Free Astronomy Magazine November-December 2017

NOVEMBER-DECEMBER 2017 A bove, a rep- resentation of a theoretical planetesimal that is held back by the gas collected by Jupiter. This mechanism could be behind the ori- gin of the C-type asteroids. [Erik Wernquist] At left, the radial distribution is shown for the virtual asteroids (100 km in diame- ter) added by the simulations in stable orbits in the main belt. [S.N. Raymond, and A. Izidoro] were almost certainly formed in a very nar- row, ring-shaped region in which the den- sity of the matter was sufficient to create the planetesimals; nothing suggests that these conditions extended to the current asteroid belt. Perhaps the S-type asteroids originated in the inner parts of the proto- planetary disk and began to be thrust be- tween the orbits of Mars and Jupiter by gravitational interac- tions with the em- bryos of the planets being formed. For similar reasons, it can be conjectured that the C-type aster- oids also arose else- where, preferably in an area closer to the giant planets, which would explain their abundance of car- bon. To test their hypothesis, the two researchers launched a series of long simulations on a supercom- puter (each of which ran for months), to create a model of the young solar system and test a possible alternative origin for the asteroids in the belt. The starting con- figuration of the simulations entailed the formation of terrestrial planets beginning with a dissipating gaseous ring (totally re-