2013年11月14日 Nature

nero1981

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The fireball that streaked across the skies above
7 t3 F8 W' b; S. L9 T" BChelyabinsk in Russia on 15 February 2013 is providing astronomers with a wealth
8 B, k- f* n% {5 jof information. Two papers in this issue present detailed reconstructions of the 0 X! v3 Q" `  F- S- A
Chelyabinsk event. From an analysis of videos, Ji?í Borovi?ka et al. determined
* o: p, q  c3 P, Mthe trajectory and velocity of the superbolide with high precision. Its orbit 2 m5 ], s9 L, u& b2 w
was similar to that of the 2-kilometre-diameter asteroid 86039 (1999 NC43),
  J& W1 M) l2 Z/ t1 S' Fsuggesting that the two bodies may be part of the same asteroid family. And they
( U$ }4 t  U3 ?7 I6 Y# i: Q/ t% Kshow that it broke into small pieces between the altitudes of 45 and 30 ; p7 ~5 t" x- n1 Z
kilometres. In the companion paper, Peter Brown et al. analysed the damage
- |/ a2 ]: S( ~' n( \4 B: T! M  C3 mcaused by the airburst which they estimate was equivalent in energy to the . V: P4 d; t% J3 o. ]9 R
detonation of 400 to 600 kilotons of TNT. They suggest that the number of
: r8 y* A. r+ K# {; T) ~  r7 N2 fimpactors with diameters of tens of metres was an order of magnitude higher than " W2 e3 e  ^) i* P9 M0 k, Z+ Y
current estimates, shifting much of the residual impact risk to these sizes. On ( n2 B: J& X: ]6 D" }$ ~
the cover, a 3D simulation by Mark Boslough using CTH code on Sandia National , g1 E8 \8 Z% J; W* u6 ]8 s, J
Laboratories' Red Sky supercomputer, rendered by Brad Carvey using Houdini FX 4 W% e8 j* [, u( ~9 _! \0 x7 {
and LightWave; background photo by Olga Kluglova, go.nature.com/wxuV58.
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