Formation of satellites of trans-Neptunian objects at the stage of rarefied preplanetesimals
Abstract
It is considered by many scientists that solid planetesimals were formed by contraction of rarefied preplanetesimals. Ipatov [1] and Nesvorny et al. [2] supposed that trans-Neptunian binaries were formed from rarefied preplanetesimals (RPPs). It was shown in [1] that the angular momenta acquired at collisions of RPPs moving in circular heliocentric orbits could have the same values as the angular momenta of discovered trans-Neptunian and asteroid binaries. Ipatov obtained [3] that the angular momenta used by Nesvorny et al. [2] as initial data in their calculations of contraction of RPPs and formation of trans-Neptunian binaries could be acquired at collisions of two RPPs moving in circular heliocentric orbits. These studies testify in favor of the formation of trans-Neptunian binaries at the stage of rarefied preplanetesimals. The fraction of RPPs collided with other RPPs during their contraction can be about the fraction of small bodies of diameter greater than 100 km with satellites (among all such small bodies), i.e., it can be about 0.3 in the trans-Neptunian belt. The model of collisions of RPPs explains negative angular momenta of some observed binaries, as about 20 percent of collisions of RPPs moving in almost circular heliocentric orbits lead to retrograde rotation. Note that if all RPPs got their angular momenta at their formation without mutual collisions, then the angular momenta of minor bodies without satellites and those with satellites could be similar (but actually they differ considerably). In my opinion, those RPPs, that formed trans-Neptunian objects with satellites, acquired most of their angular momenta at collisions. Most of rarefied preasteroids could turn into solid asteroids before they collided with other preasteroids. Some present asteroids can be debris of larger solid bodies, and the formation of many binaries with primaries with diameter smaller than 100 km can be explained by other models (not by contraction of RPPs). The model of growth of a RPP by accumulation of small objects moved in almost circular orbits does not explain a large difference between angular momenta of a single body and a body with satellites. For such model, all trans-Neptunian objects formed from such preplanetesimals would have satellites because the angular momentum of the preplanetesimal would be much greater than that for a single trans-Neptunian object. [1] Ipatov S.I., Mon. Not. R. Astron. Soc., 2010, v. 403, 405-414; [2] Nesvorny D., Youdin A.N., Richardson D.C., Astron. J., 2010, v. 140, 785-793; [3] Ipatov S.I., Abstracts of 44th LPSC, 2013, # 1488.
- Publication:
-
40th COSPAR Scientific Assembly
- Pub Date:
- 2014
- Bibcode:
- 2014cosp...40E1283I