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8 o4 _9 K6 l' Q" A/ [The fireball that streaked across the skies above
1 b2 d$ Z! W8 ]3 h) O0 T2 bChelyabinsk in Russia on 15 February 2013 is providing astronomers with a wealth & u5 _5 O+ i' O# X7 w
of information. Two papers in this issue present detailed reconstructions of the
4 G% E3 R R: i) gChelyabinsk event. From an analysis of videos, Ji?í Borovi?ka et al. determined
5 i" o" P) J( Kthe trajectory and velocity of the superbolide with high precision. Its orbit
4 [5 I; A) o9 O+ ^4 @was similar to that of the 2-kilometre-diameter asteroid 86039 (1999 NC43),
2 o( V5 a4 Z! l7 C2 Usuggesting that the two bodies may be part of the same asteroid family. And they ! o0 j6 R. A n
show that it broke into small pieces between the altitudes of 45 and 30
+ W3 S% R& c- H( s3 ?kilometres. In the companion paper, Peter Brown et al. analysed the damage + z9 |" a: f. z) N
caused by the airburst which they estimate was equivalent in energy to the 9 W( s/ g+ }6 I; J$ D; ?1 F
detonation of 400 to 600 kilotons of TNT. They suggest that the number of
' K( r- `4 ]. l3 F0 W) n4 timpactors with diameters of tens of metres was an order of magnitude higher than
. h) ]" i7 K0 e% \" J7 W5 Hcurrent estimates, shifting much of the residual impact risk to these sizes. On
( ]% R5 x2 m& h( b, Z6 J$ [the cover, a 3D simulation by Mark Boslough using CTH code on Sandia National - U q) a8 J- R3 B( ~' A
Laboratories' Red Sky supercomputer, rendered by Brad Carvey using Houdini FX 9 a/ d7 w" s! ?0 n: A
and LightWave; background photo by Olga Kluglova, go.nature.com/wxuV58.. W' M$ @% J, ~8 u$ y6 D
/ a7 T( r2 T% P) C8 S/ y5 N |
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发表于 2013-11-17 23:43
发表于 2013-11-18 08:19
