TY - JOUR

T1 - The gas-drag effect on the orbital instability of a protoplanet system

AU - Iwasaki, Kazunori

AU - Tanaka, Hidekazu

AU - Nakazawa, Kiyoshi

AU - Emori, Hiroyuki

PY - 2001

Y1 - 2001

N2 - We have investigated numerically the orbital instability of a protoplanet system while taking account of the gasdrag force due to the solar nebula. In the present work, we considered an equally spaced five-protoplanet (with the same mass of 1 x 10-7 M⊙ ) system, in which their initial orbits are coplanar and circular, and assumed that the gas-drag force is proportional to the square of the relative velocity between the gas and a protoplanet. We first reexamined and confirmed that, under a gas-free condition, log10 Tinst can be approximately written as a linear function of the initial orbital separation distance, Δã0, where Tinst is the time of the orbital instability (i.e., the time of the first orbital crossing between any two protoplanets). Next, we investigated the instability time under the gas-drag effect Tgasinst and found that Tgasinst suddenly becomes large compared with Tinst, when Δã0 is larger than a certain critical separation distance, (Δã0)crit. Furthermore, we showed that (Δã0)crit can be described semi-analytically as a function of the gaseous density. From a function extrapolated with a density in the minimum mass nebula model, we estimated (Δã0)crit in the nebula as being about 10 Hill radius at 1 AU.

AB - We have investigated numerically the orbital instability of a protoplanet system while taking account of the gasdrag force due to the solar nebula. In the present work, we considered an equally spaced five-protoplanet (with the same mass of 1 x 10-7 M⊙ ) system, in which their initial orbits are coplanar and circular, and assumed that the gas-drag force is proportional to the square of the relative velocity between the gas and a protoplanet. We first reexamined and confirmed that, under a gas-free condition, log10 Tinst can be approximately written as a linear function of the initial orbital separation distance, Δã0, where Tinst is the time of the orbital instability (i.e., the time of the first orbital crossing between any two protoplanets). Next, we investigated the instability time under the gas-drag effect Tgasinst and found that Tgasinst suddenly becomes large compared with Tinst, when Δã0 is larger than a certain critical separation distance, (Δã0)crit. Furthermore, we showed that (Δã0)crit can be described semi-analytically as a function of the gaseous density. From a function extrapolated with a density in the minimum mass nebula model, we estimated (Δã0)crit in the nebula as being about 10 Hill radius at 1 AU.

KW - Earth

KW - Gas-drag effect

KW - Instabilities

KW - Solar system: formation

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U2 - 10.1093/pasj/53.2.321

DO - 10.1093/pasj/53.2.321

M3 - Article

AN - SCOPUS:0039250548

VL - 53

SP - 321

EP - 329

JO - Publications of the Astronomical Society of Japan

JF - Publications of the Astronomical Society of Japan

SN - 0004-6264

IS - 2

ER -