March 18 2009: Newly-discovered Asteroid 2009 FH flies past Earth well within the Moon's orbit

Thursday, March 19, 2009

2009 FH's present location, right next to us.

Wow, just two weeks after the newly-discovered 2009 EW flew past Earth once again well within the Moon's orbit, now we have another one called 2009 FH that just flew past us at a very close altitude once again. This asteroid, like the other one, is quite small and thus poses no threat, but the fact that it was discovered so recently is always a tad unsettling. has some info:

Another asteroid is set to make a close approach of 79,000 km according to NASA, a distance twice that of geosynchronous orbit around the Earth. Although the 15-20 metre-wide rock is not expected to cause any problems to Earth or satellites, some observers may be lucky to spot the faint light from 2009 FH as it passes. naturally has info on the asteroid as well:

Newly-discovered asteroid 2009 FH is flying past Earth today, March 18th, only 85,000 km (0.00057 AU) away. That's a little more than twice the altitude of a geosynchronous communications satellite...It is shining about as brightly as a 14th magnitude star.

You can see why I don't really like using AU for objects that pass this close to the Earth, as the number is now so minuscule that it's almost impossible to picture. Better would be Lunar Distance (LD), where this asteroid would be at 0.22 LD (in other words, almost five times closer to us than the Moon), which is far easier to imagine.

See here if you want to play around with this asteroid's orbit to see where it'll be in the future, though note that the link always seems to shut down Firefox for me so I use Opera to open it.

As for what would happen if this asteroid had hit us, see here. It would be something like this:
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 20900 meters = 68500 ft
The residual velocity of the projectile fragments after the burst is 10.6 km/s = 6.56 miles/s
The energy of the airburst is 1.11 x 1015 Joules = 0.27 x 100 MegaTons.
No crater is formed, although large fragments may strike the surface.
So no big deal really. The chance of an object like this directly hitting a populated area is pretty much nil, and these fragments would probably end up in the ocean or (hopefully, so they could be collected later) in some place in northern Russia or Canada.


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