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The fireball that streaked across the skies above
, i2 N" x& ?, g% D" `! o0 P% |Chelyabinsk in Russia on 15 February 2013 is providing astronomers with a wealth
, J' t" l a% L7 J* i8 aof information. Two papers in this issue present detailed reconstructions of the 8 o6 M; p! i8 K z
Chelyabinsk event. From an analysis of videos, Ji?í Borovi?ka et al. determined
4 L! G( o9 ~+ b2 I- ithe trajectory and velocity of the superbolide with high precision. Its orbit
5 n/ J- R6 }6 { Iwas similar to that of the 2-kilometre-diameter asteroid 86039 (1999 NC43),
9 K7 a) A) |4 }. h5 P% hsuggesting that the two bodies may be part of the same asteroid family. And they
3 |, S- z0 Z' L2 i5 u+ f/ R2 ^9 w- Lshow that it broke into small pieces between the altitudes of 45 and 30 3 W: x3 _' ?5 G+ I' ?
kilometres. In the companion paper, Peter Brown et al. analysed the damage
+ ]/ d+ o* b4 ~; |5 l6 } wcaused by the airburst which they estimate was equivalent in energy to the . Z' ]5 o& M8 S+ R& u
detonation of 400 to 600 kilotons of TNT. They suggest that the number of
: t) C% E9 Q" Eimpactors with diameters of tens of metres was an order of magnitude higher than
' c% L7 H5 o" @) tcurrent estimates, shifting much of the residual impact risk to these sizes. On . u! {' u, s5 i7 q
the cover, a 3D simulation by Mark Boslough using CTH code on Sandia National : V0 O% W8 I3 t% m: b+ }+ L
Laboratories' Red Sky supercomputer, rendered by Brad Carvey using Houdini FX
5 |3 s! g% {/ A: X0 kand LightWave; background photo by Olga Kluglova, go.nature.com/wxuV58.
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发表于 2013-11-17 23:43
发表于 2013-11-18 08:19
