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.
- 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