Yesterday I wrote about asteroid 2010 TD54, a small rock 5-10 meters in diameter that was due to buzz by the Earth this morning at 11:25 UT. Apparently all went well, and it passed us as predicted. Amateur astronomer Patrick Wiggins was able to grab some images of the asteroid shortly before closest approach and put them together into this nifty animation: [I recommend viewing at the 480 resolution; it looks much nicer.] Nice. He used a 36 cm (14 inch) Celestron telescope with a sophisticated astronomical digital camera to get these. Each exposure was only five seconds long, giving you an idea of how quickly this rock was zipping along, even more than two hours before it actually passed us. He also has an animation where he was able to track the asteroid better, so it looks nearly stationary while stars zip by. Images like this one can actually be pretty important: they can be used to nail down the orbit of the asteroid. The orbit is calculated mathematically using images of the asteroid over time. Uncertainty in the measurements, the exact position of the asteroid, the user's location, and more can all add up to the orbit being imprecisely known. That means that we might be able to predict where it is in the near future, but as time goes on the prediction gets fuzzier. The more observations we get, the more we can smooth out those issues. And when they pass as close as TD54 did -- just 46,000 km (28,000) above the Earth! -- its orbit can change a lot due to Earth's gravity. Observations like this one can really be important to be to know where TD54 will be heading in its future travels. ... and one more thing. This is good practice. In April 2029, the 250-meter wide asteroid Apophis will be passing the Earth at about the same distance as TD54 did. We know Apophis won't hit us, but if it passes at just the right distance, Earth's gravity will bend its orbit enough to bring it back on an impact trajectory 7 years later! We're pretty sure there's literally only a one in a million chance of that happening, but if we get hundreds of observations of the asteroid when it passes, we'll have its orbit nailed down enough to predict the path of Apophis well into the future. While even Apophis isn't a huge threat (in that we don't think it'll hit any time soon), there are hundreds and thousands of other rocks out there on orbits that cross ours. Astronomy is one of the very few sciences where amateurs can make a big contribution. And in this case, they very well may literally help save the Earth.
Tip o' the Whipple Shield to scibuff.