Formation of the terrestrial planets in the solar system around 1 au via radial concentration of planetesimals

Masahiro Ogihara, Eiichiro Kokubo, Takeru K. Suzuki, Alessandro Morbidelli

(Submitted on 6 Apr 2018)

No planets exist inside the orbit of Mercury and the terrestrial planets of the solar system exhibit a localized configuration. According to thermal structure calculation of protoplanetary disks, a silicate condensation line (~ 1300 K) is located around 0.1 au from the Sun except for the early phase of disk evolution, and planetesimals could have formed inside the orbit of Mercury. A recent study of disk evolution that includes magnetically driven disk winds showed that the gas disk obtains a positive surface density slope inside ~ 1 au from the central star. In a region with positive midplane pressure gradient, planetesimals undergo outward radial drift. We investigate the radial drift of planetesimals and type I migration of planetary embryos in a disk that viscously evolves with magnetically driven disk winds. We show a case in which no planets remain in the close-in region. Radial drifts of planetesimals are simulated using a recent disk evolution model that includes effects of disk winds. The late stage of planet formation is also examined by performing N-body simulations of planetary embryos. We demonstrate that in the middle stage of disk evolution, planetesimals can undergo convergent radial drift in a magnetorotational instability (MRI)-inactive disk, in which the pressure maximum is created, and accumulate in a narrow ring-like region with an inner edge at ~ 0.7 au from the Sun. We also show that planetary embryos that may grow from the narrow planetesimal ring do not exhibit significant type I migration in the late stage of disk evolution. The origin of the localized configuration of the terrestrial planets of the solar system, in particular the deficit of close-in planets, can be explained by the convergent radial drift of planetesimals in disks with a positive pressure gradient in the close-in region.

Comments:    5 pages, 4 figures, accepted for publication in A&A Letters
Subjects:    Earth and Planetary Astrophysics (astro-ph.EP)
Cite as:    arXiv:1804.02361 [astro-ph.EP] (or arXiv:1804.02361v1 [astro-ph.EP] for this version)
Submission history
From: Masahiro Ogihara  
[v1] Fri, 6 Apr 2018 17:21:45 GMT (3222kb)
https://arxiv.org/abs/1804.02361