Category: Asteroids

Image credit: NASA

Most paleontologist believe that a gigantic asteroid struck Mexico 65 million years ago and killed all the dinosaurs; end of story. But a minority believe that the Earth’s environment was already uncomfortable for dinosaurs because of a series of asteroid strikes and volcano eruptions – the asteroid was just the straw that broke the camel’s back. By studying the life spans of colonies of one-celled organisms, paleontologist Gerta Keller has uncovered that the Cretaceous period might have lasted 300,000 years after the asteroid impact.

As a paleontologist, Gerta Keller has studied many aspects of the history of life on Earth. But the question capturing her attention lately is one so basic it has passed the lips of generations of 6-year-olds: What killed the dinosaurs?

The answers she has been uncovering for the last decade have stirred an adult-sized debate that puts Keller at odds with many scientists who study the question. Keller, a professor in Princeton’s Department of Geosciences, is among a minority of scientists who believe that the story of the dinosaurs’ demise is much more complicated than the familiar and dominant theory that a single asteroid hit Earth 65 million years ago and caused the mass extinction known as the Cretacious-Tertiary, or K/T, boundary.

Keller and a growing number of colleagues around the world are turning up evidence that, rather than a single event, an intensive period of volcanic eruptions as well as a series of asteroid impacts are likely to have stressed the world ecosystem to the breaking point. Although an asteroid or comet probably struck Earth at the time of the dinosaur extinction, it most likely was, as Keller says, “the straw that broke the camel’s back” and not the sole cause.

Perhaps more controversially, Keller and colleagues contend that the “straw” — that final impact — is probably not what most scientists believe it is. For more than a decade, the prevailing theory has centered on a massive impact crater in Mexico. In 1990, scientists proposed that the Chicxulub crater, as it became known, was the remnant of the fateful dinosaur-killing event and that theory has since become dogma.

Keller has accumulated evidence, including results released this year, suggesting that the Chicxulub crater probably did not coincide with the K/T boundary. Instead, the impact that caused the Chicxulub crater was likely smaller than originally believed and probably occurred 300,000 years before the mass extinction. The final dinosaur-killer probably struck Earth somewhere else and remains undiscovered, said Keller.

These views have not made Keller a popular figure at meteorite impact meetings. “For a long time she’s been in a very uncomfortable minority,” said Vincent Courtillot, a geological physicist at Universit? Paris 7. The view that there was anything more than a single impact at work in the mass extinction of 65 million years ago “has been battered meeting after meeting by a majority of very renowned scientists,” said Courtillot.

The implications of Keller’s ideas extend beyond the downfall of ankylosaurus and company. Reviving an emphasis on volcanism, which was the leading hypothesis before the asteroid theory, could influence the way scientists think about the Earth’s many episodes of greenhouse warming, which mostly have been caused by periods of volcanic eruptions. In addition, if the majority of scientists eventually reduce their estimates of the damage done by a single asteroid, that shift in thinking could influence the current-day debate on how much attention should be given to tracking and diverting Earth-bound asteroids and comets in the future.

Keller does not work with big fossils such as dinosaur bones commonly associated with paleontology. Instead, her expertise is in one-celled organisms, called foraminifera, which pervade the oceans and evolved rapidly through geologic periods. Some species exist for only a couple hundred thousand years before others replace them, so the fossil remains of short-lived species constitute a timeline by which surrounding geologic features can be dated.

In a series of field trips to Mexico and other parts of the world, Keller has accumulated several lines of evidence to support her view of the K/T extinction. She has found, for example, populations of pre-K/T foraminifera that lived on top of the impact fallout from Chicxulub. (The fallout is visible as a layer of glassy beads of molten rock that rained down after the impact.) These fossils indicate that this impact came about 300,000 years before the mass extinction.

The latest evidence came last year from an expedition by an international team of scientists who drilled 1,511 meters into the Chicxulub crater looking for definitive evidence of its size and age. Although interpretations of the drilling samples vary, Keller contends that the results contradict nearly every established assumption about Chicxulub and confirm that the Cretaceous period persisted for 300,000 years after the impact. In addition, the Chicxulub crater appears to be much smaller than originally thought — less than 120 kilometers in diameter compared with the original estimates of 180 to 300 kilometers.

Keller and colleagues are now studying the effects of powerful volcanic eruptions that began more than 500,000 years before the K/T boundary and caused a period of global warming. At sites in the Indian Ocean, Madagascar, Israel and Egypt, they are finding evidence that volcanism caused biotic stress almost as severe as the K/T mass extinction itself. These results suggest that asteroid impacts and volcanism may be hard to distinguish based on their effects on plant and animal life and that the K/T mass extinction could be the result of both, said Keller.

Original Source: Princeton News Release

Image credit: NASA/JPL

Five years ago NASA began a program to discover 90% of potential Earth-crossing asteroids larger than 1 km. 60% of the 1,000 to 1,200 large Near Earth Asteroids have already been found, and the search should be complete by 2008. But objects below 1 km can still be devastating, so NASA is proposing a new survey to track hundreds of thousands of these smaller objects. The new report proposes that NASA spend $236 million over the course of 20 years to find 90% of these smaller, but still devastating, objects. Another option would be to build a space-based tracking system which would increase the cost to $397 million but cut the search time down to just seven years.

NASA has released a technical report on potential future search efforts for near-Earth objects after a year of analysis by scientists working on this issue. This Science Definition Team was chartered to study what should be done to find near-Earth objects less than 1 kilometer in size. While impacts by these smaller objects would not be expected to cause global devastation, impacts on land and the tsunamis resulting from ocean impacts could still cause massive regional damage and still pose a significant long-term hazard.

In 1998 NASA commenced its part of the “Spaceguard” effort, with the goal of discovering and tracking over 90% of the near-Earth objects larger than one kilometer by the end of 2008. An Earth impact by one of these relatively large objects would be expected to have global consequences and, over time scales of a few million years, they present the greatest impact hazard to Earth. Approximately 60% of the estimated 1,000 to 1,200 large near-Earth objects have already been discovered, about 45% since NASA efforts started, and each of the five NASA-supported search facilities continue to improve their performance, so there has been good progress toward eliminating the risk of any large, undetected impactor.

To understand the next steps to discovering the population of potentially hazardous asteroids and comets whose orbits can bring them into the Earth’s neighborhood, NASA turned to this Science Definition Team of 12 scientists. The Team, chaired by Dr. Grant Stokes of the MIT Lincoln Laboratory, was asked to study the feasibility of extending the search effort to the far more numerous, perhaps hundreds of thousands, of near-Earth objects whose diameters are less than one kilometer.

NASA considers the Science Definition Team’s findings to be preliminary, and a much more in-depth program definition, refining objectives and estimating costs, would need to be conducted prior to any decision to continue Spaceguard projects beyond the current effort to 2008.

Original Source: NASA News Release

Image credit: NASA/JPL

Astronomers have long-held that collisions were the primary cause of spinning asteroids, but new research indicates that it might be something much more gentle: sunlight. In a recent study carried out by the Southwest Research Institute (SwRI) and Charles University (Prague), astronomers calculated the effect of millions and even billions of years of sunlight pressure can cause an asteroid to spin so fast it can fly apart; others can be made to stop spinning completely.

A new study by researchers at Southwest Research Institute (SwRI) and Charles University (Prague) has found that sunlight can have surprisingly important effects on the spins of small asteroids. The study indicates that sunlight may play a more important role in determining asteroid spin rates than collisions, which were previously thought to control asteroid spin rates. Results will be published in the Sept. 11 issue of Nature.

David Vokrouhlicky (Charles University), David Nesvorny and William Bottke (both of the SwRI Space Studies Department) conducted the study, which showed that sunlight absorbed and reemitted over millions to billions of years can spin some asteroids so fast they could potentially break apart. In other cases, it can nearly stop them from spinning altogether. The team even noted that the effects of sunlight, combined with the gravitational tugs of the planets, can slowly force asteroid rotation poles to point in the same direction.

Until recently, researchers thought asteroid impacts controlled the rotation speed and direction of small asteroids floating in space. The unusual spin states of 10 asteroids observed by Stephen Slivan, a researcher at the Massachusetts Institute of Technology, however, have cast doubt on this idea. Slivan’s asteroids, the first in the 15- to 25-mile-diameter range to have their spins extensively studied, are in the so-called Koronis asteroid family, a cluster of asteroid fragments produced by a highly energetic collision billions of years ago. Slivan found that not only do four of these asteroids rotate at nearly the same speed, but they also have spin axes that point in the same direction.

“The data clearly show that the spin vector alignment is real, but how they got that way has been a big puzzle,” says Slivan. “I’m delighted that others find this to be an interesting problem.”

“To picture just how weird these asteroids really are, imagine you were handed a box of spinning tops just as you were about to launch aboard the space shuttle. Given all the shaking produced by the launch, you would expect the tops to have different spin speeds and orientations by the time you reached orbit,” says Bottke. “Instead, imagine your surprise upon opening the box if the tops were all spinning at the same speed and had their handles pointing toward the constellation Cassiopeia. Now increase the size of the tops by a factor of a million and pretend that the bouncing during launch is equivalent to billions of years of asteroid collisions. This is the strange situation we find ourselves with.”

The remaining six asteroids studied by Slivan either have extremely slow spin rates, such that they rotate slower than the hour hand of a clock, or very fast spin rates, such that they are near the limit beyond which loose material on the surface of an asteroid would fly off.

“One would expect that collisions would have randomized these rotation rates. It was a big surprise to find a cluster of asteroids with such odd spin states,” says Nesvorny.

To explain the spin states of Koronis family asteroids, Vokrouhlicky, Nesvorny and Bottke investigated how asteroids reflect and absorb light from the sun and reradiate this energy away as heat. They found that while the recoil force produced by the reradiation of sunlight is tiny, it can still substantially alter an asteroid’s rotation rate and pole direction if it has enough time to act.

“Like the story about the tortoise and the hare, slow and steady sunlight wins the race over the fast-acting, but less effective, jolt of collisions between asteroids. Sunlight in space never stops,” says Bottke, “and most asteroids have been exposed to a lot of it because of their age.”

Using computer simulations, the team showed that sunlight has been slowly increasing and decreasing the rotation rates of Koronis family asteroids since they were formed 2 to 3 billion years ago. More remarkably, they found that some simulated asteroids were captured into a special spin state that forced the wobble of the asteroid’s spin axis (produced by gravitational perturbations from the sun) to “beat” at the same frequency as the wobble of the asteroid’s orbit (produced by gravitational perturbations from the planets). This state, called a spin-orbit resonance, can drive an asteroid’s rotation rate and spin axis to particular values.

“These results give us a new way to look at the asteroids,” says Vokroulicky. “It is our hope that this work will stimulate observational studies into many different regions of the main asteroid belt. We have only scratched the surface of this interesting problem.”

Original Source: SWRI News Release

Image credit: NASA

As potentially killer asteroids are announced on an almost yearly basis, the public is started to get a little jaded about the risks humanity faces. How can governments and space agencies confront a threat that can only be a “maybe” until it’s too late to do anything about it? Here’s my opinion.

Well, you can all breath a sigh of relief, 2003 qq47 isn’t going to smash into Earth on March 21, 2014 and cause widespread death and destruction. But then, if you’ve been a regular follower of space news, you’re probably not really surprised. Astronomers release a warning almost every year that a space rock has some outside chance of striking the Earth, and then revise their estimates shortly afterwards thanks to more observations.

The first big rock to freak out the public was Asteroid 1997 XF11; it was supposed to strike the Earth in October 26, 2028. Even though the original threat was still remote, the mass media picked up on this. There were full-page articles in major newspapers, the cover of magazines, and on the evening news. Astronomers quickly followed up the story with a retraction. Not only would XF11 miss the Earth, it would miss by almost a million kilometres, or 2.5 times further than the Moon.

New reports of killer asteroids have come out in the following years, with wiser astronomers being a little more conservative in their predictions. With QQ47, the first stories pegged the chances of a strike at 1 in 909,000; not much higher than the background risk that the Earth faces every year from getting hit by an asteroid. The risk has since been downgraded.

As automated asteroid searches continue to search the sky, potential planet smashers are going to be spotted quite regularly. Astronomers will provide conservative calculations, and a jaded public will treat each announcement with even more skepticism. When the 37th potential killer asteroid is announced, it’ll make little more than a blip in the general media – that’s understandable.

The unspoken goal for finding asteroids is to prevent one of them from ever striking the Earth and causing damage. In theory, the sooner you find a killer asteroid, the longer you have to adjust its orbit and save the Earth from destruction. If a collision is only a couple of months away, there’s little to do but prepare for the worst. But if it’s years or even decades away, spacecraft could be launched to nudge the asteroid into a less hazardous trajectory.

Astronomers are going to keep a watchful eye on the sky, to alert governments and the public to any future risks. But the problem is that astronomers deal in probabilities. They won’t say a certain asteroid WILL hit the Earth (like in Armageddon); instead they’ll say that it can hit the Earth.

That it may hit the Earth.

Will governments and space agencies be decisive enough to spend billions of dollars changing an asteroid’s orbit when they aren’t sure it’s even necessary. The longer you wait, the better the calculations become, but the less time you have to defend against it. With more data, astronomers will likely be tracking dozens of potential Earth-crossers with varying risks and dates that they’ll strike our planet. How do we decide which asteroids need to be moved and which can wait?

I don’t think we’re ever going to have a clear-cut challenge that will unite humanity against a common threat. If we did, it would probably only be months away and there’d be little we could do about it. Just take a look at global warming. Even though the evidence seems to be saying that humans have warmed the planet a degree in the last century, the worldwide response is denial and procrastination.

So what’s the solution? I honestly don’t know if governments and space agencies can really get organized and decisive around such a nebulous threat (the threat is real, though, with the potential for unlimited damage). Investing in basic research is probably the best solution; better funding for observatories to discover and map asteroid trajectories; new propulsion systems that could help push an asteroid out of the way. Maybe if engineers deliver better solutions, it will help procrastinating governments take action at the last minute.

Image credit: Keck

A team of astronomers have used the 10-metre Keck II telescope to create a series of images that show asteroid (511) Davida from every angle. The images of the 320 km asteroid were taken in late December, 2002 using the Keck’s adaptive optics system – a special technology that allows the telescope to compensate for distortion caused by the Earth’s atmosphere. The observations are so precise that features as small as 46 km can be seen on the surface of the asteroid.

A team of scientists from the W.M. Keck Observatory and several other research institutions have made the first full-rotational, ground-based observations of asteroid (511) Davida, a large, main-belt asteroid that measures 320 km (200 miles) in diameter. These observations are among the first high-resolution, ground-based pictures of large asteroids, made possible only through the use of adaptive optics on large telescopes. This research will help improve understanding of how asteroids were formed and provide information about their compositions and structures. Because the asteroids were formed and shaped by collisions, a process that also affected the Earth, Moon, and planets, these studies will also help astronomers understand the history and evolution of the solar system.

” Asteroid Davida was discovered 100 years ago, but this is the first time anyone has been able to see this level of detail on this object,” said Dr. Al Conrad, scientist at the W.M. Keck Observatory. “With adaptive optics, we’re finally able to transform asteroids like Davida from a single, faint point-source into an object of true geological study.”

Ground-based observations of large, main-belt asteroids are made possible only through a powerful astronomical technique called adaptive optics, which removes the blurring caused by Earth’s atmosphere. Without adaptive optics, critical surface information and details about the asteroid’s shape are lost. The techniques used at the W.M. Keck Observatory allow astronomers to measure the distortion of light caused by the atmosphere and rapidly make corrections, restoring the light to near-perfect quality. Such corrections are most easily made to infrared light. In many cases, infrared observations made with Keck adaptive optics are better than those obtained with space-based telescopes.

The observations of asteroid (511) Davida were made with the 10-meter (400-inch) Keck II telescope on December 26, 2002. Images were taken over a full rotation period of about 5.1 hours, just a few days before its closest approach to Earth. At that time, Davida’s angular diameter was less than one-ten-thousandth of a degree, about the size of a quarter as seen from a distance of 18 kilometers (11 miles). The high angular resolution allowed astronomers to see surface details as small as 46 kilometers (30 miles), about the size of the San Francisco Bay area. The next time Davida comes this close to Earth will be in the year 2030.

At the time of the observations, Davida?s north pole faced Earth. While scientists could see the asteroid spinning, only the northern hemisphere was visible. Yet the profile of the asteroid is far from circular: At least two flat facets can be seen on its surface. Although scientists knew previously from light variations that Davida must have an oblong shape, details of that shape were not available until now. Initial evaluation of the images reveal some dark features, and scientists are still working to understand to what extent these are surface markings, topographical features, or artifacts of the image processing.

” Adaptive optics on large telescopes is allowing us to make detailed studies from the ground that were previously impossible or prohibitively expensive,” said Dr. William Merline, principal scientist with the Southwest Research Institute, and a participant in this research. “We can now make observations that once required either the scarce resources of space telescopes or spacecraft missions to asteroids. While these space telescopes and space missions are still needed for complete study of the asteroids, ground-based observations such as these will help tremendously in planning the mission observations and focusing the resources where they will be most effective.”

Asteroids are the collection of rocky objects orbiting between Mars and Jupiter. They were likely prevented from forming into a planet, partly due to Jupiter’s massive gravitational influence.

? Although the asteroids began their lives colliding gently, in a way that would lead them eventually to form a planet, Jupiter’s gravity eventually stirred up their orbits, and they began to collide at higher speeds,? added participant Dr. Christophe Dumas, planetary astronomer with the Jet Propulsion Laboratory. ?These collisions tended to cause them to break up rather than gently stick together. The resulting fragments, numbering in the hundreds of thousands, are the asteroids we see today. They collide with each other and have impacted the Earth, Moon, and planets over time. One need only look at the scarred surface of our Moon to see the cumulative result. Study of the asteroid’s shape, size, and surface features helps us understand how these collisions operate and thus how our planet was, and still is, being affected by these impacts.?

Observations of the shapes of asteroids, such as those released today, can tell us about the types and severity of impacts that occurred, and possibly also give clues into the overall structure of an asteroid — for example, whether it may be solid rock, or a jumble of smaller rocks. Surface features can reveal a history of large impacts or variations in the composition that should, in turn, further help us understand the asteroid’s history.

Asteroid (511) Davida was discovered by R. S. Dugan in 1903 in Heidelberg, Germany. The (511) in Davida’s name means it was the 511th asteroid to be discovered and included in the list of asteroids maintained by the International Astronomical Union.

Team members responsible for the observations are Al Conrad, David Le Mignant, Randy Campbell, Fred Chaffee, Robert Goodrich, Shui Kwok of the W.M. Keck Observatory; Christophe Dumas, Jet Propulsion Laboratory; William Merline, Southwest Research Institute; Heidi Hammel, Space Science Institute; and Thierry Fusco, Onera, France.

The W.M. Keck Observatory is operated by the California Association for Research in Astronomy, a scientific partnership of the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration.

Source: Keck Press Release

Additional observations from astronomers have decreased the likelihood to virtually zero that Asteroid 2003 qq47 will strike the Earth in 2014. The asteroid was first discovered on August 24 by the LINEAR observatory and astronomers put its odds at 1 in 909,000 at 2003qq47 hitting the Earth, but the additional observations on Monday night extended those odds to 1 in 2.2 million, which is below the background risk of asteroid strikes on any given year. If the 1.3 km asteroid were to strike the Earth, it would cause immense damage on a continental scale… but it won’t.

When Asteroid 2003 qq47 was discovered last week from a tracking system in New Mexico, astronomers predicted that it could strike the Earth in 2014. Astronomers have now made 51 observations of its orbit and determined that the chance of 2003qq47 hitting the Earth are 1 in 909,000 and additional observations will probably reduce this possibility to zero. The space rock is estimated to be 1.2 km across and traveling at a speed of 30 km/second. If it did strike the Earth, it would cause widespread destruction across an entire continent, releasing the same amount of energy as 350 billion tonnes of TNT.

Image credit: ESO

A new image taken by the European Southern Observatory’s Very Large Telescope (VLT) shows an infrared halo around a nascent star. The image also shows jets of gas emanating from the region and colliding with the surrounding cloud. Although these rings have been theorized before, this is the first time one has actually been seen. The dust in the surrounding cloud is collapsing under its own gravity and will eventually form a true star.

A small and dark interstellar cloud with the rather cryptic name of DC303.8-14.2 is located in the inner part of the Milky Way galaxy. It is seen in the southern constellation Chamaeleon and consists of dust and gas. Astronomers classify it as a typical example of a “globule”.

As many other globules, this cloud is also giving birth to a star. Some years ago, observations in the infrared spectral region with the ESA IRAS satellite observatory detected the signature of a nascent star at its centre. Subsequent observations with the Swedish ESO Submillimetre Telescope (SEST) at La Silla (Chile) were carried out by Finnish astronomer Kimmo Lehtinen. He revealed that DC303.8-14.2 is collapsing under its own gravity, a process which will ultimately result in the birth of a new star from the gas and dust in this cloud.

Additional SEST observations of the millimetre emission of carbon monoxide (CO) molecules demonstrated a strong outflow from the nascent star. A small part of the gas that falls inward onto the central object is re-injected into the surrounding via this outward-bound “bipolar stream”.

The structure of DC303.8-14.2
The left panel in PR Photo 26a/03 shows the DC303.8-14.2 globule as it looks in red light. This image was obtained at wavelength 700 nm and has been reproduced from the Digitized Sky Survey (DSS) [1]. It covers a sky region of 20 x 20 arcmin2, or about 50% of the area of the full moon. The dust particles in the cloud reflect the light from stars, causing the cloud to appear brighter than the adjacent sky.

The brightness distribution over the cloud depends mostly on three factors connected to the dust. The first is the distribution of dust grains in the cloud, the way the dust density changes with the distance from the centre of the cloud. The second is the relative amount of light that is reflected by the dust particles. The third indicates the dominant direction in which the dust particles scatter light; this is dependent on the geometry of the grains and their preferred spatial alignment. Accurate observations of the brightness distribution over the surface of a globule allow an investigation of these properties and thus to learn more about the structure and composition of the cloud.

From the image obtained in red light (left panel in PR Photo 26a/03) it appears, somewhat surprisingly, that the brightest area of DC303.8-14.2 is not where there is most dust. Instead, it takes the form of a bright ring around the centre. This rim corresponds to a region where the intensity of the light from stars behind the cloud is reduced by a moderate factor of 3 to 5 when passing through the cloud and where the light-scattering efficiency of the dust grains in the cloud is the highest.

Observing with ISAAC on the VLT
In order to study the structure of DC303.8-14.2 in more detail, Kimmo Lehtinen and his team of Finnish and Danish astronomers [2] used the near-infrared imaging capabilities of the ISAAC multi-mode instrument on the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory (Chile). Under good observing conditions, they obtained a mosaic image of this cloud in several near-IR wavelength bands, including the J- (centered at wavelength 1.25 ?m), H- (1.65) and Ks-bands (2.17). These exposures were combined to produce images of DC303.8-14.2, two of which are shown in PR Photo 26a/03 (middle and right panels).

The middle image shows the central part of the globule in the H-band. A bright rim is clearly detected – this is the first time such a ring is seen in infrared light around a globule.

This rim has a smaller size in infrared than in visible light. This is because the absorption of infrared light by dust particles is smaller than the absorption of visible light. More dust is then needed to produce the same amount of scattering and to show a rim in infrared light. The infrared rim will therefore show up in an area where the dust density is higher, i.e. closer to the centre of the cloud, than the visible-light rim.

Similar rings were also detected in the J- and Ks-band images and, as expected, of different sizes. Thus the mere observation of the size (and shape) of a bright rim already provides information about the internal structure of the cloud. In the case of DC303.8-14.2, a detailed evaluation shows that the dust density of the centre is so high that any visible light from the nascent star in there would be dimmed at least 1000 times before it emerges from the cloud.
Getting a bonus: Jets from a young star

As an unexpected and welcome bonus, the astronomers also detected several jet- and knot-like structures in the Ks-band image (right panel in PR Photo 26a/03), near the IRAS source. The area shown represents the innermost region of the cloud (65 x 50 arcsec2, or just 1/500 of the area of the DSS image to the left).

Several knot-like structures on a line like a string of beads are clearly seen. They are most probably regions where the gas ejected by the young stellar object rams into the surrounding medium, creating zones of compressed and hot molecular hydrogen. Such structures are known by astronomers as “Herbig-Haro objects”, cf. ESO PR 17/99.

More information
A general description of the methods used to study and model surface brightness observations of small dark clouds in given in a basic paper by Kimmo Lehtinen and Kalevi Mattila in the research journal Astronomy & Astrophysics (Vol. 309, p. 570 1996). The results presented here will be published in a forthcoming paper in Astronomy & Astrophysics.
Notes

[1]: The Digitized Sky Survey was produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions.

[2]: The team is composed of Kimmo Lehtinen, Kalevi Mattila from the Observatory of the University of Helsinki (Finland), Petri V?is?nen from ESO/Chile and Jens Knude from the Observatory of the University of Copenhagen (Denmark). P. V?is?nen is also affiliated with the University of Helsinki.

Original Source: ESO News Release

Image credit: NASA

Seven asteroids were recently renamed to honour the astronauts of the space shuttle Columbia. The asteroids are all 5 to 7 km long, and were discovered on the nights of July 19-21, 2001 at the Palomar Observatory near San Diego by astronomer Eleanor F. Helin. NASA’s Jet Propulsion Laboratory proposed the idea, and it was recently approved by the International Astronomical Union, which is responsible for maintaining the names of celestial objects.

The final crew of the Space Shuttle Columbia was memorialized in the cosmos as seven asteroids orbiting the sun between Mars and Jupiter were named in their honor today.

The Space Shuttle Columbia crew– Commander Rick Husband; pilot William McCool; Mission Specialists Michael Anderson, Kalpana Chawla, David Brown, Laurel Clark; and Israeli payload specialist Ilan Ramon, will have celestial memorials, easily found from Earth.

The names, proposed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif., were recently approved by the International Astronomical Union. The official clearinghouse of asteroid data, the Smithsonian Astrophysical Observatory’s Minor Planet Center, released the dedication today.

The seven asteroids were discovered at the Palomar Observatory near San Diego on the nights of July 19-21, 2001, by former JPL astronomer Eleanor F. Helin, who retired in July 2002. The seven asteroids range in diameter from five to seven kilometers (3.1 to 4.3 miles). The Palomar Observatory is owned and operated by the California Institute of Technology, Pasadena.

“Asteroids have been around for billions of years and will remain for billions more,” said Dr. Raymond Bambery, Principal Investigator of JPL’s Near-Earth Asteroid Tracking System. “I like to think that in the years, decades and millennia ahead people will look to the heavens, locate these seven celestial sentinels and remember the sacrifice made by the Columbia astronauts.?

The 28th and final flight of Columbia (STS-107) was a 16-day mission dedicated to research in physical, life and space sciences. The seven astronauts aboard Columbia worked 24 hours a day, in two alternating shifts, successfully conducting approximately 80 separate experiments. On February 1, 2003, the Columbia and its crew were lost over the western United States during the spacecraft’s re-entry into Earth’s atmosphere.

Asteroids are rocky fragments left over from the formation of the solar system about 4.6 billion years ago. Most of the known asteroids orbit the Sun in a belt between Mars and Jupiter. Scientists think there are probably millions of asteroids, ranging in size from less than one kilometer (.62 mile) wide to hundreds of kilometers across.

More than 100,000 asteroids have been detected since the first was discovered back on January 1, 1801. Ceres, the first asteroid discovered, is also the largest at about 933 kilometers (580 miles) in diameter.

The Near-Earth Asteroid Tracking System is managed by JPL for NASA’s Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology.

Information about JPL’s Near-Earth Asteroid Tracking System is available at http://neat.jpl.nasa.gov. More information on the newly named asteroids is at http://www.jpl.nasa.gov/releases/2003/columbia-tribute.cfm.

For information about NASA on the Internet, visit: http://www.nasa.gov.

Original Source: NASA/JPL News Release

Image credit: Harvard

New images taken by the 100-inch Hooker telescope at Mount Wilson Observatory show Asteroid Juno with a huge chunk taken out of it. Harvard astronomer Sallie Baliunas used the adaptive optics system on the Hooker telescope, which compensates for distortions in the atmosphere, to take photos of the 241 km asteroid with incredible clarity. The photos show that Juno is misshapen and has a 100 km crater from an impact with another asteroid in the past.

Cambridge, MA -If someone sneaks a bite of your chocolate chip cookie, they leave behind evidence of their pilferage in the form of a crescent of missing cookie. The same is true in our solar system, where an impact can take a bite out of a planet or moon, leaving behind evidence in the form of a crater. By combining modern technology with a historical telescope, astronomers have discovered that the asteroide Juno has a bite out of it. The first direct images of the surface of Juno show that it is scarred by a fresh impact crater.

Juno, the third asteroid ever discovered, was first spotted by astronomers early in the 19th century. It orbits the Sun with thousands of other bits of space rock in the main asteroid belt between Mars and Jupiter. One of the largest asteroids, at a size of 150 miles across, Juno essentially is a leftover building block of the solar system.

Astronomer Sallie Baliunas (Harvard-Smithsonian Center for Astrophysics) and colleagues photographed Juno when it was located relatively nearby in astronomical terms, about 10 percent further from the Earth than the Earth is from the Sun. Even at that distance, Juno appeared very tiny in the sky, subtending only 330 milli-arcseconds – the equivalent of a dime seen at a distance of 7 miles. Imaging Juno at the high resolution needed to resolve surface details thus presented a challenge.

To solve the problem, the scientists used an adaptive optics system connected to the 100-inch Hooker telescope at Mount Wilson Observatory. Adaptive optics enables astronomers to compensate for the distortion created by air currents in our planet’s atmosphere, yielding images as sharp and clear as those taken in space.

Their surface maps showed that Juno, like other asteroids, is misshapen rather than round, and that it has “sharp” edges. Even better, as Juno tumbled through space during the night of observing, a “bite” came into view – an area that appeared dark as seen at near-infrared wavelengths. The astronomers concluded that the asteroid had recently (in astronomical terms) collided with another object, resulting in a 60-mile-wide crater, or possibly a smaller crater that is surrounded by a 60-mile blanket of ejecta debris.

“I look at an asteroid as a garden – a garden not of flowers and leaves, but one of rubble and dust churned up by constant impacts. This process of gardening pulverizes the asteroid’s surface into a fine-grained regolith,” said Baliunas. “The recent, large impact on Juno gives us an opportunity to see through the regolith and study excavated material from beneath the surface – a rare look into the material out of which the early Earth was formed.”

The blast that knocked a bite out of Juno may also have provided researchers with a convenient way of studying that asteroid up close without ever leaving our planet. Some meteorites found on the Earth are actually pieces of large asteroids like Juno. Those pieces were broken off and launched into space by an impact, and then fell on our planet. The newly-found impact crater on Juno may have sent samples of that asteroid to the Earth.

This remarkable result demonstrates how technology can be used to renew historical observatories, giving them a new lease on life. The Hooker telescope, now nearing the end of its first century of observing, can use adaptive optics systems to obtain views of the cosmos as clear as though the telescope were in space. Hence, the telescope that Edwin Hubble and his assistant used to discover evidence of the expanding universe continues to make groundbreaking discoveries today.

These results were published in the May 2003 issue of the astronomy journal Icarus.

Original Source: CfA News Release