice-cold waterless desert with no insulating atmosphere. The Earth's atmosphere is a blanket that also stabilises terrestrial temperatures. Beyond this, the atmosphere played a crucial role in protecting the early Earth from large incinerating meteorites.
The atmosphere thus also created beneficial stability for life to evolve.
The Earth travels at 29.8 kilometers per second around the sun, at an angle 23.5° from vertical. Thanks to the wobble of the Earth's axis, different parts of Earth experience different angles of direct sunlight for various periods of time. This is a controlled degree of instability -- a pattern that many of Earth's creatures have adapted to. The day/night cycle brings about the most basic adaptation -- which is sleep, an adaptation shared in different ways by many life forms on our planet.
The size of the planet determines its gravitational pull, and the extent to which muscles are stressed by the planet's pull. It is unlikely that very large planets could support life as we know it, as creatures would be crushed or have difficulty moving thanks to the force of gravity. On the other hand, a too small object, such as a large asteroid or mood would struggle to hold an atmosphere, let alone life forms moving on its surface.
The Moon is strangely large -- almost a quarter the size of our planet. As such, some scientists refer to the Earth and its satellite as a 'double-planet' system. The moon is an interesting contrast to Earth. It has no molten core, it is not building new mountains or terrains -- it is a fossil planet with no contiguous magnetic field. There have been reports of moonquakes that are believed to be the result of Earth-tides, and small gaseous eruptions.
The moon also has had a crucial stabilising effect. It holds the oceans in place, it may have some impact on our continental drift (spurring evolution of different creatures) and in some important sense it has provided a shield against a certain amount of space projectiles.
The stability of the sun is also important. A supernova or black hole in the galactic neighbourhood can't be good for the prospects of life. We already know that the sun is warmer today than it was before the dinosaurs.
If your planet periodically passes through asteroid or radiation belts, this can't be good for life. Incidentally, radiation reaching the Earth is deflected thanks to our Ozone later, which absorbs harmful UV rays.
Earth's landmass is still evolving, leading to new land and over time, the possibilities of different creatures forming. Earth's volcanic crust has also played a role in developing our atmospheric cushion, including during the Cryogenian period.
When one considers some of the massive meteorite impacts (such as those causing the 300km wide Vredefort dome in South Africa, and the extinction of the dinosaurs) it is easy to imagine how life, even where it manages to get a foothold, sooner or later gets wiped out by some intra-solar or interstellar projectile.
Perhaps life on Earth is so special that it is unique (for our purposes, and our quadrant of the galaxy certainly) in a hostile universe, and in cosmic time, will disappear again entirely.
Our chances of survival may depend entirely on some other civilisation rescuing us and transferring us to their home planet, but this presupposes their ability to reach us across the gulfs of space.
We - and our world - are about to face a tremendous test to survival, and if we graduate, we may be better prepared for a test not of our own making.
2008/12/12 오전 2:46
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Hawaiian Professor Larry Kimura wrote an academic report in 2008 on the discovery that the same gravitational effect that caused the explosion of light and light-producing substances back in 1792 has never existed before. Powehi was named after one of Honolulu’s most popular astronomers named Edward Powehi when he was born in 1777-1778. And all the more intriguing, it is said, because his theory of cosmic microwave background radiation causes the Milky Way and Earth to fall into white dwarfs over time. The white dwarfs are about 0.5 megapascals across, about 30 times their mass. The main reason for expanding and dying out at the end is that the universe is expanding and dying out because of the gravitational pull from the black hole. An effect called a “darkening force” that could result from a collapse of gravity, the theory goes, may explain why it continues to be made famous to this day for example, William James’ theory of the black hole, for instance.
Climbing Mount Fuji The most surprising thing about this discovery is that the galaxy is so large, with a distance of approximately one million light years, that its gravitational pull is a mere nine times that of the Sun. We don’t know much about the cosmic microwave background radiation that goes on inside the galaxies and dust that form when the dark matter around the center of the Universe heats to very high temperatures, but if it is black, it is very likely a very hot galaxy or star, known as the Milky Way, that may be directly related to supermassive black holes. As they become big enough to interact with the Universe in large numbers, they may become a regular part of the Milky Way and may even create giant stars and galaxies with mass like our own Milky Way. The Milky Way has a very dense, and supermassive black hole that may house some supermassive black holes that might be able to create black holes like the Milky Way. These black holes could be located in our solar system, in the regions of the galaxy that are called dark matter and dark energy. One of the most compelling evidence of a black hole is the gravitational attraction between an energetic black hole and a non-gravitational object like our Sun. “Black holes are made of massive mass, which makes them very hard to interact with with, like it is easier to burn a single banana or eat popcorn than to shoot black holes in a movie or some other material like a movie.” - Professor Kimura
The Black Hole Nebula Although most scientists think the black hole is a simple binary galaxy, astronomers think it is a large, and more complex galaxy (it may be up to 5 trillion light-years across)! Astronomers believe that the cosmic microwave background radiation is a remnant of cosmic microwave background radiation (Gneisser radiation) that is passing through the cosmos in the form of neutrons and excited positrons which escape through the black hole while being excited by the pulsar Pb. This, according to a new study, is the result of the gravitational collapse that was formed when a black hole slammed into its black hole neighbors. The neutrons and excited positrons, which form by interacting with the red portion of an atmosphere, enter the black hole and become the gas produced by the supermassive black hole that is just now breaking up the supermassive black hole from all other black holes (the Kuiper Belt galaxy) into its own black hole family.
The Black Hole Cluster It was discovered by a European telescope in 1947, and astronomers have been debating whether that galaxy is actually a supermassive black hole and whether it belongs to our community. The galaxy was discovered about 15 years ago with a star named WG-95445 in the constellation Ursa Major. The galaxy is much larger than other galaxies, but it does not seem to come about on a regular basis. “It is a galaxy of an important form of our universe,” says Professor Kaeli de Kees. Astronomers believe the star WG-95445 was formed by intense astrophysical explosions that had an initial explosion every 700 years in which a neutron star exploded a thousand times. De Kees speculates that there could be up to five such supermassive black holes in some form. The galaxy is found about 200 light-years away east of Earth, but it is not visible on our planet because of any gravitational event that is passing through it. This is because of the fact that the Milky Way lies at the center of light-years around the Sun. “It was a great discovery, especially a large galaxy. It was surprising to many scientists, and as astronomers, we realized it was not a very good choice.” In addition, De Kees said, “a very interesting explanation of the mystery is that for any galaxies that are big, even those with enormous diameter are extremely sparse. For a galaxy with such mass, you would have a very small mass. There is some variation in the amount of space between the distances at which astronomers call the white dwarfs from the galaxies that are from galaxy | 0.861441 | 3.92297 |
Our first two missions are with Beyond Atlas.
In June 2020 the first mission will launch, Meeting the Scrap. A small spacecraft that will orbit the Earth and navigate close to and photograph space debris. This is also a test mission, to try our navigation, propulsion, communication, etc.
The second mission will launch, hopefully, in late 2020. A little bit bigger spacecraft, that first will orbit Earth until it reaches escape velocity, then travel towards asteroid 2016 HO3 for about a year. Once there we will take pictures of the asteroid and scan it with a spectrometer to determine it’s content. The asteroid is in orbit around Earth and has been called Earth’s mini-Moon and Earth’s second Moon.
This will be the first private mission to an asteroid.
Relative navigation will be key to reaching our target. This is a picture taken in space from Mango of Tango, two Swedish spacecraft in relative navigation mission. Some of our team members were active in this mission.
Our trip will start in a GTO or MEO orbit around Earth. Both works. GTO is more of a standard destination for launch vehicles, but MEO would suit our needs better from a radiation perspective.
Once up there, the spacecraft would need to detumble, using sun sensors and reaction wheels. Once stable it would deploy its solar panels and point them towards the sun. Then the antennas would deploy, systems check, then the thrusters would be engaged.
The thrusters will be running for the whole trip, accelerating the spacecraft by a tiny amount each second, minute, hour, day, week, month until the little acceleration over time amounts to the huge delta-V necessary to get to our target.
Just to escape Earth will take some nine months. To reach the target, almost another year. On the way out we will take pictures of Earth and the Moon. As we leave the Earth-Moon system we will point the camera back to home, until home is just a dot among the stars.
We will see if orbital mechanics will let us swing by the Moon. The very smart people doing the calculations really would like us to stay clear of the Moon, but would it not be nice to swing by, for no other reason that one would be able to? Let’s see.
One challenge heading out will be to determine the position of the spacecraft. This is done by using big ground stations on earth and bouncing a signal to the spacecraft. Distance and angle to Earth can then be measured and calculated. We really would like to find another way of determining position, that does not depend on great infrastructure on earth being dedicated to my small spacecraft.
It would be nice with “lighthouses” in space, to which the spacecraft could triangulate its position. However, for this first mission, it feels like we will go with the traditional approach. But let’s keep thinking of other ways? Perhaps one could put a “lighthouse” on our asteroid?
Other challenges will be finding and, with precision fly close to the asteroid. We do want to slow down, not to make a flyby of it.
So, well, let’s say we make it, and get to spend 60 days at the asteroid, making observations, downloading data to Earth, then what?
Landing would be one option (soft crash), another would be flying back to the Moon, a third would be making a flyby of another asteroid. Who knows, that is also one of the purposes of the mission, to be able to fly/sail in space, not just to float on its currents.
Launch of Long March 3B, example of MEO launch vehicle.
Well, this is tricky. Even though the spacecraft is so small, and prices of getting into orbit is dropping, the administration fee of letting the spacecraft on board in the first place seems to be around 1-2 MUSD.
We really, really, really would hate to pay that kind of money on some admin stuff. It goes against the spirit of the whole mission. The point here is to create a model whereby shared value would make exploration affordable.
The way to go around this is to find a partner with launch capacity that sees the value of exploration. Someone who would want to share the effort, by providing the first half of the delta-V necessary (the launch) and we would provide the second half of the delta-V necessary (going from orbit to target). The CNSA could be such a partner as well as ESA or NASA.
Another way would be to find partners who would love to get into space to test components/equipment or who would like to get experiments into deep space, and then willing to share the launch cost with us. Space Flight Industries has been very helpful in this line of thinking.
In any case, finding a launch is a priority. And it feels like we are getting there.
Picture of asteroid 2016 HO3.
There is not much to be said of 2016HO3. It is 40-120 meters in diameter. Probably just a big rock. What makes it interesting for our purposes is that it never ventures very far from the Earth. It is around 56-89 lunar distances from Earth at all times.
How can that be? Well, apparently it goes in an orbit around the sun in such a way that it at times is a little ahead of Earth, and then a little behind (watch this video of 2016HO3).
So, what do we hope to find out when we get there? Well getting there in itself is, of course, an achievement. But once there we want to map its spin, size, composition (Big rock? Pile of rubble? Or A little bit of all?). We want to understand if there are volatile materials on the asteroid, and we want to understand its mineral composition.
Also, not the least do we want some nice pictures to share with you all and hang on the wall back home.
Illustration of the spacecraft.
The spacecraft has at the time of writing no name, which strikes me as a shame. Let’s call it CEC for now. CEC will be a 12 U CubeSat. It will use electric propulsion and huge solar panels will feed it with power. The solar panels will be gimbaled to always point towards the sun when the engines are engaged. In-between propulsion and solar panels an extremely efficient power management system will have to channel all the wattage, to ensure that CEC will not go up in flames due to thermal issues.
The transponder will be used for communication, but also to determine the distance and angle to earth. This is not an easy piece of equipment to be found for a spacecraft this small.
Communication with Earth will be on X-band. Flat patch antennas seem to be the way to go if one does not want to wander too far off the CubeSat norm.
The navigation equipment will track the stars and use reaction wheels and the thrusters to point the spacecraft out there in deep space.
That’s the basic rundown of the ship. | 0.848012 | 3.082245 |
Aurorae are caused by energetic particles interacting with planetary atmospheres. Part of this flux comes from the Sun (solar wind) while the rest is cosmic radiation. My main question is: could a planetary body located far away from the Sun (or any other star), with a suitable atmosphere and magnetosphere, have noticeable* aurorae, just from being exposed to cosmic rays? A related question would be: do we know how much of the aurora is caused by the solar wind, and how much by cosmic rays? And thirdly: is there any other way that a planetary body could produce aurorae, such as its own electromagnetic emissions?
*I know "noticeable" doesn't really work as a limit, but for the time being, I'm talking of electromagnetic radiation that can be distinguished clearly from the background of a planet's disc using instruments not more advanced than our current telescopes at interplanetary distances. | 0.855018 | 3.570566 |
This did make a bunch of headlines today, but I want to highlight just how phenomenally cool and under-appreciated this event is. For the first time in human history, a spacecraft has made rendezvous with a comet. It’s actually a lot of firsts/bests in one, in the rendezvous department – farthest object away, first rendezvous with a comet, I could go on and on. Ok, I am going to go on and on here. There’s going to be a bit of gushing, because this is really, incredibly exciting.
This required some serious planning, and some overwhelmingly complex orbital mechanics. The European Space Agency pulled of an amazing feat here, and they deserve major kudos. Rosetta has been on its way from Earth to the comet 67P/Churyumov-Gerasimenko (Chury for short) for ten and a half years. It launched when I was a senior in college, and now it has, after a very long and complex journey, arrived.
In order to get out to Chury, Rosetta made multiple maneuvers over the last decade. It flew past the Earth several times, gave Mars a pass, and in an elegant and carefully planned dance, traveled billions of miles to intercept a body that’s on its own 6.5 year orbit around the sun. The complexity involved in this whole endeavor is mind-blowing. It makes the orbital mechanics for the Apollo missions look like child’s play. The journey looked like this:
And they’re not even done! For their next trick, the ESA will have Rosetta continue to orbit, and launch the Philae Lander – oh no, folks, rendezvous is not enough, studying the comet up close and collecting data isn’t enough, they are also going to put a lander on the comet. Philae has all kinds of sensors, but also can drill and take samples.
These guys do not think small. They are going big, and I will be waiting with breath held and fingers crossed when Philae goes to land. That event is currently scheduled for 11 November, once a good landing site has been selected.
And if all my rambling doesn’t get you excited about this mission, this video should:
I expect Rosetta to continue with its pioneering firsts. I can’t wait for the pictures and data and other new discoveries to start hitting the news in the days to come. If you’d like to know more, there are some really great resources at the ESA Rosetta page, and this Guardian article is also quite good.
Did I mention I’m excited about this? | 0.82321 | 3.144141 |
The surface of the Earth was immersed in life-damaging radiation from nearby supernovae on several different occasions over the past nine million years. That is the claim of an international team of astronomers, which has created a computer model that suggests that high-energy particles from the supernovae created ionizing radiation in Earth’s atmosphere that reached ground level. This influx of radiation, the astronomers say, potentially changed the course of the Earth’s climate and the evolution of life.
Earlier this year, two independent teams of astronomers published evidence that several supernovae had exploded some 330 light-years from Earth. Each event showered the solar system in iron-60, an overabundance of which has been found in core samples from the bottom of the Atlantic, Pacific and Indian oceans. A discovery of the same element ‘iron-60’ was found on the moon.
Iron-60 is not all that supernovae produce – they also produce cosmic rays, which are composed of high-energy electrons and atomic nuclei. Previous work by Neil Gehrels of NASA’s Goddard Space Flight Center, was found to be incorrect as he indicated that a supernova would have to explode within 25 light-years of Earth to give our planet a radiation dose strong enough to cause a major mass extinction.
Now, a team led by Brian Thomas of Washburn University, and Adrian Melott of the University of Kansas argues that this conclusion is incorrect. The researchers looked at what would happen if a supernova exploded at a distance of 325 light-years and worked-out how its radiation would affect Earth. They found that cosmic rays accelerated towards Earth by the supernova are a different story. These have energies in the teraelectronvolt (TeV) region and are able to “pass right through the solar wind and Earth’s magnetic field and propagate much further into the atmosphere than cosmic rays normally do.”, says Melott.
When a cosmic ray strikes an air molecule, it produces a shower of secondary particles that is filled with the likes of protons, neutrons and a strong flux of muons. Ordinarily this takes place in the upper atmosphere and can be responsible for ionizing and destroying ozone in the stratosphere. However, the supernova cosmic rays are so energetic that they will pass straight through the stratosphere, lower atmosphere, and down to the surface and deep into the oceans and mantle.
Today, muons contribute a sixth of our annual radiation dose, however, the team calculated a supernova hit would result in a 20-fold increase in the muon flux that would triple the annual radiation dose of life forms on the planet.
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While there is a great deal of excitement and effort in the hopes of finding small, terrestrial sized exoplanets, another realm of exoplanet discovery that is often overlooked is that of ones of differing ages to explore how planetary systems can evolve. The first discovered exoplanet orbited a pulsar, showing that planets can be hardy enough to survive the potential violent deaths of their parent stars. On the other end, young planets can help astronomers constrain how planets form and a potential new discovery may help in those regards.
Historically, astronomers have often avoided looking at stars younger than about 100 million years. Their young nature tends to make them unruly. They are prone to flares and other eccentric behaviors that often make observations messy. Additionally, many young stars often retain debris disks or are still embedded in the nebula in which they formed which also obscures observations.
Despite this, some astronomers have begun developing targeted searches for young exoplanets. The age of the exoplanet is not independently derived, but instead, taken from the age of the host star. This too can be difficult to determine. For isolated stars, there are precious few methods (such as gyrochronology) and they generally have large errors associated with them. Thus, instead of looking for isolated stars, astronomers searching for young exoplanets have tended to focus on clusters which can be dated more easily using the main sequence turn off method.
Through this methodology, astronomers have searched clusters and other groups, such as Beta Pictoris which turned up a planet earlier this year. The Beta Pic moving group boasts an age of ~12 million years making it one of the youngest associations currently known.
Trumpler 37 (also known as IC 1396 and the Elephant Trunk Nebula) is one of the few clusters with an even younger age of 1-5 million years. This was one of several young clusters observed by a team of German astronomers led by Gracjan Maciejewski of Jena University. The group utilized an array of telescopes across the world to continuously monitor Trumpler 37 for several weeks. During that time, they discovered numerous flares and variable stars, as well as a star with a dip in its brightness that could be a planet.
The team cautions that the detection may not be a planet. Several objects can mimic planetary transit lightcurves such as “the central transit of a low-mass star in front of a large main-sequence star or red giant, grazing eclipses in systems consisting of two main-sequence stars and a contamination of a fainter eclipsing binary along the same line of sight.” Due to the physics of small objects, the size of brown dwarfs and many Jovian type planets are similar leading difficulty in distinguishing from the light curve alone. Spectroscopic results will have to be undertaken to confirm the object truly is a planet.
However, assuming it is, based on the size of the dip in brightness, the team predicts the planet is about twice the radius of Jupiter, and about 15 times the mass. If so, this would be in good agreement with models of planetary formation for the expected age. Ultimately, planets of such age will help test our understanding of how planets form, whether it be from a single gravitational collapse early on, or slow accretion over time. | 0.859888 | 3.996545 |
By Gail Jacobs
Dr. Laurance Doyle is a true renaissance man who thrives on discovery. His passion is to immerse himself into scientific mysteries and go, as the oft-quoted Star Trek phrase states, "where no man has gone before." Long before the discovery of the first planet beyond our solar system, astronomer Dr. Laurance Doyle, who joined the SETI Institute in 1987, began theorizing about the habitability of planets around other stars and clarifying the conditions needed for a planet to bear life. Relying on his expertise in signal processing, he now looks for patterns in astronomical data while searching for extrasolar planets.
Laurance has begun using these same statistical tools to look for patterns in animal communication. Drawing on central concepts of information theory, he and colleagues from the University of California at Davis have precisely measured the complexity of the songs of humpback whales, comparing them with communication in other species--including humans. In the future, he plans to expand this innovative line of research, moving to the next level of understanding animal communication, and apply it to SETI (Search for Extraterrestrial Intelligence).
Tell us about your current research project.
I'm a Participating Scientist on NASA's Kepler science team. In layman's terms, my project involves searching for "Tatooine" planets, a nickname for a binary star system coined after Luke Skywalker's home planet in Star Wars. Ideally, the goal is to find a habitable planet that is going around two stars.
Artist's photo concept taken by Robert Hunt of the Spitzer Science Center at the California Institute of Technology, Pasadena, CA. Image Credit: NASA/JPL-Caltech
I'm in charge of detecting circumbinary planets that orbit eclipsing binary stars -- planets that orbit around both stars while the two stars orbit around each other. The stars that orbit each other across our line of sight eclipse each other regularly. This allows us to study the size of stars. Most of what we know about star size comes from eclipsing binaries.
The space-borne Kepler telescope is searching for the minute dips in brightness that occur when an orbiting planet crosses in front of its star, known as a "transit." When you plot the brightness with time, it's called a "light curve." The movement of the stars around each other while the planets move across the discs of the stars results in an unusual series of dips, which complicate the detection process.
How will you know if the planet is habitable?
For a planet to have the potential to be inhabited, it must be the right distance from the star so it will receive the right amount of light. The temperature of a habitable planet should allow liquid water to exist on the surface for long periods of time.
Based on the best available ground- and space-based data, I expected there would be about 350 eclipsing binaries in the Kepler data. Actually, there turned out to be more like 3,000 to 4,000 eclipsing binaries that Kepler sees. Just in our first year, we had to look at tens of thousands of light curves to pick out these eclipsing binaries.
Why should the public care about your research?
This work is important for two reasons. If we don't find a habitable planet, that means earths are rare. It puts the earth in perspective as a somewhat isolated spaceship. That knowledge may allow us to convey the concept that we need to take care of our own planet, and that would be a good thing. People think about moving to Mars, but Mars' land surface area is only equal to earth's (since three-fourths of earth is covered with water). With earth's population currently doubling every 54 years, moving to Mars would only buy us another half century. So earth is it for now.
If we do find another earth, whether it's around a circumbinary "earth" or a regular single sun-like star, I think people's thoughts are going to transition to becoming less self-centered. Finding another earth might also make us think more positively about finding other beings in the universe. We have a very real shot at finding other earths with the Kepler Mission. We could detect a potentially habitable extrasolar planet within the next three years. Kepler is hugely important for the question of life in the universe. This is a key time in history.
What created the connection for you to take your work in astronomy and apply it to animal communication?
SETI and the Drake Equation. I began with the question Are we Alone? and realized that we share a planet with many pretty intelligent species. There are many species that apply what might be considered an elementary form of tool use and have complex social and communicative behaviors. But then I began thinking about how whales, for example, communicate with other whales. This led me to the notion of detecting non-human intelligence in the oceans as a practice for the search for extraterrestrial intelligence in space.
We've found general rules for what makes an intelligent signal so my colleagues and I looked into what is required for a signal to carry intelligence complexity. Starting with dolphins, I began plotting the frequency of occurrence of dolphin whistles as if they were linguistic phonemes. The plot landed in such a way that indicated dolphin signals had the same distribution as human linguistics. I thought that was amazing! We then looked at babies' babbling before they learned language, and the baby dolphins plotted exactly the same. We could watch mathematically how they learned their whistle language as they grew up, and they mapped the same as humans' language development. After that, I was hooked!
How are animal communication and extraterrestrial intelligence linked?
The math we use, Information Theory, is how we're going to get a handle on what constitutes an intelligent signal. Our first paper on the dolphin research was published in 1999. We want to continue applying those studies to humpback whale communication. Taking these findings into our SETI research seems a natural transition. When SETI looks for a radio signal, it's more the search for extraterrestrial technology as we don't have an intelligence filter yet. With animal communications, we're deriving an intelligence filter we can apply to signals we receive from space to determine if they land on a linguistic type distribution.
Every communication system may lend itself to this area of study and we can compare which are more complex, such as orca whistles or the dance of bees. I'd like to see Information Theory used as a mathematical tool and applied to every critter. We can then start to study general species communication intelligence, which is what SETI will detect. What we are going to get over light years, if we detect anything, is communication intelligence, so that's what we should be quantifying. We're on the way to solving this problem, but it needs more support.
A few colleagues and I have special permission through the Alaska Whale Foundation to be among these amazing humpback whales, now an endangered species. Humpbacks react similarly to humans. We increase the volume or slow our speech when our environment gets noisy. If it's still noisy, we repeat. We can watch the humpbacks change the way they think about the environment and react by changing their data rate. Introducing this new tool will be invaluable for conservation as well.
What first sparked your interest in science and astronomy in particular?
When I was six, my dad gave me a map of the solar system. He told me, "The stars are other people's suns." That was it for me -- I was never on earth again. My love for space continued throughout my education. When asked to write an essay in second grade, mine was on the nine planets. When I was 10, I was teaching an astronomy class to the neighborhood kids every Tuesday night. I put up a map of the solar system, set up chairs, the kids would come in, and I'd teach them about the solar system. I was already a professor at age 10!
You believe your true calling is to teach. You still enjoy being a professor and are often inspiring Ph.D. students as well as giving lectures on astrophysics or using the Internet to teach quantum physics to the public. Do you have advice for students?
Science is really advanced nature appreciation. It isn't a scary weird thing. And if math isn't your strongest subject, Einstein once said, "Do not worry about your problems with mathematics, I assure you mine are far greater." I think I'm tied with Einstein on that one, but math is the language you have to learn. So one piece of advice I have for young people is to not get discouraged. Additionally, while going to school, it's important to learn as much as you can about the material given while simultaneously defending your individuality as best you can. Don't compromise your own unique contribution, because your thoughts will create something new that could have been rejected in the previous generation of science.
At the high school and undergraduate levels, it's important to think about your identity and figure out what you love. I believe what you love is the universe telling you what you should be doing. At the Ph.D. level, you start contributing to learning. You're at the point where the professor can no longer teach you about this subject. You have to ask the universe, and it's that step I really enjoy.
Can you offer some advice for educators?
I'd say the number one lesson for primary school teachers is to instill in their young and impressionable students that learning is fun. If you get that across, everything else is details. At an intermediate and high-school level, it's important to teach critical thinking -- how to learn, read, study, get things out of books and talk to people. This provides youth with the foundation they'll need to discover their true calling.
You're a fan of the Drake Equation and, like Frank Drake, enjoy being the first to discover or establish something new.
My career has evolved into a journey of exploration I thought I would get by walking on the Moon. What has kept me interested and engaged, however, has been the intellectual exploration. I've been able to study and discover things no one else knows. A little more than a hundred years ago, you could be the first to locate the source of the Nile. Now, the opportunities are more ones of intellectual discovery. I was one of the first to find out the age of the rings of Saturn when working on my dissertation, and I was the first to know dolphins have linguistic distribution. My colleagues and I may have been the first to apply Information Theory to animal communications. For example, we can now quantify the reaction of humpback whales to boat noise in Glacier Bay, Alaska. Knowing something for the first time is exciting. It's also very fulfilling when my work spins off to create new areas of science, research, and even conservation.
My research has always been up and down the Drake's Equation. I've tried to pick out elements that I thought could be answered, even if they were tough or nobody else was addressing them. One of the factors of the Drake Equation is detecting earth-like planets, so I advocated the transit method. Twenty years ago, there were three people working on the transit method. We couldn't get funding; it was all voluntary. I interested various people in that project, including the SETI Institute's Jon Jenkins, now on the project, and Dr. Hans Deeg, who leads the CoRoT (Convection, Rotation & planetary Transits) eclipsing binary planet search, a smaller scale French space mission. This is another example of a spin-off.
What is your philosophy of life?
Whoever has the most fun wins! Life is an adventure, and fun is a great way to navigate through life. This doesn't mean irresponsible indulgence; it means spending your time doing something that brings you deep joy. Joseph Campbell said, "Follow your bliss." So people make quilts and raise bees and do all sorts of things if they're following their bliss. I think that's the universe saying, "I want you to do this."
Learn more about Laurance and his fascinating career in his full interview. | 0.911804 | 3.719789 |
Gibbous ♋ Cancer
Moon phase on 12 November 2068 Monday is Waning Gibbous, 18 days old Moon is in Cancer.Share this page: twitter facebook linkedin
Previous main lunar phase is the Full Moon before 3 days on 9 November 2068 at 11:40.
Moon rises in the evening and sets in the morning. It is visible to the southwest and it is high in the sky after midnight.
Moon is passing first ∠1° of ♋ Cancer tropical zodiac sector.
Lunar disc appears visually 3.1% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1879" and ∠1939".
Next Full Moon is the Cold Moon of December 2068 after 26 days on 8 December 2068 at 23:42.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 18 days old. Earth's natural satellite is moving from the middle to the last part of current synodic month. This is lunation 851 of Meeus index or 1804 from Brown series.
Length of current 851 lunation is 29 days, 17 hours and 25 minutes. It is 1 hour and 23 minutes longer than next lunation 852 length.
Length of current synodic month is 4 hours and 41 minutes longer than the mean length of synodic month, but it is still 2 hours and 22 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠209.1°. At the beginning of next synodic month true anomaly will be ∠241.5°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
4 days after point of perigee on 7 November 2068 at 20:44 in ♈ Aries. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 7 days, until it get to the point of next apogee on 19 November 2068 at 19:10 in ♍ Virgo.
Moon is 381 433 km (237 011 mi) away from Earth on this date. Moon moves farther next 7 days until apogee, when Earth-Moon distance will reach 405 230 km (251 798 mi).
2 days after its descending node on 9 November 2068 at 19:59 in ♉ Taurus, the Moon is following the southern part of its orbit for the next 11 days, until it will cross the ecliptic from South to North in ascending node on 24 November 2068 at 01:37 in ♏ Scorpio.
15 days after beginning of current draconic month in ♏ Scorpio, the Moon is moving from the second to the final part of it.
1 day after previous North standstill on 11 November 2068 at 15:07 in ♊ Gemini, when Moon has reached northern declination of ∠20.651°. Next 13 days the lunar orbit moves southward to face South declination of ∠-20.658° in the next southern standstill on 26 November 2068 at 02:57 in ♐ Sagittarius.
After 12 days on 24 November 2068 at 21:42 in ♏ Scorpio, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.061705 |
Perhaps you’ve read the news. This Fall, the big ticket show is the approach of Comet C/2012 S1 ISON. The passage of this comet into the inner solar system has been the most anticipated apparition of a comet since Hale-Bopp in 1997.
Many backyard observers will get their first good look at Comet ISON in the coming month. If you want to see this comet for yourself, here’s everything you’ll need to know!
Discovered on September 21st, 2012 by Artyom-Kislovodsk and Vitaly Nevsky using the International Scientific Optical Network’s (ISON) 0.4 metre reflector, this comet has just passed out from behind the Sun from our Earthly vantage point this summer to once again become visible in the dawn sky.
Of course, there’s much speculation as to whether this will be the “comet of the century” shining as “bright as the Full Moon” near perihelion. We caught up with veteran comet observer John Bortle earlier this year to see what skywatchers might expect from this comet in late 2013. We’ve also chronicled the online wackiness of comets past and present as ISON makes its way into the pantheon as the most recently fashionable scapegoat for “the end of the world of the week…”
But now it’s time to look at the astronomical prospects for observing Comet ISON, and what you can expect leading up to perihelion on November 28th.
Advanced amateur astronomers are already getting good images of Comet ISON, which currently shines at around +12th magnitude in the constellation Cancer. And although NASA’s Deep Impact/EPOXI mission is down for the count, plans are afoot for the Curiosity rover and the Mars Reconnaissance Orbiter to attempt imaging the comet when it makes its closest approach to the Red Planet on October 1st at 0.0724 Astronomical Units (A.U.) or 10,830,000 kilometres distant. If MSL is successful, it would be the first time that a comet has been observed from the surface of another world.
Currently, ISON sits about a magnitude below the projected light curve, (see below) but that isn’t all that unusual for a comet. Already, there’s been increasing talk of “ISON being a dud,” but as Universe Today’s Nancy Atkinson pointed out in a recent post, these assertions are still premature. The big question is what ISON will do leading up to perihelion, and if it will survive its passage 1.1 million kilometres above the surface of the Sun on November 28th to become a fine comet in the dawn skies in the weeks leading up to Christmas.
ISON is already starting to show a short, spikey tail in amateur images. Tsutomu Seki estimated it to be shining at about magnitude +11.1 on September 16th. Keep in mind, a caveat is in order when talking about the magnitudes of comets. Unlike stars, which are essentially a point source, the brightness of a comet is spread out over a large surface area. Thus, a comet may appear visually fainter than the quoted magnitude, much like a diffuse nebula. Although +6th magnitude is usually the limit for naked eye visibility, I’ll bet that most folks won’t pick up ISON with the unaided eye from typical suburban sites until it breaks +4th magnitude or so.
The forward scattering of light also plays a key role in the predicted brightness of a comet. The November issue of Astronomy Magazine has a great article on this phenomenon. It’s interesting to note that ISON stacks up as a “9” on their accumulated point scale, right at the lower threshold of comet “greatness,” versus a 15 for sungrazing Comet C/1965 S1 Ikeya-Seki. Another famous “9” was Comet C/1996 B2 Hyakutake, which passed 0.1018 A.U. or 15.8 million kilometres from Earth on March 25, 1996.
ISON will pass 0.429 A.U. or 64.2 million kilometres from Earth the day after Christmas. Bruce Willis can stay home for this one.
Here is a blow-by-blow breakdown of some key dates to watch for as ISON makes its plunge into the inner solar system:
-September 25th: ISON crosses the border from the astronomical constellation of Cancer into Leo.
-September 27th: ISON passes 2 degrees north of the planet Mars.
-October 1st: The 12% illuminated waning crescent Moon passes 10 degrees south of Mars & ISON.
-Early October: ISON may break +10th magnitude and become visible with binoculars or a small telescope.
-October 4th: New Moon occurs. The Moon then exits the dawn sky, making for two weeks of prime viewing.
–October 10th: ISON enters view of NASA’s STEREO/SECCHI HI-2A CAMERA:
-October 16th: ISON passes just 2 degrees NNE of the bright star Regulus, making a great “guidepost” to pin it down with binoculars.
-October 18th: The Full Moon occurs, after which the Moon enters the morning sky.
-October 26th: A great photo-op for astro-imagers occurs, as ISON passes within three degrees the Leo galaxy trio of M95, M96, & M105.
-October 30th: The 17% illuminated Moon passes 6 degrees south of ISON.
-Early November: Comet ISON may make its naked eye debut for observers based at dark sky sites.
-November 3rd: A hybrid (annular-total) solar eclipse occurs, spanning the Atlantic and Central Africa. It may just be possible for well placed observers to catch sight of ISON in the daytime during totality, depending on how quickly it brightens up. The Moon reaching New phase also means that the next two weeks will be prime view time for ISON at dawn.
-November 5th: ISON crosses the border from the astronomical constellation of Leo into Virgo.
-November 7th: ISON passes less than a degree from the +3.6 magnitude star Zavijava (Beta Virginis).
-November 8th: ISON passes through the equinoctial point in Virgo around 16:00 EDT/20:00 UT, passing into the southern celestial hemisphere and south of the ecliptic.
-November 14th: ISON passes less than a degree from the 10th magnitude galaxy NGC 4697.
-November 17th: The Moon reaches Full, passing into the morning sky.
-November 18th: ISON passes just 0.38 degrees north of the bright star Spica.
-November 22nd: ISON crosses into the astronomical constellation of Libra.
-November 23rd: ISON sits 4.7 degrees SSW of the planet Mercury and 4.9 SSW of Saturn, respectively.
-November 25th: ISON pays a visit to another famous comet, passing just 1.2 degrees south of short period comet 2P/Encke which may shine at +8th magnitude.
-November 27th: ISON enters the field of view of SOHO’s LASCO C3 coronagraph.
-November 28th: ISON reaches perihelion at ~18:00 PM EST/ 23:00 UT.
After that, all bets are off. The days leading up to perihelion will be tense ones, as ISON then rounds the Sun on a date with astronomical destiny. Will it join the ranks of the great comets of the past? Will it stay intact, or shatter in a spectacular fashion? Watch this space for ISON updates… we’ll be back in late November with our post-perihelion guide!
Be sure to also enjoy recently discovered Comet C/2013 R1 Lovejoy later the year.
Got ISON pics? Send ’em in to Universe Today! | 0.854441 | 3.493949 |
A group of citizen scientists and professional astronomers have discovered a star surrounded by the oldest known circumstellar disk — a primordial ring of gas and dust that orbits around a young star and from which planets can form as the material collides and aggregates.
Led by Steven Silverberg of University of Oklahoma, the team described a newly identified red dwarf star with a warm circumstellar disk, of the kind associated with young planetary systems. Circumstellar disks around red dwarfs like this one are rare to begin with, but this star, called AWI0005x3s, appears to have sustained its disk for an exceptionally long time. The findings are published by The Astrophysical Journal Letters.
“Most disks of this kind fade away in less than 30 million years,” said Silverberg. “This particular red dwarf is a candidate member of the Carina stellar association, which would make it around 45 million years old [like the rest of the stars in that group]. It’s the oldest red dwarf system with a disk we’ve seen in one of these associations.”
The discovery relied on citizen scientists from Disk Detective, a project led by NASA/GSFC’s Dr. Marc Kuchner that’s designed to find new circumstellar disks. At the project’s website, DiskDetective.org, users make classifications by viewing ten-second videos of data from NASA surveys, including the Wide-field Infrared Survey Explorer mission (WISE) and Two-Micron All Sky Survey (2MASS) projects. Since the launch of the website in January 2014, roughly 30,000 citizen scientists have participated in this process, performing roughly 2 million classifications of celestial objects.
“Without the help of the citizen scientists examining these objects and finding the good ones, we might never have spotted this object,” Kuchner said. “The WISE mission alone found 747 million [warm infrared] objects, of which we expect a few thousand to be circumstellar disks.”
“Unraveling the mysteries of our universe, while contributing to the advancement of astronomy, is without a doubt a dream come true,” says Hugo Durantini Luca from Argentina, one of eight citizen scientist co-authors.
Determining the age of a star can be tricky or impossible. But the Carina association, where this red dwarf was found, is a group of stars whose motions through the Galaxy indicate that they were all born at roughly the same time in the same stellar nursery.
Carnegie’s Gagné devised a test that showed this newly found red dwarf and its disk are likely part of the Carina association, which was key to revealing its surprising age.
“It is surprising to see a circumstellar disk around a star that may be 45 million years old, because we normally expect these disks to dissipate within a few million years,” Gagné explained. “More observations will be needed to determine whether the star is really as old as we suspect, and if it turns out to be, it will certainly become a benchmark system to understand the lifetime of disks.”
Knowing that this star and its disk are so old may help scientists understand why M dwarf disks appear to be so rare.
This star and its disk are interesting for another reason: the possibility that it could host extrasolar planets. Most of the extrasolar planets that have been found by telescopes have been located in disks similar to the one around this unusual red dwarf. Moreover, this particular star is the same spectral type as Proxima Centauri, the Sun’s nearest neighbor, which was shown to host at least one exoplanet, the famous Proxima b, in research published earlier this year
Publication: Steven M. Silverberg, et al., “A New M Dwarf Debris Disk Candidate in a Young Moving Group Discovered with Disk Detective,” The Astrophysical Journal Letters, Volume 830, Number 2, 2016; doi:10.3847/2041-8205/830/2/L28 | 0.886974 | 3.905915 |
In just six weeks of science observations, NASA’s Transiting Exoplanet Survey Satellite (TESS) has already found 50 possible new worlds for scientists to examine.
TESS finds planets by watching the dip in light as a planet passes in front of its parent star. It began science observations on July 25 and the first set of information was available to astronomers on September 5, but the first step in examining TESS’ data is to eliminate false positives. Sometimes a possible “planet” will actually be a binary star blocking its companion’s light, or it could be sunspots on the star’s surface, no second body needed.
While most of these planetary candidates will be discarded upon future analysis, principal investigator George Ricker at the Massachusetts Institute of Technology told Astronomy there are likely six new bona-fide planets lurking in this data alone. Ricker says that usually five to 20 percent of planetary candidates turn out to be true planets, once the transit method is followed up by the radial velocity method on the ground (which observes the influence of an orbiting object). And even amateurs can help with the search, he said.
“We make alerts available to astronomers worldwide, and we continue to do that, because there are a lot of amateurs with superb instruments they can use for the initial parts of the screening,” Ricker said, adding the process will likely take months or years due to the number of planetary candidates – suspected rocky planets and larger ones – to double-check.
“As we become more adept at seeking these things out, we are going to get 100 or 200 more [candidates] per sector. There will be a lot to work through. I expect there are going to be 3,000 or so potential objects of interest,” he added.
Hunt for Nearby Planets
It’s a promising start for TESS, which is supposed to find 50 rocky planets — worlds that are four times Earth’s diameter, or smaller — in its primary three-year mission. NASA is on a long-term hunt for planets like Earth, and with the long-running Kepler planet-hunter mission running low on fuel, TESS is billed as a logical successor to Kepler’s work.
While Kepler’s primary mission focused on distant stars in a zone of the constellation Cygnus, TESS is an all-sky survey optimized to look at close-up stars. It travels in a never-before-used lunar-resonant orbit that brings TESS around Earth twice for every time that the Moon circles the Earth once. TESS moves its wide view between different sectors of the sky roughly every month.
TESS will study stars that are 30 to 100 times brighter than those surveyed by Kepler. Brighter stars are easier to observe from the ground if something interesting is found, they are also likely closer than most of Kepler’s stars. So the hope is with TESS observations, there will soon be a network of telescopes doing follow-up work on the planets it finds.
All NASA missions go through periodic reviews to determine if they should receive more funding for longer periods of work. So far, indications are positive that TESS will exceed its initial goal of 50 rocky planets; TESS’ observations are already cleaner (better signal to noise) than expected. The spacecraft is also expected to find planets that are larger and gaseous, but its formal goal is more focused on rocky planets.
Furthermore the spacecraft’s trajectory is so efficient that TESS has enough remaining fuel to do its observations for another century or two; in other words, unlike Kepler, the spacecraft’s end of life will not come from running out of gas. TESS has also effectively tripled its storage capacity because the spacecraft is more stable than expected in its orbit; this means it takes fewer bits per pixel to generate an image and store it on the spacecraft. (Bits per pixel is a measurement of how much information is stored in the image; more bits per pixel requires a larger file size.)
During the extended mission, Ricker said the team will try to send information down to Earth even more quickly to catch more short-term phenomena. TESS has already spied several new near-Earth asteroids, one comet, and a supernova during its short time in orbit, but adding a more rapid response will allow astronomers to see more star explosions — as well as events such as tidal disruptions in stars that are orbiting close to another object, such as another star.
What the Future Holds for TESS
While the search for “Earth 2.0” is still ongoing, Ricker said it’s possible there already are small planets sitting in the TESS dataset. “We’ve seen indications that there are several small planets that are in this initial set, and we’re just going through the process of looking at them and making sure that we really got the properties set and it isn’t a false positive,” he said.
The candidates TESS finds will also serve as prime targets for follow up with the James Webb Space Telescope (JWST), currently set to launch in 2021. These worlds, if they possess Earth-like life, would have chemical signatures in their atmosphere visible in the infrared — exactly the wavelength regime in which JWST will operate. TESS’ sectors are also perfectly poised in JWST’s “continuous viewing zone,” which is the area of sky it will be able to observe at any time of the year during its orbit.
As TESS observations continue, the planets will come pouring in. And as telescopes on the ground and in space follow up, our galactic neighborhood will grow. | 0.915093 | 3.712282 |
How we could survive on an asteroid
The science-fiction series The Expanse is set 200 years in the future: humans have established colonies on the Moon and Mars, and have begun colonising the asteroid belt.
There are compelling reasons why we might wish to colonise the asteroid belt, but the predominant one is mining. Unlike the Earth, where precious metals tend to be buried underground, there is an abundance of metals like gold and palladium on the surface of asteroids. But they could also be used as a scientific research outpost.
The Asteroid Belt orbits the Sun between Mars and Jupiter, and is thought to be the remains of a planet. While the Asteroid Belt is the main source of asteroids, asteroids can be found throughout the Solar System and come in three basic types; stony, carbonaceous and metallic. They range in size from hundreds of metres to the size of a small house.
Companies like Planetary Resources and Deep Space Industries are already investing in asteroid mining and they could begin extraction by 2025. However, creating a settlement on an asteroid is far more complicated than simply mining one.
One of the main challenges will be the amount of radiation hitting the colonies. There will be solar radiation, Jupiter’s radiation belt and more from cosmic rays. “Cosmic rays are high energy particles, mostly just protons or high-energy nuclei. They zip straight through you and do bad things to you,” explains Martin Elvis of the Harvard-Smithsonian Centre for Astrophysics. On Earth, our atmosphere absorbs the most dangerous rays, and a space colony would need a similar shield. “A thick layer of water or ice could be used [for protection], but it would have to be several metres thick.”
其中一个主要风险是小行星殖民地将受到的高辐射量，诸如太阳辐射、木星的辐射带以及其他宇宙射线。哈佛——史密森尼天体物理中心的埃尔维斯（Martin Elvis）解释道，"宇宙射线是高能粒子，大部分是质子或高能原子核。这些高能粒子能直接穿透物体，非常危险"。在地球上，我们的大气层吸收了最危险的射线，而太空殖民地也需要类似的保护盾。 "可以利用厚重的水层或冰层（作为保护），但厚度最好能有几米。"
As well as radiation, long-term exposure to zero or micro-gravity is detrimental to the human body. “Astronauts on the ISS have to exercise for two hours every day with resistance machines and still end up with health problems from living in zero gravity for such a long time,” says astrophysicist Katie Mack, an assistant professor at North Carolina State University. Any long-term asteroid settlement would need some form of artificial gravity to mitigate this effect – possibly by spinning the entire structure.
It would also need some form of power generation. Most probes and satellites rely on solar arrays for power, but this may not be as effective for an asteroid colony. “As you move further from the Sun, you have the ‘Inverse Square Law’ coming into effect. If you are twice as far from the Sun, then you have a quarter of the energy coming in from a given area of solar collecting panels,” says science-fiction author and former astronomer Alastair Reynolds. By the time you get beyond the orbit of Mars and into Jupiter and Saturn territory then you have to build very large collecting areas to utilise solar power, but I do not see that as being a major problem.”
The ideal type of asteroid to settle would be carbonaceous, as these are often 10% water. “Water is pretty common in space, as it is [made] of the most common elements in the universe,” says Elvis. “Water can also be broken down into oxygen and hydrogen, allowing you to breathe the oxygen.” The asteroid would also need to be at least 100 metres in thickness, to provide sufficient protection from radiation.
Settlements could be buried under the surface of an asteroid, which would provide radiation shielding. However, mining and excavating an asteroid is harder than it seems. “A lot of what we think of as asteroids are very loosely organised rubble piles that do not have any intrinsic structural integrity – they are not giant boulders,” explains Reynolds. “They are more just huge blobs or gravel held together by their own gravity.”
This lack of material coherence will also mean that any attempts to spin the asteroid – to artificially generate gravity within the asteroid – would subject it to additional forces and risk it disintegrating. Therefore, some mechanism to improve the asteroid’s durability will be required. “You would have to empty it out without messing the structural integrity and then spin it up whilst making sure that spin does not put too much stress on the remaining structure,” says Mack.
One suggestion is to create a metal mesh or cage surrounding the asteroid to prevent it disintegrating. This is not as prohibitive as it may first seem, as the asteroid belt has an abundance of metallic asteroids with the necessary materials which could be used.
Many of the challenges facing asteroid settlements are similar to those of the proposed lunar base. Apart from gravity, the only other major difference is distance. The Moon and the ISS are comparatively nearby. The Moon is only a mere 225,623 miles (361,000km) away at its closest point, and the ISS is just inside the Earth’s atmosphere. On the other hand, the asteroid belt is approximately 160 million miles (256 million km) away.
Any asteroid settlement would need to be a closed eco-system, and self-sustaining, as support from Earth will be extremely limited. “It could take months to get there and back, so if you have an emergency, you will have to deal with it on the asteroid. You will need an awful lot of people, you do not just go out there and have a [Star Trek] replicator,” says Elvis. Even sending a message to Earth could take an hour.
Building a settlement on an asteroid appears to be technically feasible but carries with it significant engineering challenges. Instead, it is far more likely that asteroids could be mined remotely by automated systems and drones. An option to support this could be to build a base on Mars, which could be used for coordinating the asteroid mining systems.
“Both Mars and the Moon are more hospitable in terms of the gravity, as well as radiation shielding by using existing underground tunnels,” says Mack. There are already half a dozen satellites you can use for communications and the environment has been carefully studied.
There are some asteroids that travel in elliptical orbits around the Sun, with their path coming close to Earth and Mars. These could be hollowed out and used as a form of transport, while protecting astronauts from radiation and reducing the need for fuel. “We already know of a dozen or more asteroids that already would be easy to nudge into these orbits with anticipated technologies a few years from now,” says Elvis.
There is also a proposal to build a spaceport on Phobos, which is a moon of Mars, and is considered by some to have once been an asteroid. This spaceport could be used a stepping-off point for later settling on Mars.
Whilst planets are the preferred location for manned bases, due to their gravity and atmospheric protection, we could very well colonise an asteroid. However, they would not be particularly comfortable places to live. The benefits will have to far outweigh the daunting challenges. | 0.822329 | 3.355303 |
Scientists were amazed to spot the remains of a planet circling a dead star.
For the first time, NASA’s scientists were able to witness a solar system being destroyed, giving a window into what our demise will look like once the sun goes kaput.
NASA’s Kepler 2 Mission has found the remains of a planet circling a white dwarf, which is a dead star, about 570 light years away from us, according to a Guardian report.
The planet has been torn apart as it circles the white dwarf in the Virgo constellation, with chunks of the planet whipping around the dead star at a rate of once every five hours at a very close proximity to the star — just 520,000 miles, which is just twice the distance between the Earth and the moon.
No human has ever witnessed this, Andrew Vanderburg of the Harvard-Smithsonian Center for Astrophysics was quoted as saying in the report. He said the scientists are actually witnessing a solar system like ours get destroyed.
A star dies when the hydrogen that it depends on for nuclear reactions runs out, causing it to burn heavier elements like carbon and oxygen, leading to a dramatic expansion and causing the star to lose its outer lays with nothing but an Earth-sized core behind. This is called a white dwarf.
The Kepler 2 mission was created to find new planets, and it has more than done its job since getting launched back in 2009. Besides spotting numerous Earth-like planets well beyond our solar system, it has led to other discoveries like this one that has expanded scientists’ knowledge of our universe. Kepler 2 is capable of spotting the dimming of stars caused by planets circling them and can provide estimates of how large and how distant the planet is, as well as the speed of its orbit.
Scientists used Kepler 2 to watch a white dwarf called WD1145+017, and noticed that there was a 40 percent drop in light from the star every 4.5 hours. Other telescopes confirmed these observations, and more research seemed to indicate that there were a few lumps of rock that were orbiting the star.
The findings were published in the journal Nature, which can be found here. The abstract is excerpted below:
“Most stars become white dwarfs after they have exhausted their nuclear fuel (the Sun will be one such). Between one-quarter and one-half of white dwarfs have elements heavier than helium in their atmospheres1, 2, even though these elements ought to sink rapidly into the stellar interiors (unless they are occasionally replenished)3, 4, 5. The abundance ratios of heavy elements in the atmospheres of white dwarfs are similar to the ratios in rocky bodies in the Solar System6, 7. This fact, together with the existence of warm, dusty debris disks8, 9, 10, 11, 12, 13 surrounding about four per cent of white dwarfs14, 15, 16, suggests that rocky debris from the planetary systems of white-dwarf progenitors occasionally pollutes the atmospheres of the stars17. The total accreted mass of this debris is sometimes comparable to the mass of large asteroids in the Solar System1. However, rocky, disintegrating bodies around a white dwarf have not yet been observed. Here we report observations of a white dwarf—WD 1145+017—being transited by at least one, and probably several, disintegrating planetesimals, with periods ranging from 4.5 hours to 4.9 hours. The strongest transit signals occur every 4.5 hours and exhibit varying depths (blocking up to 40 per cent of the star’s brightness) and asymmetric profiles, indicative of a small object with a cometary tail of dusty effluent material. The star has a dusty debris disk, and the star’s spectrum shows prominent lines from heavy elements such as magnesium, aluminium, silicon, calcium, iron, and nickel. This system provides further evidence that the pollution of white dwarfs by heavy elements might originate from disrupted rocky bodies such as asteroids and minor planets.” | 0.906853 | 3.800285 |
Lab mimicry opens a window into the deep interiors of stars and planets
New work by the School of Physics & Astronomy increases our understanding of the atmosphere and chemistry of celestial objects.
The matter that makes up distant planets and even-more-distant stars exists under extreme pressure and temperature conditions. This matter includes a family of seven elements called the noble gases, some of which, such as helium and neon, are household names.
New work from the School of Physics & Astronomy used laboratory techniques to mimic stellar and planetary interiors in order to better understand how noble gases helium and neon control the atmospheres and internal chemistry of these celestial objects. Their work is published by Proceedings of the National Academy of Sciences.
The team used a diamond-anvil cell to bring the noble gases helium, neon, argon, and xenon to more than 500,000 times the pressure of Earth's atmosphere (50 gigapascals), and used a laser to heat them to temperatures ranging up to 28,000 degrees Celcius.
The gases are called “noble” due to a kind of chemical aloofness; they normally do not combine, or “react,” with other elements. Of particular interest were changes in the gases’ ability to conduct electricity as the pressure and temperature changed, because this can provide important information about the ways that the noble gases do actually interact with other materials in the extreme conditions of planetary interiors and stellar atmospheres.
Insulators are materials that are unable to conduct the flow of electrons that make up an electric current. Conductors, or metals, are materials that allow an electric current. Noble gases are not normally conductive at ambient pressures, but this study found that conductivity can be induced under higher pressures.
The researchers found that helium, neon, argon, and xenon transform from visually transparent insulators to visually opaque conductors at extreme conditions that mimic the interiors of different stars and planets.
This has several exciting implications for how noble gases behave in the atmospheres and interiors of planets and stars.
For example, it could help solve the mystery of why Saturn emits more heat from its interior than would be expected given its age. This is tied to the ability, or inability, of the noble gases to be dissolved in liquid metallic hydrogen, the main constituent of gas giant planets such as Saturn and Jupiter.
In Jupiter and Saturn, helium would be insulating near the surface and turn metal-like at depths close to both planets' cores. This change from insulator to metal is expected to allow helium to dissolve in hydrogen near the planets' rocky cores.
However, a difference was observed in the behaviour of neon between the laboratory conditions mimicking the two gas giants. The team’s results indicate that neon would remain an insulator even in Saturn’s core. As such, an ocean-like envelope of undissolved neon could collect deep within the planet and prevent the erosion of Saturn’s core compared to its neighbour Jupiter, where core materials, such as iron, would be dissolving into the surrounding liquid hydrogen.
This lack of core erosion could potentially explain why Saturn is giving off so much internal heat compared to its neighbour Jupiter. Erosion of a planet's core leads to planetary cooling as dense matter is raised upward, whereas in Saturn denser material is allowed to collect at the centre of the planet, producing hotter conditions. These findings could provide the key to solving the longstanding mystery of Saturn's internal heat.
"A tiny ocean of neon forming inside Saturn could have a surprising influence on this planet's evolution. Another tiny planetary feature that has big effects is Earth's ocean: despite making up just a fraction of a percent of the planet's total diameter, Earth's ocean plays a remarkable role in controlling the Earth system, for example by allowing mixing of the Earth's exterior and interior. In Saturn an ocean composed of noble gas instead of water could instead prevent mixing of the planet's interior and exterior. This may solve an old mystery as to why Saturn and its larger neighbour, Jupiter, look so different." Stewart McWilliams, the study's lead author.
Another implication of the team’s findings involves white dwarf stars, which are the collapsed remnants of once-larger stars, having about the mass of our Sun. They are very compact, but have faint luminosities as they give off residual heat. Dense helium is known to exist in the atmospheres of white dwarf stars and may form the surface atmosphere of some of these celestial bodies. The conditions simulated by the team’s laser-heated diamond-anvil cell indicate that this stellar helium should be more opaque (and conducting) than previously expected and this opacity could slow the cooling rates of helium-rich white dwarfs, as well as affect their colour. | 0.847045 | 4.014328 |
On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) telescope in Hawaii announced the first-ever detection of an interstellar asteroid – I/2017 U1 (aka. ‘Oumuamua). Originally though to be a comet, follow-up observations conducted by the European Southern Observatory (ESO) and others confirmed that ‘Oumuamua was actually a rocky body that had originated outside of our Solar System.
Since that time, multiple studies have been conducted to learn more about this interstellar visitor, and some missions have even been proposed to go and study it up close. However, the most recent study of ‘Oumuamua, conducted by a team of international scientists, has determined that based on the way it left our Solar System, ‘Oumuamua is likely to be a comet after all.
The study recently appeared in the journal Nature under the title “Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua)“. The study team was led by Marco Micheli of the ESA SSA-NEO Coordination Center and the INAF Osservatorio Astronomico di Roma and included members from the University of Hawaii’s Institute for Astronomy, NASA’s Jet Propulsion Laboratory, the European Southern Observatory (ESO), the Southwest Research Institute (SwRI), the Planetary Science Institute, and The Johns Hopkins University Applied Physics Laboratory (JHUAPL).
As noted, when it was first discovered – roughly a month after it made its closest approach to the Sun – scientists believed ‘Oumuamua was an interstellar comet. However, follow-up observations showed no evidence of gaseous emissions or a dusty environment around the body (i.e. a comet tail), thus leading to it being classified as a rocky interstellar asteroid.
This was followed by a team of international researchers conducting a study that showed how ‘Oumuamua was more icy that previously thought. Using the ESO’s Very Large Telescope in Chile and the William Herschel Telescope in La Palma, the team was able to obtain spectra from sunlight reflected off of ‘Oumuamua within 48 hours of the discovery. This revealed vital information about the composition of the object, and pointed towards it being icy rather than rocky.
The presence of an outer-layer of carbon rich material also explained why it did not experience outgassing as it neared the Sun. Following these initial observations, Marco Micheli and his team continued to conduct high-precision measurements of ‘Oumuamua and its position using ground-based facilities and the NASA/ESA Hubble Space Telescope.
By January, Hubble was able to snap some final images before the object became too faint to observe as it sped away from the Sun on its way to leaving the Solar System. To their surprise, they noted that the object was increasing its velocity deviating from the trajectory it would be following if only the gravity of the Sun and the planets were influencing its course.
In short, they discovered that ‘Oumuamua was not slowing down as expected, and as of June 1st, 2018, was traveling at a speed of roughly 114,000 km/h (70,800 mph). The most likely explanation, according to the team, is that ‘Oumuamua is venting material from its surface due to solar heating (aka. outgassing). The release of this material would give ‘Oumuamua the steady push it needed to achieve this velocity.
As Davide Farnocchia, a researcher from NASA’s Jet Propulsion Laboratory and a co-author on the paper, explained in a recent ESA press release:
“We tested many possible alternatives and the most plausible one is that ’Oumuamua must be a comet, and that gasses emanating from its surface were causing the tiny variations in its trajectory.”
Moreover, the release of gas pressure would also explain how ‘Oumuamua is veering off course since outgassing has been known to have the effect of perturbing the comet’s path. Naturally, there are still some mysteries that still need to be solved about this body. For one, the team still has not detected any dusty material or chemical signatures that typically characterize a comet.
As such, the team concluded that ‘Oumuamua must have been releasing only a very small amount of dust, or perhaps was releasing more pure gas without much dust. In either case, ‘Oumuamua is estimated to be a very small object, measuring about 400 meters (1312 ft) long. In the end, the hypothesized outgassing of ‘Oumuamua remains a mystery, much like its origin.
In fact, the team originally performed the Hubble observations on ‘Oumuamua in the hopes of determining its exact path, which they would then use to trace the object back to its parent star system. These new results mean this will be more challenging than originally thought. As Olivier Hainaut, a researcher from the European Southern Observatory and a co-author on the study, explained:
“It was extremely surprising that `Oumuamua first appeared as an asteroid, given that we expect interstellar comets should be far more abundant, so we have at least solved that particular puzzle. It is still a tiny and weird object, but our results certainly lean towards it being a comet and not an asteroid after all.”
Detlef Koschny, another co-author on the study, is responsible for Near-Earth Object activities under ESA’s Space Situational Awareness program. As he explained, the study of ‘Oumuamua has provided astronomers with the opportunity to improve asteroid detection methods, which could play a vital role in the study of Near-Earth Asteroids and determining if they post a risk.
“Interstellar visitors like these are scientifically fascinating, but extremely rare,” he said. “Near-Earth objects originating from within our Solar System are much more common and because these could pose an impact risk, we are working to improve our ability to scan the sky every night with telescopes such as our Optical Ground Station that contributed to this fascinating discovery.”
Since ‘Oumuamua’s arrival, scientists have determined that there may be thousands of interstellar asteroids currently in our Solar System, the largest of which would be tens of km in radius. Similarly, another study was conducted that revealed the presence of an interstellar asteroid (2015 BZ509) that – unlike ‘Oumuamua, which was an interloper to out system – was captured by Jupiter’s gravity and has since remained in a stable orbit.
This latest study is also timely given the fact that June 30th is global “Asteroid Day”, an annual event designed to raise awareness about asteroids and what can be done to protect Earth from a possible impact. In honor of this event, the ESA co-hosted a live webcast with the European Southern Observatory to discuss the latest science news and research on asteroids. To watch a replay of the webcast, go to the ESA’s Asteroid Day webpage. | 0.938833 | 3.97909 |
For the first time, astronomers have observed a star orbiting the supermassive black hole at the center of our Milky Way galaxy. And the star is dancing to the predicted tune of Albert Einstein’s general theory of relativity.The study published Thursday in the journal Astronomy & Astrophysics.Observations of the star were made by astronomers using the European Southern Observatory’s Very Large Telescope in Chile’s Atacama Desert. They saw that the star’s orbit is shaped like a rosette.Isaac Newton’s theory of gravity suggested the orbit would look like an ellipse, but it doesn’t. The rosette shape, however, holds up Einstein’s theory of relativity.“Einstein’s general relativity predicts that bound orbits of one object around another are not closed, as in Newtonian gravity, but precess forwards in the plane of motion,” said Reinhard Genzel, in a statement. He is the director at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany.
Astronomers saw a star dancing around a black hole. And it proves Einstein’s theory was right
Read more at CNN | 0.881341 | 3.010981 |
In June 2015, a black hole called V404 Cygni underwent dramatic brightening for about two weeks, as it devoured material that it had stripped off an orbiting companion star. Violent red flashes, lasting just fractions of a second, were observed during the flare-up — one of the brightest black hole outbursts in recent years.
V404 Cygni, which is about 7,800 light-years from Earth, was the first definitive black hole to be identified in our Galaxy and can appear extremely bright when it is actively devouring material.
In a new study, published in the journal Monthly Notices of the Royal Astronomical Society, an international team of astronomers, led by the University of Southampton, report that the black hole emitted dazzling red flashes lasting just fractions of a second, as it blasted out material that it could not swallow.
The astronomers associated the red colour with fast-moving jets of matter that were ejected from close to the black hole. These observations provide new insights into the formation of such jets and extreme black hole phenomena.
Lead author of the study Dr Poshak Gandhi, Associate Professor and STFC Ernest Rutherford Fellow in the University of Southampton’s Astronomy Group, comments: “The very high speed tells us that the region where this red light is being emitted must be very compact. Piecing together clues about the colour, speed, and the power of these flashes, we conclude that this light is being emitted from the base of the black hole jet. The origin of these jets is still unknown, although strong magnetic fields are suspected to play a role.
“Furthermore, these red flashes were found to be strongest at the peak of the black hole’s feeding frenzy. We speculate that when the black hole was being rapidly force-fed by its companion orbiting star, it reacted violently by spewing out some of the material as a fast-moving jet. The duration of these flashing episodes could be related to the switching on and off of the jet, seen for the first time in detail.”
Due to the unpredictable nature and rarity of these bright black hole ‘outbursts’, astronomers have very little time to react. For example, V404 Cygni last erupted back in 1989. V404 Cygni was exceptionally bright in June 2015 and provided an excellent opportunity for such work. In fact, this was one of the brightest black hole outbursts in recent years. But most outbursts are far dimmer, making them difficult to study.
Each flash was blindingly intense, equivalent to the power output of about 1,000 Suns. And some of the flashes were shorter than 1/40th of a second — about ten times faster than the duration of a typical blink of an eye. Such observations require novel technology, so astronomers used the ULTRACAM fast imaging camera mounted on the William Herschel Telescope in La Palma, on the Canary Islands.
Professor Vik Dhillon, of the University of Sheffield and co-creator of ULTRACAM, said: “ULTRACAM is unique in that it can operate at very high speed, capturing high frame-rate ‘movies’ of astronomical targets, in three colours simultaneously. This allowed us to ascertain the red colour of these flashes of light from V404 Cygni.”
Dr Gandhi concluded: “The 2015 event has greatly motivated astronomers to coordinate worldwide efforts to observe future outbursts. Their short durations, and strong emissions across the entire electromagnetic spectrum, require close communication, sharing of data, and collaborative efforts amongst astronomers. These observations can be a real challenge, especially when attempting simultaneous observations from ground-based telescopes and space satellites.” | 0.818261 | 4.036628 |
Cosmic rays are atom fragments that rain down on the Earth from outside of the solar system. They blaze at the speed of light and have been blamed for electronics problems in satellites and other machinery.
Discovered in 1912, many things about cosmic rays remain a mystery more than a century later. One prime example is exactly where they are coming from. Most scientists suspect their origins are related to supernovas (star explosions), but the challenge is that for many years cosmic ray origins appeared uniform to observatories examining the entire sky.
A large leap forward in cosmic ray science came in 2017, when the Pierre Auger Observatory (which is spread over 3,000 square kilometers, or 1,160 square miles, in western Argentina) studied the arrival trajectories of 30,000 cosmic particles. It concluded that there is a difference in how frequently these cosmic rays arrive, depending on where you look. While their origins are still nebulous, knowing where to look is the first step in learning where they came from, the researchers said. The results were published in Science.
Cosmic rays can even be used for applications outside of astronomy. In November 2017, a research team discovered a possible void in the Great Pyramid of Giza, which was built around 2560 B.C., using cosmic rays. The researchers found this cavity using muon tomography, which examines cosmic rays and their penetrations through solid objects.
While cosmic rays were only discovered in the 1900s, scientists knew something mysterious was going on as early as the 1780s. That's when French physicist Charles-Augustin de Coulomb — best known for having a unit of electrical charge named after him — observed an electrically charged sphere suddenly and mysteriously not being charged any more.
At the time, air was thought to be an insulator and not an electric conductor. With more work, however, scientists discovered that air can conduct electricity if its molecules are charged or ionized. This would most commonly happen when the molecules interact with charged particles or X-rays.
But where these charged particles came from was a mystery; even attempts to block the charge with large amounts of lead were coming up empty. On Aug. 7, 1912, physicist Victor Hess flew a high-altitude balloon to 17,400 feet (5,300 meters). He discovered three times more ionizing radiation there than on the ground, which meant the radiation had to be coming from outer space.
But tracing cosmic ray "origin stories" took more than a century. In 2013, NASA's Fermi Gamma-ray Space Telescope released results from observing two supernova remnants in the Milky Way: IC 433 and W44.
Among the products of these star explosions are gamma-ray photons, which (unlike cosmic rays) are not affected by magnetic fields. The gamma-rays studied had the same energy signature as subatomic particles called neutral pions. Pions are produced when protons get stuck in a magnetic field inside the shockwave of the supernova and crash into each other.
In other words, the matching energy signatures showed that protons could move at fast enough speeds within supernovas to create cosmic rays.
We know today that galactic cosmic rays are atom fragments such as protons (positively charged particles), electrons (negatively charged particles) and atomic nuclei. While we know now they can be created in supernovas, there may be other sources available for cosmic ray creation. It also isn't clear exactly how supernovas are able to make these cosmic rays so fast.
Cosmic rays constantly rain down on Earth, and while the high-energy "primary" rays collide with atoms in the Earth's upper atmosphere and rarely make it through to the ground, "secondary" particles are ejected from this collision and do reach us on the ground.
But by the time these cosmic rays get to Earth, it's impossible to trace where they came from. That's because their path has been changed as they travelled through multiple magnetic fields (the galaxy's, the solar system's and Earth's itself.)
Scientists are trying to trace back cosmic ray origins by looking at what the cosmic rays are made of. Scientists can figure this out by looking at the spectroscopic signature each nucleus gives off in radiation, and also by weighing the different isotopes (types) of elements that hit cosmic ray detectors.
The result, NASA adds, shows very common elements in the universe. Roughly 90 percent of cosmic ray nuclei are hydrogen (protons) and 9 percent are helium (alpha particles). Hydrogen and helium are the most abundant elements in the universe and the origin point for stars, galaxies and other large structures. The remaining 1 percent are all elements, and it's from that 1 percent that scientists can best search for rare elements to make comparisons between different types of cosmic rays. The Pierre Auger Observatory collaboration found some variations in the arrival trajectories of cosmic rays in 2017, providing some hints about where the rays could have originated.
Scientists can also date the cosmic rays by looking at radioactive nuclei that decrease over time. Measuring the half-life of each nuclei gives an estimate of how long the cosmic ray has been out there in space.
In 2016, a NASA spacecraft found most cosmic rays likely come from (relatively) nearby clusters of massive stars. The agency's Advanced Composition Explorer (ACE) spacecraft detected cosmic rays with a radioactive form of iron known as iron-60. Since this form of cosmic ray degrades over time, scientists estimate it must have originated no more than 3,000 light-years from Earth — the equivalent distance of the width of the local spiral arm in the Milky Way.
An experiment called ISS-CREAM (Cosmic Ray Energetics and Mass) launched to the International Space Station in 2017. It is expected to operate for three years, answering questions such as whether supernovas generate most cosmic ray particles, when cosmic ray particles originated, and if all the energy spectra seen for cosmic rays can be explained by a single mechanism. The ISS also hosts the CALorimetric Electron Telescope (CALET), which searches for the highest-energy types of cosmic rays. CALET launched there in 2015.
Cosmic rays can also be detected by balloon, such as through the Super Trans-Iron Galactic Element Recorder (SuperTIGER) experiment that includes participation from NASA's Jet Propulsion Laboratory and several universities. It has flown several times, including a record 55-day flight over Antarctica between December 2012 and January 2013. "With the data from this flight we are studying the origin of cosmic rays. Specifically, testing the emerging model of cosmic-ray origins in OB associations, as well as models for determining which particles will be accelerated," the SuperTIGER website said.
Citizen scientists can also participate in the search for cosmic rays by registering at the website crayfis.io. There, they will join the CRAYFIS experiment run by the Laboratory of Methods for Big Data Analysis (LAMBDA) at the National Research University Higher School of Economics in Russia. Researchers there are examining ultra-high energy cosmic rays using mobile phones.
Space radiation concerns
Earth's magnetic field and atmosphere shields the planet from 99.9 percent of the radiation from space. However, for people outside the protection of Earth's magnetic field, space radiation becomes a serious hazard. An instrument aboard the Curiosity Mars rover during its 253-day cruise to Mars revealed that the radiation dose received by an astronaut on even the shortest Earth-Mars round trip would be about 0.66 sievert. This amount is like receiving a whole-body CT scan every five or six days.
A dose of 1 sievert is associated with a 5.5 percent increase in the risk of fatal cancers. The normal daily radiation dose received by the average person living on Earth is 10 microsieverts (0.00001 sievert).
The moon has no atmosphere and a very weak magnetic field. Astronauts living there would have to provide their own protection, for example by burying their habitat underground.
Mars has no global magnetic field. Particles from the sun have stripped away most of Mars' atmosphere, resulting in very poor protection against radiation at the surface. The highest air pressure on Mars is equal to an altitude of 22 miles (35 kilometers) above the Earth's surface. At low altitudes, Mars' atmosphere provides slightly better protection from space radiation.
In 2017, NASA made some upgrades to its Space Radiation Laboratory (located at the Brookhaven National Laboratory in New York) to do more studies into how cosmic rays may affect astronauts on long voyages, including to Mars. These upgrades allow researchers to alter types of ions, and the intensity of energy, more easily due to software control. | 0.83577 | 4.094582 |
Newly spotted frozen world orbits in a binary star system.
New Zealand astronomers have played an important role in the discovery of an Earth-like planet in a binary star system located 3,000 light-years from Earth. This expands astronomers’ notions of where Earth-like—and even potentially habitable—planets can form and how to find them.
At just twice the mass of Earth, the planet (now named OGLE-2013-BLG-0341LBb) orbits one of the stars in the binary system at almost exactly the same distance from which Earth orbits the sun. However, because the planet’s host star is much dimmer than the Sun, the planet is much colder than Earth—a little colder, in fact, than Saturn’s icy moon Titan.
Four international research teams, led by Professor Andrew Gould of The Ohio State University, published their discovery in the July 4 issue of the prestigious international journal Science. New Zealand astronomers, both professional and amateur, who were members of these research teams made significant contributions to the discovery using a powerful technique called “gravitational microlensing”.
The study provides the first evidence that terrestrial planets can form in orbits similar to Earth’s, even in a binary star system where the stars are not very far apart. Although this planet itself is too cold to be habitable, the same planet orbiting a sun-like star in such a binary system would be in the so-called “habitable zone” —the region where conditions might be right for life.
“Small dim stars are the most common in our galaxy and the majority of these are found in binary systems. They have much longer lives than our Sun and could potentially provide a stable habitable environment over very large time spans”, said Stardome astronomer, Dr Grant Christie.
“Now we have shown that planets like Earth can form and survive in these systems, it opens up exciting new opportunities to explore. Planets such as this are likely to be volcanically active so potential habitats for life could exist beneath the surface.”
Detailed analysis showed that the planet is twice the mass of Earth, and orbits its star from an Earth-like distance, around 135 million kilometres. But its star is 400 times dimmer than our Sun, so the planet is very cold—around -210° Celsius. The second star in the star system is only as far from the first star as Saturn is from our Sun. But this binary companion is also very dim and contributes almost no heat to the planet.
While four other terrestrial planets have been discovered in binary systems that have similar separations using different techniques, this is the first discovery within a binary system of a planet that is both Earth-like in size and follows an Earth-like orbit.
Four amateur observatories in New Zealand contributed observations covering four nights (23-27 April, 2012) while working as part of the international MicroFUN collaboration (Microlensing Follow-up Network). In particular, Ian Porritt of Palmerston North worked through gaps in clouds to obtain the first few critical measurements that revealed the planet was in a binary star system.
The New Zealand members of MicroFUN who contributed to the discovery of this planetary system:
· Dr Grant Christie, Stardome Observatory (Auckland)
· Jennie McCormick, Farm Cove Observatory (Auckland)
· John Drummond, Possum Observatory (Gisborne)
· Ian Porritt, Turitea Observatory (Palmerston North)
The 1.8m MOA telescope at Mt John Observatory near Tekapo was also able to cover the event. This telescope is one of only two large telescopes dedicated to exploring the galaxy using gravitational microlensing. | 0.845868 | 3.934707 |
Scientists believe that they have found a second black hole near the center of our galaxy, and one which could help explain more about how these mysterious phenomena develop.
The discovery began last year, when Tomoharu Oka and other scientists from Keio University in Japan observed CO–0.40–0.22, a gas cloud 200 light years from the center of the Milky Way Galaxy. The random and quick gas flows from the cloud led to the theory that it contains an intermediate-mass black hole (IMBH).
“Based on the careful analysis of gas kinematics, we concluded that a compact object with a mass of about [100,000] solar masses is lurking in this cloud,” the scientists explained.
The Milky Way Already Harbors a Supermassive Black Hole
A supermassive black hole, Sagittarius A*, lies in the center of our galaxy; it is estimated to be millions or even billion times more massive than the sun.
This is part of what makes the discovery of a second black hole so interesting. Up until now, astronomers have managed to discover some supermassive black holes, and the much smaller stellar-massive black holes (between three and ten times the size of the sun), but not intermediate-massive black holes.
Scientists are hoping that further study of these medium giants could help determine how the supermassive variety develop over time; so far it is unclear how they reach such improbable sizes.
Since they seem to lie in the center of galaxies, it is theorized to be a combination of feeding on galactic junk (including planets and stars) and colliding with other galaxies and their own black holes.
It is also unclear how IMBHs form themselves; they are too large to come from single stars going supernova, like their stellar-massive cousins. Oko’s team theorizes that this new discovery used to be the center of its own dwarf galaxy before colliding with ours.
Image Source: Wikipedia | 0.808532 | 3.6743 |
Hyrrokkin was discovered on Dec. 12, 2004 by Scott S. Sheppard, David C. Jewitt and Jan T. Kleyna using the Subaru 8.3-m reflector telescope on Mauna Kea, Hawaii.
Hyrrokkin has a mean radius of 1.9 miles (3 kilometers), assuming an albedo (a measure of how reflective the surface is) of 0.04. It orbits Saturn at an inclination of about 151 degrees and an eccentricity of about 0.3. At a mean distance of 11.5 million miles (18.4 million kilometers) from Saturn, the moon takes about 932 Earth days to complete one orbit.
Hyrrokkin is a member of the Norse group of moons. These "irregular" moons have retrograde orbits around Saturn -- traveling around in the opposite direction from the planet's rotation. Hyrrokkin and the other Norse moons also have eccentric orbits, meaning they are more elongated than circular.
Like Saturn's other irregular moons, Hyrrokkin is thought to be an object that was captured by Saturn's gravity, rather than having accreted from the dusty disk that surrounded the newly formed planet as the regular moons are thought to have done. Hyrrokkin appears to be a member of a subgroup that also includes Skathi, Skoll, S/2006 S1, Bergelmir, Farbauti, S/2006 S3, and Kari.
How Hyrrokkin Got its Name
Originally called S/2004 S19, Hyrrokkin was named for giantess in Norse mythology who launched Baldur's enormous funeral ship with one mighty push when the gods, themselves, were unable to budge it | 0.827884 | 3.322162 |
A blue “supergiant” nine billion light years away is the most distant single star ever to be observed by astronomers.
Usually at such distances scientists can only image galaxies, collections of billions of stars such as our own Milky Way, or supernovas and gamma ray bursts, colossal cosmic explosions.
Beyond about 100 million light years it is impossible to make out individual stars even with the most powerful telescopes.
In this case, a rare cosmic alignment naturally magnified the supergiant more than 2,000 times, allowing astronomers to see it.
The B-type blue supergiant star, hundreds or even thousands of times brighter than the sun, was discovered in Hubble Space Telescope images taken over the course of a year between April 2016 and 2017.
It could only be seen because of an effect called “gravitational lensing” that occurs when massive galaxy clusters bend the light of objects behind them.
In effect the galaxies act as a magnifying glass that can render dim far away objects visible.
The lensing phenomenon, predicted by Albert Einstein, is the result of a massive object bending space-time around it and forcing light beams to take a curved path.
Lead scientist Dr Patrick Kelly, who worked on the observations while at the University of California at Berkeley, US, said: “You can see individual galaxies out there, but this star is at least 100 times farther away than the next individual star we can study, except for supernova explosions.”
The star has the long formal name MACS J1149 Lensed Star 1 (LS1), but has been dubbed “Icarus” by the astronomers.
A report on its discovery appears in the journal Nature Astronomy.
Co-author Professor Alex Filippenko, also from the University of California at Berkeley, said: “For the first time ever we’re seeing an individual normal star, not a supernova, not a gamma ray burst, but a single stable star, at a distance of nine billion light years.
“These lenses are amazing cosmic telescopes.”
He added that other gravitational lensing alignments should allow more distant stars to be studied.
“There are alignments like this all over the place as background stars or stars in lensing galaxies move around, offering the possibility of studying very distant stars dating from the early universe, just as we have been using gravitational lensing to study distant galaxies,” said Prof Filippenko. “For this type of research, nature has provided us with a larger telescope than we can possibly build.” | 0.912804 | 3.891692 |
It's not uncommon for astronomers to come across hot Jupiter-like exoplanets while surveying other star systems throughout the Milky Way galaxy. Most of these are discovered by a single exoplanet search group at a time, but the discovery of a hot Jupiter-like exoplanet made by Keele University researchers is shaking things up a bit.
Back in 2006 and 2013, both the Wide-Angle Search for Planets (WASP) and the Kilodegree Extremely Little Telescope (KELT) studied a distant star dubbed WASP-167b/KELT-13 with both the WASP-South telescope and KELT-South telescope at the South African Astronomical Observatory (SAAO).
Another observation of the same star in 2016 by the European South Observatory (ESO) confirmed the presence of an exoplanet orbiting the host star. Both giant and gassy, the exoplanet resembled a body found right here in our solar system: Jupiter. Despite the similarities, however, some important details set it apart from our familiar neighbor.
Image Credit: Keele University
The observation marked the first discovery of a hot Jupiter-like exoplanet that resulted from a collaboration between two exoplanet search groups. The findings are published in a paper available on the arXiv.org server.
“Planet-search teams are only just beginning to find hot-Jupiter planets with hot, fast-rotating host stars. This is only the second of what I hope will be many WASP planets that fall into this category. Already we are seeing characteristic properties that contrast those we’ve seen before, and I’m looking forward to filling in this emerging big picture with more new discoveries,” said Keele University astrophysics researcher Lorna Temple, the lead author of the paper.
“This is the first planet discovery where two teams have collaborated, pooling all of the data to produce the best possible characterization of the system.”
The exoplanet was dubbed WASP-167b/KELT-13b in honor of both exoplanet search groups. It’s significantly larger than Jupiter is, and it completes a full orbit around its host star in just 2.02 Earth days.
The researchers also note how the host star exhibits stellar pulsations, which are essentially expansions and contractions of the star’s outer layers. It's believed that the exoplanet's proximity to WASP-167b/KELT-13 causes these stellar pulsations.
With additional observations, we may be able to learn a bit more about this hot Jupiter-like exoplanet and the system in which it resides.
Source: Keele University | 0.807043 | 3.836447 |
Less than two decades ago, there were exactly zero known planets orbiting sunlike stars in our Milky Way galaxy. Astronomers back then were engaged in a powerful struggle to seek out exoplanets, and they succeeded, so that today there are 861 confirmed exoplanets, according to exoplanet.eu on March 25, 2013. In the past year, astronomers have begun tossing around the word billion to describe how many planets might orbit Milky Way stars. Today (April 3, 2013), astronomers at The University of Auckland in New Zealand announced their new method for finding exoplanets. They say they anticipate 100 billion planets similar to our Earth, orbiting stars in the Milky Way. Their work will appear in the journal Monthly Notices of the Royal Astronomical Society.
Lead author of the New Zealand planet search – Dr. Phil Yock from the University of Auckland’s Department of Physics – said his team’s strategy is to use a gravitational microlensing technique. Yock said his team will use a combination of data from microlensing and NASA’s Kepler space telescope.
The Kepler space telescope, by the way, has single-handedly found 105 exoplanets and an astounding 2,740 planet candidates orbiting 2,036 stars (as of January 7, 2013). Yock said:
Kepler finds Earth-sized planets that are quite close to parent stars, and it estimates that there are 17 billion such planets in the Milky Way. These planets are generally hotter than Earth, although some could be of a similar temperature (and therefore habitable) if they’re orbiting a cool star called a red dwarf.
Our proposal is to measure the number of Earth-mass planets orbiting stars at distances typically twice the sun-Earth distance. Our planets will therefore be cooler than the Earth. By interpolating between the Kepler and MOA results, we should get a good estimate of the number of Earth-like, habitable planets in the galaxy. We anticipate a number in the order of 100 billion.
But let’s back up a sec. The difficulty of detecting exoplanets from a distance has always been that planets – which are tiny in contrast to their parent stars and produce no light of their own – are extremely faint and hard to see in the glare of their stars. The first planet orbiting a sunlike star – 51 Pegasi b, discovered in 1995 – was found by what is called the radial velocity technique. That is, 51 Pegasi b was found through careful measurement of the motion of the star 51 Pegasi across the dome of night. Very detailed analysis of this motion revealed a slight wobble, revealing the presence of a small companion: a planet. This planet is called 51 Pegasi b according to the nomenclature of the International Astronomical Union.
The Kepler spacecraft finds planets in a slightly different way. It measures the loss of light from a star when a planet orbits between us and the star.
Microlensing, used by the New Zealand astronomers, is a third technique for finding planets orbiting distant suns. It measures the deflection of light from a distant star that passes through a planetary system en route to Earth. This effect was predicted by Einstein in 1936 and has been used successfully not only to find exoplanets but also to study distant objects such as quasars. The April 3, 2013 press release from University of Aukland said:
In recent years, microlensing has been used to detect several planets as large as Neptune and Jupiter. Dr. Yock and colleagues have proposed a new microlensing strategy for detecting the tiny deflection caused by an Earth-sized planet. Simulations carried out by Dr. Yock and his colleagues – students and former students from The University of Auckland and France – showed that Earth-sized planets could be detected more easily if a worldwide network of moderate-sized, robotic telescopes was available to monitor them.
Their plan is to use just such a network, now being deployed by Las Cumbres Observatory Global Telescope Network (LCOGT) in collaboration with the Scottish Universities Physics Alliance. There are three telescopes in Chile, three in South Africa, three in Australia, and one each in Hawaii and Texas. In addition, they’ll use telescopes in the Canary Island and in Tasmania. But, as Yock pointed out:
Of course, it will be a long way from measuring this number to actually finding inhabited planets, but it will be a step along the way.
He’s just saying that Earth-like does not mean inhabited. And inhabited does not mean by an intelligent civilization. And why do we want to find Earth-like planets, anyway, when getting to even the closest known Earth-like planet – Alpha Centauri Bb, only four light-years away – would require hundreds of thousands of years of travel time, using conventional technologies?
Why? Because … aren’t you curious? I know I am.
Bottom line: Astronomers have begun to use the word “billion” or even “100 billion” to describe the possible number of Earth-like planets in our Milky Way galaxy. This post discusses the April 3, 2013 announcement by astronomers at the University of Auckland in New Zealand that they’ll contribute to the planet search using a gravitational microlensing technique.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says. | 0.913323 | 3.693241 |
Star Chemistry Constrains Habitable Zone
The chemistry of a parent star can have drastic effects on the habitability of an earth-like planet.
Scientists at the University of Arizona have added another factor to consider when looking for habitable planets. PhysOrg reported,
As a star evolves, it becomes brighter, causing the habitable zone to move outwards through its solar system. The team’s study indicates that a greater abundance of oxygen, carbon, sodium, magnesium and silicon should be a plus for an inner solar system’s long-term habitability because the abundance of these elements make the star cooler and cause it to evolve more slowly, thereby giving planets in its habitable zone more time to develop life as we know it….
The stellar abundance of oxygen seems crucial in determining how long planets stay in the habitable zone around their host star. If there had been less oxygen in the Sun’s chemical makeup, for example, Earth likely would have been pushed out of the Sun’s habitable zone about a billion years ago, well before complex organisms evolved. Considering the first complex multicellular organisms only arose about 650 million years ago, such a move would have likely destroyed any chance of complex life taking hold on Earth.
There are probably other factors, too: “Habitability is very difficult to quantify because it depends on a huge number of variables, some of which we have yet to identify,” said the university’s assistant professor of School of Earth and Space Exploration, Patrick Young.
Update 9/11/2012: The BBC News claims that habitable planets may be more abundant due to the fact that water can exist under the surface, even outside the habitable zone where liquid water can exist. There are, however, constraints on how long a body’s internal heat can last. Water is not alive; many other factors are required for life. Even if life were possible in a deep, dark, subsurface ocean, it would not be the kind humans would be able to learn about or would want to contact. That being so, it remains a theoretical possibility only, not conducive to observation.
Let’s tally up the factors we’ve reported so far that make the “Goldilocks Zone” more complicated than just allowing for liquid water:
- Galactic Habitable Zone, where a star must be located (09/29/2009);
- Circumstellar Habitable Zone, the right radius from the star where liquid water can exist (10/08/2010);
- Continuously Habitable Zone, because too much variety can be lethal (07/21/2007);
- Temporal Habitable Zone, because habitable zones do not last forever (10/27/2008);
- Chemical and Thermodynamic Habitable Zone, where water can be liquid (12/30/2003);
- Ultraviolet Habitable Zone, free from deadly radiation (08/15/2006);
- Tidal Habitable Zone, which rules out most stars that are small (02/26/2011).
- Stable Obliquity Habitable Zone (1/12/2012)
- Stellar Chemistry Habitable Zone (this entry)
The list will probably continue to grow. Although the current paper assumes billions of years of evolution, it’s a problem for evolutionists of all stripes: atheistic, deistic and theistic. Why? They all need billions of years. Theistic evolutionists, for instance, would need for God to intervene and move the earth as the habitable zone evolves. If the solar system were created much more recently, this is not a problem at all. The hopes of Carl Sagan and other astronomers of the 1980s for billions and billions of worlds filled with life are looking more simplistic with each new discovery. The earth is looking more Biblical all the while. | 0.824399 | 3.655967 |
Quarter* ♏ Scorpio
Moon phase on 24 August 2001 Friday is Waxing Crescent, 6 days young Moon is in Scorpio.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 5 days on 19 August 2001 at 02:55.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Moon is passing about ∠15° of ♏ Scorpio tropical zodiac sector.
Lunar disc appears visually 0% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1898" and ∠1898".
Next Full Moon is the Harvest Moon of September 2001 after 9 days on 2 September 2001 at 21:43.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 6 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 20 of Meeus index or 973 from Brown series.
Length of current 20 lunation is 29 days, 7 hours and 32 minutes. It is 1 hour and 24 minutes shorter than next lunation 21 length.
Length of current synodic month is 5 hours and 12 minutes shorter than the mean length of synodic month, but it is still 57 minutes longer, compared to 21st century shortest.
This New Moon true anomaly is ∠358.1°. At beginning of next synodic month true anomaly will be ∠13.2°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
5 days after point of perigee on 19 August 2001 at 05:43 in ♌ Leo. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 8 days, until it get to the point of next apogee on 1 September 2001 at 23:26 in ♒ Aquarius.
Moon is 377 686 km (234 683 mi) away from Earth on this date. Moon moves farther next 8 days until apogee, when Earth-Moon distance will reach 406 332 km (252 483 mi).
8 days after its ascending node on 15 August 2001 at 17:05 in ♊ Gemini, the Moon is following the northern part of its orbit for the next 3 days, until it will cross the ecliptic from North to South in descending node on 28 August 2001 at 09:09 in ♑ Capricorn.
8 days after beginning of current draconic month in ♊ Gemini, the Moon is moving from the beginning to the first part of it.
8 days after previous North standstill on 16 August 2001 at 03:52 in ♋ Cancer, when Moon has reached northern declination of ∠23.488°. Next 4 days the lunar orbit moves southward to face South declination of ∠-23.546° in the next southern standstill on 28 August 2001 at 23:14 in ♑ Capricorn.
After 9 days on 2 September 2001 at 21:43 in ♓ Pisces, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.143204 |
Collisionless shocks and discontinuities in electron-ion-positron plasma
||Collisionless shocks and discontinuities in electron-ion-positron plasma|
||SNIC Medium Compute|
||Mark Eric Dieckmann <[email protected]>|
||2019-10-01 – 2020-10-01|
||10303 10305 |
A plasma is an ionized gas. Plasma particles can interact with each other via their Coulomb fields (binary interactions) or through the electromagnetic fields, which are generated by the current of all particles (collective interactions). We call a plasma collisionless if collective interactions dominate over binary ones. Currents due to the collective motion of particles are strong and they can affect the properties of electromagnetic waves in plasma. A plasma thus supports wave modes and structures that do not exist in vacuum. Their description is difficult in particular if they are nonlinear. Particle-in-cell (PIC) simulation codes can capture the physics of collisionless plasma and resolve all of its waves and plasma structures even in the nonlinear regime.
Plasma clouds, which stream relative to a background plasma or collide with other plasma clouds, are observed in a wide range of space-, astrophysical- and laboratory environments. If the interacting clouds are composed of collisionless plasma then their interaction gives rise to waves and nonlinear structures and to the emission of electromagnetic radiation.
We will examine with PIC simulations the instabilities and nonlinear structures that emerge when fast clouds of electrons and positrons interact with a plasma, which consists of electrons and protons. Their study is important for two reasons.
The lasers based at the recently inaugurated Extreme Light Infrastructure (ELI) in Prague have enough power and energy to create electron-positron clouds that contain so many particles that they start to behave like a pair plasma. These pair clouds have relativistic mean speeds and their interaction with an electron-ion plasma can give rise to plasma instabilities and nonlinear structures that have so far remained unexplored. We will perform simulations that model the interaction of plasma with pair clouds that have a size that is similar to the one that can be created in laboratory experiments. Our simulations will provide theoretical support for forthcoming experiments of my collaborators.
We have recently found a novel plasma structure that develops if a large and dense pair cloud interacts with an electron-proton plasma (M.E. Dieckmann et al., Astronomy and Astrophysics, 621, A142, 2019). It is a magnetic boundary that can separate a hot pair cloud from an electron-proton plasma. Its magnetic pressure is comparable to the pressure of the pair cloud. This magnetic discontinuity could form the boundary that separates the relativistic jets of electrons and positrons, which are emitted by the accreting black holes known as (micro-)quasars, from the ambient medium (the stellar wind of a companion star or interstellar medium). Its strong magnetic fields are in contact with the relativistically hot particles of the pair cloud and their radio-synchrotron emissions could contribute to the observed electromagnetic emissions of astrophysical jets. We will continue to study with PIC simulations the properties of this magnetic boundary and its robustness relative to changes in the initial conditions of our PIC simulations. | 0.829424 | 4.030851 |
The outermost reaches of our solar system are set to be studied in unprecedented detail by a NASA spacecraft scheduled for launch on Sunday.
The Interstellar Boundary Explorer, or IBEX, satellite is scheduled to be launched from a site at the Kwajalein Atoll in the south Pacific on Sunday. It will operate for two years in high-Earth orbit.
The solar wind, a stream of charged particles from the Sun, forms a huge protective bubble around the solar system called the heliosphere. At the edge of this bubble, a shock wave forms where the solar wind collides with the gas and dust in interstellar space.
IBEX is designed to detect atoms that are heated and thrown off from this boundary, which shields the solar system from dangerous charged particles called cosmic rays that come from elsewhere in the Milky Way.
“These boundaries really protect us from the fairly harsh galactic environment,” Nathan Schwadron, IBEX’s head of science operations, said during a press briefing on Friday.
“Every six months, we will make global sky maps of where these atoms come from and how fast they are travelling,” team member Herb Funsten of Los Alamos National Laboratory, said in a statement. “From this information, we will be able to discover what the edge of our bubble looks like and learn about the properties of the interstellar cloud that lies beyond the bubble.”
NASA’s two unmanned Voyager probes were the first to begin to explore this region, which begins about three times farther from the Sun than the orbit of the dwarf planet Pluto. Voyager 1 passed the inner boundary in 2004 and Voyager 2 crossed over last year (see Voyager 2 probe reaches solar system boundary).
“The heliosphere’s boundary region is enormous, and the Voyager crossings of the termination shock, while historic, only sampled two tiny areas 10 billion miles (16 billion km) apart,” NASA scientist Eric Christian said.
More on these topics: | 0.889929 | 3.315742 |
Dec 11, 2019
The Solar System is home to many devastated planets and moons.
Most of the Sun’s family of rocky bodies are heavily cratered. For instance, a bright rayed structure covers almost an entire hemisphere of Saturn’s moon Rhea. It is similar to formations found on the Moon or on Mercury. Astronomers think that some kind of impact hurled subsurface debris outward in long ejecta blankets. Bright surface rays around Kuiper crater on Mercury exhibit smaller craters mixed-in with the shallow streamers. Tiny craters around Tycho crater on Earth’s Moon are also said to be “secondary impacts” formed when chunks of regolith were thrown-out from the initial impact. However, previous Picture of the Day articles note that rayed formations are more likely to be the result of electric arcs.
Mercury, like Rhea, has no atmosphere and no magnetic field to shield it from the Sun, so it seems reasonable to describe it using terminology applied to the Moon. If the craters and rays so prominent there can be explained by electrical activity, then Mercury’s features, along with those on Rhea, might also benefit from an electrical hypothesis.
Electric Universe pioneer, Ralph Juergens, took issue with how lunar cratering events can occur:
“….not only the presence of the secondary craters in connection with ‘each ray element,’ but their placement always ‘at the near end,’ poses a problem for the ejection hypothesis. Is it conceivable that larger objects randomly mixed with fines in ejecta streams would always manage to drop to the surface just at the inner ends of fallout patterns produced by the fines? The strange proportions of Tycho’s long rays seem all-but-impossible to reconcile with ejection origins. Enormous velocities of ejection must be postulated to explain the lengths of the rays, yet the energetic processes responsible for such velocities must be imagined to be focused very precisely to account for the ribbon thin appearance of the rays.”
Juergens thought that the hard, radar-reflective floor of Tycho indicates kinetic forces from mechanical impact are not a good theory for its formation. Tycho’s rays, rather than being “fall-back ejecta” are the paths that electrons took when the secondary discharge erupted into space, completing a circuit with a lighting leader stroke. Based on the concept, rays around craters are not ejected material, but are caused by charged particles rushing toward the center, dragging dust along with them.
Getting back to Rhea, around one of its large craters, the rays are not deep, but instead appear to be a thin layer of dust, like on the Moon. They were probably deposited by an “ionic wind” as plasma arcs reduced the surface rocks to fine powder, and then blew them away as ionized particles. These are only a few out of many such huge structures that indicate Rhea did not undergo a slow, steady formation out of a nebular cloud.
Phobos, a moon of Mars, is about the same size as asteroids Mathilde, Eros and Ida, revealing features like the relatively gigantic craters that are endemic to those bodies. What is the common event that creates such similar structures without obliterating the objects in the first place? The answer is electricity.
In previous Pictures of the Day about Mars, scenarios for how it was devastated by electric arcs in the recent past were presented. Those events gouged-out Valles Marineris, Olympus Mons and Arabia Terra in a relatively short period, ejecting gigatons of rock from the planet. Could it be that Phobos and Deimos are remnants of that overwhelming cataclysm?
The thunderbolts that carved up Mars threw big chunks of its crust into orbit, as well as into long ellipses around the Sun. They were smoothed and eroded by the arcs while accelerating through the planet’s electric fields. Touchdown points where the electric discharges were most intense became deeply incised craters. That is why Phobos and the asteroids mentioned are covered in dust, have little or no large boulders, and are defined by huge craters that look like they are half-melted.
Recently, NASA announced that the OSIRIS-Rex Mission, circling asteroid Bennu, detected pebbles and other smaller particles that seemed to be ejected from the asteroid. The reasons for the events are mysterious, suggesting that micro-meteors are bombarding the asteroid, or that water vapor is escaping from hidden pockets. As the observations above conclude, however, the electric force ought to be included in any theoretical analysis.
The Thunderbolts Picture of the Day is generously supported by the Mainwaring Archive Foundation. | 0.857116 | 3.921715 |
What would be our next step in the exploration of the outer system once New Horizons has visited one or more Kuiper Belt objects (KBOs)? One intriguing target with a nearby ice giant to recommend it is Triton, Neptune’s unusual moon, which was imaged up close only once, by Voyager 2 in 1989. The views were spectacular but at the time of the encounter, most of Triton’s northern hemisphere remained unseen because it was in darkness. Only one hemisphere showed up clearly as the spacecraft passed the moon at a distance of 40,000 kilometers.
Our next visit should tell us much more, but we’re still working out the concept. Thus Steven Oleson’s Phase II grant from NASA’s Innovative Advanced Concepts (NIAC) office. Oleson (NASA GRC) calls the idea Triton Hopper. In his Phase I study, he identified the various risks of the mission, analyzing its performance and its ability to collect propellant. For Triton Hopper — moving from point to point — would rely on a radioisotope engine that would collect nitrogen ice and use it for propellant, mining the moon’s surface to keep the mission viable.
Image: Graphic depiction of Triton Hopper: Exploring Neptune’s Captured Kuiper Belt Object. Credit: S. Oleson.
Triton is interesting on a number of levels, one of which has received recent examination As with other outer system moons, we’re learning that there may be a liquid ocean beneath the crust. Let me quote a short presentation from Terry Hurford (NASA GSFC) on this:
There is compelling evidence that Triton should be considered an ocean world. Fractures observed on Triton’s surface are consistent in location and orientation with tidal stresses produced by the decay of Triton’s orbit as it migrates toward Neptune. Tidal stresses can only reach levels to fracture the surface if a subsurface ocean exists; a solid interior will result in smaller tidal stress and likely no tectonic activity. Tidal stresses therefore provide a mechanism for fracturing and volcanism analogous to activity observed on Enceladus and, possibly, Europa. Given that Triton’s interior has dissipated a tremendous amount of energy as heat, which likely drove differentiation, and that this heat may remain until the present day, an energy source likely exists to drive geologically recent activity. Moreover, it is possible that tidal volcanism has facilitated, if not dictated, the expression of this activity on Triton’s surface.
Triton’s surface seems to be in geological motion, given how few craters show up in the Voyager views. We can also factor in that this is the only large moon in the Solar System with a retrograde orbit, leading to the view that it is a captured dwarf planet from the Kuiper Belt. That nitrogen that Steven Oleson wants to use should be abundant at the surface, with a mostly water-ice crust to be found below. Also of considerable interest: Triton’s surface deposits of tholins, organic compounds that may be precursor chemicals to the origin of life.
Image: Triton’s south polar terrain photographed by the Voyager 2 spacecraft. About 50 dark plumes mark what may be ice volcanoes. This version has been rotated 90 degrees counterclockwise and artificially colorized based on another Voyager 2 image. Credit: NASA/JPL.
Geologically active places like Triton are intriguing — think of Io and Europa, Enceladus and Titan — and we can add Triton’s nitrogen gas geysers into the mix, along with its tenuous nitrogen atmosphere. No question a lander here would offer abundant science return. Oleson proposes heating that surface nitrogen ice under pressure and using it as a propellant that would allow a continuing series of ‘hops’ as high as 1 kilometer and 5 kilometers downrange. Thus we would get images and videos while aloft, and surface analysis while on the ground.
Intriguing. The thin atmosphere and even the geysers could be sampled by a Triton Hopper in the same way we have looked at the Enceladus plumes, by passing directly through them.
Working with GRC colleague Geoffrey Landis, Oleson presented Triton Hopper last year at the Planetary Science Vision 2050 Workshop in Washington DC. The thinking is to land near the south pole in 2040, in the area where geysers have already been detected. The surface can then be explored in as many as 60 hops, covering some 300 kilometers. Using in situ ices as propellants offers a uniquely renewable potential for mobility.
Oleson’s Phase II work will cover, in addition to mission options to reach Triton and descend to the surface in about 15 years, details of safe landing and takeoff of the hopper. Propellant gathering is obviously a major issue, one that will be explored through a bevameter experiment on frozen nitrogen (a bevameter can measure the properties of a surface in terms of interaction with wheeled or tracked vehicles). Also in play: How to collect and heat the nitrogen propellant and find ways to increase hop distance, solutions that could play into other icy moon missions.
Be aware, too, of a Phase II grant to Michael VanWoerkom (ExoTerra Resource), who will be studying in situ resource utilization (ISRU) and miniaturization. VanWoerkom’s NIMPH project (Nano Icy Moons Propellant Harvester) will deepen his investigation into mission refueling at destination, producing return propellant on site. The work thus complements Triton Hopper and deepens our catalog of strategies for sample return from a variety of surfaces.
The NASA precis for Oleson’s Phase II study is here. The NIMPH precis is here. The Hurford presentation is available as Hurford et al., “Triton’s Fractures as Evidence for a Subsurface Ocean,” Lunar and Planetary Science XLVIII (2017) (full text), but see as well Should we reconsider our view on Neptune’s largest moon?, which ran at Astronomy.com. | 0.894658 | 3.949965 |
Similar to the way Earth revolves around the Sun, every exoplanet revolves around a star. Hence, in general, it is difficult to acquire images of an exoplanet, as the light of its star is highly dazzling. However, a group of astronomers, headed by a scientist from the University of Geneva (UNIGE) and member of NCCR PlanetS, conceptualized to detect specific molecules that exist in the atmosphere of the exoplanet to render it visible, as long as the same molecules are not present on its star.
This novel method makes the device sensitive to only the selected molecules, rendering the star invisible and enabling the astronomers to directly observe the planet. The outcomes of the study have been reported in the Astronomy & Astrophysics journal.
To date, direct observation of the exoplanets discovered by astronomers was possible only very rarely, since they are mostly concealed by the tremendous luminous intensity of their stars. Only a handful of planets located quite far from their host stars can be differentiated on a picture, specifically with the help of the SPHERE instrument installed on the Very Large Telescope (VLT) in Chile, and similar instruments positioned in other places. Jens Hoeijmakers, researcher at the Astronomy Department of the Observatory of the Faculty of Science of the UNIGE and member of NCCR PlanetS, thought whether it would be feasible to trace the molecular composition of the planets.
“By focusing on molecules present only on the studied exoplanet that are absent from its host star, our technique would effectively ‘erase’ the star, leaving only the exoplanet,” he explained.
Erasing the Star, Thanks to Molecular Spectra
In order to investigate this innovative method, Jens Hoeijmakers and an international group of astronomers used archival images captured by the SINFONI instrument of the star beta pictoris, known to be orbited by a giant planet, beta pictoris b. Each pixel in the images includes the spectrum of light received by that pixel. Then, the astronomers compared the spectrum included in the pixel with a spectrum corresponding to a given molecule, for instance, water vapor, to observe whether there is a correlation. In case a correlation occurs, it indicates that the molecule exists in the planet’s atmosphere.
Jens Hoeijmakers applied this method to beta pictoris b and noticed that the planet became distinctively visible while looking for carbon monoxide (CO) and water (H2O). However, when the method was applied to ammonia (NH3) and methane (CH4), the planet remains invisible, suggesting the absence of these molecules in the atmosphere of beta pictoris b.
Molecules, New Planetary Thermometer
In all four situations, the host star beta pictoris was observed to be invisible. In fact, this star is exceptionally hot, and at higher temperatures, the four molecules are destroyed.
“This is why this technique allows us not only to detect elements on the surface of the planet, but also to sense the temperature which reigns there,” explained the astronomer of the UNIGE.
Hence, the certainty that it is not possible for astronomers to find beta pictoris b with the help of the spectra of ammonia and methane is consistent with a temperature evaluated at 1700 degrees for this planet, which is very high for the molecules to exist.
“This technique is only in its infancy,” stated Jens Hoeijmakers. “It should change the way planets and their atmospheres are characterized. We are very excited to see what it will give on future spectrographs like ERIS on the Very Large Telescope in Chile or HARMONI on the Extremely Large Telescope which will be inaugurated in 2025, also in Chile,” he concluded. | 0.831111 | 4.012368 |
[TORONTO] A group of astronomers has actually carried out among the greatest resolution observations in huge history by observing 2 extreme areas of radiation, 20 kilometres apart, around a star 6500 light-years away.
The observation is comparable to utilizing a telescope in the world to see a flea on the surface area of Pluto.
The amazing observation was enabled by the unusual geometry and qualities of a set of stars orbiting each other. One is a cool, light-weight star called a brown dwarf, which includes a “wake” or comet-like tail of gas. The other is an unique, quickly spinning star called a pulsar.
” The gas is serving as like a magnifying glass right in front of the pulsar,” states Robert Main, lead author of the paper explaining the observation being released May 24 in the journal Nature “We are basically taking a look at the pulsar through a naturally taking place magnifier which occasionally enables us to see the 2 areas independently.”
Main is a PhD astronomy trainee in the Department of Astronomy & & Astrophysics at the University of Toronto, dealing with coworkers at the University of Toronto’s Dunlap Institute for Astronomy & & Astrophysics and Canadian Institute for Theoretical Astrophysics, and the Border Institute.
The pulsar is a neutron star that turns quickly– over 600 times a 2nd. As the pulsar spins, it produces beams of radiation from the 2 hotspots on its surface area. The extreme areas of radiation being observed are related to the beams.
The brown dwarf star has to do with a 3rd the size of the Sun. It is approximately 2 million kilometres from the pulsar– or 5 times the range in between the Earth and the moon– and orbits around it in simply over 9 hours. The dwarf buddy star is tidally locked to the pulsar so that one side constantly faces its pulsating buddy, the method the moon is tidally locked to the Earth.
Due To The Fact That it is so near the pulsar, the brown dwarf star is blasted by the strong radiation originating from its smaller sized buddy. The extreme radiation from the pulsar heats up one side of the fairly cool dwarf star to the temperature level of our Sun, or some 6000 ° C.
The blast from the pulsar might eventually spell its buddy’s death. Pulsars in these kinds of double stars are called “black widow” pulsars. Simply as a black widow spider consumes its mate, it is believed that the pulsar, offered the ideal conditions, might slowly deteriorate gas from the dwarf star till the latter is taken in.
In addition to being an observation of exceptionally high resolution, the outcome might be a hint to the nature of strange phenomena called Quick Radio Bursts, or FRBs.
” Numerous observed homes of FRBs might be described if they are being enhanced by plasma lenses,” state Main. “The homes of the enhanced pulses we discovered in our research study reveal an exceptional resemblance to the bursts from the duplicating FRB, recommending that the duplicating FRB might be lensed by plasma in its host galaxy.”
1. The pulsar is designated PSR B1957+20 Previous work led by Main’s co-author, Prof. Marten van Kerkwijk, from the University of Toronto, recommends that it is most likely among the most huge pulsars understood, and more work to precisely determine its mass will assist in comprehending how matter acts at the greatest recognized densities, and equivalently, how huge a neutron star can be prior to collapsing into a great void.
2. Main and his co-authors utilized information gotten with the Arecibo Observatory radio telescope prior to Cyclone Maria harmed the telescope in September2017 The partners will utilize the telescope to make follow-up observations of PSR B1957+20
Paper: Severe plasma lensing of the Black Widow pulsar
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Disclaimer: We can make errors too. Have a good day. | 0.873569 | 3.722266 |
Cygnus’ swan is flying down the Milky Way in our nighttime skies
In Our Skies
Emerging into our northeastern skies during the later evening hours of these warming late-May nights is one of the more easily recognizable of the constellations: Cygnus, the swan.
Cygnus’ brightest stars are arranged in the shape of a large cross, and indeed Cygnus is sometimes referred to as the Northern Cross, but sky-watchers in darker rural sites should be able to see the dimmer stars that fill out the wings which, together with an outstretched neck, distinctly convey the image of a swan flying down the summertime Milky Way.
The region of sky around the tip of Cygnus’ northwestern wing was the location examined by the Kepler spacecraft during its primary mission which lasted from 2009 to 2013. Kepler’s goal was to examine the stars in this region for regular small drops in brightness which might indicate the presence of orbiting planets. Thus far the Kepler data has produced over 2,300 confirmed planets – about 20 of which are twice the size of Earth, or smaller, and located within their parent star’s habitable zone – and almost 4,500 possible additional planets that remain to be confirmed.
The Kepler data has also produced what could be considered as the most mysterious star in our entire galaxy at least, at this time. Officially designated as KIC 8462852, it is more commonly referred to as the Tabby’s Star or sometimes as Boyajian’s Star after astronomer Tabetha Boyajian formerly at Yale University, now at Louisiana State University, who first called widespread attention to it a year and a half ago. Tabby’s Star is somewhat brighter and larger than our sun, and is located approximately 1,200 light-years away from us; it can be detected with moderate-size backyard telescopes.
Kepler detected its planets by detecting regular drops in a star’s brightness as an orbiting planet crossed in front of it. These drops in brightness are very tiny: even a Jupiter-size planet would produce a change in brightness no more than about 1 percent, and of course would do on a regular basis as the planet continued on its orbit. Tabby’s Star, however, was found to be undergoing drops in brightness as large as 10 percent to 20 percent or more, and to be doing so at irregular intervals. The Kepler data also suggests that there was an overall drop of about 3 percent in the star’s brightness over the four years that Kepler examined it, and meanwhile an examination of Tabby’s Star in archived photographs extending back to the late 19th century seemed to suggest that it has decreased in brightness by close to 15 percent during this time frame, although this has not been verified.
What could be causing such behavior? A number of explanations have been advanced, although none are entirely satisfactory and all have substantial issues. A large swarm of comets, possibly in the act of breaking up, seems to be the best solution thus far, although there are definitely some problems with this explanation, including the fact that this phenomenon has not been observed anywhere else. Small clouds of thick dust that might lie along the way between Tabby’s Star and us constitute another explanation, although the fact that no other stars, including those close to Tabby’s Star in the sky, exhibit anything similar to the large brightness drops argues against this type of explanation.
One potential explanation which received a lot of popular attention was pointed out by Penn State University astronomer Jason Wright, who suggested that the brightness drops could be produced by large artificial alien megastructures, possibly of a type known as a Dyson Sphere that has been hypothesized by American physicist Freeman Dyson. As intriguing as such an idea might be, its likelihood must be regarded as extremely low, however it is nevertheless worth investigating. A search by the Allen Telescope Array in northern California for alien radio signals from Tabby’s Star has been unsuccessful, and the star also does not exhibit the infrared radiation that a structure like a Dyson Sphere would be expected to give off.
One significant problem has been that all the brightness drops of Tabby’s Star have been in the past tense; all of them were found in archived data. What has been needed is a study of such a brightness drop in real time – and that has now happened. Just over a week ago, on May 18, a drop in brightness began, and within a day this had grown to about 2 percent. An entire armada of telescopes both on the ground and in space have since been studying Tabby’s Star, even though the brightness drop appears to have been short-lived: by May 22 the star was back to its normal brightness.
Still, this is a lot more data than we’ve had before, and analysis of the data collected during those few days is ongoing. And, certainly, Tabby’s Star is being closely monitored for any additional drops in brightness that might take place in the not-too-distant future.
Hopefully, before much longer we’ll have some solid ideas as to what is causing this star to behave in such a bizarre manner.
Alan Hale is a professional astronomer who resides in Cloudcroft. Hale is involved in various space-related research and educational activities throughout New Mexico and elsewhere. His web site is http://www.earthriseinstitute.org. | 0.806917 | 3.903426 |
The naked-eye Pleiades star cluster has long been known to professional and amateur astronomers for the striking visible nebulosity that envelopes the cluster’s brightest stars, scattering their light like fog around a streetlamp.
Radio and infrared observations in the 1980s established that this nebulosity results from a chance encounter by the young stars of the Pleiades with an interstellar cloud, rather than being caused by debris from the cluster’s formation. New data obtained at Kitt Peak National Observatory suggest that the Pleiades are actually encountering two clouds, giving rise to an extraordinary and previously unknown occurrence: a three-body collision in the vast emptiness of interstellar space.
This new perspective on the motion of interstellar gas near the cluster comes from high-resolution spectra obtained at an adjunct facility of Kitt Peak’s 2.1-meter telescope known as the Coudé Feed. The investigator was Richard White of Smith College in Northampton, MA, who worked in collaboration with students from Smith College and Amherst College.
“The idea of the Pleiades and one gas cloud in an interstellar train wreck already made this nearby cluster an especially interesting region for astronomers seeking to understand the details of physical and chemical processes in the interstellar medium,” White says. “The presence of a second cloud interacting with the first cloud and with the cluster creates a situation more like a three-car crash in a demolition derby, which makes the Pleiades altogether unique as natural laboratory.”
The time scale for the unfolding of the interstellar collisions in the Pleiades is several hundred thousand years. “That is good news for those who enjoy the magnificent color images of the Pleiades images that grace textbooks and coffee table books, which suffer no danger of obsolescence,” White says. “It is bad news for those who would like to see celestial fireworks unfolding from year to year.”
Known as the Seven Sisters for the seven stars said to be visible with the naked eye, the Pleiades (M45) consists of more than 500 stars roughly 100 million years old in a cluster located about 400 light-years from Earth.
Sodium atoms in gas found between Earth and the stars absorb two specific wavelengths of yellow starlight (the same wavelengths of yellow light emitted by low-pressure sodium streetlamps). Because of the Doppler effect (analogous to the shift in siren pitch produced when an ambulance is moving toward or away from a listener), the motion of the gas along our line of sight produces subtle shifts in the observed wavelengths.
In a paper published in the October 2003 Astrophysical Journal Supplement, White interprets the new observations of sodium atoms in the Pleiades region in the context of other recent observations of the Pleiades region. These observations include significant new optical images of the Pleiades from the Burrell Schmidt telescope on Kitt Peak, published earlier this year in the Astrophysical Journal by Steven Gibson of the University of Calgary and Kenneth Nordsieck of the University of Wisconsin, and radio maps of neutral hydrogen that formed part of Gibson’s doctoral thesis.
The orientation of features in the optical and radio imagery provides clues to gas and dust motions across the sky, which can be combined with the spectroscopically measured velocities from Kitt Peak to allow astronomers to reconstruct the three-dimensional configuration of the interstellar matter near the Pleiades.
The sodium absorption lines reveal that there always is one feature between Earth and the Pleiades stars, moving toward the cluster with a line of sight velocity of about 10 kilometers per second. White associates this feature with the Taurus-Auriga interstellar cloud complex, the bulk of which lies about 40 light-years to the east.
Toward some stars, however, there are two or more absorption features. White argues that a shock-wave from the collision between the Pleiades and gas associated with the Taurus-Auriga complex can account for splitting of one feature into three in some areas, primarily on the south and east sides of the Pleiades. However, the presence of an additional feature in the data, primarily on the west side and moving into the cluster at about 12 kilometers per second, defies understanding unless a second cloud also is converging on the Pleiades, he concludes.
The only previously known three-body collisions in interstellar space are inferred close encounters by a star and a neighboring binary or triple star system within a globular cluster or in the cores of galaxies.
Previously released images of the Pleiades from Kitt Peak that amply demonstrate the surrounding nebulosity are available in the NOAO Image Gallery (linked above).
Located southwest of Tucson, AZ, Kitt Peak National Observatory is part of the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under a cooperative agreement with the National Science Foundation. | 0.856553 | 4.031476 |
Using new technology at the telescope and in laboratories, researchers have discovered an important pair of prebiotic molecules in interstellar space. The discoveries indicate that some basic chemicals that are key steps on the way to life may have formed on dusty ice grains floating between the stars.
The scientists used the National Science Foundation’s Green Bank Telescope (GBT) in West Virginia to study a giant cloud of gas some 25,000 light-years from Earth, near the center of our Milky Way Galaxy. The chemicals they found in that cloud include a molecule thought to be a precursor to a key component of DNA and another that may have a role in the formation of the amino acid alanine.
One of the newly-discovered molecules, called cyanomethanimine, is one step in the process that chemists believe produces adenine, one of the four nucleobases that form the “rungs” in the ladder-like structure of DNA. The other molecule, called ethanamine, is thought to play a role in forming alanine, one of the twenty amino acids in the genetic code.
“Finding these molecules in an interstellar gas cloud means that important building blocks for DNA and amino acids can ‘seed’ newly-formed planets with the chemical precursors for life,” said Anthony Remijan, of the National Radio Astronomy Observatory (NRAO).
In each case, the newly-discovered interstellar molecules are intermediate stages in multi-step chemical processes leading to the final biological molecule. Details of the processes remain unclear, but the discoveries give new insight on where these processes occur.
Previously, scientists thought such processes took place in the very tenuous gas between the stars. The new discoveries, however, suggest that the chemical formation sequences for these molecules occurred not in gas, but on the surfaces of ice grains in interstellar space.
“We need to do further experiments to better understand how these reactions work, but it could be that some of the first key steps toward biological chemicals occurred on tiny ice grains,” Remijan said.
The discoveries were made possible by new technology that speeds the process of identifying the “fingerprints” of cosmic chemicals. Each molecule has a specific set of rotational states that it can assume. When it changes from one state to another, a specific amount of energy is either emitted or absorbed, often as radio waves at specific frequencies that can be observed with the GBT.
New laboratory techniques have allowed astrochemists to measure the characteristic patterns of such radio frequencies for specific molecules. Armed with that information, they then can match that pattern with the data received by the telescope. Laboratories at the University of Virginia and the Harvard-Smithsonian Center for Astrophysics measured radio emission from cyanomethanimine and ethanamine, and the frequency patterns from those molecules then were matched to publicly-available data produced by a survey done with the GBT from 2008 to 2011.
A team of undergraduate students participating in a special summer research program for minority students at the University of Virginia (U.Va.) conducted some of the experiments leading to the discovery of cyanomethanimine. The students worked under U.Va. professors Brooks Pate and Ed Murphy, and Remijan. The program, funded by the National Science Foundation, brought students from four universities for summer research experiences. They worked in Pate’s astrochemistry laboratory, as well as with the GBT data.
“This is a pretty special discovery and proves that early-career students can do remarkable research,” Pate said.
The researchers are reporting their findings in the Astrophysical Journal Letters.
Dave Finley, Public Information Officer | 0.908767 | 4.119737 |
Dec 17, 2014
Direct statements concerning dramatic changes in the appearance of planets are few and far between in ancient sources.
A classic example is a fragment from the obscure Greek astronomer Castor of Rhodes (1st century BCE), as cited by his contemporary, the Roman grammarian Marcus Terrentius Varro, who was in turn cited by the church father Augustine of Hippo (354-430 CE). According to this tantalisingly brief passage, the planet Venus once “changed its colour, size, shape and course, a thing which has never happened before or since.” This information, frequently considered in catastrophist theories, presents quite a puzzle.
A conservative approach would be to assume that the observation of Venus’ erratic presentation was due to some change in the earth’s own properties. After all, the ‘green flash’ and the ‘blue flash’ frequently seen on Venus, like the twinkling of all celestial bodies, is caused by variations in the earth’s atmosphere. However, whereas these might shed light on alterations in Venus’ apparent colour and possibly size, they do not affect its shape and orbit. A temporary jolt in the earth’s motion, without any actual change in Venus, is an equally unlikely solution, because this would produce simultaneous changes in the positions of all other stars and planets – which is not what Castor reported.
The German philologist Johann Gottlieb Radlof (1775-1827/1829), writing in 1823, may have been the first to advocate a straightforward, literal take on the account. Other catastrophists, including Alexander Braghine (1878-1942) and Immanuel Velikovsky (1895-1979), followed suit: apparently, Venus was once observed to have changed its orbit. Par for the course, for this interpretation overlooks a crucial aspect of Augustine’s testimony, which is rarely – if ever – mentioned: “the altered course of Venus did not long continue, but the usual course was resumed”. If the planet’s features returned to the status quo ante within the time frame of a few years at most, a true modification of its orbit is of course highly implausible.
Unlike the situation on the earth, Venus’ native magnetic field is almost negligible. Its magnetosphere is induced by the enveloping solar wind. Satellite data show that the planet at times sports a magnetotail which can assume enormous proportions, ‘fluttering’ in the solar wind. The precise conditions and variables involved are the subject of on-going research. Could the assumption that Venus’ tail, on an exceptional occasion, glowed in visible light be on the right track? Short-lived visibility of Venus’ appendage could account at once for all changes mentioned in Castor’s report: the tail would have its own colour, appear to enlarge Venus, change it from a dot to a streak of light and, because of its drifting in the solar wind, seem to modify the planet’s orbit.
Presumably, such an event would have been the result of a solar superstorm, the like of which has not been seen in millennia. A magnetic storm of such intensity would likely affect the earth as well and it may not be coincidental that, according to the otherwise unknown mathematicians Adrastus of Cyzicus and Dio of Naples, cited by Augustine in the same context, the portent “happened in the reign of Ogygus”, that is to say, concomitantly with the legendary flood of Ogyges. Although the physical relationship between a solar superstorm and a terrestrial flood is not easily explained and the date of the legendary Ogyges is a vexing subject in its own right, the correlation is bound to be relevant. This was pointed out as early as 1684, by the English theologian and royal chaplain Thomas Burnet (c. 1635? – 1715):
“This is a great presumption that she suffer’d her dissolution about the same time that our Earth did. I do not know that any such thing is recorded concerning any of the other Planets, but the body of Mars looks very rugged, broken, and much disorder’d.”
With these sentiments, written just a few years after Isaac Newton had presented his theory of gravity, Burnet qualifies as the earliest known planetary catastrophist.
Rens Van Der Sluijs | 0.857351 | 4.002232 |
Black holes stunt growth of dwarf galaxies
Astronomers at the University of California, Riverside, have discovered that powerful winds driven by supermassive black holes in the centers of dwarf galaxies have a significant impact on the evolution of these galaxies by suppressing star formation.
Dwarf galaxies are small galaxies that contain between 100 million to a few billion stars. In contrast, the Milky Way has 200-400 billion stars. Dwarf galaxies are the most abundant galaxy type in the universe and often orbit larger galaxies.
The team of three astronomers was surprised by the strength of the detected winds.
"We expected we would need observations with much higher resolution and sensitivity, and we had planned on obtaining these as a follow-up to our initial observations," said Gabriela Canalizo, a professor of physics and astronomy at UC Riverside, who led the research team. "But we could see the signs strongly and clearly in the initial observations. The winds were stronger than we had anticipated."
Canalizo explained that astronomers have suspected for the past couple of decades that supermassive black holes at the centers of large galaxies can have a profound influence on the way large galaxies grow and age.
"Our findings now indicate that their effect can be just as dramatic, if not more dramatic, in dwarf galaxies in the universe," she said.
Study results appear in The Astrophysical Journal.
The researchers, who also include Laura V. Sales, an assistant professor of physics and astronomy; and Christina M. Manzano-King, a doctoral student in Canalizo's lab, used a portion of the data from the Sloan Digital Sky Survey, which maps more than 35% of the sky, to identify 50 dwarf galaxies, 29 of which showed signs of being associated with black holes in their centers. Six of these 29 galaxies showed evidence of winds—specifically, high-velocity ionized gas outflows—emanating from their active black holes.
"Using the Keck telescopes in Hawaii, we were able to not only detect, but also measure specific properties of these winds, such as their kinematics, distribution, and power source—the first time this has been done," Canalizo said. "We found some evidence that these winds may be changing the rate at which the galaxies are able to form stars."
Manzano-King, the first author of the research paper, explained that many unanswered questions about galaxy evolution can be understood by studying dwarf galaxies.
"Larger galaxies often form when dwarf galaxies merge together," she said. "Dwarf galaxies are, therefore, useful in understanding how galaxies evolve. Dwarf galaxies are small because after they formed, they somehow avoided merging with other galaxies. Thus, they serve as fossils by revealing what the environment of the early universe was like. Dwarf galaxies are the smallest galaxies in which we are directly seeing winds—gas flows up to 1,000 kilometers per second—for the first time."
Manzano-King explained that as material falls into a black hole, it heats up due to friction and strong gravitational fields and releases radiative energy. This energy pushes ambient gas outward from the center of the galaxy into intergalactic space.
"What's interesting is that these winds are being pushed out by active black holes in the six dwarf galaxies rather than by stellar processes such as supernovae," she said. "Typically, winds driven by stellar processes are common in dwarf galaxies and constitute the dominant process for regulating the amount of gas available in dwarf galaxies for forming stars."
Astronomers suspect that when wind emanating from a black hole is pushed out, it compresses the gas ahead of the wind, which can increase star formation. But if all the wind gets expelled from the galaxy's center, gas becomes unavailable and star formation could decrease. The latter appears to be what is occurring in the six dwarf galaxies the researchers identified.
"In these six cases, the wind has a negative impact on star formation," Sales said. "Theoretical models for the formation and evolution of galaxies have not included the impact of black holes in dwarf galaxies. We are seeing evidence, however, of a suppression of star formation in these galaxies. Our findings show that galaxy formation models must include black holes as important, if not dominant, regulators of star formation in dwarf galaxies."
Next, the researchers plan to study the mass and momentum of gas outflows in dwarf galaxies.
"This would better inform theorists who rely on such data to build models," Manzano-King said. "These models, in turn, teach observational astronomers just how the winds affect dwarf galaxies. We also plan to do a systematic search in a larger sample of the Sloan Digital Sky Survey to identify dwarf galaxies with outflows originating in active black holes." | 0.846215 | 4.045523 |
July 8th 2015
Discovered in 2861 by amateur explorer Errol Navis, the system that he named after his daughter featured six distinctive worlds orbiting a white Type-F main sequence star. Oso was quickly set upon by survey teams and corporate groups seeking to lay claim to the latest worlds potentially ripe for terraforming. However within the year, interests changed dramatically. The discovery of higher life forms on Oso II forced the government to issue it protectorate status under the Fair Chance Act. The declaration made the system off limits for economic development, but some of the less-than-scrupulous surveying corporations leaked their planetary assessment findings. They attempted to make a case to the UEE Senate that Oso II could potentially be terraformed for Human habitation without destroying all of the indigenous life. The question of ‘uplifting’ began to circle the Empire. Ultimately, a slim majority in the Senate chose to adhere to the tenets of the Fair Chance Act. They established a permanent garrison near the system’s initial jump point to let the species develop without outside interference. Despite this, travel to the system to engage in black market trade opportunities remains significant.
The system’s first planet is a tidally locked world that features one of the most impressive ‘day and night’ differences in the explored galaxy. The side locked towards the sun is an endless sea of lava while the dark side is a stark, black iron-rich landscape too cold to ever sustain Human life (though a landing with proper equipment is possible). Extensive mineral surveys of Oso I’s night side were conducted before the system was placed under the Fair Chance Act, but little of value was ultimately discovered. Today, the planet is best known for its impressive visual display (viewed remotely) rather than for anything worth extraction.
A lush biosphere with a variety of distinct regions and climates, Oso II boasts an increased gravity much higher than Earth’s. The planet is mostly known as the home to the most developed primitive species ever encountered by the UEE. Known as Osoians, this multi-limbed race actively communicates with one another using patterned flashes of color generated by head-mounted chameleon cells. Osoian communication studies are ongoing today (within the limitations of the Fair Chance Act).
Beyond the Osoians, the planet is also home to a great deal of lesser species, most of which have evolved to be entirely unlike anything discovered elsewhere to date. Though direct study is a violation of the Fair Chance Act, some scientists are able to receive permission from the UEE to establish off-world research platforms to study the species from a distance. These platforms are carefully supervised and are allowed to operate only for short periods of time.
The third planet in the Oso system is a gas giant. Oso III began life as a rogue Jupiter that fell into rotation around the system’s star. The planet is distinguished by slight green and white color variations generated by its silicate clouds. From a scientific standpoint, it’s frequently cited as evidence to support the theory that gas giants can act as ‘comet shields’ which allow higher forms of life to evolve. Unmanned scientific monitoring stations are positioned at the planet’s Lagrange points to track and catalog meteor impacts.
Oso IV is an uninhabited coreless planet that boasts a surface rich in gems and mineral resources that were likely exposed due to some sort of planetary catastrophe. These resources have become an issue for the Army who has had ongoing issues with rogue mining operations dating back to the system’s initial discovery. Oso IV has no atmosphere and there is an ongoing (but not especially vehement) argument in the scientific community as to whether or not an atmosphere ever existed.
Observation Base Chimera is home to Oso’s rotating military contingent charged with protecting the system from outside interference. While its intention is noble, the base’s effectiveness has been under fire recently as allegations of negligence caused a Senate inquiry into the daily operations of the base. This review revealed consistent average and below average performance reports for nearly all Army personnel assigned to the station, as well as evidence of corruption, bribery and even extortion. Despite a regular crew rotation, Army station reports have corroborated the Senate’s findings and have made public Chimera’s internally well-known reputation of hosting burnouts and failures. While the situation says little for the Army’s reputation, the Senate report painted a myriad of opportunities for any entrepreneur willing to work outside the law. At any time desired, it was possible to pay off the local crews to avoid interception, visit Oso II and escape the system unharmed (and unscanned).
The effects of this inquiry are still being felt today. The Imperator cited the findings in his decree to High Command to immediately restructure Chimera’s operating policy and implement consistent checks from civilian auditors to make sure it was operating ethically.
Note that the edict against travel to Oso is actually only enforced against those approaching the inner planets. A high volume of legitimate transports and other ships transit through the system on unrelated routes, to the point that a Covalex shipping hub was granted a special lease and has been established in the outer reaches.
Orbiting far away from the warmth of the sun, ice giant Oso V is a churning mass of ammonia vapor while Oso VI is a small rocky dwarf planet. The two isolated worlds see more traffic than many of the inner worlds thanks to their distance from Oso III making construction of various utility stations a much safer prospect.
“To look into the eyes of an Osoian is to look into our own past and see the potential to evolve and grow that lies within us all. For every species we encounter who we shadow with our advancements, you must ask, is there yet still a species out there by whom we ourselves will be overshadowed?”– Professor JT Collins, A Step Onto the Precipice
“An Osoian walks into a bar and orders a drink. The bartender says I’m sorry, but I’m not allowed to serve you because your culture hasn’t discovered alcohol yet. The Osoian thinks for a second and then says, if you leave a bottle on the counter, I’m pretty sure I’ll be able to discover it myself.”– Jimmy Snart, Laugh Till It Hurts | 0.902633 | 3.003125 |
This July 4th may be the most stellar since 1776. NASA’s Juno spacecraft is quickly approaching Jupiter, the largest gas giant in our solar system, reaching speeds of 150,000 miles per hour, assisted by the planet’s huge gravitational pull. Juno is currently headed toward Jupiter’s north pole and is expected to reach the Jovian planet’s orbit by roughly 9 p.m. PDT tonight.
Was it a success? Watch live here:
JUNO to JUPITER: Here We Come!
It’s almost nail biting time here at JPL. Juno finally moving into the most frightening part of its journey to Jupiter. The insertion into the planets orbit. By all accounts this could be dicey. There’s a reason scientists on this mission call Jupiter a big bad planet. It has the harshest environment of any planet and at 7:30 tonight the final leg of the journey scientists have all been waiting for begins as Juno enters an atmosphere so unpredictable because of the millions of electrons moving at the speed of light.
Heidi Becker is the Lead Radiation Investigation She says,“These are high energy electrons that are so energetic that they’re moving at the speed of light."
She compares them to machine gun bullets and says there will be millions of them.
If all goes as planned at 7:30 Juno will arrive over the planet’s North Pole. An engine burn will take place at 8:18 pm (Pacific Time) to slow the spacecraft. The burn will be completed at 8:53 and, then, at 9:30 pm Juno will turn toward the sun. Since this is a solar powered probe if there is no power Juno can't operate.
By the way, Juno is carrying what may be the world's most valuable legos. Three titanium pieces of Galileo, Jupiter and Jupiter's wife/sister Juno. We're told these are one of a kind pieces.
This mission’s goal is to peer beyond Jupiter’s dense cloud coverage and discover more about the gas giant’s origins, atmosphere, magnetosphere and structure. Juno could even help NASA learn more about the beginnings of our solar system, as it is believed that Jupiter was one of the first created comprising much of the same light gases found in the sun.
A spacecraft has never flown this close to Jupiter, so as this long-awaited moment nears, here is everything you need to know about NASA’s Juno mission:
- The Juno spacecraft itself is 3,513 pounds and is carrying with it 1,658 pounds of fuel.
- Juno is the first spacecraft and mission designed to operate in the heart of Jupiter’s radiation belts. To put that in perspective, the cosmic radiation Earth is exposed to from space is about .39 RAD (Radiation Absorbed Dose). Juno is expected to encounter 20 million RAD Juno at Jupiter.
- The gas giant’s magnetic field is 14 times stronger than Earth’s.
- Juno will take the highest resolution images of the largest Jovian planet in history.
- Juno is the first space mission that will orbit an outer planet from north to south poles.
- Juno is the first mission to operate a solar-powered spacecraft at the Jovian planet.
- Will be the fastest spacecraft to enter orbit around a planet, at 130,000 mph (129,518 mph/57.9 km/s) relative to Earth.
- Juno will be the first mission to fly as close as 2,600 miles to Jupiter’s cloud tops.
- If Juno flew as fast as a commercial jet it would take 342 years to complete its entire mission.
- The planet has storm systems that can rage on for long periods of time, one of them being the notable Great Red Spot which is twice as wide as our blue planet.
- Jupiter is a giant ball of gas 11 times wider than earth and takes 12 years to orbit the sun.
- The initial launch of Juno was August 5, 2011.
- Juno will orbit Jupiter for 20 months which equals 37 of Jupiter’s orbits.
Great Information Video from NASA Jet Propulsion Laboratory
Copyright 2016 FOX 11 Los Angeles : Download our mobile app for breaking news alerts or to watch FOX 11 News | Follow us on Facebook, Twitter, Instagram, and YouTube. Be a citizen journalist for FOX 11 and get paid – download the Fresco News App today. | 0.868909 | 3.193713 |
There cannot be very many of us who have never spent summer evenings lying on the ground looking at the stars, especially when camping well away from town. When doing this, most of us would have also wondered how our ancestors managed, in those random scatterings of stars, to see animals, heroes and mythical beasts. These groupings of stars are called constellations. One thing almost all constellations have in common is they don’t look much like what they are supposed to represent. Aries looks nothing like a ram, Aquila nothing like an eagle, and Auriga, with its bright star Capella which is in the north east late these evenings, looks nothing like a charioteer. Actually there is a constellation high in the east these evenings that looks exactly as its name says it should; three faintish stars form a triangle, and the constellation is named Triangulum – The Triangle. Moreover, The “Big Dipper” does look like a pot with a handle, and in England is often referred to as “The Saucepan”. It is also called “The Plough”, because a little imagination makes it resemble the agricultural instrument. It also looks a bit like a wagon, without wheels or horses, and is called “Charles’ Wain” – Charles’ Wagon. However, this clustering of stars is not a constellation, it is only part of one. The constellation containing the stars of the Dipper is Ursa Major – “The Great Bear”.
If you look carefully at all the bright and faint stars in the constellation, it does look something like a large quadruped, with a long snout, but not much like a bear. In particular, no bear has a tail that long. Its neighbour, Ursa Minor, the “Little Bear”, with Polaris “The North Star”, or “Pole Star” at the end of its tail, also has a ridiculously long tail. It has been suggested that the bears have long tails because that’s how they were pulled up into the heavens
An additional thing about constellations is that they only look as they do from our viewing point. Stars looking close in the sky may actually be at very different distances from us. Imagine looking at the lights of a town at night from a point on a nearby hill. You can connect the lights, making “constellations.” However, if you move to another hill and look again, all your constellations will have gone, or changed into different patterns.
We have a nice demonstration in the library at our observatory. The constellation of Orion, “The Hunter,” has been set up using balls hanging on strings, arranged as they really are, with the stars at differing distances. If you look from the position of the little ball representing the Earth, you see the familiar shape of Orion, which is one of the few constellations that looks something like what it represents. However, shift your point of view and Orion vanishes; we just see an unfamiliar arrangement of stars. It’s interesting how we can use the constellations to navigate our ships, and to navigate spacecraft around the Solar System. However, it won’t work for interstellar travellers. Imagine what the big dipper might look like from the side. Imagine looking at the sky of some planet orbiting another star and seeing an exotic constellation, where one of its member stars is the Sun.
Jupiter rises around 9 p.m., Mars comes up around 2 a.m. The Moon will reach first quarter on the 3rd.
Ken Tapping is an astronomer with the National Research Council’s Herzberg Institute of Astrophysics, and is based at the Dominion Radio Astrophysical Observatory, Penticton. | 0.821751 | 3.500973 |
Life as we know it needs three things: energy, water and chemistry.
Saturn’s icy moon Enceladus has them all, as NASA spacecraft Cassini confirmed in the final years of its mission to that planet.
While Cassini explored the Saturnian neighborhood, its sensors detected gas geysers that spewed from Enceladus’s southern poles. Within those plumes exists a chemical buffet of carbon dioxide, ammonia and organic compounds such as methane.
Crucially, the jets also contained molecular hydrogen – two hydrogen atoms bound as one unit. This is a coin of the microbial realm that Earth organisms can harness for energy.
Beneath Enceladus’s ice shell is a liquid ocean. Astronauts looking for a cosmic vacation destination would be disappointed. The moon is oxygen-poor. There is darkness down below, too, because the moon’s ice sheets reflect 90 percent of the incoming sunlight.
Despite frigid temperatures at the surface, the water is thought to reach up to 194 degrees Fahrenheit at the bottom.
As harsh as the moon’s conditions are, a recent experiment suggests that Enceladus could support organisms like those that thrive on Earth.
Tiny colonies of microbes that dwell near our planet’s hydrothermal vents can tolerate a simulated Enceladus habitat, according to a new report by a team of researchers in Austria and Germany.
“We tried to reproduce the putative Enceladus-like conditions in the lab,” said Simon Rittmann, who studies microbes called archaea at the University of Vienna in Austria.
Archaea are microscopic, single-celled organisms. Under magnification, they resemble bacteria. Yet archaea have their own domain of life – they are as closely related to humans as they are to bacteria.
Near hydrothermal vents, beyond the reach of sunlight, their lives are fueled by chemical nutrients.
Rittmann and his colleagues constructed several growth chambers to simulate the Enceladus environment. All of their recipes included molecular hydrogen.
Astrobiologists hypothesize that a process called serpentinization creates these hydrogen molecules, a result of the chemical reaction between the moon’s rocky core and its hot ocean water.
The scientists, to reflect the uncertainty of the Enceladus environment, varied the amount of molecular hydrogen available to the organisms. They also altered the pH, pressure and gas concentrations in the test habitats.
“We tried to be as broad as possible with our assumptions,” Rittmann said.
There are no direct measurements for what exists beneath Enceladus’s ice crust.
“No one will be able to tell if these conditions are really occurring on Enceladus,” he said. “However, we did our best to be as careful as possible.”
One species tested, an archaeon called Methanothermococcus okinawensi, fared the best on faux Enceladus.
Scientists discovered this organism at a hydrothermal vent system near Okinawa, Japan, 3,000 feet below sea level. M. okinawensi uses carbon dioxide as a carbon source and molecular hydrogen for energy, as a suspected Enceladus microbe might.
Not only did M. okinawensi survive most conditions, including the highest pressure tested, but also the archaeon produced methane as it grew.
An organism with a similar lifestyle might explain methane’s presence on Enceladus, the scientists concluded in their study, published Wednesday in the journal Nature Communications.
There are, however, some important caveats. Cassini detected formaldehyde on Enceladus, which can disrupt the life cycle of even the hardiest archaea.
M. okinawensi could resist certain concentrations of formaldehyde but only to a point. It failed to grow at the highest formaldehyde concentrations detected by the Cassini probe.
The study also assumes that hydrothermal systems exist on Enceladus. As Rittmann emphasized, this remains an assumption.
“No evidence exists for these systems,” he said. What’s more, biology is not required to explain the presence of methane on Enceladus. Nonbiological processes also can create the gas.
A much-needed step, Rittmann said, will be to identify the biomarkers that serve as telltale signs of life in the solar system’s deep and dark seas.
2018 © The Washington Post
This article was originally published by The Washington Post. | 0.806493 | 3.817627 |
Stellar streams are the remnants of dwarf galaxies and globular clusters that have been/are being eaten by some host galaxy. They are formed by tidal forces ripping apart some progenitor object as it orbits the host galaxy. The featured image above is the ‘Field of Streams’ found in SDSS. The featured image above was made by V. Belokurov and shows a number of the discovered streams. You can read all about it here.
The first stellar stream was discovered by Ibata et al. (1997). Since then, many more of these objects have been found. Not only are these living fossils of the Milky Way’s formation, they also can tell us about the dark matter halo of the galaxy. Most of the time in astronomy we only see a snapshot of where some object is at the current moment. But streams tell us where the progenitor was and where it is going. It’s possible to use that orbit information to constrain the shape and structure of our Galaxy’s dark matter halo!
During my Ph.D., I worked with Prof. Widrow at Queen’s University to attempt to find the shape of the Milky Way’s dark matter halo using stellar streams. For our first attempt, we used the Sagittarius stream and a suite of other constraints to find the shape of the halo. Ultimately, we found a shape that is kind of like a hamburger turned on its side. For a more detailed read you can read our paper called “The Sagittarius stream and halo triaxiality“.
However, we soon found that our first attempt was flawed in a variety of key ways. We had treated the stream like an orbit, but there are some systematic errors that are associated with this method (see Sanders & Binney (2013) for more details). Secondly, we assumed that the symmetry axes of the halo were aligned with the disk, which doesn’t need to be true. It turns out that the alignment assumption can cause the inferred shape to be completely different from the actual shape if the halo is misaligned.
We looked at all this in our paper “Incorporating streams into Milky Way models“. At first this might seem a little bit depressing because it seems like we’ve stepped back from our initial results. But one of the really exciting things that we found is that fitting multiple streams simultaneously is just as good as using a single long stream. So the story is really that streams are powerful constraints on the potential of the Milky Way, but it is important to explore all the available models, to use as many constraints as possible, and to be careful to use an appropriate stream modeling method.
Since that time, I’ve explored a bit of the other stream modeling methods, but haven’t really focused on this area extensively. But stellar streams are an area that I am eager to return to as these objects promise to be some of the most informative about the structure of not only our home galaxy, but other galaxies as well. The dark matter halo of a galaxy is a bit like an invisible animal. We know it’s there and that it’s large. But to figure out if it’s an invisible rhino or elephant we need to spray it with water and look at how it drips off the animal. Stellar streams are the sprays of water revealing whether dark matter halos are shaped like hamburgers or cigars! | 0.812856 | 3.933118 |
Binary and recycled pulsars: 30 years after observational discovery
Space Research Institute, Russian Academy of Sciences, Profsoyuznaya str. 84/32, Moscow, 117997, Russian Federation
Binary radio pulsars, first discovered by Hulse and Taylor in 1974 , are a unique tool for experimentally testing general relativity (GR), whose validity has been confirmed with a precision unavailable in laboratory experiments. In particular, indirect evidence of the existence of gravitational waves has been obtained. Radio pulsars in binary systems (which have come to be known as recycled) have completed the accretion stage, during which neutron star spins reach millisecond periods and their magnetic fields decay 2 to 4 orders of magnitude more weakly than ordinary radio pulsars. Among about a hundred known recycled pulsars, many have turned out to be single neutron stars. The high concentration of single recycled pulsars in globular clusters suggests that close stellar encounters are highly instrumental in the loss of the companion. A system of one recycled pulsar and one `normal’ one discovered in 2004 is the most compact among binaries containing recycled pulsars . Together with the presence of two pulsars in one system, this suggests new prospects for further essential improvements in testing GR. This paper considers theoretical predictions of binary pulsars, their evolutionary formation, and mechanisms by which their companions may be lost. The use of recycled pulsars in testing GR is discussed and their possible relation to the most intriguing objects in the universe — cosmic gamma-ray bursts — is examined. | 0.849124 | 3.706184 |
A new study published today in Nature reports discovery of a rare event — that Earth’s moon slowly moved from its original axis roughly 3 billion years ago. Ancient lunar ice indicates the moon’s axis slowly shifted by 125 miles, or 6 degrees, over 1 billion years. Earth’s moon now a member of solar system’s exclusive ‘true polar wander’ club, which includes just a handful of other planetary bodies.
Planetary scientist Matt Siegler at Southern Methodist University, Dallas, and colleagues made the discovery while examining NASA data known to indicate lunar polar hydrogen. The hydrogen, detected by orbital instruments, is presumed to be in the form of ice hidden from the sun in craters surrounding the moon’s north and south poles. Exposure to direct sunlight causes ice to boil off into space, so this ice — perhaps billions of years old — is a very sensitive marker of the moon’s past orientation.
An odd offset of the ice from the moon’s current north and south poles was a tell-tale indicator to Siegler and prompted him to assemble a team of experts to take a closer look at the data from NASA’s Lunar Prospector and Lunar Reconnaissance Orbiter missions. Statistical analysis and modeling revealed the ice is offset at each pole by the same distance, but in exactly opposite directions.
This precise opposition indicates the moon’s axis — the imaginary pole that runs north to south through it’s middle, and around which the moon rotates — shifted at least six degrees, likely over the course of 1 billion years, said Siegler.
“This was such a surprising discovery. We tend to think that objects in the sky have always been the way we view them, but in this case the face that is so familiar to us — the Man on the Moon — changed,” said Siegler, who also is a scientist at the Planetary Science Institute, Tucson, Ariz.
“Billions of years ago, heating within the Moon’s interior caused the face we see to shift upward as the pole physically changed positions,” he said. “It would be as if Earth’s axis relocated from Antarctica to Australia. As the pole moved, the Man on the Moon turned his nose up at the Earth.”
The discovery is reported today in an article in the scientific journal Nature, “Lunar true polar wander inferred from polar hydrogen.” Siegler’s primary co-authors are astrophysicist Richard S. Miller, a professor at the University of Alabama Huntsville, and planetary dynamicist James T. Keane, a graduate student at the University of Arizona.
Very few planetary bodies known to permanently shift their axis
Planetary bodies settle into their axis based on their mass: A planet’s heavier spots lean it toward its equator, lighter spots toward the pole. On the rare occasion mass shifts and causes a planet to relocate on its axis, scientists refer to the phenomenon as “true polar wander.”
Discovery of lunar polar wander gains the moon entry into an extremely exclusive club. The only other planetary bodies theorized to have permanently shifted location of their axis are Earth, Mars, Saturn’s moon Enceladus and Jupiter’s moon Europa.
What sets the moon apart is its polar ice, which appears to effectively “paint out” the path along which its poles moved.
Moon’s axis likely started relocating about 3 billion years ago
On Earth, polar wander is believed to have happened due to movement of the continental plates. Polar wander on Mars resulted from a heavy volcanic region. The moon’s change in mass was internal — the shift of a large, single mantle “plume.” Ancient volcanic activity some 3.5 billion years ago melted a portion of the moon’s mantle, causing it to bubble up toward its surface, like goo drifting upward in a lava lamp.
“The moon has a single region of the crust, a large basaltic plain called Procellarum, where radioactive elements ended up as the moon was forming,” Siegler said. “This radioactive crust acted like an oven broiler heating the mantle below.”
Some of the material melted, forming the dark patches we see at night, which are ancient lava, he said.
“This giant blob of hot mantle was lighter than cold mantle elsewhere,” Siegler said. “This change in mass caused Procellarum — and the whole moon — to move.”
The moon likely relocated its axis starting about 3 billion years ago or more, slowly moving over the course of a billion years, Siegler said, etching a path in its ice.
Over time, the axis shifted 125 miles or 200 kilometers — about half the distance from Dallas to Houston, or equal the distance from Washington D.C. to Philadelphia.
Neutrons can indicate the presence of water or ice
Polar wander explains why the moon appears to have lost much of its ice.
Siegler compares true polar wander to holding a glass filled with water. Most planets are like a steady hand holding a glass, their axis doesn’t shift and the water stays put. A planet whose mass is changing is like a wobbly hand, causing its axis to shift and the water to spill out. Similarly, as Earth’s moon changed its axis, much of its ice ceased to be hidden from the sun and was lost.
Co-author Richard Miller mapped the moon’s remaining ice by using data from NASA’s Lunar Prospector mission, which orbited the moon from 1998 to 1999. The presence of ice is inferred by measuring the energy of neutrons emitted from the lunar surface. Instruments on NASA’s satellite, including a neutron spectrometer, measured neutrons liberated from the moon by a rain of stellar particles scientists call cosmic rays. Low energy neutrons indicate the presence of hydrogen, the dominant molecule in water and ice.
“The maps show four key features,” said Siegler and his colleagues. “First, the largest quantity of hydrogen is offset from the current rotation axis of the moon by roughly 5.5 degrees. Second, the hydrogen enhancements are of similar magnitude at both poles. Third, the asymmetric enhancements do not correlate with expectations from the current thermal or permanently shadowed environment. And lastly, and most significantly, the spatial distributions of polar hydrogen appear to be nearly antipodal.”
Lunar ice is ancient time capsule; may hold answers to deep mysteries
Siegler’s discovery opens the door to further discoveries around an even deeper question — the mystery of why there is water on the moon and on Earth. Scientific theory surrounding the formation of the solar system postulates water could not have formed much closer to the sun than Jupiter, Siegel said.
“We don’t know where the Earth’s water came from. It appears to have come from the outer solar system well after the Earth and moon formed,” he said. “Ice on other bodies, like the moon or Mercury, might give us a clue to its origin.”
The fact lunar ice correlates so well with true polar wander implies that it predates this motion, Siegler said, making the ice very ancient.
“The ice may be a time capsule from the same source that supplied the original water to Earth,” he said. “This is a record we don’t have on Earth. Earth has reworked itself so many times, there’s nothing that old left here. Ancient ice from the moon could provide answers to this deep mystery.”
Other co-authors on the scientific paper include Matthieu Laneuville, David A. Paige, Isamu Matsuyama, David J. Lawrence, Arlin Crotts and Michael J. Poston.
M. A. Siegler, R. S. Miller, J. T. Keane, M. Laneuville, D. A. Paige, I. Matsuyama, D. J. Lawrence, A. Crotts, M. J. Poston. Lunar true polar wander inferred from polar hydrogen. Nature, 2016; 531 (7595): 480 DOI: 10.1038/nature17166 | 0.839034 | 3.864032 |
Comets made up of two lobes, such as 67P/Churyumov–Gerasimenko, visited by the Rosetta spacecraft, are produced when the debris resulting from a destructive collision between two comets clumps together again. Such collisions could also explain some of the enigmatic structures observed on 67P. This discovery, made by an international team coordinated by Patrick Michel, CNRS researcher at the laboratoire Lagrange (CNRS/Observatoire de la Côte d’Azur/Université de Nice-Sophia Antipolis), was published on 5 March 2018 in Nature Astronomy.
Ever since Giotto visited Halley’s comet in 1986, a few spacecraft have flown close to several cometary nuclei. It turns out that most of them appeared to be elongated or even made up of two lobes, such as the well-known 67P/Churyumov–Gerasimenko, which was observed at very short range by the Rosetta spacecraft in 2014 and 2015. Astronomers believe that this astonishing shape can be explained by the merger of two formerly separate comets. The two comets would have to exhibit very low density and be rich in volatile elements, and therefore be moving very slowly, to enable them to come together and collide gently without exploding. For a number of reasons it is usually assumed that this type of gentle encounter only occurred in the initial stages of the Solar System, more than four billion years ago. However, there remains a mystery: how could such fragile bodies of the size of P67, formed so long ago, have survived until now, given that they are constantly subjected to collisions in the regions where they orbit?
An international team, including in particular a French researcher at the Lagrange Laboratory, now proposes a completely different scenario, using numerical simulations partly run at the Mésocentre Sigamm at the Observatoire de la Côte d’Azur. The simulations show that, during a destructive collision between two comets, only a small part of the material is pulverized at high speed and reduced to dust. However, on the sides opposite the point of impact, materials rich in volatile elements are able to withstand the collision and are ejected at relative speeds low enough for them to attract each other and re-accrete, forming many small bodies which in turn clump together to form just one. Astonishingly, this process only takes a few days, or even a few hours. In this way, the comet formed keeps its low density and its abundant volatiles, just like 67P/Churyumov–Gerasimenko.
This process is thought to be possible even in impacts at speeds of 1 km/s, which are typical in the Kuiper belt, the disc of comets extending beyond Neptune where P67 originated.
Since this type of collision between comets takes place regularly, P67 may have formed at any point in the history of the Solar System and not necessarily at its beginnings, as previously thought, thus solving the problem of its long-term survival.
This new scenario also explains the presence of the holes and stratified layers observed on P67, which would have built up naturally during the re-accretion process, or later, after its formation.
A final point is that, during the collision that forms this type of comet, no significant compaction or heating occurs, and their primordial composition is therefore preserved: the new comets continue to be primitive objects. Even if P67 formed recently, analyzing its material will still enable us to go back to the origins of the Solar System.
Publication: Stephen R. Schwartz, et al., “Catastrophic disruptions as the origin of bilobate comets,” Nature Astronomy (2018) doi:10.1038/s41550-018-0395-2 | 0.902531 | 4.026388 |
Scientists are asking for the public’s help to find the origin of hundreds of thousands of galaxies that have been discovered by the largest radio telescope ever built: LOFAR. Where do these mysterious objects that extend for thousands of light-years come from? A new citizen science project, LOFAR Radio Galaxy Zoo, gives anyone with a computer the exciting possibility to join the quest to find out where the black holes at the centre of these galaxies are located.
Astronomers use radio telescopes to make images of the radio sky, much like optical telescopes like the Hubble space telescope make maps of stars and galaxies. The difference is that the images made with a radio telescope show a sky that is very different from the sky that an optical telescope sees. In the radio sky, stars and galaxies are not directly seen but instead an abundance of complex structures linked to massive black holes at the centres of galaxies are detected. Most dust and gas surrounding a supermassive black hole gets consumed by the black hole, but part of the material will escape and gets ejected into deep space. This material forms large plumes of extremely hot gas, it is this gas that forms large structures that is observed by radio telescopes.
The Low Frequency Array (LOFAR) telescope, operated by the Netherlands Institute for Radio Astronomy (ASTRON), is continuing its huge survey of the radio sky and 4 million radio sources have now been discovered. A few hundred thousand of these have very complicated structures. So complicated that it is difficult to determine which galaxies belong to which radio source, or in other words, which black hole belongs to which galaxy?
While the international LOFAR team consists of more than 200 astronomers from 18 countries, it is simply too small to take on this daunting task of identifying which radio structures belong to which host galaxy. Therefore, LOFAR astronomers are asking the public to help. In the context of the citizen science project ‘LOFAR Radio Galaxy Zoo’, the public is asked to look at images from LOFAR and images of galaxies and then associate radio sources with galaxies.
“LOFAR’s new survey has revealed millions of previously undetected radio sources. With the help of the public we can investigate the nature of these sources: Where are their black holes? In what kind of galaxies are the black holes located?’’ says Huub Röttgering from Leiden University (The Netherlands).
Tim Shimwell, ASTRON and Leiden University, explains why this is significant: “Your task is to match the radio sources with the right galaxy. This will help researchers understand how radio sources are formed, how black holes evolve, and how vast quantities of material can be ejected into deep space with such unprecedented amounts of energy”, he says.
Radio Galaxy Zoo: LOFAR is part of the Zooniverse project, the world’s largest and most popular platform for people-powered research. This research is made possible by volunteers — more than a million people around the world who come together to assist professional researchers.
Caption image: As an example, take the case of the famous radio source 3C236. The upper image is the radio source, the middle one an optical image showing many stars and galaxies and the lower image an overlay of the radio and the optical image. In this case, for the human eye the origin of the radio emission is clear, it is the bright point-like radio source at the center of the radio image. This is the location of the massive black hole that is driving all the radio activity. From the overlay with the optical images the galaxy that hosts the black hole can then be identified.
Image credit: Aleksandar Shulevski, Erik Osinga & The LOFAR surveys team.
More images can be found here
The Radio Galaxy Zoo: LOFAR page is accessible here
The tutorial video can be viewed here | 0.811991 | 3.982605 |
Astronomers have caught sight of an unusual galaxy that has illuminated new details about a celestial "sandbar" connecting two massive islands of galaxies. The research was conducted in part with NASA's Spitzer Space Telescope.
These "sandbars," or filaments, are known to span vast distances between galaxy clusters and form a lattice-like structure known as the cosmic web. Though immense, these filaments are difficult to see and study in detail. Two years ago, Spitzer's infrared eyes revealed that one such intergalactic filament containing star-forming galaxies ran between the galaxy clusters called Abell 1763 and Abell 1770.
This diagram shows an unusual galaxy with bent jets (see callout). The galaxy was found with the help of NASA's Spitzer Space Telescope in a filament (purple area) connecting two massive islands of galaxies. The little dots in the diagram are other galaxies. The twin jets of material are bending backwards as they sweep through the hot gas in the filament.
Image credit: NASA/JPL-Caltech
Now these observations have been bolstered by the discovery, inside this same filament, of a galaxy that has a rare boomerang shape and unusual light emissions. Hot gas is sweeping the wandering galaxy into this shape as it passes through the filament, presenting a new way to gauge the filament's particle density. Researchers hope that other such galaxies with oddly curved profiles could serve as signposts for the faint threads, which in turn signify regions ripe for forming stars.
"These filaments are integral to the evolution of galaxy clusters -- among the biggest gravitationally bound objects in the universe -- as well as the creation of new generations of stars," said Louise Edwards, a postdoctoral researcher at the California Institute of Technology in Pasadena, and lead author of a study detailing the findings in the Dec. 1 issue of the Astrophysical Journal Letters. Her collaborators are Dario Fadda, also at Caltech, and Dave Frayer from the National Science Foundation's National Radio Astronomy Observatory, based in Charlottesville, Virginia.
Blowing in the cosmic breeze
Astronomers spotted the bent galaxy about 11 million light-years away from the center of the galaxy cluster Abell 1763 during follow-up observations with the WIYN Observatory near Tucson, Ariz., and radio-wave observations by the Very Large Array near Socorro, N.M. The WIYN Observatory is named after the consortium that owns and operates it, which includes the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatories.
The galaxy has an unusual ratio of radio to infrared light, as measured by the Very Large Array and Spitzer, making it stand out like a beacon. This is due in part to the galaxy having twin jets of material spewing in opposite directions from a supermassive black hole at its center. These jets have puffed out into giant lobes of material that emit a tremendous amount of radio waves.
Edwards and her colleagues noticed that these lobes appear to be bent back and away from the galaxy's trajectory through the filament. This bow shape, the astronomers reasoned, is due to particles in the filament pushing on the gas and dust in the lobes.
By measuring the angle of the arced lobes, Edwards' team calculated the pressure exerted by the filaments' particles and then determined the density of the medium. The method is somewhat like looking at streamers on a kite soaring overhead to judge the wind strength and the thickness of the air.
According to the data, the density inside this filament is indeed about 100 times the average density of the universe. This value agrees with that obtained in a previous X-ray study of filaments and also nicely matches predictions of supercomputer simulations.
Galaxies tend to bunch together as great islands in the void of space, called galaxy clusters. These galaxy groupings themselves often keep company with other clusters in "superclusters" that loom as gargantuan, gravitationally associated walls of galaxies. These structures evolved from denser patches of material as the universe rapidly expanded after the Big Bang, some 13.7 billion years ago.
The clumps and threads of this primordial matter eventually cooled, and some of it has condensed into the galaxies we see today. The leftover gas is strewn in filaments between galaxy clusters. Much of it is still quite hot -- about one million degrees Celsius (1.8 million degrees Fahrenheit) -- and blazes in high-energy X-rays that permeate galaxy clusters. Filaments are therefore best detected in X-ray light, and one direct density reading of the strands has previously been obtained in this band of frequencies.
But the X-ray-emitting gas in filaments is much more diffuse and weak than in clusters, just as submerged sandbars are extremely hard to spot at sea compared to islands poking above the water. Therefore, obtaining quality observations of filaments is time-consuming with current space observatories.
The technique by Edwards and her colleagues, which uses radio frequencies that can reach a host of ground-based telescopes, points to an easier way to probe the interiors of galaxy-cluster filaments. Instead of laboring to find subtle X-rays clues, astronomers could trust these arced "lighthouse" galaxies to indicate just where cosmic filaments lie.
Knowing how much material these filaments contain and how they interact with galaxy clusters will be very important for understanding the overall evolution of the universe, Edwards said.
The Spitzer observations were made before it ran out of its liquid coolant in May 2009 and began its warm mission.
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech, also in Pasadena. Caltech manages JPL for NASA. For more information about Spitzer, visit http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer .
Contacts and sources:
Written by Adam Hadhazy
Jet Propulsion Laboratory, Pasadena, Calif. | 0.816556 | 3.986047 |
As we’ve seen in our study of the Jovian planets, the actual planets themselves aren’t the only important space-related object that provides useful and insightful information. Every Jovian planet has some sort of celestial object orbiting or surrounding it, especially the moons surrounding Jupiter. Discovered by Galileo Galilei way back in 1610 (on January 10th), the four different Galilean moons (which include Io, Europa, Ganymede, and Callisto) exhibit different tectonic, spatial, and compositional characteristics that make each world unique and interesting to study!
Starting with the innermost-orbiting moon, we discuss Io, the most volcanically active world in our Solar System. Sizing up at around the dimensions of a dwarf planet, Io contains large volcanoes littered throughout the entire moon’s surface. Seldom does the moon have impact craters, as the super-frequent eruptions remove them from the surface almost immediately. Similar to Earth, the volcanoes on Io follow a similar outgassing pattern (however, for Io, it’s with Sulfur Dioxide). And lastly, Io’s constantly active volcanoes indicate to scientists that it experiences tidal heating (tidal forces causing constant flexes and stretches of the moon’s core), allowing it to be so active!
Onto the second innermost-orbiting moon, we discuss Europa, one of the most intriguing celestial bodies in our Solar System. It sits as a stark contrast to Io — not only is its surface covered by water ice, but it additionally seems like liquid water is flowing throughout its interior (since there are a lack of impact craters, some type of geographical movement is occurring). Scientists believe that there’s internal heat hot enough to melt some of the surface ice for the internal flowing as a result of photographical evidence, gravitational measurements, and magnetic fields. All in all, Europa could be the first place we find liquid water outside our own Earth (which would be pretty cool!).
For the third and fourth moons, we discuss both Ganymede and Callisto. As the largest moon in the Solar System, Ganymede’s surface of relatively young ice suggests a constant upwelling of water / slush to the surface (which would mean there’s an ocean there too, like Europa’s). However, because Ganymede is so large, it makes sense that it’s still active (at least, much more so than Europa). Additionally, we can’t forget to mention Callisto, a heavily cratered ball of ice that represents the stereotypical Jovian moon. It has old-looking surface littered with craters and ice-like material. However, as it lacks any sort of tectonic or volcanic activity, it isn’t seemingly as significant as the other three moons (though it may have a subsurface ocean, like the other moons).
All in all, the four different Galilean moons represent an eclectic collection of different quirks and characteristics that make them unique! If you’d like to further research the different moons of Jupiter, more information can be found at the linked website! And finally, a picture of the different moons can be found below. | 0.829992 | 3.913461 |
Globular Clusters have a story to tell. These dense clumps of thousands of stars are relics of the early history of our galaxy, preserving information of the galaxy’s properties from their formation. Knowing this, astronomers have used globular clusters for nearly 30 years to probe how our galaxy has evolved. New observations from Hubble, add surprising new insight to this picture.
One of the advantages to studying clusters, is that the large number of stars allows astronomers to accurately determine some properties of the constituent stars far better than they could if the stars were isolated. In particular, since clusters all form in a short span of time, all stars will have the same age. More massive stars will die off first, peeling away from the main sequence before their lower mass brothers. How far this point, where stars leave the main sequence, has progressed is indicative of the age of the cluster. Since globular clusters have such a rich population of stars, their H-R diagrams are well detailed and the turn-off becomes readily apparent.
Using ages found in this manner, astronomers can use these clusters to get a snapshot of what the conditions of the galaxy were like when it formed. In particular, astronomers have studied the amount of elements heavier than helium, called “metals”, as the galaxy has aged. One of the first findings using globular clusters to probe this age-metallicity relationship was that there was a notable difference in the way the inner portion and the outer portion of the galaxy has evolved. Globular clusters revealed that the inner 15 kpc evolved heavier elements faster than the outer portions. Such findings allow for astronomers to test models of galactic formation and evolution and have helped to support models involving halos of dark matter.
While these results have been confirmed by numerous follow-up studies, the sampling of globular clusters is still somewhat skewed. Many of the globular clusters studied were part of the Galactic Globular Cluster Treasury project conducted using the Hubble Space Telescope’s Advanced Camera for Surveys (HST/ACS). In order to minimize the time spent using the much demanded telescope, the team was only able to target relatively nearby globular clusters. As such, the most distant cluster they could observe was NGC 4147 which is ~21 kpc from the galactic center. Other studies have made use of Hubble’s Wide Field Planetary Camera 2 and pushed the radius back to over 50 kpc from the galactic center. However, currently only 6 globular clusters with distances over 50 kpc have been included in this larger study. Interestingly, there has been a notable absence of clusters between 15 and 50 kpc, leaving a gap in the fuller knowledge.
This gap is the target of a recent study by a team of astronomers led by Aaron Dotter from the Space Telescope Science Institute in Maryland. In the new study, the team examines 6 globular clusters. Three of them (IC 4499, NGC 6426, and Ruprecht 106) are towards the inner edge of this range, lying between 15 and 20 kpc from the galactic center while the other three (NGC 7006, Palomar 15, and Pyxis) each lie around 40 kpc.
Again making use of the HST/ACS, the team found that all of the clusters were younger than globular clusters from the inner portions of the galaxy with similar metalicities. But three of the clusters, IC 4499, Ruprecht 106, and Pyxis were significantly younger to the tune of 1-2 billion years younger again supporting the picture that inner clusters had evolved faster. Additionally, this finding of a sharp difference helps to support the picture that the outer clusters underwent a different evolutionary process, aside from the rapid enrichment in the inner halo. One suggestion is that many of the outer halo clusters were originally formed in dwarf galaxies and later accreted into the Milky Way due to the timescales on which clusters in such smaller galaxies are thought to evolve. | 0.860523 | 4.123868 |
Feb. 24 (UPI) -- Researchers have published the first scientific papers that rely on data collected by NASA's InSight lander, which touched down on Mars just over a year ago.
Observations made by the lander's super-sensitive seismometer, the Seismic Experiment for Interior Structure, have allowed scientists to gain new insights into the structure of the Red Planet's interior.
In September 2019, InSight's seismometer recorded 174 seismic events. Since then, SEIS has recorded a total of 450 Marsquakes, an average of nearly two a day in recent months, but they have not yet been formally analyzed by scientists.
One type of Marsquake features low-frequency seismic waves and register magnitudes between 3 and 4 on the seismomter. There were 24 such quakes prior to November 2019.
The second family of quakes feature high frequency waves trapped in the Martian crust. These shallower quakes are smaller in magnitude and more common. SEIS recorded 150 such quakes prior to November 2019.
"Marsquakes have characteristics already observed on the Moon during the Apollo era, with a long signal duration -- 10 to 20 minutes -- due to the scattering properties of the Martian crust," study author Domenico Giardini, professor of geophysics at ETH Zurich in Switzerland, said in a news release.
Analysis of the seismic waves recorded by SEIS suggests the lander touched down on a shallow patch of sand. The sandy layer extends just a few feet beneath the surface. The initial analysis of Marsquakes suggests that below the sandy layer, the Martian crust is a lot like Earth's crystalline crust but more fractured.
Additionally, scientists suspect they dissipate more quickly in the Red Planet's upper mantle than in its lower mantle.
Mars is without tectonic planets, but it does boast volcanically active regions. As detailed in one of the Nature papers, scientists were able to link at least two larger quakes with one such region, Cerberus Fossae. Satellite images showed boulders were dislodged and tumbled down cliff sides around the time the quakes were recorded.
Cerberus Fossae is characterized by a pair of deep channels that were created by lava flows some 10 million years ago. These flows feature fissures that scientists suspect were created by rumblings resulting from volcanic activity. Some of the fractures may be as young as 2 million years old.
"It's just about the youngest tectonic feature on the planet," planetary geologist Matt Golombek of NASA's Jet Propulsion Laboratory said in a news release. "The fact that we're seeing evidence of shaking in this region isn't a surprise, but it's very cool."
The early scientific results from the InSight mission suggest the lander touched down during an unusually quiet period, in terms of seismic activity. Researchers expect a full Martian year of observations, two Earth years, will offer scientists more detailed insights into Mars inner composition. | 0.803973 | 3.696499 |
Is there life on Saturn's moons?
The Cassini Huygens spacecraft has spent over a decade studying Saturn for NASA and the European Space Agency (ESA). It has discovered that its moons Titan and Enceladus have some key conditions for supporting life.
Scientists have discovered organic molecules containing nitrogen and oxygen on Saturn’s moon Enceladus, according to a new study.
Enceladus, which is Saturn’s sixth-largest moon and about 500 kilometres in diameter, is an icy orb believed to contain a deep subsurface ocean underneath its icy crust.
Discovering organic molecules on Enceladus is noteworthy because water, energy and organic molecules could be the ingredients for some type of extraterrestrial life.
RELATED: Crazy discovery about Saturn’s rings
Enceladus shot the material out in plumes from cracks in its south polar crust, according to scientists.
For the new study, German and US researchers examined the Cosmic Dust Analyser’s data and found new organic compounds, according to the paper published in the Monthly Notices of the Royal Astronomical Society for November.
The molecules included amines, which are nitrogen-and oxygen-containing organic molecules that have some similar traits to those on Earth, according to the study’s abstract.
This article originally appeared on Fox News and was reproduced with permission | 0.856148 | 3.015055 |
Rosetta Spacecraft Waking Up for Final Leg of Comet Landing
The first spacecraft to orbit a comet and land a probe on these icy nomads is now waking up after more than two years of slumber, and videos filmed as part of an international competition will help greet the spacecraft after it awakens.
Comets are some of the most primitive building blocks of the solar system, with many dating to soon after its formation. Comets also likely helped seed Earth with water and other ingredients of life. By analyzing the composition of the comet, the European Space Agency’s Rosetta spacecraft will help scientists learn more about the role comets have played in the evolution of the solar system and life on Earth.
Rosetta launched from Europe’s spaceport in French Guiana in 2004. It has since traveled around the sun five times, reaching a distance of about 500 million miles (800 million kilometers) away from the sun.
The mission’s final destination is the mysterious comet 67P/Churyumov–Gerasimenko, which Rosetta is scheduled to reach in August. A comet is made of a solid nucleus or core surrounded by a gaseous envelope known as a coma and trailing a large tail. Rosetta will become the first spacecraft to orbit the nucleus of a comet, and in November, it will be the first to land a probe, named Philae, on a comet’s surface. It will also be the first mission to escort a comet as it travels around the sun.
For the coldest leg of Rosetta’s mission, as it traveled out toward the orbit of Jupiter, the spacecraft was placed into hibernation in order to help it save energy. After 31 months of sleep, researchers are now waking Rosetta up, with its internal alarm clock set for 10 a.m. Greenwich Mean Time on January 20. Once the spacecraft has warmed itself up, it should reestablish communication with Earth several hours later.
To celebrate the spacecraft’s waking, ESA initiated the "Wake Up Rosetta" campaign, inviting people worldwide to upload video clips of them shouting "Wake up, Rosetta!" to Rosetta’s Facebook page. As of January 15, there were more than 70 entries.
"Some are cute, some are short, some are long. All are entertaining," said Daniel Scuka, who works on the social media team of ESA’s European Space Operations Center at Darmstadt, Germany. "We are really impressed and pleasantly surprised with the creativity and effort that we’ve seen. Several submissions include full costumes and scenes with singing and dancing, and folks are ensuring their dogs, cats and kids are well-represented."
Videos have not only been submitted by individuals, but also families, schools and groups of friends. A number of videos have been stop-motion or full-digital animations. Submissions have been received from around the world. A number of astronauts have sent videos as well.
One submission even came from NASA’s Jet Propulsion Laboratory to promote the contest to U.S. audiences, Scuka said.
"We’re quite pleased to see the inter-agency cooperation — this highlights the fact that Rosetta really is a cooperative mission that would not be as successful if it were just ESA alone," said ESA spokesman Markus Bauer.
Visitors to Rosetta’s Facebook page can vote on their favorite videos. The top 10 videos will be transmitted from Earth into space with 20,000 watts of power in February via one of ESA’s deep-space tracking stations, and those who made them will receive gift bags. Two winning entries will also be invited to ESA’s control center in Darmstadt, Germany for an event celebrating the first landing on a comet.
Although Rosetta will not rendezvous with the comet until August, the spacecraft is set to wake up on January to give researchers enough time to completely test the spacecraft and make it ready for arrival.
"There is a lot to prepare for rendezvousing and landing on the comet," said ESA cometary scientist Gerhard Schwehm. "First we have to switch on and check that all 11 instrument packages on the orbiter and 10 on lander are working. Then we need time to track the comet so we can prepare our rendezvous maneuvers."
The researchers also want to study the comet as Rosetta approaches it in case certain parts of the comet are active. When a comet orbits near the sun, it gives off fountains of gas that could be obstacles for Rosetta or its probe Philae.
"We’d want to avoid getting too close to those!" Schwehm said. "Choosing a landing site for Philae will also take careful consideration, and then we have to finalize the commands to deliver the lander to the surface based on that selection. We certainly have plenty to do before we arrive at the comet in August."
During Rosetta’s 31 months of hibernation, most of the spacecraft’s systems were shut down, except for the onboard "alarm clock" and several heaters set to periodically turn on and off to make sure Rosetta did not freeze up completely. When the probe wakes up, it will switch on its star trackers to determine its orientation and eventually point at Earth, transmitting a signal to let the world know that it has reawakened, said Rosetta spacecraft operations manager Andrea Accomazzo.
The Wake Up Rosetta competition will accept entries until 5:30 p.m. Greenwich Mean Time on January 20, and the winners will be announced on January 24. The contest is open to all, but prizes can only be won by citizens and permanent members of European Union countries, the United States, and ESA member and cooperating states.
ESA also invites people to join the Wake Up Rosetta campaign via Twitter and shout #WakeUpRosetta at @ESA_Rosetta. The agency especially wants to see shouts on January 20, between 10 a.m. and 5:30 p.m. Greenwich Mean Time. | 0.839471 | 3.292689 |
Hubble Space Telescope data, analyzed by a Yale astronomer using gravitational lensing techniques, has generated a spatial map demonstrating the clumped substructure of dark matter inside clusters of galaxies.
Clusters of galaxies (about a million, million times the mass of our sun), are typically made up of hundreds of galaxies bound together by gravity. About 90 percent of their mass is darkmatter. The rest is ordinary atoms in the form of hot gas and stars.
Although little is known about it, cold dark matter is thought to have structure at all magnitudes. Theoretical models of the clumping properties were derived from detailed, high resolution simulations of the growth of structure in the Universe. Although previous evidence supported the ?concordance model? of a Universe mostly composed of cold, dark matter, the predicted substructure had never been detected.
In this study, Yale assistant professor of astronomy and physics Priyamvada Natarajan and her colleagues demonstrate that, at least in the mass range of typical galaxies in clusters, there is an excellent agreement between the observations and theoretical predictions of the concordance model.
Using gravitational lensing made it possible for the observers to visualize light from distant galaxies as it bent around mass in its way. This allowed the researchers to measure light deflections that indicated structural clumps in the dark matter.
?We used an innovative technique to pick up the effect of precisely the clumps which might otherwise be obscured by the presence of more massive structures,? said Natarajan. ?When we compared our results with theoretical expectations of the concordance model, we found extremely good agreement, suggesting that the model passes the substructure test for the mass range we are sensitive to with this technique.?
?We think the properties of these clumps hold a key to the nature of dark matter ? which is presently unknown,? said Natarajan. ?The question remains whether these predictions and observations agree for smaller mass clumps that are as yet undetected.?
Co-author on the study, funded by Yale University, is Volker Springel, MPA, Garching, Germany. Other collaborators include. Jean-Paul Kneib, LAM ? OAMP, Marseille, France, Ian Smail, University of Durham, U.K., and Richard Ellis of Caltech.
Original Source: Yale News Release | 0.863322 | 4.03535 |
C|Net's Hubble spots drop-dead gorgeous spiral galaxy tucked into Leo links to NASA's Hubble Spots Stunning Spiral Galaxy which shows the image below.
The caption on the NASA page doesn't mention the color coding, nor does it mention a reference to a technical page for the image's construction or history.
Question: Is this close to a "straight RGB" image of NGC 2903, or were filters used at certain wavelengths, possibly including IR or UV, in order to highlight certain regions and emissions, then assigned false colors. If the latter, is it a standard color coding?
The NASA page says:
NGC 2903 is located about 30 million light-years away in the constellation of Leo (the Lion), and was studied as part of a Hubble survey of the central regions of roughly 145 nearby disk galaxies. This study aimed to help astronomers better understand the relationship between the black holes that lurk at the cores of galaxies like these, and the rugby-ball-shaped bulge of stars, gas and dust at the galaxy’s center — such as that seen in this image. Text credit: ESA (European Space Agency)
Click to view full size! | 0.800397 | 3.154662 |
Black holes are one of the strangest things in the Universe. They don’t seem to make any sense at all. It is an enormous amount of matter packed into a minimal area. To better understand, think of a star ten times more massive than the Sun packed into a sphere approximately the size of New York City. This results in a gravitational field so strong that even light can’t escape. Because no light can get out of black holes, they are invisible. It requires a space telescope with special tools to find a black hole. These help us see how stars close to the black hole act differently than the other stars. In this article, let us discuss the black hole in detail.
How Are Black Holes Formed?
A collection of massive hydrogen atoms is what makes a star. In their core, hydrogen atoms fuse into helium, releasing a tremendous amount of energy. The liberated energy, in the form of radiation, pushes against gravity and maintains a delicate balance between the two forces. A star is stable enough as long as there is fusion in the core. In stars, much more massive than Sun, the heat and pressure at the core allow them to fuse into heavier elements until they form iron. Iron builds up in the centre of the core until it reaches a certain critical point, and suddenly, the balance between radiation and gravity is broken. This results in the core collapsing and imploding into itself. Moving at about the quarter of the speed of light, it feeds even more mass into the core. It is at this very moment that all the heavier elements in the Universe are formed. As the stars die in a supernova explosion, they either turn into a neutron star or a black hole depending on the mass of the star.
Types of Black Hole
There are four types of black holes as follows:
The commonly known way of how a black hole is formed is by stellar death. As stars reach their end-stage of their lives, most will lose mass, will inflate and cool to create a white dwarf. But the largest of these, those ten times or 20 times more massive than Sun are destined to become either a super-dense neutron star or the stellar-mass black holes.
Can a Black Hole Destroy Earth?
Earth will not fall into a black hole because no black hole is close to the Solar system for the Earth to do that. Besides, black holes do not go around the Universe swallowing stars and planets. Suppose a black hole were to take the place of the Sun. Earth would still not fall into it and would orbit the black hole as it would orbit the Sun.
Scientists are using spacecraft and telescopes travelling in space to learn more about black holes. These spacecraft are what help the scientists answer the unanswered questions of the Universe.
Since you are here, you might want to check out the following articles:
If you wish to learn more Physics concepts with the help of interactive video lessons, download BYJU’S – The Learning App. | 0.909046 | 3.889024 |
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- General considerations
- Light from the stars
- Stellar magnitudes
- Bulk stellar properties
- Stellar masses
- Stellar statistics
- Stellar structure
- Star formation and evolution
- Later stages of evolution
R Coronae Borealis variables are giant stars of about the Sun’s temperature whose atmospheres are characterized by excessive quantities of carbon and very little hydrogen. The brightness of such a star remains constant until the star suddenly dims by several magnitudes and then slowly recovers its original brightness. (The star’s colour remains the same during the changes in brightness.) The dimmings occur in a random fashion and seem to be due to the huge concentrations of carbon. At times the carbon vapour literally condenses into soot, and the star is hidden until the smog blanket is evaporated. Similar veiling may sometimes occur in other types of low-temperature stars, particularly in long-period variables.
Flare stars are cool dwarfs (spectral type M) that display flares apparently very much like, but much more intense than, those of the Sun. In fact, the flares are sometimes so bright that they overwhelm the normal light of the star. Solar flares are associated with copious emission of radio waves, and simultaneous optical and radio-wave events appear to have been found in the stars UV Ceti, YZ Canis Minoris, and V371 Orionis.
Spectrum and magnetic variables, mostly of spectral type A, show only small amplitudes of light variation but often pronounced spectroscopic changes. Their spectra typically show strong lines of metals such as manganese, titanium, iron, chromium, and the lanthanides (also called rare earths), which vary periodically in intensity. These stars have strong magnetic fields, typically from a few hundred to a few thousand gauss. One star, HD 215441, has a field on the order of 30,000 gauss. (Earth’s magnetic field has an average strength of about 0.5 gauss.) Not all magnetic stars are known to be variable in light, but such objects do seem to have variable magnetic fields. The best interpretation is that these stars are rotating about an inclined axis. As with Earth, the magnetic and rotation axes do not coincide. Different ions are concentrated in different areas (e.g., chromium in one area and the lanthanides in another).
The Sun is an emitter of radio waves, but, with present techniques, its radio emission could only just be detected from several parsecs away. Most discrete radio-frequency sources have turned out to be objects such as old supernovas, radio galaxies, or quasars, though well-recognized radio stars also have been recorded on occasion. These include flare stars, red supergiants such as Betelgeuse, the high-temperature dwarf companion to the red supergiant Antares, and the shells ejected from Nova Serpentis 1970 and Nova Delphini. The radio emission from the latter objects is consistent with that expected from an expanding shell of ionized gas that fades away as the gas becomes attenuated. The central star of the Crab Nebula has been detected as a radio (and optical) pulsar.
Measurements from rockets, balloons, and spacecraft have revealed distinct X-ray sources outside the solar system. The strongest galactic source, Scorpius X-1, appears to be associated with a hot variable star resembling an old nova. In all likelihood this is a binary star system containing a low-mass normal star and a nonluminous companion.
A number of globular clusters are sources of cosmic X-rays. Some of this X-ray emission appears as intense fluctuations of radiation lasting only a few seconds but changing in strength by as much as 25 times. These X-ray sources have become known as bursters, and several such objects have been discovered outside of globular clusters as well. Some bursters vary on a regular basis, while others seem to turn on and off randomly. The most popular interpretation holds that bursters are the result of binary systems in which one of the objects—a compact neutron star or black hole (see below End states of stars)—pulls matter from the companion, a normal star. This matter is violently heated in the process, giving rise to X-rays. That the emission is often in the form of a burst is probably caused by something interrupting the flow of matter onto (or into) the compact object or by an eclipsing orbit of the binary system. | 0.898717 | 3.898477 |
It’s relatively easy for galaxies to make stars. Start out with a bunch of random blobs of gas and dust. Typically those blobs will be pretty warm. To turn them into stars, you have to cool them off. By dumping all their heat in the form of radiation, they can compress. Dump more heat, compress more. Repeat for a million years or so.
Eventually pieces of the gas cloud shrink and shrink, compressing themselves into a tight little knots. If the densities inside those knots get high enough, they trigger nuclear fusion and voila: stars are born.
Imagine yourself in a boat on a great ocean, the water stretching to the distant horizon, with the faintest hints of land just beyond that. It’s morning, just before dawn, and a dense fog has settled along the coast. As the chill grips you on your early watch, you catch out of the corner of your eye a lighthouse, feebly flickering through the fog.
The combined observations from two generations of X-Ray space telescopes have now revealed a more complete picture of the nature of high-speed winds expelled from super-massive black holes. Scientist analyzing the observations discovered that the winds linked to these black holes can travel in all directions and not just a narrow beam as previously thought. The black holes reside at the center of active galaxies and quasars and are surrounded by accretion discs of matter. Such broad expansive winds have the potential to effect star formation throughout the host galaxy or quasar. The discovery will lead to revisions in the theories and models that more accurately explain the evolution of quasars and galaxies.
The observations were by the XMM-Newton and NuSTAR x-ray space telescopes of the quasar PDS 456. The observations were combined into the graphic, above. PDS 456 is a bright quasar residing in the constellation Serpens Cauda (near Ophiuchus). The data graph shows both a peak and a trough in the otherwise nominal x-ray emission profile as shown by the NuSTAR data (pink). The peak represents X-Ray emissions directed towards us (i.e.our telescopes) while the trough is X-Ray absorption that indicates that the expulsion of winds from the super-massive black hole is in many directions – effectively a spherical shell. The absorption feature caused by iron in the high speed wind is the new discovery.
X-Rays are the signature of the most energetic events in the Cosmos but also are produced from some of the most docile bodies – comets. The leading edge of a comet such as Rosetta’s P67 generates X-Ray emissions from the interaction of energetic solar ions capturing electrons from neutral particles in the comet’s coma (gas cloud). The observations of a super-massive black hole in a quasar billions of light years away involve the generation of x-rays on a far greater scale, by winds that evidently has influence on a galactic scale.
The study of star forming regions and the evolution of galaxies has focused on the effects of shock waves from supernova events that occur throughout the lifetime of a galaxy. Such shock waves trigger the collapse of gas clouds and formation of new stars. This new discovery by the combined efforts of two space telescope teams provides astrophysicists new insight into how star and galaxy formation takes place. Super-massive blackholes, at least early in the formation of a galaxy, can influence star formation everywhere.
Both the ESA built XMM-Newton and the NuSTAR X-Ray space telescope, a SMEX class NASA mission, use grazing incidence optics, not glass (refraction) or mirrors (reflection) as in conventional visible light telescopes. The incidence angle of the X-rays must be very shallow and consequently the optics are extended out on a 10 meter (33 foot) truss in the case of NuSTAR and over a rigid frame on the XMM-Newton.
The ESA built XMM-Newton was launched in 1999, an older generation design that used a rigid frame and structure. All the fairing volume and lift capability of the Ariane 5 launch vehicle was needed to put the Newton in orbit. The latest X-Ray telescope – NuSTAR – benefits from tens years of technological advances. The detectors are more efficient and faster and the rigid frame was replaced with a compact truss which required all of 30 minutes to deploy. Consequently, NuSTAR was launched on a Pegasus rocket piggybacked on a L-1011, a significantly smaller and less expensive launch system.
So now these observations are effectively delivered to the theorists and modelers. The data is like a new ingredient in the batter from which a galaxy and stars are formed. The models of galaxy and star formation will improve and will more accurately describe how quasars, with their active super-massive black-holes, transition into more quiescent galaxies such as our own Milky Way.
In a galaxy four billion light-years away, three supermassive black holes are locked in a whirling embrace. It’s the tightest trio of black holes known to date and even suggests that these closely packed systems are more common than previously thought.
“What remains extraordinary to me is that these black holes, which are at the very extreme of Einstein’s Theory of General Relativity, are orbiting one another at 300 times the speed of sound on Earth,” said lead author Roger Deane from the University of Cape Town in a press release.
“Not only that, but using the combined signals from radio telescopes on four continents we are able to observe this exotic system one third of the way across the Universe. It gives me great excitement as this is just scratching the surface of a long list of discoveries that will be made possible with the Square Kilometer Array.”
The system, dubbed SDSS J150243.091111557.3, was first identified as a quasar — a supermassive black hole at the center of a galaxy, which is rapidly accreting material and shining brightly — four years ago. But its spectrum was slightly wacky with its doubly ionized oxygen emission line [OIII] split into two peaks instead of one.
A favorable explanation suggested there were two active supermassive black holes hiding in the galaxy’s core.
An active galaxy typically shows single-peaked narrow emission lines, which stem from a surrounding region of ionized gas, Deane told Universe Today. The fact that this active galaxy shows double-peaked emission lines, suggests there are two surrounding regions of ionized gas and therefore two active supermassive black holes.
But one of the supermassive black holes was enshrouded in dust. So Deane and colleagues dug a little further. They used a technique called Very Long Baseline Interferometry (VLBI), which is a means of linking telescopes together, combining signals separated by up to 10,000 km to see detail 50 times greater than the Hubble Space Telescope.
Observations from the European VLBI network — an array of European, Chinese, Russian, and South American antennas — revealed that the dust-covered supermassive black hole was once again two instead of one, making the system three supermassive black holes in total.
“This is what was so surprising,” Deane told Universe Today. “Our aim was to confirm the two suspected black holes. We did not expect one of these was in fact two, which could only be revealed by the European VLBI Network due [to the] very fine detail it is able to discern.”
Deane and colleagues looked through six similar galaxies before finding their first trio. The fact that they found one so quickly suggests that they’re more common than previously thought.
Before today, only four triple black hole systems were known, with the closest pair being 2.4 kiloparsecs apart — roughly 2,000 times the distance from Earth to the nearest star, Proxima Centauri. But the closest pair in this trio is separated by only 140 parsecs — roughly 10 times that same distance.
Although Deane and colleagues relied on the phenomenal resolution of the VLBI technique in order to spatially separate the two close-in black holes, they also showed that their presence could be inferred from larger-scale features. The orbital motion of the black hole, for instance, is imprinted on its large jets, twisting them into a helical-like shape. This may provide smaller telescopes with a tool to find them with much greater efficiency.
“If the result holds up, it’ll be very cool,” binary supermassive black hole expert Jessie Runnoe from Pennsylvania State University told Universe Today. This research has multiple implications for understanding further phenomena.
The first sheds light on galaxy evolution. Two or three supermassive black holes are the smoking gun that the galaxy has merged with another. So by looking at these galaxies in detail, astronomers can understand how galaxies have evolved into their present-day shapes and sizes.
The second sheds light on a phenomenon known as gravitational radiation. Einstein’s General Theory of Relativity predicts that when one of the two or three supermassive black holes spirals inward, gravitational waves — ripples in the fabric of space-time itself — propagate out into space.
Future radio telescopes should be able to measure gravitational waves from such systems as their orbits decay.
“Further in the future, the Square Kilometer Array will allow us to find and study these systems in exquisite detail, and really allow us [to] gain a much better understanding of how black holes shape galaxies over the history of the Universe,” said coauthor Matt Jarvis from the Universities of Oxford and Western Cape.
The research was published today in the journal Nature.
The large black holes that reside at the center of galaxies can be hungry beasts. As dust and gas are forced into the vicinity around the black holes, it crowds up and jostles together, emitting lots of heat and light. But what forces that gas and dust the last few light years into the maw of these supermassive black holes?
It has been theorized that mergers between galaxies disturbs the gas and dust in a galaxy, and forces the matter into the immediate neighborhood of the black hole. That is, until a recent study of 140 galaxies hosting Active Galactic Nuclei (AGN) – another name for active black holes at the center of galaxies – provided strong evidence that many of the galaxies containing these AGN show no signs of past mergers.
The study was performed by an international team of astronomers. Mauricio Cisternas of the Max Planck Institute for Astronomy and his team used data from 140 galaxies that were imaged by the XMM-Newton X-ray observatory. The galaxies they sampled had a redshift between z= 0.3 – 1, which means that they are between about 4 and 8 billion light-years away (and thus, the light we see from them is about 4-8 billion years old).
They didn’t just look at the images of the galaxies in question, though; a bias towards classifying those galaxies that show active nuclei to be more distorted from mergers might creep in. Rather, they created a “control group” of galaxies, using images of inactive galaxies from the same redshift as the AGN host galaxies. They took the images from the Cosmic Evolution Survey (COSMOS), a survey of a large region of the sky in multiple wavelengths of light. Since these galaxies were from the same redshift as the ones they wanted to study, they show the same stage in galactic evolution. In all, they had 1264 galaxies in their comparison sample.
The way they designed the study involved a tenet of science that is not normally used in the field of astronomy: the blind study. Cisternas and his team had 9 comparison galaxies – which didn’t contain AGN – of the same redshift for each of their 140 galaxies that showed signs of having an active nucleus.
What they did next was remove any sign of the bright active nucleus in the image. This means that the galaxies in their sample of 140 galaxies with AGN would essentially appear to even a trained eye as a galaxy without the telltale signs of an AGN. They then submitted the control galaxies and the altered AGN images to ten different astronomers, and asked them to classify them all as “distorted”, “moderately distorted”, or “not distorted”.
Since their sample size was pretty manageable, and the distortion in many of the galaxies would be too subtle for a computer to recognize, the pattern-seeking human brain was their image analysis tool of choice. This may sound familiar – something similar is being done with enormous success with people who are amateur galaxy classifiers at Galaxy Zoo.
When a galaxy merges with another galaxy, the merger distorts its shape in ways that are identifiable – it will warp a normally smooth elliptical galaxy out of shape, and if the galaxy is a spiral the arms seem to be a bit “unwound”. If it were the case that galactic mergers are the most likely cause of AGN, then those galaxies with an active nucleus would be more probable to show distortion from this past merger.
The team went through this process of blinding the study to eliminate any bias that those looking at the images would have towards classifying AGN as more distorted. By both having a reasonably large sample size of galaxies and removing any bias when analyzing the images, they hoped to definitively show whether the correlation between AGN and mergers exists.
The result? Those galaxies with an Active Galactic Nucleus did not show any more distortion on the whole than those galaxies in the comparison sample. As the authors state in the paper, “Mergers and interactions involving AGN hosts are not dominant, and occur no more frequently than for inactive galaxies.”
This means that astronomers can’t point towards galactic mergers as the main reason for AGN. The study showed that at least 75% of AGN creation – at least between the last 4-8 billion years – must be from sources other than galactic mergers. Likely candidates for these sources include: “galactic harrassment”, those galaxies that don’t collide, but come close enough to gravitationally influence each other; the instability of the central bar in a galaxy; or the collision of giant molecular clouds within the galaxy.
Knowing that AGN aren’t caused in large part by galactic mergers will help astronomers to better understand the formation and evolution of galaxies. The active nuclei in galaxies that host them greatly influence galactic formation. This process is called ‘AGN feedback’, and the mechanisms and effects that result from the interplay between the energy streaming out of the AGN and the surrounding material in the center of a galaxy is still a hot topic of study in astronomy.
Mergers in the more distant past than 8 billion years might yet correlate with AGN – this study only rules out a certain population of these galaxies – and this is a question that the team plans to take on next, pending surveys by the Hubble Space Telescope and the James Webb Space Telescope. Their study will be published in the January 10 issue of the Astrophysical Journal, and a pre-print version is available on Arxiv.
It seems oddly appropriate to be writing about astrophysical jets on Thanksgiving Day, when the New York football Jets will be featured on television. In the most recent issue of Science, Carlos Carrasco-Gonzalez and collaborators write about how their observations of radio emissions from young stellar objects (YSOs) shed light one of the unsolved problems in astrophysics; what are the mechanisms that form the streams of plasma known as polar jets? Although we are still early in the game, Carrasco-Gonzalez et al have moved us closer to the goal line with their discovery.
Astronomers see polar jets in many places in the Universe. The largest polar jets are those seen in active galaxies such as quasars. They are also found in gamma-ray bursters, cataclysmic variable stars, X-ray binaries and protostars in the process of becoming main sequence stars. All these objects have several features in common: a central gravitational source, such as a black hole or white dwarf, an accretion disk, diffuse matter orbiting around the central mass, and a strong magnetic field.
When matter is emitted at speeds approaching the speed of light, these jets are called relativistic jets. These are normally the jets produced by supermassive black holes in active galaxies. These jets emit energy in the form of radio waves produced by electrons as they spiral around magnetic fields, a process called synchrotron emission. Extremely distant active galactic nuclei (AGN) have been mapped out in great detail using radio interferometers like the Very Large Array in New Mexico. These emissions can be used to estimate the direction and intensity of AGNs magnetic fields, but other basic information, such as the velocity and amount of mass loss, are not well known.
On the other hand, astronomers know a great deal about the polar jets emitted by young stars through the emission lines in their spectra. The density, temperature and radial velocity of nearby stellar jets can be measured very well. The only thing missing from the recipe is the strength of the magnetic field. Ironically, this is the one thing that we can measure well in distant AGN. It seemed unlikely that stellar jets would produce synchrotron emissions since the temperatures in these jets are usually only a few thousand degrees. The exciting news from Carrasco-Gonzalez et al is that jets from young stars do emit synchrotron radiation, which allowed them to measure the strength and direction of the magnetic field in the massive Herbig-Haro object, HH 80-81, a protostar 10 times as massive and 17,000 times more luminous than our Sun.
Finally obtaining data related to the intensity and orientation of the magnetic field lines in YSO’s and their similarity to the characteristics of AGN suggests we may be that much closer to understanding the common origin of all astrophysical jets. Yet another thing to be thankful for on this day. | 0.899706 | 4.058618 |
From the beginning the spark of life is everywhere, longing to spring up in the universe.
The Human Phenomenon – Pierre Teilhard de Chardin ( 1881 – 1955 ).
On May 10th NASA’s Kepler mission announced the discovery of the largest collection of planets ever to be found, a staggering 1,284. Launched in March 2009, Kepler is the first NASA mission to have detected earth – size planets orbiting stars in or near the habitable zone – the orbital region around a star in which liquid water may pool on a planet’s surface.
We have been learning more and more about the origin and structure of the universe, whilst yet remaining in complete ignorance as to whether or not mankind remains the only living system.
Some time before the launch of the Kepler telescope the mathematician Amir Aczel in his book Probability 1 went to great pains to demonstrate the existence of other intelligent life in the universe simply by applying the Drake equation. In fact, according to the astronomer Frank Drake ( 1930 – ) the number ( N ) of possible extra-terrestrial civilisations depends on the product of seven factors, or variables: i) N*, the number of stars in our galaxy; ii) fp , the fraction of those stars with planetary systems; iii) ne , the number of planets per star with environments favourable to the formation of life; iv) fl , the fraction of suitable planets on which life actually appears; v) fi , the fraction of planets on which intelligent life evolves; vi) fc , the fraction of planets with civilizations able to communicate; vii) L, the length of time such civilizations release detectible signs into space.
When seven dice are tossed the probability of achieving a number seven is given by the product of getting a number one from each die, i.e. 1/6 ·1/6 · 1/6 · 1/6 ·1/6 · 1/6 ·1/6, or ( 1/6 ) 7 , where the symbol (·) as used in mathematical equations means multiply. In similar fashion, the probability of getting (N ) intelligent civilisations in our galaxy is given by N* · fp · ne · fl · fi · fc · L.
The conclusion arrived at by Drake and Aczel was that the existence of intelligent life in the Milky Way was a certainty. Let us now tackle the Drake equation once more, this time using a more prudent approach.
If we estimate the number of stars in the Milky Way to be 300 billion, then ( N* ) where only 5% ( fp ) are sun-like would be N* · fp = 300 billion · 0.05 = 15 billion.
According to the astronomer Mayor, who discovered the first extra solar planet, every sun-like star possesses at least one planet. This assumption the Kepler mission has now validated. In addition, if the research community is to believed, there could be many more planets than sun-like stars. Thus, if we seek to determine which planets are orbiting a distant star in the habitable zone, there should be at least 15 billion planets for us to investigate. Several scientists interviewed by Aczel are of the opinion that the fraction of planets with chemistry suitable for triggering the lottery of life should be in the region of 10%. Using a far more conservative estimate we might say it could be in the region of 0.1%, or 0.001 ( ne ).
Thus, N* · fp · ne = 15 million.
Even though a statistically based estimate of the fraction of planets with the right environmental factors for life is not possible, scientists involved in Drake’s equation have conjectured that the value of the factor, or variable, fl, should be 10%, or 0,1. By adopting a rather more conservative approach, dividing 0,1 by 100, fl becomes equal to 0,001. Thus, N* · fp · ne · fl = 15,000.
While it remains arguable whether intelligence is not just a fluke in the genetic development of life, there is a considerable difference between life and intelligent life. According to the scientists discussing Drake’s equation, of all planets supporting life the proportion of those supporting intelligent life, fi, could be in the region of 10%. Again dividing by 100 in pursuit of a more prudent approach, we obtain fi = 0.001.
Thus, by multiplying: N* · fp · ne · fl · fi , we find 15 intelligent planets in the Milky Way.
The Greek, Roman, Egyptian or Mayan civilisations did not have the means to communicate with other extra-terrestrial worlds, thus the factor fc of Drake’s equation can be considered as a sort of technological index, whilst the factor L marks the longevity of a civilisation, given that intelligent civilisations may eventually destroy themselves. An estimate of L might be the distance in time between Marconi inventing the radio and the destruction of Hiroshima.
Several scientists have attributed a probability ratio of about 3 % to both factors fc and L. By once again dividing both percentages by 100 for prudence sake, we could complete the Drake equation as follows,
N = 15 · 0.032/1002 = 0.00000135. In this way we arrive not at the certainty promulgated by Drake and Aczel, but at the evanescent 1.35 / 1,000,000 probability of the existence of other intelligent planets in the Milky Way.
According to the latest estimates by astrophysicists there are at least 100 billion galaxies in the Universe.
By applying the above evanescent probability to each and every galaxy, we would then have, according to the Law of Large Numbers, 0.00000135 · 100,000,000,000 = 135,000 overall intelligent planets.
In order to determine the probability of Earth being the most intelligent planet, given the complete dearth of information, the principle of symmetry has to be applied, namely that all planets have the same probability of securing first prize. This probability is equal to 1/135,000, or 0,0000074074.
The diameter of the Milky Way spans over 200,000 light-years of space and it takes 50,000 years for the light from its centre to reach the Earth. Bearing in mind that light travels at a speed of 186,000 miles per second, in one earth year light travels almost six trillion miles.
The closest star to Earth is Alpha Centauri, situated at a distance of 4.3 light-years. A hypothetical phone conversation with inhabitants of a planet orbiting this star would last several dozen years, since one would have to wait no less than nine years to get an answer to any question one might wish to pose. In short, should we receive a signal of whatever kind from another intergalactic civilisation, it is quite possible that by the time we receive the signal that civilisation may have disappeared.
Stellar distances preserve Earth’s future from extra-terrestrial aggressors, but not from internal ones.
Ennio Falabella London, 3rd August 2016 | 0.865869 | 3.485725 |
HD 208487 is a 7th magnitude G-type main sequence star located approximately 144 light-years away in the constellation of Grus. It has the same spectral type as our sun, G2V. However, it is probably slightly less massive and more luminous, indicating that it is slightly older. As of 2008, there is one known extrasolar planet confirmed to be orbiting the star.
There is one known planet orbiting the star HD 208487, which is designated HD 208487 b. It has a mass at least half that of Jupiter and is located in an eccentric 130-day orbit.
The discovery of a second planet in the system was announced on September 13, 2005, by P.C. Gregory. The discovery was made using Bayesian analysis of the radial velocity dataset to determine the planetary parameters. However, further analysis revealed that an alternative 2-planet solution for the HD 208487 system was possible, with a planet in a 28-day orbit instead of the 908-day orbit postulated, and it was concluded that activity on the star is more likely to be responsible for the residuals to the one-planet solution than the presence of a second planet.
* List of extrasolar planets
1. ^ Tinney et al.; Butler, R. Paul; Marcy, Geoffrey W.; Jones, Hugh R. A.; Penny, Alan J.; McCarthy, Chris; Carter, Brad D.; Fischer, Debra A. (2005). "Three Low-Mass Planets from the Anglo-Australian Planet Search". The Astrophysical Journal 623 (2): 1171–1179. doi:10.1086/428661. http://www.iop.org/EJ/article/0004-637X/623/2/1171/61345.html.
* Butler et al.; Wright, J. T.; Marcy, G. W.; Fischer, D. A.; Vogt, S. S.; Tinney, C. G.; Jones, H. R. A.; Carter, B. D. et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal 646 (1): 505–522. doi:10.1086/504701. http://www.iop.org/EJ/article/0004-637X/646/1/505/64046.html.
* "Notes for star HD 208487". The Extrasolar Planets Encyclopaedia. http://exoplanet.eu/star.php?st=HD+208487. Retrieved 2008-08-29. | 0.856376 | 3.610451 |
If you are an early riser, you will have noticed that four of the five naked-eye planets are visible in a great arc from the southeastern to the southwestern sky. For the next couple of weeks, elusive Mercury joins the tableau. You’ll be able to see all the planets visible to humans until the discovery of Uranus just 235 years ago.
Start about an hour before sunrise. You’ll need a southern horizon clear of trees and buildings. You are looking for an arc of bright objects starting in the SSW rising to the south and sinking again to the southeast.
It also helps to have a sky map. You’ll find a good one at http://earthsky.org/science-wire/when-will-all-five-visible-planets-appear-simultaneously.
Look SSW for bright Jupiter, the fifth planet from the sun. Pretty far to the left of Jupiter to the WSW is the star Spica. Almost directly south and near the top of the arc is dim, reddish Mars.
Down and to the left of Mars along the arc is yellowish Saturn. Don’t confuse it with the star Antares, which is down and to the right of Saturn.
Down and to the left of Saturn and almost directly southeast is blazingly white Venus. Down and to the left of Venus and very low on the horizon is difficult-to-see Mercury.
Seeing the five naked-eye planets over the course of a night is commonplace to those of us who have spent a few thousand nights outdoors. Seeing all eight of the major planets is more difficult. In fact, in my misspent youth I spent a few nights doing “planet marathons,” when I saw all of the nine planets, Pluto included, over a single night. Just for fun, we threw in a few bright asteroids – what are now called dwarf planets – like Ceres and Vesta.
Invariably, some were setting in the evening or rising in the morning just before the sun rose. The planets are visible most of the time. Each one spends a bit of time too close to the sun too see, but they are mostly visible if you know when and where to look and you’re willing to lose a night’s sleep.
Go beyond the naked-eye five, and you’ll need some help. Uranus will take binoculars, and Neptune and the asteroids require a telescope. Pluto requires a big telescope and a detailed star map to distinguish it from the plethora of stars that look exactly like it.
The “fabulous five” are easy enough for any beginner. You can see them with the binoculars you were born with, but binoculars might help you when trying to spot Mercury. Again, you might have to stay up all night to see them most of the time.
Their appearance at the same moment is more unusual. The last time it happened was at the end of 2004 and briefly into 2005. If you don’t like dragging yourself out of bed before the sun rises, take heart. By August, all of the original five will have migrated to the evening sky, so you’ll get another opportunity.
The problem child here is Mercury. The closest planet to the sun never gets very far from it from our point of view. It reaches its greatest elongation – when it appears farthest from the sun in the sky – during the first week of February. After that, it will dive closer to the sun, and your chances of seeing it diminish with each passing day. What with central-Ohio clouds and all, I’ve seen the most elusive of naked-eye planets only a dozen or so times. If you see it, you will become one of the elite few who have done so throughout the course of human history. Take the opportunity to do so while you have bright Venus to point the way.
There’s another reason to give it a go this time around. Note how the planets seem to mark an arc across the southern sky. The arc is part of a great sky circle called the ecliptic, the path the sun appears to take as it makes its yearly trek around the sky.
What it really marks is the plane Earth travels as it orbits the sun. The other major planets travel in orbits that are pretty close to that plane. Thus, their positions are pretty close to the ecliptic. Connect the planetary dots and you’ll see the ecliptic, not on some star map but with your own two eyes.
But you are also seeing something more. Astronomers say with a high degree of certainty that the planets formed from a spinning, flattened disk of dust and gas.
How can they be so certain? Well, there it is. They all move slowly around the sky in the same direction, and they all move more or less along the plane of the original flattened disk. There really is no better explanation, and you can see so for yourself and not have to take some blessed astronomer’s word for it.
Go out. Look. Be the seeker after truth that you may secretly know in your heart of hearts you were born to be.
Tom Burns is director of the Perkins Observatory in Delaware. | 0.808053 | 3.342319 |
Don’t get me wrong, black holes are cool, but they’re also giant voids of terror: These gravitational abysses have been known to snack on stars in occurrences called Tidal Disruption Events (TDEs). It’s always the same horror story — an unsuspecting star wanders too close to a black hole, only to get ripped apart by the black hole’s gravity. Isn’t space pleasant?
Traditionally, astronomers have searched for TDEs in sky surveys that encompass thousands of galaxies, leading them to believe that these events were extremely rare — only one tidal disruption every 10,000 to 100,000 years per galaxy. But after observing a likely TDE in a sky survey of just 15 galaxies, a team of researchers at the University of Sheffield in the UK has concluded black holes may be ripping up stars 100 times more often than previously assumed, based on this relatively small sample size. Their research was published today in Nature Astronomy.
“Each of these 15 galaxies is undergoing a ‘cosmic collision’ with a neighbouring galaxy,” Dr James Mullaney, Lecturer in Astronomy and co-author of the study, said in a press release.
“Our surprising findings show that the rate of TDEs dramatically increases when galaxies collide. This is likely due to the fact that the collisions lead to large numbers of stars being formed close to the central supermassive black holes in the two galaxies as they merge together.”
Earlier this month, a team of researchers released their findings on the longest-recorded TDE, which clocked in at 10 years. While we can’t normally see black holes — as they swallow everything, light included — we can see flare ups of energy as stars are in the process of being devoured. Learning more about the destructive tendencies of black holes today will give us a better understanding of how they will shape the cosmos in the future, especially within our own galaxy.
“Based on our results for [a galaxy known as] F01004-2237, we expect that TDE events will become common in our own Milky Way galaxy when it eventually merges with the neighbouring Andromeda galaxy in about 5 billion years,” Clive Tadhunter, Professor of Astrophysics and lead author of the study, said in a press release.
“Looking towards the center of the Milky Way at the time of the merger we’d see a flare [from a tidal disruption event] approximately every 10 to 100 years. The flares would be visible to the naked eye and appear much brighter than any other star or planet in the night sky.”
It’s worth noting that this is just one study, which came to its conclusions based on a single TDE, which still needs to be confirmed by further investigation. There’s a lot more work to be done if we want to truly nail down the behaviour of these elusive beasts.
“First, let me say that finding a TDE in a starburst galaxy, as these authors seem to have done, is an important discovery, as it has never been seen before,” Nicholas Stone, a postdoctoral Einstein Fellow in the Columbia Astrophysics Laboratory, told Gizmodo. “However, I think more follow-up observations may be necessary to confirm this TDE candidate as a true TDE. In particular, I am a little concerned by the possible late-time increase in luminosity in this flare, which would not be expected for most TDEs. Further monitoring of this galaxy can ascertain whether the flare is re-brightening or dimming.”
Ah, the brightening and dimming of a star’s abbreviated life. Cheers to many more years of stellar cannibalism! | 0.819184 | 4.01569 |
* Neutralization (Mixing acid+base=water and a salt).
* Photosynthesis -co2 and water are changed into sugars.
* Cooking examples: cake, pancakes, and eggs/bacon
* Oxidation examples: rust or tarnishing
* Ripening examples: bananas, tomatoes or potatoes
* Change of odor
* Change of color
* Change in temp or energy, such as the production (exothermic) or loss (endothermic) of heat.
* Change of form (for example, burning paper).
* Light, heat, or sound is given off.
* Formation of gases, often appearing as bubbles.
* Formation of precipitate (insoluble particles).
* The decomposition of organic matter (for ex rotting food).
How did Dalton’s atomic theory help support the law of conservation of mass?
According to Dalton’s atomic theory :
1. All matter is made up of atoms
2. ATOMS CAN NEITHER BE CREATED NOR DESTROYED
3. Atoms of the same element are identical
4. Atoms of different elements have different properties
5. compounds consisted of atoms of different elements combined together in a particular ratio
forms of energy
heat, light, sound, electrical, chemical, nuclear and mechanical
Work is the amount of energy transferred during an interaction
amount of energy before a transformation = amount of energy after. In most energy transformations, some energy is converted to thermal energy.
fusion vs fission
fission splits a massive element into fragments, releasing
energy in the process.
Fusion joins two light elements, forming a
more massive element, and releasing energy in the process
They both release energy because of the binding energy per nucleon curve
conversion of mass to energy
In the special theory of relativity Einstein demonstrated that neither mass nor energy were conserved separately, but that they could be traded one for the other and only the total “mass-energy” was conserved. The relationship between the mass and the energy is e=mc2
the speed of light squared is a very large number, a small amount of mass corresponds to a huge amount of energy
forms of energy
Energy is found in different forms including light, heat, chemical, and motion. There are many forms of energy, but they can all be put into two categories: potential and kinetic.
Potential energy is stored energy and the energy of position — gravitational energy
*Chemical Energy is energy stored in the bonds of atoms and molecules
*Mechanical Energy is energy stored in objects by tension.
*Nuclear Energy is energy stored in the nucleus of an atom — the energy that holds the nucleus together.
*Gravitational Energy is energy stored in an object’s height.
Electrical Energy is what is stored in a battery
Kinetic energy is motion
*Radiant Energy is electromagnetic energy that travels in transverse waves
*Thermal Energy, or heat, is the vibration and movement of the atoms and molecules within substances.
*Motion Energy is energy stored in the movement of objects. The faster they move, the more energy is stored
*Sound is the movement of energy through substances in longitudinal (compression/rarefaction) waves
is the measure of the energy required to increase the temperature of a unit quantity of a substance by a unit of temperature. For example, the energy required to raise water’s temperature by one kelvin (equal to one degree Celsius) is 4186 J/kg.
first law of thermodynamics
an expression of the principle of conservation of energy, states that energy can be transformed (changed from one form to another), but cannot be created or destroyed. It is usually formulated by saying that the change in the internal energy of a system is equal to the amount of heat supplied to the system, minus the amount of work done by the system on its surroundings.
second law of thermodynamics
an expression of the universal principle of decay observable in nature.
It is measured and expressed in terms of a property called entropy, stating that the entropy of an isolated system which is not in equilibrium will tend to increase over time or (equivalently) that perpetual motion machines are impossible.
is a macroscopic property of a system that is a measure of the microscopic disorder within the system
discovered the law of conservation of mass and defined an element as a basic substance that could not be further broken down by the methods of chemistry
used the concept of atoms to explain why elements always react in ratios of small whole numbers (the law of multiple proportions) and why certain gases dissolve better in water than others. He proposed that each element consists of atoms of a single, unique type, and that these atoms can join together to form chemical compounds. Dalton is considered the originator of modern atomic theory.
In 1869, building upon earlier discoveries by such scientists as Lavoisier, Dmitri Mendeleev published the first functional periodic table. The table itself is a visual representation of the periodic law, which states that certain chemical properties of elements repeat periodically when arranged by atomic number
The physicist J. J. Thomson, through his work on cathode rays in 1897, discovered the electron, and concluded that they were a component of every atom. Thus he overturned the belief that atoms are the indivisible
plum pudding model
J. J. Thomson postulated that the low mass, negatively charged electrons were distributed throughout the atom, possibly rotating in rings, with their charge balanced by the presence of a uniform sea of positive charge.
gold foil experiment
In 1909, bombarded a sheet of gold foil with alpha rays—by then known to be positively charged helium atoms—and discovered that a small percentage of these particles were deflected through much larger angles than was predicted using Thomson’s proposal. suggesting that the positive charge of a heavy gold atom and most of its mass was concentrated in a nucleus at the center of the atom—the Rutherford model
in 1913, physicist Niels Bohr suggested that the electrons were confined into clearly defined, quantized orbits, and could jump between these, but could not freely spiral inward or outward in intermediate states.An electron must absorb or emit specific amounts of energy to transition between these fixed orbits. When the light from a heated material was passed through a prism, it produced a multi-colored spectrum. The appearance of fixed lines in this spectrum was successfully explained by these orbital transitions
depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the solar system, but with electrostatic forces providing attraction, rather than gravity.
The model also violates the uncertainty principle in that it considers electrons to have known orbits and definite radius, two things which can not be directly known at once
The electron configuration of an atom is the particular distribution of electrons among available shells. It is described by a notation that lists the subshell symbols, one after another. Each symbol has a superscript on the right giving the number of electrons in that subshell. For example, a configuration of the lithium atom (atomic number 3) with two electrons in the 1s subshell and one electron in the 2s subshell is written 1s^2 2s^1.
The number of electrons in an atom of an element is given by the atomic number of that element
periodicity: atomic radius
One periodic property of atoms is that they tend to decrease in size from left to right across a period of the table. the atomic radii increases top to bottom and right to left in the periodic table.
periodicity: ionization energy
The energy needed to remove the most loosely held electron from an atom is known as ionization energy. Ionization energies are periodic. The ionization energy tends to increase as atomic number increases in any horizontal row or period. In any column or group, there is a gradual decrease in ionization energy as the atomic number increases. Metals typically have a low ionization energy. Nonmetals typically have a high ionization energy.
The attraction of an atom for an electron is called electron affinity. Metals have low electron affinities while nonmetals have high electron affinities. The general trend as you go down a column is a decreasing tendency to gain electrons. As you go across a row there is also a trend for a greater attraction for electrons.
chemical reactivity: same period
*metal atoms tend to transfer electrons to nonmetals
*nonmetal atoms tend to gain or share electrons
In the same period:
smaller the number of electrons transferred, more vigorous reaction
chemical reactivity: same group
In the same group:
elements have the same # of outershell electrons, the atomic radius largely determines reactivity.
*larger metals loose outer shell electrons more easily
*smaller nonmetals are more likely to take electrons away/share w metals
the radii generally decrease along each period (row) of the table, from the alkali metals to the noble gases
increase down each group (column).
The radius increases sharply between the noble gas at the end of each period and the alkali metal at the beginning of the next period. These trends of the atomic radii (and of various other chemical and physical properties of the elements) can be explained by the electron shell theory of the atom; they provided important evidence for the development and confirmation of quantum theory.
charge of types of radiation
alpha rays carry a positive charge
beta rays carry a negative charge
gamma rays are neutral
mass number A and atomic number Z
An alpha particle (A=4, Z=2) emitted from nucleus
daughter is A-4 (top number) and Z-2 (bottom number)
A nucleus emits an electron and an antineutrino
daughter is A, Z-1
mass number A and atomic number Z
Excited nucleus releases a high-energy photon (gamma ray)
daughter is the same A,Z
the speed of an object is the magnitude of its velocity (the rate of change of its position); it is thus a scalar quantity.
the rate of change of displacement (position). It is a vector quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is speed
v = delta x / delta t
The rate of change of velocity is acceleration – how an object's speed or direction changes over time, and how it is changing at a particular point in time.
The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval
A free falling object is an object that is falling under the sole influence of gravity
All free-falling objects (on Earth) accelerate downwards at a rate of 9.8 m/s/s
an object is moving at its terminal velocity if its speed is constant due to the restraining force exerted by the air, water or other fluid through which it is moving.
A free-falling object achieves its terminal velocity when the downward force of gravity (Fg) equals the upward force of drag (Fd). This causes the net force on the object to be zero, resulting in an acceleration of zero- continues falling at a constant speed. More drag means a lower terminal velocity, increased weight means a higher
the number of occurrences of a repeating event per unit time. The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency.
ex: 1 year is the period of the Earth’s orbit around the Sun, and the Earth’s rotation on its axis has a frequency of 1 rotation per day.
the variable representing the value being manipulated or changed
It is customary to use x for the independent variable
the dependent variable is the observed result of the independent variable being manipulated.
It is customary to use y for the dependent variable
newton’s first law of motion
“An object at rest will remain at rest, and an object moving at a constant velocity will continue moving at a constant velocity, unless it is acted upon by an unbalanced force.” Another name is Law of Inertia
newton’s second law of motion
A body of mass m subject to a force F undergoes an acceleration a that has the same direction as the force and a magnitude that is directly proportional to the force and inversely proportional to the mass, i.e., F = ma
newton’s third law of motion
The mutual forces of action and reaction between two bodies are equal, opposite and collinear. This means that whenever a first body exerts a force F on a second body, the second body exerts a force −F on the first body. F and −F are equal in magnitude and opposite in direction. This law is sometimes referred to as the action-reaction law, with F called the “action” and −F the “reaction”.
*the resistance an object has to a change in its state of motion*
The tendency of an object to resist changes in its state of motion varies with mass. A more massive object has a greater tendency to resist changes in its state of motion.
amount of energy transferred by a force acting through a distance. Like energy, it is a scalar quantity, with SI units of joules
the force that opposes the motion of one surface as it moves across another surface
a quantity that is often understood as the ability to perform work. This quantity can be assigned to any particle, object, or system of objects as a consequence of its physical state.
Different forms of energy include kinetic, potential, thermal, gravitational, sound, elastic and electromagnetic energy.
Any form of energy can be transformed into another form. When energy is in a form other than thermal energy, it may be transformed with good or even perfect efficiency, to any other type of energy. With thermal energy, however, there are often limits to the efficiency of the conversion to other forms of energy, due to the second law of thermodynamics
a mechanical device that changes the direction or magnitude of a force. In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force
6 simple machines
* Wheel and axle
* Inclined plane
Simple machines fall into two classes; those dependent on the vector resolution of forces (inclined plane, wedge, screw) and those in which there is an equilibrium of torques (lever, pulley, wheel).
(kg·m/s, or N·s) is the product of the mass and velocity of an object (p = mv)
conservation of momentum
Since momentum is always conserved, the sum of the momenta before the collision must equal the sum of the momenta after the collision
There are two types of collisions that conserve momentum: elastic collisions, which also conserve kinetic energy, and inelastic collisions, which do not.
force due to gravity between two objects
Fg = G (m1 x m2) / r2
Fg – is the force due to gravity
G – is the universal gravitational constant
m1 – is the mass of the first object
m2 – is the mass of the second object
r – is the distance between the centres of the two objects
When using the SI units, G is 6.67 x 10-11 N m2 / Kg2
for a sunken object the volume of displaced fluid is the volume of the object, and for a floating object on a liquid, the weight of the displaced liquid is the weight of the object.
Buoyancy = weight of displaced fluid
states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid’s potential energy
**as the velocity of a fluid increases, the pressure exerted by that fluid decreases
why planes fly
loudness vs pitch
Loudness is a function of the sound wave’s amplitude. The greater the amplitude, the greater the volume. Pitch is related to its frequency. The higher the frequency, the higher the pitch.
A mole is the quantity of anything that has the same number of particles found in 12.000 grams of carbon-12.
That number of particles is Avogadro’s Number, which is roughly 6.02×10^23
a mole of any pure substance has a mass in grams exactly equal to that substance’s molecular or atomic mass; e.g., 1mol of calcium-40 is approximately equal to 40g,
Determine the empirical formula
for a compound which is 54.09% Ca, 43.18% O, and 2.73% H
Divide each percent by that element’s atomic weight. To get the answers to whole numbers, divide through by the smallest one.
Ca = 54.09/40 = 1.352 1.352/1.352 = 1
O = 43.18/16 = 2.699 2.699/1.352 = 2
H = 2.73/1 = 2.73 2.73/1.352 = 2
gram atomic mass
The mass of one mole of atoms of an element. Also called gram-atomic weight.
process or reaction that releases energy usually in the form of heat, but also in the form of light (e.g. a spark, flame, or explosion), electricity (e.g. a battery), or sound(e.g. burning hydrogen)
process or reaction that absorbs energy in the form of heat.
specific heat of water
The specific heat of water is 1 calorie/gram °C = 4.186 joule/gram °C
Real images can be produced by concave mirrors and converging lenses.
the image produced on a detector in the rear of a camera, and the image produced on a human retina (the latter two pass light through an internal convex lens).
wavelength changes frequency remains constant
resistors in parallel
have the same potential difference v1=v2=v3 etc..
power dissipated by a resistor is equal to current times the potential difference p=IV
freezing point of a solution
depends on the concentration of ions in solution as well as other factors.
For a solution with a liquid as solvent, the temperature at which it freezes to a solid is slightly lower than the freezing point of the pure solvent. This phenomenon is known as freezing point depression and is related in a simple manner to the concentration of the solute.
haploid number (n)
Human germ cells (sperm and egg) have one complete set of chromosomes from the male or female parent. Germ cells, also called gametes, combine to produce somatic cells. Somatic cells therefore have twice as many chromosomes. The haploid number (n) is the number of chromosomes in a gamete. A somatic cell has twice that many chromosomes (2n).
meiosis vs mitosis
mitosis=genetically identical diploid cells
meiosis=genetically unique haploid cells
An autosomal recessive disorder means two copies of an abnormal genegene must be present in order for the disease or trait to develop.
r/K selection theory
trade off between quantity or quality of offspring.
where r is the growth rate of the population (N), and K is the carrying capacity of its local environmental setting. Typically, r-selected species exploit less-crowded ecological niches, and produce many offspring, each of which has a relatively low probability of surviving to adulthood. In contrast, K-selected species are strong competitors in crowded niches, and invest more heavily in fewer offspring
fixed action pattern
an instinctive behavioral sequence that is indivisible and runs to completion. Fixed action patterns are invariant and are produced by a neural network known as the innate releasing mechanism in response to an external sensory stimulus known as a sign stimulus or releaser (a signal from one individual to another)
a class of relationship between two organisms where one organism benefits but the other is unaffected
cattle egrets foraging in fields among cattle or other livestock. As cattle, horses, and other livestock graze on the field, they cause movements that stir up various insects. As the insects are stirred up, the cattle egrets following the livestock catch and feed upon them. The egrets benefit from this relationship because the livestock have helped them find their meals, while the livestock are typically unaffected by it.
the solid part of the earth consisting of the crust and outer mantle
the envelope of gases surrounding any celestial body
the watery layer of the earth’s surface including water vapor
the layer closest to Earth, where almost all weather occurs; the thinnest layer. begins at the surface and extends to between 7 km (23,000 ft) at the poles and 17 km (56,000 ft) at the equator. Is mostly heated by transfer of energy from the surface, so on average temperature decreases with altitude. This promotes vertical mixing
the layer of the atmosphere that lies between the troposphere and the mesosphere and in which temperature increases as altitude increases; contains the ozone layer. jets fly.
after the stratosphere, before thermosphere.
where most meteors burn up upon entering the atmosphere. Temperature decreases with height. The mesopause, the temperature minimum that marks the top of the mesosphere, is the coldest place on Earth and has an average temperature around −85 °C (−121 °F; 188.1 K). Due to the cold temperature, water vapor is frozen, forming ice clouds (or Noctilucent clouds). A type of lightning referred to as either sprites or ELVES, form many miles above thunderclouds in the troposphere.
the biggest of all the layers of the earth’s atmosphere directly above the mesosphere and directly below the exosphere. Within this layer, ultraviolet radiation causes ionization. The International Space Station has a stable orbit within the middle of the thermosphere, between 320 and 380 kilometres (200 and 240 mi). Auroras also occur in the thermosphere.
outermost layer of Earth’s atmosphere extends from the exobase upward. Here the particles are so far apart that they can travel hundreds of km without colliding with one another. Since the particles rarely collide, the atmosphere no longer behaves like a fluid. These free-moving particles follow ballistic trajectories and may migrate into and out of the magnetosphere or the solar wind. The exosphere is mainly composed of hydrogen and helium.
a layer in Earth's atmosphere which contains relatively high concentrations of ozone (O3). This layer absorbs 97-99% of the sun's high frequency ultraviolet light, which is potentially damaging to life on earth. It is located in the lower portion of the stratosphere
Ozone concentrations are greatest between about 20 and 40 km, where they range from about 2 to 8 parts per million. If all of the ozone were compressed to the pressure of the air at sea level, it would be only a few millimeters thick
period of time from the formation of the Earth (4.6 billion years ago) to the rise of life forms
The largest defined unit of time is the supereon, composed of eons. Eons are divided into eras, which are in turn divided into periods, epochs and ages
the time since the formation of life-forms to the present day; divided into three eras: Paleozoic, Mesozoic, and Centzoic
early life (570-286 million years ago); single cell organisms, shells, mollusks, brachiopods, rise of first vertebrates, rise of land plants, amphibians, insects, seed plants, and trees, and reptiles
middle life (245-144 million years ago); rise of mammals and dinosaurs; the rise of birds; extinction of dinosaurs, rise of flowering plants
is the most recent of the three classic geological eras and covers the period from 65.5 million years ago to the present. Rise of mammals, homo sapiens. marked by the Cretaceous-Tertiary extinction at the end of the Cretaceous, the demise of the dinosaurs and the end of the Mesozoic Era. is divided into two periods, the Tertiary and the Quaternary
single-celled organism without nuclei (bacteria)
single-celled organism with nuclei (algae, protozoans)
Linnean classification system
Kingdom, Phylum, Class, Order, Family, Genus, Species (Kings Play Chess On Fine Glass Surfaces; King Phillip Came Over For Good Spaghetti)
taxonomic rank below Kingdom and above Class. “Phylum” is equivalent to the botanical term division, Informally, phyla can be thought of as grouping organisms based on general body plan, as well as developmental or internal organizations. ex: Chordata, the phylum to which humans belong, along with all other vertebrate species, as well as some invertebrates such as the lamprey
loosely based on the traditional five-kingdom system but divides the kingdom Monera into two “domains,” leaving the remaining eukaryotic kingdoms in the third domain.
on the basis of differences in 16S rRNA genes, these two groups and the eukaryotes each arose separately from an ancestor with poorly developed genetic machinery, often called a progenote.
To reflect these primary lines of descent, he treated each as a domain, divided into several different kingdoms.
Archaea- prokaryotic, no nuclear membrane, possess unique ancient evolutionary history for which they are considered some of the oldest species of organisms on Earth; traditionally classified as archaebacteria; often characterized by living in extreme environments
Bacteria Domain – prokaryotic, no nuclear membrane, traditionally classified as bacteria, contain most known pathogenic prokaryotic organisms
Eukarya Domain – eukaryotes, nuclear membrane
characteristics of all living things
homeostasis, organization, metabolism, growth, adaptation, response to stimuli, reproduction
“cellular power plants” they generate most of the cell’s supply of adenosine triphosphate (ATP) through respiration, used as a source of chemical energy- citric acid cycle, or the Krebs Cycle
the mitochondrion has its own independent genome.its DNA shows substantial similarity to bacterial genomes.
non membrane bounded organelles responsible for protein synthesis from all amino acids
The DNA sequence in genes is copied into a messenger RNA (mRNA). Ribosomes then read the information in this RNA and use it to create proteins. This process is known as translation
membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell’s genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins to form chromosomes. maintains the integrity of these genes and controls the activities of the cell by regulating gene expression
non-membrane bound structure composed of proteins and nucleic acids found within the nucleus mainly involved in the assembly of ribosomes. After being produced in the nucleolus, ribosomes are exported to the cytoplasm where they translate mRNA
A vacuole is a membrane bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. are essentially enclosed compartments filled with water containing inorganic and organic molecules, isolating harmful material, waste products, maintain turgor,
translation and folding of new proteins in rough endoplasmic reticulum- is covered with ribosomes, expression of lipids in smooth endoplasmic reticulum, single membrane compartment, all eukaryotes
sorting and modification of proteins, single membrane compartment, all eukaryotes
breakdown of large molecules (e.g., proteins + polysaccharides)
involved in the organization of the mitotic spindle and in the completion of cytokinesis
an organelle that serves as the main microtubule organizing center of the animal cell as well as a regulator of cell-cycle progression Although the centrosome has a key role in efficient mitosis in animal cells, it is not necessary
series of events that takes place in a cell leading to its division and duplication (replication)
In cells with a nucleus (eukaryotes), the cell cycle can be divided in two periods: interphase—during which the cell grows, accumulating nutrients needed for mitosis and duplicating its DNA—and the mitosis (M) phase, during which the cell splits itself into two distinct cells, often called “daughter cells”.
phase of the cell cycle in which the cell spends the majority of its time and performs the majority of its purposes including preparation for cell division, increases its size and makes a copy of its DNA. gets itself ready for mitosis or meiosis
mitotic m phase
mitosis separates the chromosomes in its cell nucleus into two identical sets in two nuclei. It is followed by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells. Mitosis and cytokinesis together define the mitotic (M) phase of the cell cycle – the division of the mother cell into two daughter cells, genetically identical to each other and to their parent cell.
stages are interphase, prophase, prometaphase, metaphase, anaphase and telophase. During the process of mitosis the pairs of chromosomes condense and attach to fibers that pull the sister chromatids to opposite sides of the cell. The cell then divides in cytokinesis, to produce two identical daughter cells.
usually composed of metal cations and nonmetal anions, are electrically neutral, usually solid crystals at room temp, high melting point
*not named with prefixes
made up of molecules, nonmetallic, solid liquid or gas, low melting point ex: carbon monoxide, water
*only compound named with prefixes
two or more atoms of the same element, electrically neutral, smallest unit of a substance that retains the properties of that substance ex: O2
metals, positive, name is same as element like sodium cation Na+ and atomic sodium Na
nonmetals, negative, name typically ends in -ide like sulfide
compounds that produce hydrogen ions when dissolved in water, combination of anions connected to as many hydrogen ions as are needed to make the molecule electrically neutral
naming binary compound
*name ends in -ide
*if nonmetallic it is binary molecular; use prefix (N2O3 dinitrogen trioxide)
*If metallic and in group A name ions (BaS barium sulfide)
*if metallic not group A name ions and use roman numeral with cation (FeCl2 iron (II) chloride)
compound is an acid?
Starts with “H” (HNO3 nitric acid)
name a polyatomic ion compound
*name ends with -ite or -ate
*First element in group A, name the ions (Li2CO3 lithium carbonate)
*not in group A, name the ions use roman numerals with the cation (CuSO4 copper (II) sulfate)
-ite or -ate
polyatomic ion that included oxygen in the formula
indicates a binary compound- two nonmetallic elements, prefixes are used to indicate how many atoms of each are present
gram atomic mass
mass of one mole (6.02×10^23 atoms) of an element
gram molecular mass
mass of one mole of a molecular compound
gram formula mass
mass of one mole of an ionic compound
mass in grams of one mole of the substance
*multiply the number of moles of a substance by the molar mass to get the mass of the substance
*divide mass of substance by molar mass to get number of moles
one mole of any gas at STP
occupies a volume of 22.4 L
(STP= 1atm pressure, 0deg C)
*density of any gas at STP is its molar mass divided by 22.4 L
IUPAC nomenclature of organic compounds: alkanes
compounds that consist only of the elements carbon (C) and hydrogen (H) (i.e., hydrocarbons), wherein these atoms are linked together exclusively by single bonds (i.e., they are saturated compounds).
take the suffix “-ane” and are prefixed depending on the number of carbon atoms in the chain
1=meth, 2=eth, 3=prop ex:methane propane butane
IUPAC nomenclature: alkenes and alkynes
**Alkenes are unsaturated compound containing at least one carbon to carbon double bond
Alkenes are named for their parent alkane chain with the suffix “-ene” and an infixed number indicating the position of the double-bonded carbon in the chain
**Alkynes have a tripple bond between two carbons
are named using the same system, with the suffix “-yne” indicating a triple bond
IUPAC nomenclature: alcohols
Alcohols (R-OH) take the suffix “-ol” with an infix numerical bonding position prefix hydroxy-
IUPAC nomenclature: amines
Amines (R-NH2) organic compounds and functional groups that contain a basic nitrogen atom with a lone pair.
are named for the attached alkane chain with the suffix “-amine” (e.g. CH3NH2 Methyl Amine)
ex: amino acids
synonym of saccharide, organic compound with the empirical formula Cm(H2O)n, that is, consists only of carbon, hydrogen and oxygen, with the last two in the 2:1 atom ratio.
divided into four chemical groupings: monosaccharides & disaccharides (sugars end in -ose), oligosaccharides, and polysaccharides (starch glycogen cellulose)
when electrons are shared to form an octet
between atoms with same electronegativity, nonpolar
between atoms with differing electronegativity, polar
a hydrogen covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of another electronegative atom, strong relative to other dipole interactions
involves a metal and a nonmetal ion (or polyatomic ions such as ammonium) through electrostatic attraction. In short, it is a bond formed by the attraction between two oppositely charged ions.
preferable to use the term metallic bonding, because this type of bonding is collective in nature and a single “metallic bond” does not exist, electrons are shared over many nuclei allows for electrical conductivity
ideal gas law
combination of Boyle’s law and Charles’s law. It can also be derived from kinetic theory.
The state of an amount of gas is determined by its pressure, volume, and temperature. The modern form of the equation is:
pV = nRT
where p is the absolute pressure of the gas; V is the volume; n is the amount of substance; R is the gas constant; and T is the absolute temperature.
For a fixed amount of an ideal gas kept at a fixed temperature, P [pressure] and V [volume] are inversely proportional (while one increases, the other decreases)
At constant pressure, the volume of a given mass of an ideal gas increases or decreases by the same factor as its temperature on the absolute temperature scale (i.e. the gas expands as the temperature increases)
a kind of redox reaction in which any combustible substance combines with an oxidizing element, usually oxygen, to generate heat and form oxidized products
which atoms have their oxidation number (oxidation state) changed. This can be either a simple redox process, such as the oxidation of carbon to yield carbon dioxide (CO2) or the reduction of carbon by hydrogen to yield methane (CH4), or a complex process such as the oxidation of sugar(C6H12O6) in the human body through a series of complex electron transfer processes.
is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.
is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.
Electroplating is a plating process that uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal. The part to be plated is the cathode of the circuit. The anode is made of the metal to be plated on the part. Both components are immersed in a solution electrolyte containing one or more dissolved metal salts that permit the flow of electricity. A power supply supplies a direct current to the anode, oxidizing its metal atoms, dissolving in the solution. At the cathode, the dissolved metal ions in the electrolyte solution are reduced at the interface between the solution and the cathode, such that they “plate out” onto the cathode.
refers to “reduction division” because homologues chromosomes separate and the 2 haploid daughter cells have only half the chromosome number
chromosome pairs of the same length, centromere position, and staining pattern with genes for the same characteristics at corresponding loci. One homologous chromosome is inherited from the organism’s mother, the other from the organism’s father.
meiosis 1 phases
prophase 1, metaphase 1, anapahse 1, telophase 1 and cytokinesis
meiosis 2 phases
Prophase II Metaphase II Anaphase II Telophase II
*Chromosomes condense and attach to the nuclear envelope.
*Synapsis occurs (pair of homologous chromosomes lines up closely together), tetrad is formed, tetrad is composed of four chromatids.
*Crossing over may occur.
*Chromosomes thicken and detach from the nuclear envelope
*centrioles migrate away from one another and both the nuclear envelope and nucleoli break down
*chromosomes begin their migration to the metaphase plate
exchange of sections of genetic material between homologous chromosomes during prophase I of meiosis
Tetrads align at the metaphase plate.
Tetrads align at the metaphase plate.
the centromeres of homologous chromosomes are oriented toward the opposite cell poles.
the paired chromosomes consisting of four chromatids
the region of the chromosome that holds the two sister chromatids together during mitosis
*Chromosomes move to the opposite cell poles. Similar to mitosis, the microtubules and the kinetochore fibers interact to cause the movement.
Unlike in mitosis, the homologous chromosomes move to opposite poles yet the sister chromatids remain together.
Replicated forms of a chromosome joined together by the centromere and eventually separated during mitosis or meiosis II.
The spindles continue to move the homologous chromosomes to the poles.
Once movement is complete, each pole has a haploid number of chromosomes
In most cases, cytokinesis occurs at the same time as telophase I.
At the end of telophase I and cytokinesis, two daughter cells are produced, each with one half the number of chromosomes of the original parent cell.
Depending on the kind of cell, various processes occur in preparation for meiosis II. There is however a constant: The genetic material does not replicate again.
the disappearance of the nucleoli and the nuclear envelope again as well as the shortening and thickening of the chromatids. Centrioles move to the polar regions and arrange spindle fibers for the second meiotic division
* The chromosomes line up at the metaphase II plate at the cell’s center.
* The kinetochores of the sister chromatids point toward opposite poles.
the centromeres contain two kinetochores that attach to spindle fibers from the centrosomes (centrioles) at each pole. The new equatorial metaphase plate is rotated by 90 degrees when compared to meiosis I, perpendicular to the previous plate
Meiosis II is the second part of the meiotic process. Much of the process is similar to mitosis. The end result is production of four haploid cells (23 chromosomes, 1N in humans) from the two haploid cells (23 chromosomes, 1N * each of the chromosomes consisting of two sister chromatids) produced in meiosis I. The four main steps of Meiosis II are: Prophase II, Metaphase II, Anaphase II, and Telophase II
where the centromeres are cleaved, allowing microtubules attached to the kinetochores to pull the sister chromatids apart. The sister chromatids by convention are now called sister chromosomes as they move toward opposing poles.
is similar to telophase I, and is marked by uncoiling and lengthening of the chromosomes and the disappearance of the spindle. Nuclear envelopes reform and cleavage or cell wall formation eventually produces a total of four daughter cells, each with a haploid set of chromosomes. Meiosis is now complete and ends up with four new daughter cells.
meiosis generates genetic diversity
in two ways: (1) independent alignment and subsequent separation of homologous chromosome pairs during the first meiotic division allows a random and independent selection of each chromosome segregates into each gamete; and (2) physical exchange of homologous chromosomal regions by homologous recombination during prophase I results in new combinations of DNA within chromosomes.
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly equal shares of these cellular components.
a cell grows (G1), continues to grow as it duplicates its chromosomes (S), grows more and prepares for mitosis (G2), and finally it divides (M) before restarting the cycle.
In plant cells only. In highly vacuolated plant cells, the nucleus has to migrate into the center of the cell before mitosis can begin. This is achieved through the formation of a phragmosome, a transverse sheet of cytoplasm that bisects the cell along the future plane of cell division. the formation of a ring of microtubules and actin filaments (called preprophase band) underneath the plasma membrane around the equatorial plane of the future mitotic spindle.
(Normally, the genetic material in the nucleus is in a loosely bundled coil called chromatin)
*chromatin condenses together into a highly ordered structure called a chromosome.
*genetic material has already been duplicated earlier in S phase
*replicated chromosomes have two sister chromatids, bound together at the centromere by the cohesion complex
The nuclear envelope disassembles and microtubules invade the nuclear space. This is called open mitosis, and it occurs in most multicellular organisms.
Each chromosome forms two kinetochores at the centromere, one attached at each chromatid.
a complex protein structure that is analogous to a ring for the microtubule hook; it is the point where microtubules attach themselves to the chromosome
When a microtubule connects with the kinetochore, the motor activates, using energy from ATP to “crawl” up the tube toward the originating centrosome. This motor activity provides the pulling force necessary to later separate the chromosome’s two chromatids.
In the fishing pole analogy, the kinetochore would be the “hook” that catches a sister chromatid or “fish”. The centrosome acts as the “reel” that draws in the spindle fibers or “fishing line”.
the centromeres of the chromosomes convene along the metaphase plate or equatorial plane, an imaginary line that is equidistant from the two centrosome poles
proteins that bind sister chromatids are cleaved, separating into distinct sister chromosomes.
they are pulled apart by shortening kinetochore microtubules and move toward the respective centrosomes to which they are attached.
Next, the nonkinetochore microtubules elongate, pulling the centrosomes (and the set of chromosomes to which they are attached) apart to opposite ends of the cell.
These two stages are sometimes called early and late anaphase
is a reversal of prophase events. It “cleans up” the after effects of mitosis.
the nonkinetochore microtubules continue to lengthen, elongating the cell even more. Corresponding sister chromosomes attach at opposite ends of the cell. A new nuclear envelope forms around each set of separated sister chromosomes.
Both sets of chromosomes, now surrounded by new nuclei, unfold back into chromatin. Mitosis is complete, but cell division is not yet complete.
is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent. ratio of solute to solvent stays the same, won’t settle out. Substance present in larger amount is solvent.
Solvents can be gases, liquids, or solids. The solution has the same physical state as the solvent.
point at which a solution of a substance can dissolve no more of that substance and additional amounts of it will appear as a precipitate. This point of maximum concentration, the saturation point, depends on the temperature of the liquid, pressure, contaminates, as well as the chemical nature of the substances involved.The solubility of liquids in liquids is generally less temperature-sensitive than that of solids or gases.
a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances.
are prepared or result when some condition of a saturated solution is changed, for example temperature, volume (as by evaporation), or pressure
Carbonated water is a supersaturated solution of carbon dioxide gas in water. At the elevated pressure in the bottle, more carbon dioxide can dissolve in water than at atmospheric pressure. At atmospheric pressure, the carbon dioxide gas escapes very slowly from the supersaturated liquid. This process may be accelerated by the presence of nucleation sites within the solution, such as small bubbles, caused by shaking the bottle, or another solute, such as sugar powder or a widget. A Diet Coke and Mentos eruption is a rather extreme example.
*is any substance containing free ions that make the substance electrically conductive.
*most typical is an ionic solution
*commonly exist as solutions of acids, bases or salts
*normally formed when a salt is placed into a solvent such as water and the individual components dissociate due to the thermodynamic interactions between solvent and solute molecules, in a process called solvation
a compound unable to ionize and does not conduct electricity
the process of attraction and association of molecules of a solvent with molecules or ions of a solute.
As ions dissolve in a solvent they spread out and become surrounded by solvent molecules
involves different types of intermolecular interactions: hydrogen bonding, ion-dipole, and dipole-dipole attractions or van der Waals forces.
hydrogen bonding, ion-dipole, and dipole-dipole interactions occur only in polar solvents. Ion-ion interactions occur only in ionic solvents
distinct from dissolution and solubility. Dissolution is a kinetic process, and is quantified by its rate. Solubility quantifies the dynamic equilibrium state achieved when the rate of dissolution equals the rate of precipitation.
reacts with metals and carbonates, turns blue litmus paper red, and has a pH less than 7.0 in its standard state
Acids can occur in solid, liquid or gaseous form, depending on the temperature. They can exist as pure substances or in solution
Reactions of acids are often generalized in the form
HA <--> H+ + A−
where HA represents the acid and A− is the conjugate base. Acid-base conjugate pairs differ by one proton, and can be interconverted by the addition or removal of a proton
the stronger of two acids will have a higher disassociation constant (k suba)
pKa = -log10 Ka. Stronger acids have a smaller pKa than weaker acids
assigned by computing the difference between the number of valence electrons that a neutral atom of that element would have and the number of electrons that “belong” to it in the Lewis structure.
electrons in a bond between atoms of different elements belong to the most electronegative atom; electrons in a bond between atoms of the same element are split equally, and electrons in a lone pair belong only to the atom with the lone pair.
while in ions the algebraic sum of the oxidation states of the constituent atoms must be equal to the charge on the ion.
are named according to their anions. That ionic suffix is dropped and replaced with a new suffix (and sometimes prefix). For example, HCl has chloride as its anion, so the -ide suffix makes it take the form hydrochloric acid.
strong vs weak acid
refers to its ability or tendency to lose a proton. A strong acid is one that completely dissociates in water; in other words, one mole of a strong acid HA dissolves in water yielding one mole of H+ and one mole of the conjugate base, A−, and none of the protonated acid HA | 0.842478 | 3.153931 |
When we look up at the night sky outside of the bright city, we can see a dazzling array of stars and galaxies. It is more difficult to see the clouds of gas within galaxies, however, but gas is required to form new stars and allow galaxies to grow. Although gas makes up less than 1% of the matter in the universe, “it’s the gas that drives the evolution of the galaxy, not the other way around,” says Felix “Jay” Lockman of the National Radio Astronomy Observatory (NRAO).
With radio telescopes and surveys such as the Green Bank Telescope (GBT) in West Virginia, the Atacama Large Millimeter/submillimeter Array (ALMA), and the Arecibo Legacy Fast ALFA (ALFALFA) survey, Lockman and other astronomers are learning more about the role of gas in galaxy formation. They presented their results at the annual American Association for the Advancement of Science (AAAS) meeting in San Jose.
Although we have an excellent view of our part of the Milky Way, and we can tell that it has a disk-shaped structure — that is the origin of its name, after all — it is not so simple to study how the galaxy formed. Lockman described the situation with an analogy: if you were trying to understand how your own house was built without leaving it, you would look and listen throughout the house and you would look out the window to learn what you can from your neighbors’ homes. Andromeda is the Milky Way’s largest neighbor, and they both have “satellite” galaxies traveling around them, some of which appear to have gas.
In addition, Lockman and his colleagues found clouds of gas between Andromeda and one of its satellites, Triangulum, which could be a “source of fuel for future star formation” for the galaxies. As a dramatic example of high-velocity clouds, Lockman presented new GBT images of the Smith Cloud, which was first discovered in 1963 by a student in the Netherlands. The Smith Cloud is a newcomer to the Milky Way and could provide enough gas to form a million stars and solar systems. Based on its speed and trajectory, “we think in a few million years, splash!” as it collides with our galaxy.
Kartik Sheth, another scientist at NRAO, continued with a description of astronomers’ current state of knowledge of the assembly of disk and spiral galaxies, of which the Milky Way and Andromeda are only two examples. Spiral galaxies typically have many gas clouds forming new stars, often referred to as stellar nurseries, and now with ALMA, “a fantastic telescope at 16,500-ft elevation,” Sheth and his colleagues are studying them in more detail.
In particular, Sheth presented newly published results by Adam Leroy in the Astrophysical Journal, in which they examine star-forming clouds in the heart of the nearby starbursting galaxy, Sculptor, to study “the physics of how gas got converted into stars.” Sculptor and other starbursts form stars at a rate about 1,000 times faster than typical spiral galaxies like the Milky Way. “Only with ALMA can we actually accomplish observations like this” of objects outside our galaxy. By comparing the concentration and distribution of ten gas clouds in Sculptor, they find that the clouds are more massive, ten times denser, and more turbulent than similar clouds in more typical galaxies. Because of the density of these stellar nurseries, they can form stars much more efficiently.
Other astronomers at the AAAS meeting, such as Claudia Scarlata (University of Minnesota) and Eric Wilcots (University of Wisconsin), presented a larger-scale picture of how spiral galaxies collide with each other to form more massive elliptical-shaped galaxies. These galaxies typically appear older and have stopped forming stars, but they can grow by “merging” with a neighboring galaxy in its group. “I will contend that most galaxy transformations take place in groups,” says Wilcots. In a paper based on ALFALFA data published in the Astronomical Journal, Kelley Hess and Wilcots find gas-rich galaxies distributed primarily in the outskirts of groups, and therefore these systems tend to grow from the inside out.
In a related issue, both Priyamvada Natarajan (Yale University) and Scarlata discussed how the evolution of massive black holes at the centers of galaxies appear to be related to that of the galaxy as a whole, when astronomers follow them from “cradle to adulthood.” In particular, Natarajan explained how mature galaxies’ black holes can heat the gas in a galaxy and drive gas outflows, thus preventing continued star formation in the galaxy.
Finally, astronomers look forward to much more upcoming cutting-edge research on gas in galaxies. Ximena Fernández (Columbia University) described the COSMOS HI Large Extragalactic Survey (CHILES) of hydrogen gas in galaxies with the Very Large Array. They have completed a pilot survey so far, in which they have obtained the most distant detection so far of a galaxy containing gas. They plan to peer even further into the distant past than previous surveys, expecting to detect gas in 300 galaxies up to 5 billion light-years away—250 times further than the galaxy observed by Leroy.
Fernández also described MeerKAT, a radio telescope under construction in South Africa, and the Deep Investigation of Neutral Gas Origins (DINGO) in Australia, both of which will serve as precursors for the Square Kilometer Array in the 2020s. These new telescopes will add to astronomers’ increasingly complex view of the formation and evolution of galaxies. | 0.804998 | 4.030101 |
Citizen science project discovers new brown dwarf
One night three months ago, Rosa Castro finished her dinner, opened her laptop, and uncovered a novel object that was neither planet nor star. Therapist by day and amateur astronomer by night, Castro joined the NASA-funded Backyard Worlds: Planet 9 citizen science project when it began in February—not knowing she would become one of four volunteers to help identify the project's first brown dwarf, formally known as WISEA J110125.95+540052.8.
After devoting hours to skimming online, publicly available "flipbooks" containing time-lapse images, she spotted a moving object unlike any other. The search process involves fixating on countless colorful dots, she explained. When an object is different, it simply stands out. Castro, who describes herself as extremely detail oriented, has contributed nearly 100 classifications to this specific project.
A paper about the new brown dwarf was published on May 24 in The Astrophysical Journal Letters. Four citizen scientists are co-authors of the paper, including Castro. Since then, Backyard Worlds: Planet 9 has identified roughly 117 additional brown dwarf candidates.
The collaboration was inspired by the recently proposed ninth planet, possibly orbiting at the fringes of our solar system beyond Pluto.
"We realized we could do a much better job identifying Planet Nine if we opened the search to the public," said lead researcher Marc Kuchner, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Along the way, we're hoping to find thousands of interesting brown dwarfs."
It's been roughly two decades since researchers first discovered brown dwarfs, and the scientific community opened its eyes to this new class of objects between stars and planets. Although they are as common as stars and form in much the same way, brown dwarfs lack the mass necessary to sustain nuclear fusion reactions. They therefore do not have the energy to maintain their luminosity, so they slowly cool over the course of their lifetimes. Their low temperatures also render them intrinsically dim.
For years, Kuchner has been fascinated by infrared images of the entire sky captured by NASA's Wide-field Infrared Survey Explorer (WISE), launched in 2009. The space telescope is specially designed to observe cold objects emitting light at long wavelengths—objects like brown dwarfs. With its initial mission complete, WISE was deactivated in 2011. It was then reactivated in 2013 as NEOWISE, a new mission funded by the NEO Observations Program with a different goal: to search for potentially hazardous near-Earth objects (NEOs).
Previously, Kuchner had focused on stationary objects seen by WISE. But the Backyard Worlds: Planet 9 project shows the WISE and NEOWISE data in a way custom-tailored for finding fast-moving objects. His team layers many images of the same location to create a single, comprehensive snapshot. These are then combined with several similarly "co-added" pictures to form flipbooks that show motion over time.
Anyone with internet access can scour these flipbooks and click on anomalies. If they would like to call the science team's attention to an object they found, they can submit a report to the researchers or share their insights on a public forum. Kuchner and his colleagues then follow up the best candidates using ground-based telescopes to glean more information.
According to Backyard Worlds: Planet 9 citizen scientist Dan Caselden, participants are free to dig as deep into the results as they choose. A security researcher by trade, Caselden developed a series of tools allowing fellow participants to streamline their searches and visualize their results, as well as aggregate various user statistics. He also helped identify several of the additional brown dwarf candidates while the first discovery was being confirmed.
Kuchner and his co-author, Adam Schneider of Arizona State University, Tempe, agree WISEA J110125.95+540052.8 is an exciting discovery for several reasons. "What's special about this object—besides the way it was discovered—is that it's unusually faint," Schneider said. "That means our citizen scientists are probing much deeper than anyone has before."
While computers efficiently sift through deluges of data, they can also get lost in details that human eyes and brains easily disregard as irrelevant.
However, mining this information is extremely arduous for a single scientist or even a small group of researchers. That's precisely why collaborating with an enthusiastic public is so effective—many eyes catch details that one pair alone could miss.
While Kuchner is delighted by this early discovery, his ultimate goal for Backyard Worlds: Planet 9 is to find the smallest and coldest brown dwarfs, called Y dwarfs. Some of these Y dwarfs many even be lurking closer to us than Proxima Centauri, the nearest star to the sun.
Their low temperatures make Y dwarfs extremely dim, according to Adam Burgasser at the University of California San Diego. "They're so faint that it takes quite a bit of work to pull them from the images, that's where Kuchner's project will help immensely," he said. "Anytime you get a diverse set of people looking at the data, they'll bring unique perspectives that can lead to unexpected discoveries."
Kuchner anticipates the Backyard Worlds effort will continue for several more years—allowing more volunteers like Caselden and Castro to contribute.
As Castro put it: "I am not a professional. I'm just an amateur astronomer appreciating the night sky. If I see something odd, I'll admire and enjoy it."
Backyard Worlds: Planet 9 is a collaboration between NASA, UC Berkeley, the American Museum of Natural History in New York, Arizona State University, the Space Telescope Science Institute in Baltimore and Zooniverse, a collaboration of scientists, software developers and educators who collectively develop and manage citizen science projects on the internet.
NASA's Jet Propulsion Laboratory in Pasadena, California, manages the NEOWISE mission for NASA's Planetary Defense Coordination Office within the Science Mission Directorate in Washington. The Space Dynamics Laboratory in Logan, Utah, built the science instrument. Ball Aerospace & Technologies Corp. of Boulder, Colorado, built the spacecraft. Science operations and data processing take place at the Infrared Processing and Analysis Center at Caltech in Pasadena. Caltech manages JPL for NASA. | 0.88179 | 3.610344 |
A mission dubbed BepiColombo is bound for Mercury, but in order to reach its destination, it needs to take the scenic route, beginning with a flyby of Earth later this month, during which skywatchers may be able to spot the probe.
BepiColombo, which launched in October 2018, is a joint project of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA). The mission is scheduled to arrive at Mercury in December 2025, when it will split into two component spacecraft and begin observing the tiniest planet in our solar system up close. But, in order to reach the small planet, BepiColombo will need to complete a total of nine planetary flybys in order to achieve the right speed to orbit its target. The first of these flybys will be the only one of Earth and it happens on April 10.
“This is the last time we will see BepiColombo from Earth,” Joe Zender, BepiColombo deputy project scientist at ESA, said in a statement. “After that it will head deeper into the inner solar system.”
This maneuver was scheduled long ago, but the spread of the COVID-19 pandemic on Earth has threatened ESA’s ability to prepare as desired for the flyby. In response to the pandemic, the agency put four other missions into safe hold mode, pausing their science operations for more than a week in order to prioritize flyby preparations. (Those missions have resumed normal activity, according to an ESA statement released April 2.)
“The Earth swing-by is a phase where we need daily contact with the spacecraft,” Elsa Montagnon, BepiColombo spacecraft operations manager at ESA, said in the statement. “This is something that we cannot postpone. The spacecraft will swing by Earth independently in any case.”
But spacecraft personnel would very much prefer to be on hand for the maneuver, rather than leave BepiColombo to do it alone. That concern is in part because the flyby is one step that will determine the success of the entire mission.
During this flyby, the spacecraft will be carefully aligned with Earth so that the probe slows down a smidge, about 3 miles (5 kilometers) per second, compared to the sun, which will send it deeper into the heart of the solar system. The nudge will align the spacecraft for two similar flybys of Venus this October and in August 2021 that will also tweak the probe’s trajectory.
BepiColombo will make its closest approach to Earth on April 10 at 12:25 a.m. EST (425 GMT), when it will be 7,877 miles (12,677 km) away, according to a website set up by Italian National Institute for Astrophysics, which is participating in the mission.
During the flyby, skywatchers may be able to catch sight of the spacecraft with a telescope or relatively large binoculars, although the brightness of a fairly full moon will reduce visibility. Skywatchers near the equator, particularly in the Southern Hemisphere, will have the best odds of spotting the probe, according to viewing tips provided by ESA.
Whether or not you can spot BepiColombo, the spacecraft will be looking toward you. Scientists on the mission will be using the maneuver as an opportunity to test some of the instruments on board the probe. Among the devices that will make observations are magnetometers, a host of particle detectors, an infrared spectrometer and, of course, a trio of cameras.
“We will see the Earth approaching and getting bigger,” Zender said in the statement. “When it reaches the nearest point, we will take a few images, and then we are planning to capture a whole sequence of photographs over several hours looking at the Earth-moon system as it gets smaller and smaller until we lose it completely.” | 0.851353 | 3.061699 |
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