2009 FH fly past, only 85,000 km away from Earth (NASA)
[/caption]Another asteroid is set to make a close approach of 79,000 km according to NASA, a distance twice that of geosynchronous orbit around the Earth. Although the 15-20 metre-wide rock is not expected to cause any problems to Earth or satellites, some observers may be lucky to spot the faint light from 2009 FH as it passes.
Interestingly, this new object comes only two weeks after a larger (50 metre wide) asteroid was spotted passing the Earth at a similar distance. So it begs the question, why are we seeing so many asteroids lately?
“This asteroid flyby will be a good viewing opportunity for both professional and amateur astronomers,” said Don Yeomans from the Near-Earth Object Office at NASA’s Jet Propulsion Laboratory in Pasadena, California. “The asteroid poses no risk of impact to Earth now or for the foreseeable future.”
NASA is always very quick to point out these objects are harmless, passing the Earth at a very safe distance, often beyond the Moon’s orbit. However, 2009 FH will pass at a similar distance to the 50 metre-wide 2009 DD45 on March 2nd.
The orbit of 2009 FH (NASA JPL Small-Body Database Browser)In this case, 2009 FH will pass through the constellation of Gemini, as bright as a 14th magnitude star. Unfortunately there appears to be some fuzziness as to the time of observing opportunity. SpaceWeather.com reports that the best time to observe the asteroid has already passed (after sunset on March 17th, over North America), however, the NASA JPL news release states that close approach occurs at 5:17 am PST Wednesday morning. There is little more information available. However, check the 2009 FH ephemerides for more information.
This discovery was made by NASA’s Near Earth Object Observation Program, known as Spaceguard, to detect and track potentially hazardous asteroids that stray close to the Earth. It appears the Spaceguard team are getting better and better at spotting these chunks of rock. Although it might seem there are a lot more asteroids than before, this isn’t the case, we’re just getting better at finding them.
This image was taken near the point of closest approach to Mars on Feb. 17, 2009, during Dawn's gravity assist flyby. Image credit: NASA/JPL/MPS/DLR/IDA, and the Dawn Flight Team
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Recently, the Dawn spacecraft – on its circuitous route to the asteroid belt — used the gravity of Mars to provide a little ‘kick’ to the spacecraft’s velocity. Universe Today finally had the chance to catch up with the team from the Dawn mission following this maneuver to find out how things went, and how the spacecraft is doing following the gravity assist operations. “The gravity assist accomplished exactly what we needed to get on course for Vesta,” Dawn Chief Engineer Marc Rayman told UT. “In addition to the gravity assist, we decided to undertake some bonus instrument calibrations, taking advantage of flying by such a well-studied planet. In doing so, we obtained some performance data on some of our instruments.” The image seen here of Mars’ surface is one of the results of those calibrations.
Dawn will be visiting two different asteroids, Vesta and Ceres. Because of its distinctive ion engine, the spacecraft will be able to enter orbit around Vesta in August of 2011, remain there until May of 2012, then leave orbit and head to Ceres, arriving in February of 2015.
The thrusters work by using an electrical charge to accelerate ions from xenon fuel to a speed 10 times that of chemical engines. But what does this mean for a gravity assist – is there any difference between an ion engine versus and a chemical thruster in a gravity assist?
“In most ways, there is no difference,” said Rayman. “We used the ion thruster to get on course for the gravity assist, but the spacecraft coasted for most of the 4.5 months before it reached Mars. When we had to refine the trajectory, we used the ion thruster because it is so much more efficient than conventional propulsion. Moreover, because the ion propulsion affords so much flexibility in the mission, we did not have to hit as small a ‘window’ at Mars.” Dawn's trajectory. Credit: JPL
Generally, a gravity assist is used to increase a spacecraft’s velocity and propel it outward in the solar system, much farther away from the Sun than its launch vehicle would have been capable of doing.
Dawn got as close as 549 kilometers (341 miles) to the Red Planet during the Tuesday, Feb. 17, flyby. JPL said that if Dawn had to perform these orbital adjustments on its own, with no Mars gravitational deflection, the spacecraft would have had to fire up its engines and change velocity by more than 9,330 kilometers per hour (5,800 miles per hour).
At maximum thrust, each engine produces a total of 91 millinewtons — about the amount of force involved in holding a single piece of notebook paper in your hand. You would not want to use ion propulsion to get on a freeway: At maximum throttle, it would take Dawn’s system four days to accelerate from 0 to 60 miles per hour.
Using the gravity of Mars was an important part of the Dawn mission that makes going to the asteroid belt possible.
A sequence of four images reveal the motion of asteroid 2009 DD45 (at center) over 36 minutes during its discovery on February 27th. Credit: Robert McNaught / ANU / UA
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As I’m writing this (13:40 UT) a newly-discovered asteroid, 2009 DD45, is flying past Earth at only 74,800 km (46,478.5 miles or 0.000482 AU) away. That’s only about twice the height of a typical geostationary communications satellite, and well inside the moon’s orbit. According to Spaceweather.com, the 30- to 40-meter wide space rock is similar in size to the Tunguska impactor of 1908, but this time there is no danger of a collision. At closest approach on March 2nd, (which just occurred) 2009 DD45 will speed through the constellation Virgo shining as brightly as an 11th magnitude star. So if you’re in the Pacific region like Hawaii or Tahiti, go out and take a look! But this rock is moving fairly fast, and by tonight, it will only be 13th magnitude, and fading fast. UPDATE: Below see video of 2009 DD45 as seen from Australia:
(thanks to Aaron Slack for the heads up on the video)
The asteroid was only discovered three days ago by the prolific asteroid hunter Robert McNaught at Siding Spring Observatory in Australia, when the space rock was already within 2,414,016 km (1½ million miles) of Earth and closing fast. If you want to try and track it, here’s the ephemeris information from the Minor Planet Center.
Artist's depiction of the asteroid belt between Mars and Jupiter. Credit: David Minton and Renu Malhotra
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When Mars and Jupiter migrated to their present orbits around 4 billion years ago, they left scars in the asteroids belt that are still visible today.
The evidence is unveiled in a new paper in this week’s issue of the journal Nature, by planetary scientists David Minton and Renu Malhotra from the University of Arizona in Tucson.
The asteroid belt has long been known to harbor gaps, called Kirkwood gaps, in distinct locations. Some of these gaps correspond to unstable zones, where the modern-day gravitational influence of Jupiter and Saturn eject asteroids. But for the first time, Minton and Malhotra have noticed that some clearings don’t fit the bill.
“What we found was that many regions are depleted in asteroids relative to other regions, not just in the previously known Kirkwood gaps that are explained by the current planetary orbits,” Minton wrote in an email. In an editorial accompanying the paper, author Kevin Walsh added, “Qualitatively, it looks as if a snow plough were driven through the main asteroid belt, kicking out asteroids along the way and slowing to a stop at the inner edge of the belt.”
Walsh hails from the Observatoire de la Côte d’Azur in France. In his News and Views piece, he explains that the known Kirkwood gaps, discovered by Daniel Kirkwood in 1867, “correspond to the location of orbital resonances with Jupiter — that is, of orbits whose periods are integer ratios of Jupiter’s orbital period.” For example, if an asteroid orbited the Sun three times for every time Jupiter did, it would be in a 3:1 orbital resonance with the planet, he wrote. Objects in resonance with a giant planet have inherently unstable orbits, and are likely to be ejected from the solar system. When planets migrated, astronomers believe objects in resonance with them also shifted, affecting different parts of the asteroid belt at different times.
“Thus, if nothing has completely reshaped the asteroid belt since the planets settled into their current orbits, signatures of past planetary orbital migration may still remain,” Walsh wrote. And that’s exactly what Minton and Malhotra sought.
The asteroid belt easily gave up its secrets, showing the lingering evidence of planetary billiards on the inner edge of the asteroid belt and at the outer edge of each Kirkwood gap. The new finding, based on computer models, lends additional support to the theory that the giant planets — Jupiter, Saturn, Uranus and Neptune — formed twice as close to the sun as they are now and in a tighter configuration, and moved slowly outward.
“The orbit of Pluto and other Kuiper belt objects that are trapped in [orbits that resonate] with Neptune can be explained by the outward migration of Neptune,” Minton and Malhotra write in the new study. “The exchange of angular momentum between planetesimals and the four giant planets caused the orbital migration of the giant planets until the outer planetesimal disk was depleted.” Planetesimals are rocky and icy objects left over from planet formation.
“As Jupiter and Saturn migrated,” the authors continue, they wreaked havoc on the young asteroid belt, “exciting asteroids into terrestrial planet-crossing orbits, thereby greatly depleting the asteroid belt population and perhaps also causing a late heavy bombardment in the inner Solar System.”
The late heavy bombardment is proposed to have occurred about 3.9 billion years ago, or 600 million years after the birth of the Solar System, and it’s believed to account for many of the Moon’s oldest craters. Walsh said a reasonable next step, to corroborate the theory about the newly described clearings in the asteroid belt, is to link them chronologically with the bombardment.
LEAD PHOTO CAPTION: Artist’s depiction of the asteroid belt between Mars and Jupiter. Credit: David Minton and Renu Malhotra
Did the asteroid that hit the Earth, creating the Moon, originate from one of Earth's Lagrangian points? (ESA)
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Two solar telescopes launched to study coronal mass ejections and the solar wind have been sent to do an entirely different task. Currently, the Solar Terrestrial Relations Observatory (STEREO) probes are flying in opposite directions; one directly in front of Earth’s orbit and the other directly behind. This unique observatory is intended to view the solar-terrestrial environment in unprecedented detail, allowing us to see the Sun from two vantage points.
This might sound like an exciting mission; after all, how many space-based observatories have such a unique perspective on the Solar System from 1 AU? However, both STEREO probes are currently moving further away from the Earth (in opposite directions), approaching a gravitational no-man’s land. STEREO is about to enter the Earth-Sun Lagrangian points L4 and L5 to hunt for some sinister lumps of rock…
The Lagrangian points of a two-body system, such as the Earth and the Sun.Lagrangian points in planetary systems are islands of gravitational stability. They are volumes of space where the gravity of two massive bodies cancel out. The first two Lagrangian points in the Earth-Sun system are fairly obvious. The L1 point is located directly between the Earth and Sun, about 1.5 million km from the surface of the Earth, the point at which the gravitational pull of the Sun and Earth cancel each other out.
The L2 point is located at approximately the same distance, but on the opposite side of the Earth. In this case, the Earth is constantly eclipsing the Sun. The L3 point is on the opposite side of the Sun from the Earth, at approximately 1AU. Now this is where it starts to get a little strange. The L4 and L5 points are located 60° in front and 60° behind the Earth’s orbit. The 4th and 5th Lagrangian points are also the most gravitationally stable regions, primordial debris lurks, trapped in the Lagrangian prisons. Although the L1 point is often considered to be the most stable of the Lagrangian points (as it’s directly locked between the gravity of the Sun and Earth), even space observatories (such as SOHO and ACE) have to carry out complex orbits to remain in place. Otherwise the delicate balance will be lost and they will drop away from L1.
L4 and L5 are in fact the most stable locations, balanced by a complex cage of competing gravitational components from the Earth and the Sun. It is thought that these two regions have trapped lumps of rock and dust all the way through the evolution of the Solar System, making them a very interesting place to send a space mission. And the two solar probes of STEREO are currently racing toward L4 and L5, about to explore the gravitational dead zone, whether they like it or not.
It is a known fact that other planets in the Solar System possess these islands of gravitational calm, and asteroids have been observed sitting in stable locations in front and behind of Jupiter’s orbit for example (called “Trojans” and “Greeks”). Does Earth have a swarm of asteroids sitting in its L4 and L5 points? Scientists believe this is a certainty. However, no asteroids have ever been observed.
Although millions of kilometres across, L4 and L5 can only be observed at dawn and dusk. Any possibility of spotting a large asteroid diminishes rapidly as they are obscured by the Sun. So, the STEREO space telescopes are going to take the dive into L4 and L5 to see, first hand, what lies in wait.
Artist impression of the STEREO probes going their separate ways (NASA)Early on in the STEREO mission, scientists discussed the possibility of stopping the spacecraft inside the two islands of calm to provide an advanced warning of incoming charged particles from coronal mass ejections during solar maximum. However, slowing the craft down would have cost the mission too much fuel, so the decision was made to let the solar telescopes pass straight through. It will take a few months to complete the journey through the huge Solar System badlands, but it will serve a valuable purpose, STEREO has become NASA’s makeshift asteroid hunting mission.
Although STEREO wasn’t designed for this work, the mission already has a team of volunteer near-Earth asteroid hunters at the ready and their optics are more than capable of looking out for large lumps of rock invisible from Earth.
“The close-up investigation of L4 and L5 is completely new. That makes it something we should be driving,” says Richard Harrison of the Rutherford Appleton Laboratory in Oxfordshire, UK and a member of the STEREO project. “Wouldn’t it be spectacular if we actually backed past an asteroid? Saw it come creeping into view around the camera.” Now that would be a huge discovery.
This isn’t simply out of academic curiosity however. The Earth’s Moon is thought to have been formed after a huge cosmic impact with a small planetary body. The problem comes when trying to explain where the offending planetary body could have come from; too far away and it will have had too much energy. Rather than punching into the side of the Earth it would have shattered our planet. So the body must have formed a lot closer to our planet.
Did this body evolve in either the L4 and L5 points? If it did, and then somehow got kicked out of the gravitational island, perhaps careering toward the Earth, causing the cataclysmic impact that seeded the formation of the Moon.
It is exciting to think that STEREO may make some ground-breaking discoveries not Sun related. I just hope they don’t bump in to any chunks of rock, it could be pretty crowded out there…
Bolide in Italy. Credit: Ferruccio Zanotti of Ferrara, Italy, via Spaceweather.com
A fireball seen over Texas during the daytime on Sunday, Feb. 15th, triggered widespread reports that debris from the recent satellite collision was falling to Earth. The FAA even issued a statement that airplanes should watch for falling debris. However, those reports and statements were premature. Researchers have studied video of the event and concluded that the object was more likely a natural meteoroid about one meter wide traveling more than 20 km/s–much faster than orbital debris. Meteoroids hit Earth every day, and the Texas fireball was apparently one of them. Additionally, a spokeswoman for U.S. Strategic Command said the fireball spotted in the Texas skies Sunday was unrelated to the satellite collision. And as always, the Bad Astronomer was on top of it from the beginning, so check out his first post here (which includes several updates as the news broke), and a follow-up here. There were other fireballs, too….
There was one bolide event in central Kentucky on Friday, February 13. People heard loud booms, felt their houses shake, and saw a fireball streaking through the sky. This occurred just hours after another fireball at least 10 times brighter than a full Moon lit up the sky over Italy. Although it is tempting to attribute these events to debris from the Feb. 10th collision of the Iridium 33 and Kosmos 2251 satellites, the Kentucky and Italy fireballs also seem to be meteoroids, not manmade objects. Italian scientists are studying the ground track of their fireball, which was recorded by multiple cameras, and they will soon begin to hunt for meteorites.
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Air Force Major Regina Winchester said that Joint Space Operations Center at California’s Vandenberg Air Force Base has been monitoring the debris from the collision, and that could not have caused the dramatic sight. She also said the fireball was not related to the estimated 18,000 man-made objects that the center also monitors.
“There was no predicted re-entry,” Winchester said about the objects in Earth’s orbit.
She said it was likely a natural phenomenon such as a meteorite.
Image where PHA 2009 BD81 (left) was discovered. PHA 2008 EV5 is on the right. Image courtesy Robert Holmes.
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While observing a known asteroid on January 31, 2009, astronomer Robert Holmes from the Astronomical Research Institute near Charleston, Illinois found another high speed object moving nearby through the same field of view. The object has now been confirmed to be a previously undiscovered Potentially Hazardous Asteroid (PHA), with several possible Earth impact risks after 2042. This relatively small near-Earth asteroid, named 2009 BD81, will make its closest approach to Earth in 2009 on February 27, passing a comfortable 7 million kilometers away. In 2042, current projections have it passing within 5.5 Earth radii, (approximately 31,800 km or 19,800 miles) with an even closer approach in 2044 2046. Data from the NASA/JPL Risk web page show 2009 BD81 to be fairly small, with a diameter of 0.314 km (about 1000 ft.) Holmes, one of the world’s most prolific near Earth object (NEO) observers, said currently, the chance of this asteroid hitting Earth in 33 years or so is quite small; the odds are about 1 in 2 million, but follow-up observations are needed to provide precise calculations of the asteroid’s potential future orbital path.
In just the past couple of years, Holmes has found 250 asteroids, 6 supernovae, and one comet (C/2008 N1 (Holmes). However, he said he would trade all of them for this single important NEO discovery.
“I was doing a follow up observation of asteroid 2008 EV5,” Holmes told Universe Today, “and there was another object moving right next to it, so it was a pretty easy observation, actually. But you just have to be in the right place at the right time. If I had looked a few hours later, it would have moved away and I wouldn’t have seen it.” A map generated by Holmes showing the path of 2009 BD 81. Credit: Robert Holmes
A few hours later, teacher S. Kirby, from Ranger High School in Texas, who was taking part in a training class on how to use the data that Holmes collects for making observations used Holmes’ data measuring 2008 EV5 and also found the new object. Shortly after that, a student K. Dankov from the Bulgarian Academy of Science, Bulgaria who is part of ARO education and public outreach also noticed the new asteroid. Holmes listed both observers as co-discovers as well as another astronomer who made confirmation follow-up observations of what is now 2009 BD81.
Holmes has two telescopes, a 24-inch and 32-inch. Holmes' 24 inch telescope. Courtesy Robert Holmes
He works night-after-night to provide real-time images for the IASC program, uploading his images constantly during the night to an FTP site, so students and teachers can access the data and make their own analysis and observations from them. IASC is a network of observatories from 13 countries all around the world.
Holmes is proud of the work he does for education, and proud of the students and teachers who participate.
“They do a great job,” he said. “A lot of the teachers are doing this entirely on their own, taking it upon themselves to create a hands-on research class in their schools.” Holmes said recently, two students that have been involved with IASC in high school decided to enter the astrophysics program in college.
“I feel like we are making a difference in science and education,” he said, “and it is exciting to feel like you’re making a contribution, not just following up NEO’s but in people’s lives.”
Holmes also owns some of the faintest observations of anyone in the world.
“My telescopes won’t go to 24th magnitude,” Holmes said, “but I’ve got several 23rd magnitudes.”
“Getting faint observations is one of the things NASA wants to achieve, so that’s one of the things I worked diligently on,” Holmes continued. The statistics on the site bear that out clearly, which shows graphs and comparisons of various observatories.
To what does Holmes attribute his success? “It’s obviously not the huge number nights we have in Illinois to work,” Holmes said. The East-Central region of Illinois is known for its cloudy winter weather, when we often have our poorest astronomical “seeing.”
“However, I work every single night if it’s clear, even if it’s a full moon,” he said. “Most observatories typically shut down three days on either side of a full moon. But I keep working right on through. I found that with the telescopes I work with, I’ve been able to get to the 22nd magnitude even on a full moon night. Last year, I got about 187 nights of observing, which is the same number as the big observatories in the Southwest, when you take off the number of cloudy nights the 6 nights a month they don’t’ work around full moons. Sometimes you just have to work harder, and work when others aren’t to be able to catch up. That’s how we are able to do it, by working every single chance we have.”
He works alone at the observatory, running the pair of telescopes, and doing programming on the fly. “I refresh the confirmation page of new discoveries every hour so I can chase down any new discovery anyone has found,” he said. “If I just pre-programmed everything I wouldn’t have a fraction of the observations I have each year. I’d miss way too many because some of the objects are moving so fast.”
Holmes said some objects are moving 5,000 arc-seconds an hour on objects that are really close to Earth. “I’ve seen them go a full hour of right ascension per day and that’s pretty quick. They can go across the sky in four or five days,” said Holmes. “And there have been some that have gone from virtually 50 degrees north to 50 degrees south in one night. That’s was a screaming fast object, and you can’t preprogram for something like that, you actually have to be running the telescope manually.”
Overhead view of 2009 BD81's path. Courtesy Robert Holmes
2009 BD81 is listed as a “risk” object on the NASA/JPL website. This is the 1,015th PHA discovered to date.
“It ranks high as a NEO in general,” said Holmes, “although not in a super-high category as far as the Torino scale,” which categorizes the impact hazard of NEOs. “At this point it’s considered a virtual impactor and that is typically is as high of a rating that you get at this point.”
“Because it is a virtual impactor, it will remain on that webpage and ask for observations every single night until it is removed as a virtual impactor or becomes too faint to see,” said Holmes. “In the past year, we’ve removed 23 virtual hazardous objects, which means there have been enough observations that the orbit of that object is no longer considered a threat to our planet.” 2009 BD81. Courtesy Robert Holmes
Because of the small number of observations of of 2009 BD81, the current chance of it hitting Earth is small. “The odds are really small right now,” said Holmes, “however, the smaller your orbital arc is the wider the path is at that point is of potential impact. The longer the arc gets, the narrower the cone of opportunity of impact becomes, and once that cone is no longer pointing at earth in the future, it is removed as a possible impactor.”
Holmes said the excitement of this discovery has been exhilarating. “It’s been a lot of fun. The energy level gets pretty high when you have something like this show up,” he said. “It’s pretty rare, and this is the first time I’ve ever had a NEO discovery. I’ve had several hundred asteroids, and just since the beginning of the school year we have had about 40 asteroids that students and teachers have discovered in the program. So having this as a NEO is kind of a nice thing.”
Holmes said he’ll track 2009 BD81 as long as he possibly can.
Holmes previously was a commercial photographer who had over 4,500 photographs published worldwide in over 50 countries. “At first astronomy was just a hobby in the evening,” said Holmes. “I worked with schools, who used the data and made some discoveries of supernovae and asteroids. It came to a point where it was really hard to work all day as a photographer and work all night in astronomy getting data for students.” So, he chose astronomy over photography.
Holmes now works under a grant from NASA to use astrometry to follow-up new asteroid discoveries for the large sky surveys and help students look for new asteroid discoveries for educational outreach programs.
One would assume that as a former commercial photographer, Holmes would attempt to capture the beauty of the night sky in photographs, but that’s not the case.
“The only thing I’m really interesting in is the scientific and educational aspect of astronomy,” said Holmes. “I’ve never taken a single color, pretty picture of the sky in the half a million images I’ve taken of the sky. It’s always been for research or education.”
Holmes is considered a professional astronomer by the Minor Planet Center and International Astronomical Union because he is funded by NASA, so that means he wasn’t eligible to receive the Edgar Wilson award when he found a comet last year.
Because of Holmes outstanding astronomical work, he is also an adjunct faculty member in the physics department at Eastern Illinois University in Charleston, Illinois.
Artist’s impression of the asteroid (234) Barbara. Thanks to a unique method that uses ESO’s Very Large Telescope Interferometer, astronomers have been able to measure sizes of small asteroids in the main belt for the first time. Their observations also suggest that Barbara has a complex concave shape, best modelled as two bodies that may possibly be in contact. Credit: ESO/L. Calçada
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It’s one thing to know the position of an asteroid out in space. It’s quite another to know the size and shape of a particular asteroid that might be heading our way. A team of French and Italian astronomers have devised a new method for measuring the size and shape of asteroids that are too small or too far away for traditional techniques by using ESO’s Very Large Telescope Interferometer (VLTI). This will increase the number of asteroids that can be measured by a factor of several hundred, and provide the ability to resolve asteroids as small as about 15 km in diameter located in the main asteroid belt, 200 million kilometers away. This is equivalent to being able to measure the size of a tennis ball a distance of a thousand kilometers.
“Knowledge of the sizes and shapes of asteroids is crucial to understanding how, in the early days of our Solar System, dust and pebbles collected together to form larger bodies and how collisions and re-accumulation have since modified them,” says Marco Delbo from the Observatoire de la Côte d’Azur, France, who led the study.
Direct imaging with adaptive optics on the largest ground-based telescopes such as the Very Large Telescope (VLT) in Chile and space telescopes, or radar measurements are currently the best methods of asteroid measurement. However, direct imaging, even with adaptive optics, is generally limited to the one hundred largest asteroids of the main belt, while radar measurements are mostly constrained to observations of near-Earth asteroids that experience close encounters with our planet. Another double asteroid. Credit: ESO
Delbo and his colleagues have devised a new method using interferometry that will not only increase the number of objects that can be measured, but, more importantly, bring small asteroids that are physically very different from the well studied larger ones into reach.
The interferometric technique combines the light from two or more telescopes. Astronomers proved their method using ESO’s VLTI, combining the light of two of the VLT’s 8.2-metre Unit Telescopes.
“This is equivalent to having vision as sharp as that of a telescope with a diameter equal to the separation between the two VLT Unit Telescopes used, in this case, 47 meters,” says co-author Sebastiano Ligori, from INAF-Torino, Italy.
The researchers applied their technique to the main belt asteroid (234) Barbara, which was earlier found, by co-author Alberto Cellino, to have rather unusual properties. Although it is so far away, the VLTI observations also revealed that this object has a peculiar shape. The best fit model is composed of two bodies each the size of a major city – with diameters of 37 and 21 km – separated by at least 24 km. “The two parts appear to overlap,” says Delbo, “so the object could be shaped like a gigantic peanut or, it could be two separate bodies orbiting each other.”
If Barbara proves to be a double asteroid, this is even more significant: by combining the diameter measurements with the parameters of the orbits, astronomers can then compute the density of these objects. “Barbara is clearly a high priority target for further observations,” concludes Ligori.
The team will now begin a large observing campaign to study small asteroids.
2009 BD is approximately 400,000 miles from Earth (NASA)
[/caption]A 10 meter-wide asteroid named 2009 BD discovered earlier this month is making a slow pass of the Earth, coming within 400,000 miles (644,000 km) of our planet. The near-Earth asteroid (NEO) poses no threat to us, but it is an oddity worth studying. Astronomers believe the rock is a rare “co-orbital asteroid” which follows the orbit of the Earth, not receding more than 0.1 AU (15 million km) away. It is stalking us.
On looking at the NASA JPL Small-Body Database orbital plot, it is hard to distinguish between the orbital path of the Earth and 2009 BD, showing just how close the asteroid is shadowing the Earth on its journey around the Sun…
In 2006, NASA announced that Earth’s “second moon” was an asteroid called 2003 YN107 (with a diameter of about 20 meters) and it was about to leave the vicinity of Earth, leaving its “corkscrewing” orbit around our planet for seven years, only to return again in 60 years time. 2003 YN107 was of no threat (and wont be in the future), but it is interesting to study these bodies to understand how they interact with Earth. Having NEOs in stable orbits around the Earth could be of benefit to mankind in the future as missions can be planned, possibly sending mining missions to these rocky visitors so we can tap their resources.
The orbital path of 2009 BD (blue line) (JPL Small Body Database)
So far, little is known about the new 10 meter asteroid in our near-Earth neighbourhood, but it provides us with an exciting opportunity to track its laborious orbit to see whether it will eventually be ejected after making a close pass to the Earth’s gravitational field (as was the case with 2003 YN107 in 2006). From preliminary observations, 2009 BD is projected to shadow our planet for many months (possibly years) to come. Until November 2010 at least, the asteroid will hang around the Earth, within a distance of 0.1 AU.
It is worth emphasising that 2009 BD is of no threat to the Earth, its closest approach takes it 644,000 km from us. For comparison, the Moon’s apogee is 400,000 km, so 2009 BD is stalking us from afar, beyond lunar orbit.
As time goes on, astronomers will be able to track 2009 BD’s orbit with more precision (for updates, keep an eye on the JPL Small-Body Database), but for now, we have a micro-second moon following the Earth on its orbit around the Sun…
Pan-STARRS 1 prototype, part of the Panoramic Survey Telescope and Rapid Response System, Haleakala mountain, Maui. Photo / MIT Lincoln Laboratory
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A prototype telescope with an enhanced ability to find moving objects will soon be operational, and its mission will be to detect asteroids and comets that could someday pose a threat to Earth. The system is called Pan-STARRS (for Panoramic Survey Telescope and Rapid Response System) located on Haleakala mountain in Maui,Hawaii, and is the first of four telescopes that will be housed together in one dome. Pan-STARRS will feature the world’s largest and most advanced digital camera, providing more than a fivefold improvement in the ability to detect Near Earth Asteroids and comets. “This is a truly giant instrument,” said University of Hawaii astronomer John Tonry, who led the team developing the new 1.4-gigapixel camera. “We get an image that is 38,000 by 38,000 pixels in size, or about 200 times larger than you get in a high-end consumer digital camera.” The Pan-STARRS camera will cover an area of sky six times the width of the full moon and it can detect stars 10 million times fainter than those visible to the naked eye.
The Lincoln Laboratory at the Massachusetts Institute of Technology (MIT) developed charge-coupled device (CCD) technology is a key enabling technology for the telescope’s camera. In the mid-1990s, Lincoln Laboratory researchers developed the orthogonal-transfer charge-coupled device (OTCCD), a CCD that can shift its pixels to cancel the effects of random image motion. Many consumer digital cameras use a moving lens or chip mount to provide camera-motion compensation and thus reduce blur, but the OTCCD does this electronically at the pixel level and at much higher speeds.
The challenge presented by the Pan-STARRS camera is its exceptionally wide field of view. For wide fields of view, jitter in the stars begins to vary across the image, and an OTCCD with its single shift pattern for all the pixels begins to lose its effectiveness. The solution for Pan-STARRS, proposed by Tonry and developed in collaboration with Lincoln Laboratory, was to make an array of 60 small, separate OTCCDs on a single silicon chip. This architecture enabled independent shifts optimized for tracking the varied image motion across a wide scene.
“Not only was Lincoln the only place where the OTCCD had been demonstrated, but the added features that Pan-STARRS needed made the design much more complicated,” said Burke, who has been working on the Pan-STARRS project. “It is fair to say that Lincoln was, and is, uniquely equipped in chip design, wafer processing, packaging, and testing to deliver such technology.”
The primary mission of Pan-STARRS is to detect Earth-approaching asteroids and comets that could be dangerous to the planet. When the system becomes fully operational, the entire sky visible from Hawaii (about three-quarters of the total sky) will be photographed at least once a week, and all images will be entered into powerful computers at the Maui High Performance Computer Center. Scientists at the center will analyze the images for changes that could reveal a previously unknown asteroid. They will also combine data from several images to calculate the orbits of asteroids, looking for indications that an asteroid may be on a collision course with Earth.
Pan-STARRS will also be used to catalog 99 percent of stars in the northern hemisphere that have ever been observed by visible light, including stars from nearby galaxies. In addition, the Pan-STARRS survey of the whole sky will present astronomers with the opportunity to discover, and monitor, planets around other stars, as well as rare explosive objects in other galaxies.
