Asteroids Can Create Their Own Mini Planetary Systems

Illustration of a binary asteroid. Credit: Courtesy ESO/L. Calcada

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From a University of Colorado-Boulder press release:

While the common perception of asteroids is that they are giant rocks lumbering about in orbit, a new study shows they actually are constantly changing “little worlds” that can give birth to smaller asteroids that split off to start their own lives as they circle around the sun.

Astronomers have known that small asteroids get “spun up” to fast rotation rates by sunlight falling on them, much like propellers in the wind. The new results show when asteroids spin fast enough, they can undergo “rotational fission,” splitting into two pieces which then begin orbiting each other. Such “binary asteroids” are fairly common in the solar system.

An international team of astronomers led by Petr Pravec of the Astronomical Institute in the Czech Republic found that many of these binary asteroids do not remain bound to each other but escape, forming two asteroids in orbit around the sun when there previously was just one. The study appears in the Aug. 26 issue of Nature.

The researchers studied 35 so-called “asteroid pairs,” separate asteroids in orbit around the sun that have come close to each other at some point in the past million years — usually within a few miles, or kilometers — at very low relative speeds. They measured the relative brightness of each asteroid pair, which correlates to its size, and determined the spin rates of the asteroid pairs using a technique known as photometry.

“It was clear to us then that just computing orbits of the paired asteroids was not sufficient to understand their origin,” said Pravec. “We had to study the properties of the bodies. We used photometric techniques that allowed us to determine their rotation rates and study their relative sizes.”

The research team showed that all of the asteroid pairs in the study had a specific relationship between the larger and smaller members, with the smallest one always less than 60 percent of the size of its companion asteroid.

The conclusion fits a theory of binary asteroid formation originated by co-author Daniel Scheeres, from the University of Colorado, Boulder. His theory predicts that if a binary asteroid forms by rotational fission, the two can only escape from each other if the smaller one is less than 60 percent the size of the larger asteroid. Of all the asteroid pairs in the study, the smallest of each pair was always less than 60 percent of the mass of its companion asteroid.

Scheeres’ theory predicts that if a binary asteroid forms by rotational fission, the two can only escape from each other if the smaller one is less than 60 percent of the size of the larger asteroid. When one of the asteroids in the pair is small enough, it can “make a break for it” and escape the orbital dance, essentially moving away to start its own “asteroid family,” he said. During rotational fission, the asteroids separate gently from each other at relatively low velocities.

“This is perhaps the clearest observational evidence that asteroids aren’t just large rocks in orbit about the sun that keep the same shape over time,” said Scheeres. “Instead, they are little worlds that may be constantly changing as they grow older, sometimes giving birth to smaller asteroids that then start their own life in orbit around the sun.”

Read more at the University of Colorado-Boulder.

WISE Cryostat is Depleting

An image released in August 2010 from WISE image of the Small Magellanic Cloud. Image credit: NASA/JPL-Caltech/WISE Team

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NASA’s Wide-field Infrared Survey Explorer, or WISE, is losing its cool. The spacecraft is running out of the frozen coolant needed to keep its heat-sensitive instrument chilled, and will only be in operation for 2-3 more months. While the spacecraft was designed to be rather short-lived – 7 to 10 months — it still is sad to see the mission winding down. But WISE has completed its primary mission, a full scan of the entire sky in infrared light, which was accomplished by July 17, 2010. The mission has taken more than 1.5 million snapshots so far, uncovering hundreds of millions of objects, including asteroids, stars and galaxies. It has discovered more than 29,000 new asteroids to date, more than 100 near-Earth objects and 15 comets.

The telescope has two coolant tanks that keep the spacecraft’s normal operating temperature at 12 Kelvin (minus 438 degrees Fahrenheit). The outer, secondary tank is now depleted, causing the temperature to increase. One of WISE’s infrared detectors, the longest-wavelength band most sensitive to heat, stopped producing useful data once the telescope warmed to 31 Kelvin (minus 404 degrees Fahrenheit). The primary tank still has a healthy supply of coolant, and data quality from the remaining infrared detectors remains high.

WISE is continuing a second survey of about one-half the sky as originally planned. It’s possible the remaining coolant will run out before that scan is finished. Scientists say the second scan will help identify new and nearby objects, as well as those that have changed in brightness. It could also help to confirm oddball objects picked up in the first scan.

NASA is hoping to find more Near Earth Objects with WISE’s remaining days of operations.
“WISE’s prime mission was to do an infrared background map,” said Lindley Johnson, program executive for the Near-Earth Objects Observation program at NASA, speaking at a workshop this week to define objectives for exploring asteroids. “But we realized in talking with scientists that it would also make a good asteroid detector by comparing images. It has done a good job of finding a lot of objects for us.”

Source: NASA

WISE Mission Completes All-sky Infrared Survey

This view of the Pleiades star cluster is a composite of hundreds of WISE images, a tiny fraction of all those collected to complete the full-sky survey. Image credit: NASA/JPL-Caltech/UCLA

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If you take a lot of digital pictures, you’re probably familiar with the frustration of keeping track of dozens of files, and always running out of hard drive space to store them. Well, the scientists and engineers on NASA’s Wide-field Infrared Survey Explorer (WISE) mission have no pity for you. Their spacecraft just finished photographing the entire sky in exquisite detail: a total of 1.3 million photos.

“The eyes of WISE have not blinked since launch,” said William Irace, the mission’s project manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Both our telescope and spacecraft have performed flawlessly and have imaged every corner of our universe, just as we planned.”

WISE surveys the sky in strips as it orbits the earth. It takes six months of constant observing to map the entire sky. By pointing at every part of the sky, astronomical surveys deliver excellent data covering both well-known objects and those that have never been seen before.

“WISE is filling in the blanks on the infrared properties of everything in the universe from nearby asteroids to distant quasars,” said Peter Eisenhardt of JPL, project scientist for WISE. “But the most exciting discoveries may well be objects we haven’t yet imagined exist.”

One example of a well-known object seen in new light by WISE is the Pleiades cluster: a group of young blue stars shrouded by dust that the cluster is currently passing through. In WISE’s false-color infrared vision, the hot stars look blue but the cooler dust clouds give off longer wavelengths of infrared light, causing them to glow in shades of yellow and green.

The WISE survey is particularly significant because such a wide range of objects in the universe are visible in infrared light. Giant molecular clouds glow in infrared light, as do brown dwarfs – objects that are bigger than planets but smaller than true stars. WISE can also see ultra-bright, extremely distant galaxies whose visible light has been stretched into the infrared by the expansion of the universe during its multi-billion-year journey.

The recently completed WISE survey also observed 100,000 asteroids in our solar system, many of which had never been seen before. 90 of the newly discovered asteroids are near-earth objects, whose orbits cross our own, making them potentially dangerous but also potential targets for future mission.

You might think that 1.3 million pictures would be plenty, but WISE will keep mapping the sky for another three months, covering half of the sky again and allowing astronomers to search for changes. The mission will end when the spacecraft’s solid hydrogen coolant finally runs out and the infrared detectors warm up (they don’t work as well when they are warm enough to emit the same wavelengths of infrared light that they are meant to detect).

But even as the telescope warms up, the astronomers on the WISE team will just be getting warmed up too. With nearly two million images, they will be busy making new discoveries for years to come.

Hayabusa Sample Return Capsule Retrieved

Hayabusa's sample return cannister and parachute on the ground in the Australian outback. Credit: JAXA

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Scientists from Japan were given the go-ahead to retrieve the sample return capsule from the Hayabusa spacecraft, which is hoped to contain the first piece of asteroid ever brought to Earth, perhaps providing insight into the origins of asteroids – and our universe. The capsule was ejected three hours before reaching Earth, and the sample canister descended through Earth’s atmosphere, preceding the spacecraft which broke up in spectacular fashion (click here to see the video) over the Australian Outback. The capsule lay in the Woomera Prohibited Area until morning when Aboriginal elders deemed it had not landed in any indigenous sacred sites, giving the OK for the scientists to retrieve it.

The insulated and cushioned re-entry capsule, 40 cm in diameter and 25 cm deep has a mass of about 20 kg. The capsule had a convex nose covered with a 3 cm thick ablative heat shield to protect the samples from the high velocity (~13 km/s) re-entry.

Apparently, it landed right on target. The director of the Woomera test range, Doug Gerrie, said the probe had completed a textbook landing in the South Australian desert. “They landed it exactly where they nominated they would.

Hayabusa's heat shield was also recovered from the Australian outback. Credit: JAXA

The capsule will remain sealed until it arrives at the JAXA facility near Tokyo, and may remain unopened for weeks as it undergoes testing.

The mission launched in 2003, and endured a series of technical glitches over its five-billion-kilometer (three-billion-mile) journey to the asteroid Itokawa and back. A large solar flare in late 2003 “injured” the solar panels, providing less power to Hayabusa’s ion engines, delaying the rendezvous with the asteroid. Then, as the spacecraft approached Itokawa, Hayabusa lost the use of its Y-axis reaction wheel. While it flew near the asteroid and sent back data, scientists and engineers aren’t sure if the spacecraft was successful in obtaining samples, as while it appears Hayabusa landed briefly, it is not certain the “bullets” fired to stir up dust for the container to capture. The return to Earth was delayed by three years from more thruster and navigational failures, but the JAXA team nursed and coaxed the spacecraft back home to a spectacular return. There was concern that the parachute batteries may be been depleted due to the extra time it took to get back to Earth, but obviously they worked quite well.

Sources: JAXA, NASA, AFP

Hayabusa on the Homestretch on Return to Earth

Hayabusa's sample return capsule descends under parachute toward the Woomera desert, Australia. Credit: Corby Waste and Tommy Thompson for NASA / JPL

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After overcoming multiple serious glitches, and a three-year delay in its four billion miles (six billion kilometers) round-trip journey, JAXA’s Hayabusa spacecraft is expected to land in Australia around 14:00 UTC on Sunday, June 13; (midnight local time in Australia, 11 pm in Japan and 11:00 a.m. ET in the US). Scientists and space enthusiasts alike are hoping there is some precious cargo aboard in the sample return capsule: dust from an asteroid.

The latest word from JAXA, as of this writing, is that all systems were doing well on Hayabusa. The teams assessed the trajectory of Hayabusa and confirmed that everything was nominal.

If all goes well, Hayabusa will release a canister that will land in the Woomera Prohibited Area in the outback of South Australia; Hayabusa itself will follow, putting on a show over Australia as it breaks up and incinerates in Earth’s atmosphere.

You can follow the landing in several ways. A NASA team will be attempting to observe the re-entry of Hayabusa in a DC-8 plane, and they hope to have a webcast at this link.

There will be a “Hayabusa Live” website and a Hayabusa blog will be updated frequently, plus this Hayabusa Twitter feed.

Here’s a link to a finder chart and more from Paul Floyd at his website, Night Sky Online.

The Hayabusa spacecraft, formerly known as MUSES-C launched on May 9, 2003 and rendezvoused with the asteroid Itokawa in mid-September 2005. Hayabusa studied the asteroid’s shape, spin, topography, color, composition, density, and history. Then in November 2005, it attempted to land on the asteroid to collect samples but failed to do so. However, it is hoped that some dust swirled into the sampling chamber. You can listen to Universe Today writer Steve Nerlich (from Cheap Astronomy) tell the story of Hayabusa’s trials and tribulations on this 365 Days of Astronomy podcast.

The aim of the $200 million Hayabusa project was to learn more about asteroids and to help in our understanding of the origin and evolution of the solar system.

If Hayabusa is indeed carrying samples from the asteroid, it would be only the fourth sample return of space material in history — including the moon matter collected by the Apollo missions, comet matter by Stardust and solar matter in the Genesis mission.

We’re all hoping for the best for this first sample return from an asteroid, and it should be an interesting time in Australia. Dozens of scientists will be watching and waiting to see the return.

A view of Woomera from the Ghan train. Credit: Col Maybury

Plus, as Col Maybury from radio station 2NUR in Australia tells me, all traffic around the area will be stopped, including the Ghan train, one of the world’s great trains that travels from south to north across the continent of Australia, and it happens to be passing through Woomera right at the time Hayabusa should be returning. Col said he called the train company, and was told that the train engineers are to keep a look out for the entry trail.

“So a mighty train named after Afghan camel drivers may have to halt for a small spacecraft or be hit by a flying object,” Col wrote me in an email. He will have a live report on Radio 2NUR-FM on Tuesday the 15th at 10:20 am in Newcastle, 12:20 GMT, talking with the Woomera officials for a follow-up of the Hayabusa event.

Preliminary analysis of the samples will be carried out by the team in Japan, but after one year scientists around the world can apply for access to bits of the asteroid material for research.

WISE Pictures the Tadpole Nebula with a String of Pearls

This image from WISE shows the Tadpole nebula. Image credit: NASA/JPL-Caltech/UCLA

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The Tadpole nebula is looking very stylish in this new infrared image from the WISE spacecraft, NASA’s Wide-field Infrared Survey Explorer. An asteroid appears like a string of pearls — seen as a line of yellow-green dots in the boxes near center — in this stitched together mosaic. The Tadpole is a star-forming region in the Auriga constellation about 12,000 light-years from Earth. As WISE scanned the sky, it happened to catch asteroid 1719 Jens in action, moving across WISE’s field of view. A second asteroid was also observed cruising by, as highlighted in the boxes near the upper left (the larger boxes are blown-up versions of the smaller ones).

More on this image below, but the WISE team received a bit of bad news this week.

WISE principal investigator Ned Wright and his team had proposed a three-month “warm” extension of the mission after the supply of hydrogen that cools the telescope and detectors on board runs out. However, according to an article in Space News, NASA’s 2010 Astrophysics Senior Review Committee recommended that the mission not be extended, and end as originally planned in October of this year.

While WISE is expected to produce significant results, the committee said there was not adequate scientific justification to continue the mission.

The proposed additional three months, known as Warm WISE – where the spacecraft would observe in two of the four infrared wavelengths it has available when WISE is cooled –would have added $6.5 million to the program’s $320 million price tag.

Currently, WISE produces approximately 7,500 images a day.

And this latest image is a “gem.”

It consists of twenty-five frames, taken at all four of the wavelengths and were combined into one image: infrared light of 3.4 microns is color-coded blue: 4.6-micron light is cyan; 12-micron-light is green; and 22-micron light is red.

But wait, there’s more! Also visible in the image are two satellites orbiting above WISE (highlighted in the ovals). They streak through the image, appearing as faint green trails. The apparent motion of asteroids is slower than satellites because asteroids are much more distant, and thus appear as dots that move from one WISE frame to the next, rather than streaks in a single frame.

This Tadpole region is chock full of stars as young as only a million years old — infants in stellar terms — and masses over 10 times that of our sun. It is called the Tadpole nebula because the masses of hot, young stars are blasting out ultraviolet radiation that has etched the gas into two tadpole-shaped pillars, called Sim 129 and Sim 130. These “tadpoles” appear as the yellow squiggles near the center of the frame. The knotted regions at their heads are likely to contain new young stars. WISE’s infrared vision is helping to ferret out hidden stars such as these.

WISE is an all-sky survey, snapping pictures of the whole sky, including everything from asteroids to stars to powerful, distant galaxies.

Sources: JPL, Space News

Possible Destination? Researchers Find Water Ice and Organics on Asteroid

Asteroid Itokawa. Credit: JAXA

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We usually think of asteroids as dark, dry, lifeless chunks of rock, just like the image of Asteroid Itokawa, above. But some asteroids may be more like “minor planets” after all. Researchers have found evidence on one asteroid – 24 Themis – of water ice and organic materials. This discovery is exciting on two fronts: one, this evidence supports the idea that asteroids could be responsible for bringing water and organic material to Earth, and two, if the proposed path for NASA is to visit an asteroid, having water and organics at the destination makes things a bit more interesting.

24 Themis, a 200-kilometer wide asteroid sits halfway between Mars and Jupiter. Using NASA’s Infrared Telescope Facility on Hawaii’s Mauna Kea, Josh Emery from the University of Tennessee, Knoxville and Andrew Rivkin of Johns Hopkins University measured the spectrum of infrared sunlight reflected by the asteroid and found the spectrum consistent with frozen water. They determined that 24 Themis is coated with a thin film of ice. They also detected organic material.

“The organics we detected appear to be complex, long-chained molecules. Raining down on a barren Earth in meteorites, these could have given a big kick-start to the development of life,” Emery said.

Finding ice on the surface of 24 Themis was a surprise because its proximity to the sun causes ice to vaporize. Plus, the surface temperatures are too warm for ice to stick around for a long time.

This image shows the Themis Main Belt which sits between Mars and Jupiter. Asteroid 24 Themis, one of the largest Main Belt asteroids, was examined by University of Tennessee scientist, Josh Emery, who found water ice and organic material on the asteroid's surface. His findings were published in the April 2010 issue of Nature. Credit: Josh Emery/University of Tennessee, Knoxville

“This implies that ice is quite abundant in the interior of 24 Themis and perhaps many other asteroids,” Emery said, and therefore the ice is regularly being replenished.

This might be done by “outgassing” in which ice buried within the asteroid escapes slowly as vapor migrates through cracks to the surface or as vapor escapes quickly and sporadically when 24 Themis is hit by space debris.

The discovery of abundant ice on 24 Themis may mean that water is much more common in the Main Belt of asteroids than previously thought. Since Themis is part of an asteroid “family” that was formed from a large impact and the subsequent fragmentation of a larger body long ago, this scenario means the parent body also had ice and has deep implications for how our solar system formed.

Ice on asteroids may be the answer to the puzzle of where Earth’s water came from, Emery said.

“Asteroids have generally been viewed as being very dry. It now appears that when the asteroids and planets were first forming in the very early Solar System, ice extended far into the Main Belt region,” Emery said. “Extending this refined view to planetary systems around other stars, the building blocks of life — water and organics — may be more common near each star’s habitable zone. The coming years will be truly exciting as astronomers search to discover whether these building blocks of life have worked their magic there as well.”

In choosing a possible destination for future explorations, 24 Themis would perhaps be a good candidate.

The findings are published in the April 29 issue of the journal “Nature.”

Source: EurekAlert

Newly Discovered Asteroid Will Pass by Earth April 8

Orbit of asteroid 2010 GA6. Image credit: NASA/JPL

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Good to know the Spaceguard teams are keeping an eye out for us. The eagle-eyed observers at the Catalina Sky Survey have spotted an asteroid which will pass relatively close to Earth this Thursday, April 8, 2010 at 23:06 U.T.C. (4:06 p.m. PDT, 7:06 pm EDT). But it should pose no problem, as at the time of closest approach asteroid 2010 GA6 will be about 359,000 kilometers (223,000 miles) away from Earth – about 9/10ths the distance from to the moon. The asteroid is approximately 22 meters (71 feet) wide.

“Fly bys of near-Earth objects within the moon’s orbit occur every few weeks,” said Don Yeomans of NASA’s Near-Earth Object Office at the Jet Propulsion Laboratory in Pasadena, Calif.

This one, however, is a bit bigger than other recent asteroid alerts NASA’s Near Earth Observation program has issued. In November 2009, a 7-meter asteroid called 2009 VA came within 14,000 km (8,700 miles) of Earth and in January, 2010 AL30 was about 10-15 meters long and came within only 128,000 km (about 80,000 miles).

NASA’s NEO program, also called Spaceguard, discovers these objects, characterizes a subset of them and plots their orbits to determine if any could be potentially hazardous to our planet.

So while you’re waiting for this one to pass by you can read Don Yeoman’s top ten favorite asteroid facts.

The Catalina telescope is in Tucson, Arizona.

For more information about asteroids and near-Earth objects, visit NASA’s Asteroid Watch page.

Asteroid Might be Visible to Naked Eye on Feb. 17

Asteroid Vesta as seen by NASA's Hubble Space Telescope. Image credit: NASA/ESA/U of Md./STSci/Cornell/SWRI/UCLA

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An asteroid could be visible with binoculars, or even the naked eye on Wednesday, February 17, 2010. No, it’s not coming close to Earth, although this second most massive object in the asteroid belt will be at its closest point to Earth in its orbit, about 211,980,000 kilometers (131,700,000 miles) away. Asteroid Vesta – one of the asteroids that the Dawn spacecraft will visit – will be at opposition on Wednesday, meaning it is opposite the sun as seen from Earth, and is closest to us. Vesta is expected to shine at magnitude 6.1, and that brightness should make it visible for those with clear skies and a telescope, but perhaps even those blessed with excellent vision and little or no light pollution. Vesta will be visible in the eastern sky in the constellation Leo, and will continue to be visible — although less so — in the coming months.

What makes this space rock so prominent these days? Along with its relative proximity at this point, a full half of the asteroid is being bathed by sunlight when seen from Earth, making it appear brighter. Another attribute working in the observer’s favor is that Vesta has a unique surface material that is not as dark as most main belt asteroids – allowing more of the sun’s rays to reflect off its surface.

For more info about observing Vesta, check out this article from Sky & Telescope.

If you get lucky enough to see Vesta, and want to learn more about it, check out this info on the Dawn mission website. Dawn is currently motoring its way through the asteroid belt, will begin its exploration of Vesta in the summer of 2011.

Source: JPL

Hubble Takes A Look at Possible Asteroid Collision

Hubble Views of Comet-like Asteroid P/2010 A2. Credit: NASA, ESA, and D. Jewitt (UCLA)

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We reported earlier that on January 6, 2010, ground-based observatories may have spotted evidence of an asteroid collision in the asteroid belt. Now, the Hubble Space Telescope has taken a look at the mysterious X-shaped debris pattern and trailing streamers of dust. With Hubble’s sharp vision, astronomers believe a head-on collision between two asteroids has actually occured. Astronomers have long thought the asteroid belt is being ground down through collisions, but such a smashup has never been seen before.

“This is quite different from the smooth dust envelopes of normal comets,” said principal investigator David Jewitt of the University of California at Los Angeles. “The filaments are made of dust and gravel, presumably recently thrown out of the nucleus. Some are swept back by radiation pressure from sunlight to create straight dust streaks. Embedded in the filaments are co-moving blobs of dust that likely originated from tiny unseen parent bodies.”

Asteroid collisions would likely have an average impact speed of more than 11,000 miles per hour, or five times faster than a rifle bullet. The comet-like object imaged by Hubble, called P/2010 A2, was first discovered by the Lincoln Near-Earth Asteroid Research, or LINEAR, program sky survey on Jan. 6. New Hubble images taken on Jan. 25 and 29 show a complex X-pattern of filamentary structures near the nucleus.
Hubble shows the main nucleus of P/2010 A2 lies outside its own halo of dust. This has never been seen before in a comet-like object. The nucleus is estimated to be 460 feet in diameter.

Close-up of Comet-like Asteroid P/2010 A2. Credit: NASA, ESA, and D. Jewitt (UCLA)

Normal comets fall into the inner regions of the solar system from icy reservoirs in the Kuiper Belt and Oort Cloud. As a comet nears the sun and warms up, ice near the surface vaporizes and ejects material from the solid comet nucleus via jets. But P/2010 A2 may have a different origin. It orbits in the warm, inner regions of the asteroid belt where its nearest neighbors are dry rocky bodies lacking volatile materials.

This leaves open the possibility that the complex debris tail is the result of an impact between two bodies, rather than ice simply melting from a parent body.

“If this interpretation is correct, two small and previously unknown asteroids recently collided, creating a shower of debris that is being swept back into a tail from the collision site by the pressure of sunlight,” Jewitt said.

The main nucleus of P/2010 A2 would be the surviving remnant of this so-called hypervelocity collision.

“The filamentary appearance of P/2010 A2 is different from anything seen in Hubble images of normal comets, consistent with the action of a different process,” Jewitt said. An impact origin also would be consistent with the absence of gas in spectra recorded using ground-based telescopes.

The asteroid belt contains abundant evidence of ancient collisions that have shattered precursor bodies into fragments. The orbit of P/2010 A2 is consistent with membership in the Flora asteroid family, produced by collisional shattering more than 100 million years ago. One fragment of that ancient smashup may have struck Earth 65 million years ago, triggering a mass extinction that wiped out the dinosaurs. But, until now, no such asteroid-asteroid collision has been caught “in the act.”

At the time of the Hubble observations, the object was approximately 180 million miles from the sun and 90 million miles from Earth. The Hubble images were recorded with the new Wide Field Camera 3 (WFC3).

Source: HubbleSite