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The fireball that streaked across the skies above
3 D9 N( A2 M. I( K# HChelyabinsk in Russia on 15 February 2013 is providing astronomers with a wealth
' G- H: I$ f( l9 P+ q9 v5 ~! d3 {of information. Two papers in this issue present detailed reconstructions of the
) M+ l `; V8 u: b- J3 x6 S1 nChelyabinsk event. From an analysis of videos, Ji?í Borovi?ka et al. determined # k' D1 q, A/ p, {9 w
the trajectory and velocity of the superbolide with high precision. Its orbit 4 k, q* B5 V0 I: J/ ^" I* q6 v, Q
was similar to that of the 2-kilometre-diameter asteroid 86039 (1999 NC43),
9 }8 n: q' ?4 X8 D7 ysuggesting that the two bodies may be part of the same asteroid family. And they , r- x( R/ h h8 r" E) y
show that it broke into small pieces between the altitudes of 45 and 30 # O) E/ B: x- J7 t2 H8 p
kilometres. In the companion paper, Peter Brown et al. analysed the damage
3 h% Y* C! h8 Acaused by the airburst which they estimate was equivalent in energy to the
, i& H: |. \0 k7 V& z% a" [detonation of 400 to 600 kilotons of TNT. They suggest that the number of
/ ^, n) f" d2 i7 y7 J! C+ f; q5 Jimpactors with diameters of tens of metres was an order of magnitude higher than $ q1 h, X1 |/ l* F6 O( K5 j/ v: w
current estimates, shifting much of the residual impact risk to these sizes. On
{: ]+ V9 v+ o n @the cover, a 3D simulation by Mark Boslough using CTH code on Sandia National . n$ I: V# F/ A g
Laboratories' Red Sky supercomputer, rendered by Brad Carvey using Houdini FX
7 R# l A0 u/ p2 S8 m+ T3 ^, mand LightWave; background photo by Olga Kluglova, go.nature.com/wxuV58.
B" K2 G y9 U0 y( q' B+ n/ w# [( y+ q' H/ G# [
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发表于 2013-11-17 23:43
发表于 2013-11-18 08:19
