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Well, that didn’t take long: The WISE spacecraft (Wide-field Infrared Survey Explorer) spotted its first near-Earth asteroid on January 12, 2010, two days before the official start of its all-sky survey. That’s a pretty good catch, considering WISE just popped it lens cover a couple of weeks ago (December 29, 2009) and released its “first light” image on January 6. This is the first of what researchers hope will be thousands of previously undiscovered asteroids in the main asteroid belt, and hundreds of new near-Earth asteroids. By mapping the whole sky in infrared light, it should also be able to capture millions of new stars and galaxies.
WISE’s software picked up the object, 2010 AB78, moving against a background of stationary stars. Researchers followed up and confirmed the discovery with the University of Hawaii’s 2.2-meter (88-inch) visible-light telescope near the summit of Mauna Kea.
This asteroid does not pose any foreseeable impact threat to Earth, but scientists will continue to monitor it. 2010 AB78 is currently about 158 million kilometers (98 million miles) from Earth. It is estimated to be roughly 1 kilometer (0.6 miles) in diameter and circles the sun in an elliptical orbit tilted to the plane of our solar system. The object comes as close to the sun as Earth, but because of its tilted orbit, it is not thought to pass near our planet.
Source: JPL
I’ve always been curious about the number of dead long-term comets out there. (dead meaning they do not outgas anymore)
Since they spend most of their time away from us and since they are not reflective, we really don’t have a good way of tracking them and getting enough of a sample to indicate the size of their population.
If an object take 1000 years to orbit, .out which only a few month are spend anywhere near the orbit of the Earth, then each one we see represents several thousands out there.
As far as Earth smacking probabilities go, since they travel faster, even smaller ones are dangerous, and since they only come around once every millennium, we can’t track them in advance like we can track NEOs.
Because they are likely non-reflective, I hope that they will be visible in the far IR just as black bodies as they pass through. (I hope WISE looks inwards as well, that is)
I’m surprised at the size of it … The very first find is 1km across.
I thought it was generally thought that we had a good handle on all the civilization-killers.
How many more will we find?
@CrazyEddieBlogger ,
IIRC, the IRAS infrared observatory detected faint debris trails in the inner solar system linked to both known and undiscovered comets. These debris trails stood out at infrared wavelengths and should be readily visible to WISE as it completes its all sky survey. IRAS also discovered 3200 Phaethon (parent body of the Geminid meteor shower) and several other asteroids, a task that WISE has just begun.
@Surak: IIRC, the various surveys are estimated to discover ~90% of all NEOs bigger than ~1 km, but only by ~2015 (I could be badly mis-remembering though).
When Pan-STARRS and the LSST have been at work for 10 years, I think the estimates are that essentially all NEOs bigger than ~0.3 km will have been discovered, but that won’t be for quite a while yet!
In any case, getting a confident handle on all potentially deadly long-period comets is, today, not possible (nor in the forseeable future either). Fortunately, it does seem that these are much rarer than PHAs (potentially hazardous asteroids).
I have pondered whether these NEO orbits might provide a test for dilute amounts of dark matter. DM in space would introduce a for F ~ kr that would act as a minor perturbation to these orbits.
LC
“”CrazyEddieBlogger Says:
January 25th, 2010 at 9:13 am
I’ve always been curious about the number of dead long-term comets out there. (dead meaning they do not outgas anymore)””
There are a number of objects with comet like orbits which are thought to be dead comets. They are called Damocloids, last time I checked nearly 50 of them had been identified.
Agmartin –
Thanks – I knew there were some that were identified, but here’s the rub:
50 NEOs, once discovered, stand for 50 NEOs. What you see is what you get.
On the other hand, 50 Long Duration Asteroids (LDAs?) observed while in transit near the orbit of Earth stand for maybe 50000 LDAs that are currently somewhere on their 1000 year orbit, too far to observe. So while the total number of LDAs near Earth’s orbit will remain 50, they will be a different 50 (out of that larger population) on any given year, so there’s no way to predict their trajectory or get advanced warning.
It will be interesting to find out. I always get the feeling that NEOs are the most visible yet least dangerous bunch.
I wonder if there’s any way to find out by looking at lunar or Martian craters what the origin of the creating objects was – long duration objects should have higher velocities.