A city-block-sized asteroid will swing by Earth on November 8

By Phil Plait | October 28, 2011 7:00 am

On November 8, an asteroid 400 meters across will pass by the Earth, missing us by the very comfortable margin of about 320,000 kilometers (200,000 miles). Named 2005 YU55, it’s been known for some time that this pass will occur, and astronomers are jumping on the chance to observe it.

First off, it’s no danger to Earth right now. It’s what’s called a Potentially Hazardous Asteroid because its orbit intersects ours, but observations have shown it won’t be a danger to Earth for at least a century, and probably much more. There’s been some scare-mongering about it over the past few months, but as usual that’s all baloney. This rock will pass us safely, sailing on into the night.

But given that this is close in astronomical terms, astronomers will be observing it carefully. There are plans to use NASA’s Deep Space Network of radio telescopes, as well as the Arecibo ‘scope in Puerto Rico (which was used to make the image above back in April 2010). They’ll be able to see features on this rock as small as two meters across, which means we’ll actually get some interesting images of it, I hope. I’ll post those as soon as I see ’em (which will be after November 8).

It’ll only get to a magnitude of about 11 — only 1/100th as bright as the faintest star you can see with your unaided eye — so you’ll need a decent-sized (12.5 cm at least) telescope to see it. 320,000 km is 3/4 of the way to the Moon, and this asteroid is small and very dark. Observing it will be tough, but you can get more info on how to do it at the Minor Planet site and on The Minor Planet Bulletin (PDF).

When I was a kid, asteroids were not much more than mysterious points of light, but now we have the technology to see them in detail from the ground, and even send space probes to get good, close looks at them! And, of course, the technology to spread those images and information as quickly as the speed of light around the globe. Sometimes that’s used to spread misinformation, but it also can be used to show people what a cool place we live in. I prefer the latter.

Related posts:

Armageddon delayed by at least a century… this time
No, 2005 YU55 won’t destroy the Earth
Asteroid 2007 TU24: No Danger to Earth
2007 TU24: Told ya so

CATEGORIZED UNDER: Astronomy, Cool stuff
MORE ABOUT: asteroid, YU55

Comments (36)

Links to this Post

  1. Nos Visitará 2005 YU55. | Pablo Della Paolera | October 28, 2011
  2. Analysis of Discourse Material « lequi100 | October 29, 2011
  1. Carey

    Arecibo is a radio scope right? So that image is in the RF part of the spectrum?

  2. Joseph G

    I’m drooling already! I trust you’ll hook us up with all the near-earth object goodness when it passes :)

    Also, that I love the idea of bouncing radar off of objects from earth and getting actual images from them. How cool is that? I wonder if the moon has ever been Aricebonated like this?
    Also, it’s fascinating that we’ll have both radar and visual images to compare. I assume that visible light albedo features and radar albedo features will be quite different.
    Though that image is making me scratch my head, come to think of it. If it’s a radar image, why does it look like the “light source” is coming from off to one side, as if it’s being illuminated by the sun?

  3. Cool news thanks. :-)

    We’re also still learning – or have just learnt what more we’ve learnt – from the Rosetta‘s fly past of asteroid Lutetia too according to this :


    online news item whilst in other news the NPP (NPOESS Preparatory Project) weather and climate observation satellite was successfully launched some hours ago. :-)

    See :




    for more info on that mission. :-)

  4. Scott

    I have a question regarding this. So we have known about this asteroid for a number of years. From the name, at least since 2005. It is going to pass close to the planet, at least in the scale of the universe. So why are we sending robotic missions to the asteroid belt, when we have one coming to us? Or at least why are we not sending one to this asteroid?

  5. One of these days we’ll figure out a way to determine the composition of these near earth guys and if they are of value put them someplace to mine. The returns on such an endeavour would be amazing (and I’m sure that even a commercial venture would allow scientists to go in first to gather data). Man, the possibilities!

  6. Messier Tidy Upper

    @ ^ Larian LeQuella : Absolutely. I think there are already several plans for the first human space mission to investigate a near-Earth asteroid.


    Also in small solar system bodies news :


    Comet Elenin is no more having broken apart – not that it ever posed us any threat before as NASA noted here :


    But it sure doesn’t now. Maybe if we’re very lucky (& the outer planets gravity perturbs the meteorid stream just right) in a few millennnia (or twelve) we’ll get a good meteor shower out of it? 😉

    Finally, in another piece of asteroid related news :


    The WISE guys have ruled one suspect for being involved in the dinosaurs demise out.

  7. Joseph G

    @#3 Larian LeQuella: I always thought mining asteroids was one of those cool places where science fiction and fact will probably converge (if there is near-term profit to be had in space, it’s probably in exploiting asteroids).
    I wonder exactly how this would be accomplished, though. Would we send robotic probes to dig up chunks and fling them at earth, or would we need to slow it down and bring it into orbit around earth?
    Given the kinetic energy of one of these bad boys, and the cost per kilo of payload, I wonder if it’d be economically feasible at all to launch a large “tugboat” with enough delta-v capacity to match speeds with the asteroid and slow it enough to bring it into Earth orbit? I’d think that bit might cost more then the mining itself.

  8. Anonymosity

    It will come closer than the Moon! Oh no! We’re all gonna die!!!!!111!!!!

    Dumb question. Is there a chance that it could hit the moon? I think you would have mentioned that if there were. :)

  9. Infinite123Lifer

    For #2 Joseph G: Thats a good question about the light source and radar imaging in general.

    For #3 Larian LeQuella: What a great idea! All we need is a planetary sized Johnny Bench! :) These things have got to be coming in awfully hot and really fast.

    Also, doesn’t spectroscopy give us a narrowed down version of the composition of asteroids and such?

    I don’t know if they can see “into” an asteroid but I think there is a pretty good idea of the surface. I am in a little over my head here (ok a lot). I think all matter gives off certain radiation, which can then be compared to known spectrums (but like I said, I am in over my head here).

    Also, if this dude was going to hit the Earth would we have as much success at plotting its course as we did with ROSAT and UARS? i.e. hardly locatable down to a specific country.

  10. Trebuchet

    @Anonymosity: I also assume they’ve determined it won’t hit the moon. I’d guess it will pass above or below the moon’s orbit. It does make me wonder what would happen if (when?) one of these does hit the moon? Might be pretty spectacular as seen from earth. Of course the chances of it hitting the far side are probably greater than the near side.

  11. @ ^ Infinite123Lifer : Pretty sure we did track one small asteroid or meteoroid down to a landing in Africa somewhere a few years ago.

    EDIT : Checks – yep : 2008 TC3 which was spotted shortly before burning up over Sudan. Click on my name for link or cut’n’paste ‘Incoming Asteroid Burned Up in Earth’s Atmosphere Right on Time’ into the search box published on 80beats blog on the 8th October 2008. The BA also mentioned that TC2008 case in his blog post : ‘Incoming!!!’ posted October 6th, 2008 1:50 PM.

  12. Naked Bunny with a Whip

    It must be Danny the Street on his way to becoming Danny the World.

  13. SkyGazer

    “the very comfortable margin of about 320,000 kilometers”

    320,000 km is comfortable?

    The moment I look at it it´s a mere second away!!!!
    And you dare to call something like that comfortable?

    You must be a denier.

    Comforting us…. writing this stuff without your black trousers on.

  14. Ivan Berg

    NASA advocates $billion star treking while the solar system sends really good stuff within spitting distance of Earth 20+ times/year. Hey NASA, pluck the low-hanging fruit.

  15. Jon Hanford


    “Is there a chance that it could hit the moon?”

    Not on this flyby: http://www.universetoday.com/wp-content/uploads/2011/10/2005_YU55_approach_movie.gif

  16. Infinite123Lifer

    For #8 MTU:

    Much appreciated for the input as always :)

    Hmmm…sounds like 2008TC3 was sort of a test at the time. I wonder what the overall success rate of scientist’s has been with ALL of our calculations of the sort (*I would think it improves over time however with all the variables perhaps every event is vastly different despite what we have learned from our past successes and/or failures).

    I also wonder how that success rate has changed over time with the addition of new technology and past experience. I would have to guess that there is always many unforeseeable circumstances which could cause our best calculations to wind up “no where close” especially being that no falling object is exactly like any other in trajectory in speed in mass in composition or in timing (*reiterated i guess). Luckily they all follow the same laws of physics!!! :) :)

    In the article it mentioned that there was still a few kinks that needed to be ironed out. . .”some kinks” in these type of calculations must be more like “monumental tricks of the trade”. (i tried clicking the blue but the link is gone I think) Nevertheless, pretty inspiring of good news!

    Good Lookin Out! literally :)

  17. Joseph G

    @8 MTU: Cool! Your post made me wonder – if small rocks are constantly hitting Earth, wouldn’t many also hit the moon, and wouldn’t the big ones make visible flashes?
    Sure enough, I found this:

    Video of a largish bowling-ball sized asteroid (meteoroid? Is it different if it hits the moon?) making a new crater :)

  18. Runar from Norway

    It won’t be spinning of into the night Phil. “Into the night” will actually meaning hitting the planet on the dark side. Bad bad bad Astronomer. So you though you could get away with that one? lol

  19. Pete Jackson

    It’s weird how the 2010 encounter radar image looks like a spherical object seen in the ‘first-quarter’ phase. But true radar images will of necessity look like the ‘full-moon’ phase.
    Either the asteroid really has that strange shape, …

    Or, perhaps, this isn’t a real image, but is a plot of intensity returned versus time and frequency (as were the first radar maps of Venus back in the 1960s) andyou need an interferometer to make a real image. Guess I need to read the actual paper!

  20. Chris Winter

    It would really be cool to “tag” this asteroid as it swings past — to drop a few rugged radar corner reflectors on it so that we could track it throughout its orbit.

    Of course, if a mission like that is mounted, it would aim to do much more. But given the ΔV, landing something delicate would be a challenge. Corner reflectors might survive a reasonably fast impact.

    I wonder what the asteroid’s relative speed will be at closest approach.

  21. flip

    “320,000 km is 3/4 of the way to the Moon”

    That right there should convince people it’s not going to hit us. But then, some people just won’t see a phrase like that in their local newspapers.

    Runar #19, I thought the exact same thing! :)

  22. DLC

    No no, it’s going to hit us, but not until Dec. 21 2012 !
    [tries hard to not break up laughing]

  23. @ ^ DLC : Thought it was the 31st of December that we (don’t) need to worry about? 😉

    @18. Joseph G :

    @8 MTU: Cool! Your post made me wonder – if small rocks are constantly hitting Earth, wouldn’t many also hit the moon, and wouldn’t the big ones make visible flashes? Sure enough, I found this: [link snipped] Video of a largish bowling-ball sized asteroid (meteoroid? Is it different if it hits the moon?) making a new crater.

    Nice clip thanks. :-)

    As for terminology a “meteoroid” is just a very small asteroid. Or a very large particle of zodiacal dust. Not sure exactly where they draw the line between the two. Wikipedia (source linked to my name ) notes :

    “A meteoroid is a sand- to boulder-sized particle of debris in the Solar System. …(snip) … Beech and Steel, writing in Quarterly Journal of the Royal Astronomical Society, proposed a new definition where a meteoroid is between 100 µm and 10 m across. The NEO definition includes larger objects, up to 50 m in diameter, in this category. Very small meteoroids are known as micrometeoroids.”

    What object they’re impacting on – Earth, Moon or Pluto – makes no difference to what the meteoroid is called although it could be described as a small comet fragment or asteroid depending on composition. “Bolide” covers pretty much every catgeory of impacting object.

    @17. Infinite123Lifer : Thanks. My pleasure. :-)


    PS. Today (29th October 2011 is exactly the 20th anniversary of the first ever asteroid fly past when in 1991 Galileo became the first spacecraft to visit an asteroid when it made a flyby of 951 Gaspra. (Wikipedia front page.)

  24. RwFlynn

    November 8th? That’s Election Day here in VA!!! I smell a CONSPIRACY! :O

  25. Joseph G

    @MTU: Ahh, I see.
    For some reason, I associated “meteor” with “meteorology” and took it to have something to do with Earth’s atmosphere in particular. Can you tell I’ve never studied the least bit of Latin? 😉

  26. vince charles

    15. Ivan Berg Said:
    October 28th, 2011 at 9:50 am

    “NASA advocates $billion star treking while the solar system sends really good stuff within spitting distance of Earth 20+ times/year. Hey NASA, pluck the low-hanging fruit.”

    No. As the vast majority of NEOs are small (regardless of albedo), the vast majority aren’t spotted until weeks to months beforehand. It takes months just to run comprehensive testing on a spacecraft, let alone run through a launch campaign on any orbital launcher. Getting a deep-space probe on its way on these unreal timescales would take the same billions you complain about.

    There have been two options, somewhat. Sounding-rocket missions can be built and lit on these timescales, particularly if you’re re-flying an old instrument. However, you’d have to be satisfied with remote sensing via small-aperture telescopes. Something tells me that, aside from fewer and fewer bands that can’t be observed despite the atmosphere, that there isn’t much science to be gained from nearby objects by a sounding rocket, compared to a giant ground telescope or the odd orbiting telescope.

    Years ago, there was a proposal for asteroid probes in on-orbit storage. Small probes would be launched to LEO, then boosted at some later date towards nearby asteroids yet undiscovered at launch time. The mission wasn’t approved, possibly because “asteroids yet undiscovered” doesn’t make a compelling science case. Particularly after Galileo, NEAR, etc. already bagged several of the more-accessible asteroid types already.

  27. Joseph G

    The posting thingy is doing odd things…

  28. Joseph G

    @#28 vince charles: I also would add to that that once you’re in orbit, the amount of energy required to get somewhere isn’t dependent on distance, but on factors like the relative speeds of the Earth and the target object (and whether you have the opportunity to do any gravity slingshot maneuvers) . The delta-v budget required to reach some near-earth objects is fairly low, as little as half that required to get to Mars (about 6.3 kilometers per second) but some of the ones with the really eccentric orbits have delta-v costs of over 28 kps. As you know, you might have a rock that just barely misses the Earth by a few hundred miles, but if it’s going fast enough, a rendezvous might take a far more powerful rocket then was required to send New Horizons to Pluto (delta-v of the third stage was just over 16 kps).

    I never knew about that on-orbit probe storage idea. I like it, but given current budget concerns, I can see how that’d go over like a lead balloon these days :)

    EDIT: By rendezvouz, of course I meant matching speeds, sticking around to get a good look at the thing. Obviously, doing a flyby of something coming that close would be trivial, but you’d also have almost no time to get a close look. As you said, at that point you may as well stick to ground-based ‘scopes.

  29. Joseph G

    Weird, it double posted on me.

  30. j. paul

    @18, @24: According to “They Might Be Giants”:

    “A shooting star or meteor,
    whichever name you like/
    The minute it falls down to earth,
    it’s called a a meteorite.”

  31. reidh

    well, get yer act together and instead of just taking pictures, do something to alter its orbit and prove that you could if you had to! best would be to set into a new orbit around the sun near us so we could mine it. or send it into the sun.

  32. Peter Davey

    Some commentators have suggested crashing such objects into the Moon, thus rendering them safe, from the point of view of the Earth, whilst still remaining conveniently available for mining.

    I’m not sure what any Lunar colonists would think of that arrangement, though.

    “Are there no stones in Heaven but what serve for the thunder?” – Othello.

  33. ChrisB

    Call me an old worrywart, but I’m less consoled by that “it won’t be a danger to Earth for at least a century, and probably much more” than everybody else seems to be. We’re trying to stop global warming because it’ll kill millions of people over the next hundred years; we should, surely, be putting a comparable effort into something that could send 500-metre tsunamis over NYC to the Appalachians.

  34. Someone asked a question about an asteroid that may hit Earth in 20-30 years and his question said the asteroid is about the size of a football field. 100 yards doesn’t sound all that big in relative terms. How big must an asteroid be for it to make it all the through our atmosphere without burning up?


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar