Earlier this week, a hunk of rock called asteroid 2005 YU55 came within smashing distance of Earth. It was purported to be the size of an aircraft carrier, and wound up flying by us at a distance of just under 200,000 miles, much closer than the Moon.
But as close as the asteroid came to Earth, it seems the best we've managed to produce imaging-wise are highly pixelated images like the ones up top (alright, so the one in the middle is actually pretty decent, with a resolution of about 4 meters/pixel...although my favorite is the one on the far right, which I'm still not convinced isn't actually a fuzzy picture of peanut M&M). But you have to remember these images were captured using radio telescopes (well, the first two were — the M&M is actually the first optical/near-infrared image of the asteroid, but we'll get to that in a minute).
Radio telescopes work a lot like a highway patrolman's radar gun, only they work over hundreds of thousands of kilometers and they're actually accurate. By directing short pulses of focused radio waves at the asteroid and waiting for them to bounce back, radio telescopes like the Aricebo radio telescope (which captured the image of the asteroid on the far left back in 2010), and the deep-space network antenna at the Goldstone observatory (which resolved the image of 2005 YU55 featured in the middle) can determine everything from the asteroid's size, to its shape, to its rotation in space.
In fact, it was with the Goldstone telescope that NASA created this 6-frame movie of the asteroid when it was still on its approach, at a distance of 860,000 miles away from Earth.
So what's the deal with the Peanut M&M? Well, that image was captured by the Keck II telescope in Kamuela, Hawaii, by detecting near-infrared photons from asteroid YU55 just a couple of hours after the asteroid passed its point of closest approach to Earth. And while this (still unprocessed) image might not look like much, we can actually learn a lot from it. For example, the image seems to confirm that the asteroid has no small companion satellites. It also indicates that the asteroid has a shape more like a potato than a sphere, and that the rock — long thought to be around 400 meters across — is probably closer to 240 meters. So only half an aircraft carrier.
In any case, the raw imagery of 2005 YU55 captured at the Keck observatory won't be done processing for at least a few more days, but when it is scientists are hoping they'll have enough data to produce some cool new images of the rock, and maybe even a 3D view. In the meantime, here's a small collection of some of the asteroid footage captured by stargazers around the globe.
This video was created from hundreds of images, captured by Mike Renzi at the Starhoo Observatory in Massachusetts.
This image was captured by David Cortner of Rutherford College, NC. Cortner writes: "Here's a stack of 30 second exposures showing this 1200 foot charcoal briquette zooming through the stars of Pegasus... stacked the short frames then added color data after the asteroid left the field."
A similar image, by Chris Cook in Cape Cod, MA. Cook writes: "I was able to capture Asteroid 2005 YU55 as it made its closest approach to Earth on Novemeber 8, 2011. My image was taken between 6:52-6:57pm EST. It was much fainter than I thought it would be.... but it sure is moving fast!"