[AR] Re: u-oh ! return of Phaeton
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sat, 16 Dec 2017 19:53:33 -0500 (EST)
On Sun, 17 Dec 2017, John Dom wrote:
Size 5 km dia. asteroid rock zipped by today at a distance of about 10
times the distance of the Moon if I got that right.
Nope, 10Mkm -- about 27x lunar distance. Asteroids come that close with
some frequency, although 5km ones are not that common.
Calculation of impact energy (angular, mass and velocity data):
astronomers should know.
Passing at about 32km/s this time. Diameter about 5km -- I seem to recall
there were some radar observations planned, which should give us a better
estimate of its size and probably some information about its shape. Mass
uncertain because density unknown, but circa 2.7 would be a reasonable
first guess if it's rocky. (Hard to tell -- spectral type would suggest a
carbonaceous chondrite but the albedo is kinda high for that.)
Damage to be expected with impact, anybody?
Zero, since its orbit is accurately known and it can't hit Earth any time
soon. :-)
5km at 32km/s would be a Bad Day on a planetary scale. Not as bad as
Chicxulub, but definitely a planet-wide disaster.
Henry
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