Another tiny rock will pass Earth tomorrow

Bad Astronomy
The entire universe in blog form
May 28 2012 12:15 PM

Another tiny rock will pass Earth tomorrow

[tl;dr: A small 5-10 meter asteroid will pass us tomorrow; it poses no danger to us.]

[UPDATE (May 29, 16:30 UTC): The JPL website for this asteroid has been updated - the rock passed us at the predicted distance of about 14,500 km from the Earth's surface. The new numbers use 50 observations of the asteroid (the earlier orbit calculations used far fewer), so this looks pretty solid to me. As we knew all along, it was a close pass, but nothing to worry about.]

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

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I recently wrote about near-Earth asteroid 2012 KP24, a house-sized (25 meter) rock. As I write this it passed us safely just a few hours ago, as predicted.

But thanks to scibuff and AsteroidWatch on Twitter, I just learned of another tiny visitor that will buzz past us tonight/tomorrow, May 29, at around 07:00 UTC (03:00 Eastern US time). Called 2012 KT42, this one is even smaller than KP24: it's probably less than 10 meters across -- about the size of a school bus or more likely a minivan. And it'll be a close shave: though the orbit is still not nailed down, the nominal miss distance is about 14,500 kilometers (8900 miles). That's a bit bigger than the diameter of the Earth itself.



[UPDATE (19:15 UTC): There's more info on KT42 in on the Italian Remanzacco Observatory blog (h/t TredySas). There's also a cool animation made from five exposures of it:


I'll add more here if I hear anything.]



[UPDATE (19:55 UTC): No new info as such, but Alex Gibbs from the Catalina Sky Survey sent me this nice 4-tile mosaic of the discovery images of KT42, taken with the Mt. Lemmon 60" telescope:

Very cool!]



Bear in mind, it was only discovered last night, so the current orbit is preliminary. Many small rocks that pass close to Earth are discovered shortly before they breeze past us (and some not until after), so this is nothing out-of-the ordinary.

And since some people tend to get upset about these things, I'll point out that as of right now, it looks like it will miss us. And even if newer observations show it hitting us, this rock is way too small to do any damage. At that size, it'll break up in the atmosphere and make a spectacular light show, but not much else. This has happened countless times with asteroids this size, like the Peekskill meteor in 1992, or the more recent fireball over California last April. These can produce meteorites which fall to Earth, but the odds of getting by one are so small they're basically zero.

Put it this way: the Earth has a surface area of more than 500 trillion square meters. Your surface area is less than 1 square meter (as seen from above). Those are pretty good odds you'll be OK.

Another way to think about this is that rocks this size pass us all the time, but you never hear about them hurting us; that's because they don't! The smaller the asteroid the more common they are, but the less they can do to us. At this size, there's no danger.

And as usual, I'll point out that this discovery is a good thing! It shows we can find them, and that's important. If we ever do discover an asteroid on a collision course that's big enough to hurt us, the first step is to find it. And we're getting better at that all the time.



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