Kelly Beatty at Sky and Telescope reports that an asteroid about100 30 meters across will pass the Earth on March 2, missing us by a scant 60,000 kilometers! That's a clean miss, but still pretty close. The rock, called 2009 DD45, was discovered only a few days ago -- it's small and faint, making it easy to miss. Closest approach is at 13:44 UT, and it happens over the Pacific. Hopefully lots of amateur astronomers will get images of it; it'll be bright enough for awhile to catch. The problem is it'll be moving really fast across the sky... well, fast meaning half a degree per minute, which in turn means getting images of it will be very tough; it'll streak through a telescope's field of view like a meteor at that rate.
You'll never see it naked eye; at magnitude 10 at brightest it's a fraction as bright as what you can see with just your eye. It's also too high up to be a danger to any satellites (space is big, so even one getting much closer is really unlikely to smack into something). Still, it's pretty cool.
And I'll add that while news like this scares some people, it actually makes me feel somewhat better: we're getting really good at finding these kinds of things. Sure, if this rock had happened to be headed right for us we'd only have a few days warning before it hit (generating an enormous blast, as much as a high-yield nuclear weapon). But the thing is we're looking for and finding such rocks. That's the first step; identifying potentially dangerous impactors. We've shown we can do it.
The next step is to do something about them. Smart folks are working on it, and I bet in the next few years we'll have a realistic and deployable plan on what action to take if we do see one drawing a bead on us. Since the odds of getting hit at any given time are low, statistically speaking we still have time to figure this all out.
But we don't have forever. Let's let 2009 DD45 be a reminder of that. We need to start doing something about these things, before we find one that really is scary.
[Note: Please digg the original article from S&T, not my post. Kelly deserves the credit!]