WISE uncovers its first near-Earth asteroid!

By Phil Plait | January 25, 2010 2:00 pm

The Wide-field Infrared Satellite Explorer has detected its first near-Earth asteroid! Named 2010 AB78, it was discovered in mid-January by the orbiting observatory. Here’s an image of the rock:


AB78 is about a kilometer (0.6 miles) or so across, making it one of the bigger asteroids that can buzz the Earth. The orbital information on it isn’t perfect yet, but we already know its orbit doesn’t actually cross the Earth’s so it can’t hit us. At closest approach it’s still many million of kilometers away from us, and poses no threat.

However, I’ll be honest and say this discovery is mildly alarming (stressing the word mildly). One of the missions of WISE is to find such asteroids; some rocks are dark and therefore hard to detect using telescopes which search in visible light. However, AB78 is warm, so it glows in the infrared, making it an easy target for WISE. That’s why searching for such asteroids is one of WISE’s main goals.

The thing is, statistically speaking we should already know of almost all the kilometer-sized rocks that are in near-Earth orbits; given the rates and methods of finding them, our catalog should be about 90% complete. Finding an asteroid this size that eluded detection up until now is somewhat unsettling. How many more have we missed?

Let me be clear: this could be a statistical fluke; even if we know of 90% of all the NEAs out there, 10% still lurk out in the black. It could simply be that this first one found by WISE is somewhat on the hefty side, and the next 20 will be far smaller. Remember too, this one is bright in the IR (in the above picture, red is actually at a wavelength of 12 microns, 15 times longer what the human eye can see) and so it was easy to spot. Smaller ones are fainter, so they may not be as obvious and will take longer to detect. Also, AB78 is on a weird orbit, tipped substantially (about 33°) to the plane of the solar system, again making it more difficult to spot.

And in a way, this is good news! The more we know about these things, the better. AB78 may be a fluke, or there may be more rocks this size out there hiding, but either way I want as much info as we can get. Just knowing how many asteroids of a given size orbit the Sun and get near the Earth is an important piece of data, so that we can apply some statistics to them and try to figure out, on average, how often we get hit. That’s one of the things WISE will do over its 10-month-long mission, so in a year or so we’ll be in a better position to understand these orbiting worldlets.

Emily Lakdawalla at The Planetary Society has more info as well.

Image credit: NASA/JPL-Caltech/UCLA


Comments (24)

  1. eddie

    Stupid question; why would an asteroid be warm? Just relative temperature as opposed to more distant objects in the background?

  2. This article is perhaps slightly more depressing then:

    Report says scientists lack funds to meet Congressional goal for finding smaller “near-Earth asteroids”

    Especially since the amount of money we’re talking about is in the low millions of dollars.

    Edited to respond to eddie: Just guessing, but maybe its orbit takes it closer to the sun? Maybe it still retains heat after being cleft off a larger body by collision?

  3. Cal

    Anything black absorbs light and anything white reflects it; so in this case it is absorbing light/energy from the sun and re-emitting a lot more infrared light (heat) instead of the visible light say an ice white comet would show us.

    Unless BA wants to correct me ūüėČ

  4. WISE is only funded for 10 months? Is there a technical reason for this? Or is it just a funding issue? That just seems like an incredibly short mission.

  5. Mike Mullen

    If you want to builsd something that can vaporize a city the funding will be found. If you want to find something that could vaporize a city well that’s just a waste of money…

  6. Number 6

    #4: WISE has a block of solid hydrogen that it uses to keep its sensors
    cool. When it evaporates, it can continue operation, but its images will be
    substantially degraded. That’s expected to happen after ~10 months.

    No doubt it will have a ‘supplemental mission’ after that.

  7. T.

    It was mentioned by the CSS folk on the MPML that this one would have been picked up by the normal surveys – it just so happened that there was bad weather all across the US Southwest at that time.

  8. Well this is just silly. How could they not have seen that asteroid like WAY earlier? I mean look at it, it is this bright read color AND it has this huge arrow pointing out.

    My dog could have found that. Well, maybe not.

  9. M. Brown

    Any bets on how long it takes the doomsayers to jump on this, quote out of context, blow it out of all proportion, maintain NASA is hiding the real facts, and some YouTuber claims an official sighting of whatever it is that is going to destroy us all in 2012?

  10. tacitus

    I’m just trying to picture being “mildly alarmed”…

    Oh, noes. There might be a massive asteroid up there that’s about to fall on our heads, but since I just found out that I don’t know if there is or not I’ll just walk slowly around the house waving my arms around a bit and go “eek” a couple of times.

    I think I’ll choose to be mildly concerned instead. :-)

  11. Marcus

    It seems like this is a problem for Bayes theorem: you have a Prior (probability distribution of how many 1 km asteroids are out there that have not been found yet) and an observation (in X amount of observing time one asteroid was found). If you can make a probability distribution of the likelihood of time-to-first-asteroid-of-size-greater-than-1-km-observation, then you can use Bayes theorem to make your new pdf of the number of not-yet-found 1 km asteroids.

    Of course, determining those two distributions will be hard: the first, maybe less so (you mentioned an estimate of 90% found, so presumably people have some ideas of the prior): the 2nd requires assumptions about the population of asteroids out there and their visibility characteristics. Assuming that the population of the 10% or so not-found asteroids is like the 90% found asteroids is probably poor, because we’ve found the easy to find ones, so the remaining ones are probably weirdos. And if our new observing technology can’t pick up asteroids with Stealth Bomber technology, then we have no additional information on how many of those might still be out there….

  12. dre

    Ridiculous. That’s clearly five objects flying in a delta formation. A squadron of Cylon Raiders! To the bunkers!

  13. eddie

    @ Cal: Thank you. I should have thought of that myself, but obviously, I didn’t.

  14. Steve Jeffers

    It alarms me that astronomers have only just detected something that’s bright red and has a giant arrow pointing at it.

  15. gss_000

    One thing the mainstream press picked up on that wasn’t mentioned here was how quickly this was found. IIRC it was observed January 12, before even the spacecraft’s full sky survey started.

  16. Crux Australis

    Respected astronomer Phil Plait was quoted today as saying, “I‚Äôll be honest…this discovery is…alarming”.

    RUN! RUN FOR THE HILLS!!1!!11!!one

  17. Gary Ansorge

    In the military, they say you never hear the bullet with your name on it. I expect the same applies to extinction level asteroid impacts.

    We’re checking for asteroids in or near the solar ecliptic. IF we ever get a nearly complete map of those, THEN we’re still left with all those buggers that could come in from elsewhere and there’s a LOT of elsewhere. A sane approach would suggest we launch a few hundred WISE satellites, covering the entire sky. Then, of course, we should also be able to refresh their on board hydrogen supplies.

    Gee! It looks more and more like we should have a solid human presence in space.

    GAry 7

  18. Regner Trampedach

    Gary @ 17: Why would human presence in space help on this issue? Would you like to man the presently automated all-sky survey telescopes with grad-students? Or maybe TSA personnel? I think they might get a bit lonely out there… Or do you just want people to re-fill the dewar with hydrogen? I think you might find that such a servicing mission would be similarly expensive to building a new telescope and launch it. It could, however, make some sense to build telescopes on the Moon, and it seems like they could carry out observations for most of the year from Shackleton at the South Pole.
    Btw. WISE is scheduled to perform an all-sky survey. Earth-bound surveys have concentrated on the ecliptic neighbourhood, but are also moving away from that plane, depending on progress and funding.
    Cheers, Regner

  19. Chris Winter

    Interesting related story:


    Report says scientists lack funds to meet Congressional goal for finding smaller “near-Earth asteroids”
    Robin Lloyd, Scientific American, Jan 22, 2010

    I wonder how President Obama’s proposed spending freeze will play into this.

  20. Jon Hanford

    This is obviously the long-awaited discovery image of Nemesis!, just in time for 2012. According to the Nemesis wiki page: “If Nemesis is a brown dwarf, as proposed by Dr. Dan Whitmire and Albert A. Jackson IV, then the WISE mission should easily find it.” Guess NASA knew all along.

    Even Phil admits: “‚ÄúI‚Äôll be honest‚Ķthis discovery is‚Ķalarming‚ÄĚ. [Thanx Crux :) ]

  21. Pi-needles

    ^ [Princess Leia voice on] “A little small for a nemesis don’chya think?”

    [/Princess Leia voice off, Luke voice on.]

    “Huh? Oh you mean the asteroid! I’m with Obi-WISE The Scope* we’ve come to rescue you!” ūüėČ [/Luke voice off.]

    Congrats to the WISE guys! :-)

    * Pronounced “Scope-E” in this case. ūüėČ

  22. Messier Tidy Upper

    44 days into its mission too going on the elapsed time clock on their homepage :


    (Well one of their homepages anyhow.)

    I wonder when it’ll find its first brown dwarf?

    Well done to the WISE team – I’m betting (& hoping & expecting) that’s just the first of many significant discoveries they’ll make. :-)

  23. Gary Ansorge

    18. Regner Trampedach

    Actually, what I was thinking was about was the difficulty of re-filling the H2 coolant( I know WISE was not built with that option in mind but future WISE sats could be so designed). Spirit and Opportunity are both tele-operated robots and they show how difficult it is to control those from 40 million miles away. Light delay makes fine control really difficult. I expect the best way to perform in space manufacturing, construction and topping off coolant tanks or re-fueling them would be by using tele-operated ‘bots, with the operators close enough to maintain real time control but safe inside their space station or space craft.

    GAry 7

  24. j kittle

    The WISE scope has probably already taken images of brown dwarfs but it takes time to confirm. I expect and announcement in a few months. Meanwhile there are LOTS of potential asteroid images in the data being collected but they require confirmation. The higher the latitude of the object relative to earth the more images get put together, ( as a consequence of a polar orbit, so high inclination asteroids are favored for early discovery. finally, it would be MOST helpful if Pan-Starrs survey scope was working to get early confirmation of orbits of candidate objects. I suspect that the communications between NASA ( running WISE) and the group at University of Hawaii ( running Pan-starrs)are not too good. They need to stop playing for turf and start comparing images.


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