2013年11月14日 Nature

nero1981

3 k+ d/ q& E! O4 j
The fireball that streaked across the skies above
2 p9 F- U* }, L- n# O' U+ `Chelyabinsk in Russia on 15 February 2013 is providing astronomers with a wealth   {7 }4 n. L# o4 Z1 t6 X  w
of information. Two papers in this issue present detailed reconstructions of the
, G+ B: u" A' V" ?5 O( ~' q- j# TChelyabinsk event. From an analysis of videos, Ji?í Borovi?ka et al. determined " k  }; H0 d  A. k. b
the trajectory and velocity of the superbolide with high precision. Its orbit
& I4 b6 B1 S, Y8 k$ fwas similar to that of the 2-kilometre-diameter asteroid 86039 (1999 NC43), : q; |4 o1 g* ~' s$ O3 f8 r( p/ j
suggesting that the two bodies may be part of the same asteroid family. And they 3 @$ s  k4 z0 t3 G9 `2 D' o
show that it broke into small pieces between the altitudes of 45 and 30 + |5 G! ~- W4 ^
kilometres. In the companion paper, Peter Brown et al. analysed the damage
8 b  ~' q8 n7 Pcaused by the airburst which they estimate was equivalent in energy to the
% t% G" O/ Z8 b4 Qdetonation of 400 to 600 kilotons of TNT. They suggest that the number of : j; {  u- t4 d$ ~! V# R
impactors with diameters of tens of metres was an order of magnitude higher than
. s/ ^4 C% Q& F  ~current estimates, shifting much of the residual impact risk to these sizes. On
; K% g) C9 S/ W( ^' P- l+ n2 mthe cover, a 3D simulation by Mark Boslough using CTH code on Sandia National 8 k* K% U; T! Y2 M: p
Laboratories' Red Sky supercomputer, rendered by Brad Carvey using Houdini FX , w$ |2 G4 O4 a. L) @
and LightWave; background photo by Olga Kluglova, go.nature.com/wxuV58.
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& ~9 A; F' K( V- G6 i1 N5 ]

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