Asteroid 2011 GP59 spins right round baby right round

By Phil Plait | April 14, 2011 2:40 pm

The asteroid 2011 GP59 is a small rock with an orbit that takes it from just inside the orbit of Venus to just outside that of the Earth. On April 15th at around 19:00 UTC, it’ll cruise by us at a distance of about 533,000 kilometers (330,000 miles) — farther away than the Moon. This asteroid poses no threat to us, but because it does get relatively close, amateur astronomers have been able to capture it in their telescopes.

In fact, Nick James of Chelmsford, Essex, England, took a series of images on April 11, 2011 and made this video:

You may have to watch it more than once; the asteroid starts in the center of the frame and moves to the lower right. The stars appear to move as the telescope tracks the asteroid, so it can be tricky.

See how the asteroid appears to wink on and off? It’s spinning as it orbits the Sun, and must have an elongated shape. When we see the side of it we see a bigger area, which means it reflects more light and it looks brighter. When the narrow part is pointed toward us the area is smaller, and it looks dimmer. The overall size is something like 50 meters in diameter, but given the change in brightness as it spins — by a factor of over 6 times! — it must be quite elongated, more cylindrical than spherical.

Even at closest approach you’d need a decent telescope to even see GP59. Still, it’s pretty neat that we can learn so much about this rock just from a few observations, even when it was still millions of kilometers away.

Related posts:

Kleopatra and her kids
Another tiny rock will whiz past us tomorrow
Repeat after me: Apophis is not a danger
Asteroid 2007 TU24: No danger to Earth

CATEGORIZED UNDER: Astronomy, Cool stuff
MORE ABOUT: 2011 GP59, asteroid

Comments (23)

  1. Keith Bowden

    Cylindrical? The Ramans do everything in threes…

  2. Andrew W

    As I watch it it seems more like a coin shaped object spinning like a flipped coin, but I guess that’s because the resolution’s probably not good enough to show it’s actual dimensions.

  3. Archer Sully

    Way cool! Its like those tumbling satellites that one sometimes sees.

  4. chris

    Has Phil got ‘Best Of The 80s’ in his car CD player right now?

  5. Zucchi

    Super keen. What’s the time scale? How often is it really rotating?

  6. ceramicfundamentalist

    is it normal for such a small asteroid to be rotating so quickly?

  7. Ben H.

    Cool! Is it in a fairly stable orbit or is a close pass like this going to change its orbit a bit?

  8. Joseph G

    Perhaps we’ll see this on ūüėČ

    (If you don’t get it, consider yourself lucky)

  9. Messier Tidy Upper

    Great clip – made even greater when you realise what you’re seeing! :-)

  10. JB of Brisbane

    All we want to know is – is it going “to move in just a little bit clos-EEEERRRRR?”

  11. Kenneth Polit

    Thanks Phil, now that song is stuck in my head.

    2/3 down

    At least 1218 asteroids cruise within spitting distance of Earth. NASA burns $billions on little vehicles making heroic publicity spews. Meanwhile, primordial bodies are knocking on Earth’s door saying “grab me.” Apophis might choose to break and enter.

    Is there anything within NASA’s charter that prohibits it from accomplishing something interesting?

  13. Aw, I was expecting the video would play that song…oh well.

    @#1. It couldn’t be Rama, as that was spinning on its long axis and had almost zero difference in its light curve, and was like a thousand times larger.

    Now excuse me while I science a bit: According to my calculations, and other sources, the rock is spinning roughly every four minutes. That would imply a centripetal acceleration of about 1/4000 g. It’s own surface gravity would be around a hundred times weaker than that, so it’s almost certainly a single solid body. Probably some boulder that was knocked off of another asteroid millions of years ago and has been drifting ever since.

  14. Tom

    Only tangentially related, after I was done watching Youtube suggested this interesting video of a whole string of geosynchronous satellite flares:

    “Amateur” astronomers can sure make some cool videos!

  15. Messier Tidy Upper

    @ Arik Rice : Thanks – great comment & nice calculatin’ there. :-)

    @ 12. Uncle Al : “Is there anything within NASA‚Äôs charter that prohibits it from accomplishing something interesting?”

    You don’t find landing people on the Moon, flying spaceplanes or sending spacecraft to explore every planet – & many moons, asteroids and comets – in our solar system interesting? :roll:

  16. What makes us so sure that it’s not piebald like Iapetus? Granted, that wouldn’t be the way to bet, given what we think about how Iapetus got that way, and a potato is much more likely…


  17. SustainedEuphoria

    OT: Do we know how Iapetus got to the shape it is now?

  18. Messier Tidy Upper

    @ ^ SustainedEuphoria : Yes – gravity! ūüėČ

    It had enough mass to become rounded and be in hydrostatic equilibrium. Or pretty clse to it anyhow just like Mimas and the other larger moons in our solar system – & presumably everywhere else.

    I guess you were refering to why Iapetus, sometimes called the “yin-yang moon” is half dark and half light in colour instead? ūüėČ

    If so, the explanation for the hemispherical colour disparity is that dark material from the outer moon Phoebe has collected on Iapetus’es drak side and a feedback process of sublimation basedon the contrasting albedo has then exacerbated this creating the two-tone effect.

    (I’ll post a link or three for you but you probably won’t see them until tomorrow as they’ll have to pass through moderation.)

  19. Messier Tidy Upper
  20. Wzrd1

    Uncle Al, I’m sorry that my starship wasn’t interesting to you. Next pass, I’ll have it tow something more interesting to your house. Would a 100 meter object get your attention?

    As you abused a NASA derived technology to spout your idiocy here, I’d expect more respect.
    But, as has been noted recently, the velocity of light is NOT QUITE a constant, hence we must derive the ORIGINAL AND CURRENT constant, idiocy. To THAT, you are above a standard candle!

    Keith, that is a misconception. Actually, this was my mudder ship. As it wasn’t raining enough recently, it could not divert and land. ūüėČ
    The udder two are only to deliver milk.

  21. Mark

    Cylindrical is an unreasonable interpretation, since it is physically unstable (can break easily). More likely to be coin-shape or disk shape.


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