演講資訊

摘要：

The ice-giant planet Uranus probably underwent a giant impact, given that its spin axis is tilted by 98 degrees, That its satellite system is equally inclined and prograde suggests that it was formed as a consequence of the impact. However, the disks predicted by the impact simulations generally have sizes one order smaller and masses two orders larger than those of the observed system at present. Here we show, by means of a theoretical model, that the Uranus satellite formation is regulated by the evolution of the impact-generated disk that has mostly vaporized. We predict that the disk lost a substantial amount of water vapour mass and spread to the levels of the current system until the disk cooled down enough for ice condensation and accretion of icy particles to begin. From the predicted distribution of condensed ices, our N-body simulation is able to reproduce the observed mass-orbit configuration of Uranus satellites. This scenario contrasts with the giant-impact model for the Earth's Moon, in which about half of the compact, impact-generated, solid or liquid disk is immediately incorporated into the Moon on impact.

作者：

Shigeru Ida et al

期刊：

Nature Astronomy Vol.4, September 2020, 880-885