Asteroid 2009 DD45 passed by the Earth yesterday

Tuesday, March 03, 2009

Edit 8 April: some people are arriving on this page doing a Google search for asteroid yesterday - that's this asteroid, 2010 GA6. Neil deGrasse Tyson also mentioned it on his most recent Colbert Report interview.


See that moon there on the right? That's Dactyl, and it's a bit over 1 km in diameter. Even Dactyl would dwarf this asteroid that just flew by the Earth.

So, an asteroid discovered just a few days ago flew by us today, well within the Moon's orbit (74,800 km compared to 384,400 km or so for the Moon). The fact that it was only discovered a bit before it flew by means that it wasn't that large, and it seems to be about 30 m to 40 m in diameter.

To determine the approximate effect of an impact of an asteroid you can always check here. Let's say the asteroid is 40 m in diameter, made of rock and falls about 100 km from your house, you get the following:

The projectile begins to breakup at an altitude of 54000 meters = 177000 ft
The projectile bursts into a cloud of fragments at an altitude of 10800 meters = 35500 ft
The residual velocity of the projectile fragments after the burst is 7.1 km/s = 4.41 miles/s
The energy of the airburst is 1.20 x 1016 Joules = 2.87 x 100 MegaTons.
No crater is formed, although large fragments may strike the surface.
The air blast at this location would not be noticed. (The overpressure is less than 1 Pa)

and considering that the Earth is mostly uninhabited, the chance of it even being that close are pretty much nil. What would be most likely would be a landing in the ocean somewhere, or perhaps some uninhabited part of Russia or Canada.

Here's a video of the asteroid tracked from Australia (it's in the centre, moving slowly to the left):

I'm a very big believer in finding niche areas for small nations to participate in space development, and one area that I could see this happening is through sending up small probes to fly by asteroids that are fairly close to the Earth. If an asteroid like this had been discovered well ahead of time it would have been possible to send a probe up into a gradually-increasing orbit around the Earth that would result in a close encounter with the asteroid as it flew by. A nation like Korea or Brazil should be able to do something like that with little difficulty given enough time to construct the probe in the first place.


Unknown said...

ye it was our good luck we r save today

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