Nature2014-06-19 4:03 PM

小行星Chariklo有一个自己的环系统 A ring system detected around the Centaur (10199) Chariklo


对(10199) Chariklo (一个在土星和天王星之间绕轨道运行的、“半人马座”级别的outer-system小行星)产生的“恒星掩星”现象所做观测显示,它有一个环系统,这是以前只对四个巨型行星观测到的一个特征。直径约为250公里的Chariklo有两个狭窄而致密的环,二者被一个小的间隙分开,这可能是由于存在一个尚未发现的、直径达到公里尺度的卫星。这些环的发现提出了关于行星环的形成及动态演变的一些问题。其中的一点是,行星环看来似乎要比人们以前所认为的普遍得多。


Hitherto, rings have been found exclusively around the four giant planets in the Solar System. Rings are natural laboratories in which to study dynamical processes analogous to those that take place during the formation of planetary systems and galaxies. Their presence also tells us about the origin and evolution of the body they encircle. Here we report observations of a multichord stellar occultation that revealed the presence of a ring system around (10199) Chariklo, which is a Centaur—that is, one of a class of small objects orbiting primarily between Jupiter and Neptune—with an equivalent radius of 124     9 kilometres (ref. 2). There are two dense rings, with respective widths of about 7 and 3 kilometres, optical depths of 0.4 and 0.06, and orbital radii of 391 and 405 kilometres. The present orientation of the ring is consistent with an edge-on geometry in 2008, which provides a simple explanation for the dimming of the Chariklo system between 1997 and 2008, and for the gradual disappearance of ice and other absorption features in its spectrum over the same period. This implies that the rings are partly composed of water ice. They may be the remnants of a debris disk, possibly confined by embedded, kilometre-sized satellites.






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