Updated movie of asteroid YU55, plus bonus SCIENCE

By Phil Plait | November 14, 2011 7:00 am

Last week, the asteroid 2005 YU55 passed by the Earth. Lots of observations were made, including using the Goldstone radio telescope in California. I wrote about how this works last week. NASA just released a new video showing an updated animation containing 28 frames, showing YU55 rotating as it swung past us:

That’s pretty nifty. Mind you, this isn’t an image like an optical telescope would make, but instead is a constructed 2D representation using what’s called the Doppler Delay technique; that’s why it looks like it’s illuminated from the top. That’s not real; read Emily Lakdawalla’s excellent writeup to get more info on how that works.

However, from looking at the animation you can see several features, including some broad depressions (YU55 is about 400 meters across, so some of those dips are the size of football fields). There are also several bright spots which I find interesting. Those are areas which are particularly reflective of radar pulses from the telescope; you can see them brighten and fade as the rock spins. These may be boulders on the surface, which change brightness as the angle between them and the telescope changes. There’s also an indication of an equatorial ridge, which is a feature seen on other small near-Earth asteroids as well.

The asteroid passed close enough to Earth (320,000 km) that its orbit was changed by our gravity! Astronomer JL Galache of the Minor Planet Center in Cambridge, Massachusetts, left a comment in a previous post about this, saying that YU55’s inclination (the tilt of its orbit) has changed, and that the points of its orbit where it makes its closest and farthest approaches to the Sun (perigee and apogee) have changed a bit as well.

I’ll also note that when I posted the Swift observations of YU55, I bet that some people would claim it was under intelligent control. BABloggee Ivan Simic sent me several links to precisely such claims. Most were from people whose grasp of reality may be somewhat tenuous, but one in particular caught my eye; he claims there are two close-ups of YU55 that were made, but then shows images from the comet Itokawa! In other words, that’s like saying Mars isn’t red and then showing pictures of Uranus.

It’s wearying knowing that every advance made in astronomy seems to be more fodder for those who would promote pseudoscience. But I don’t let that knowledge slow me down. Why not?

Because this stuff is real. Giant rocks pass by the Earth! We sometimes know about it years in advance! We can ping them with pulses of invisible radar and get their distance, size, shape, rotation speed, and see features on their surface! We can point orbiting spacecraft at them!

This stuff is so cool, and it’s real science.

That’s what we have going for us. Semper veritas, my friends.

Related posts:

A Swiftly passing asteroid
NASA primer on YU55
Just to be clear: asteroid YU55 is no danger to Earth
A city-block-sized asteroid will swing by Earth on November 8


Comments (15)

  1. Jonathan

    Hey Phil,

    Did YU55 pass through a keyhole and in so doing spell doom for our planet down the line? Is it too early to tell?

  2. It looks almost round, could someone check if there is a little blonde boy and a rose living on YU55? And if there is, please NUKE those anoying characters?

  3. “In other words, that’s like saying Mars isn’t red and then showing pictures of Uranus.”

    There’s a really dirty joke in there lying in wait, but I lack the testicular fortitude to explicate it here…

  4. Orlando

    OT: Soyuz TMA-22 was successfully launched today from Baikonur carrying NASA astronaut Dan Burbank and Russians Anton Shkaplerov and Anatoly Ivanishin.


    I hope the danger of ISS decrewing is vanishing…

  5. Maria

    The sad thing about that Itokawa/YU55 video is that the idea of encountering alien probes isn’t really that far fetched. I assume that actually encountering a probe is highly improbable when factoring in the vast distances and harsh environment involved, but it’s still within the realm of reality based speculation, and it’s based on our own present day technology and development.

    Using our limited tech we’ve sent out probes for explicit scientific missions. Held within them is the modest hope that an object of ours could be intercepted by some advanced life form. We are a species that hopes and dreams otherwise we never would have attached plaques to the things in the first place.

    It’s not pseudo science to extrapolate from our situation, on the assumption that there could be life out there, and that this life would send out probes as well.

    What is pseudo science is how some people see probes, aliens, and conspiracies in every single thing without any real evidence or how they fabricate their evidence out of thin air, digital noise, image manipulation, and random images swiped off of Google search.

  6. ASFalcon13

    Minor nitpick here: Goldstone has a variety of radio telescopes of various sizes and capabilities. Do you happen to know which dish this was taken with? Was it the big 70m?

  7. @1. Jonathan asked :

    Hey Phil, Did YU55 pass through a keyhole and in so doing spell doom for our planet down the line? Is it too early to tell?

    Hmm.. I’m not the BA but I think I can answer that for you :

    I) Folks were never worried about YU55 passing through a keyhole to later impact. Were you thinking of asteroid Apophis* instead?

    II) No. See this comment here :


    from the older ‘A Swiftly passing asteroid’thread – #9 by JL Galache on November 11th, 2011 at 3:11 pm for details and info link.

    III) Too early? Depends how long youwish to know about! Earth’s safe for the next few centuries – from this specific rock anyhow – but in millennia to come who knows? Long term, orbits, incl. asteroidal orbits are subect to chaos theory. (Pluto’s orbit providing an early key example of that!)

    * Apophis being this one :




    In the unlikely event folks need their memories refreshed on it.

  8. @1. Jonathan : “Did YU55 pass through a keyhole and in so doing spell doom for our planet down the line?”

    I’ve already got a reply currently in moderation with more but the short answer is :


    See comment #9 by JL Galache on November 11th, 2011 at 3:11 pm in the older ‘A Swiftly passing asteroid’ thread for more details and info link.

  9. Messier Tidy Upper

    UPDATE – @1 Jonathan again :

    Just saw this today which answers your question a bit more specifically :

    Predictions that stretch ahead as far as 2111 do not suggest the rock (2005 YU55 – ed.) will collide with Earth.

    Source : “Asteroid Fly-by”, Page 4, New Scientist 12th November 2011 issue.

    No further explanation than that but NS is usually pretty accurate and reliable.

    Just in case folks are still reading this thread and interested.

  10. reidh

    last one june 2011, this one november 2011, next one april 2012? what are odds?

  11. mzza

    The asteroid is big. It’s about the sam mass as the Burg Kalipha tower in Abu dhabi. The shape is strangely conical. Sort of like an arrow head in many ways. However while it is big the asteroid is not large enough to have enough gravity to keep boulders attached to the surface.

    Those interesting protrusions and ridges are more interesting now huh?

    It would be fun to view the copious amounts of detailed high res images that were taken by military assets around the world.


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