Boreskov

OP‐2GRAVITATIONAL INSTABILITY IN THE PROTO‐PLANET DISKBrushlinskii K.V., Pliner L.A., Zabrodina E.A., Menshov I.S.,Zhukov V.T., Dolgoleva G.V., Legkostupov M.S.Keldysh Institute for Applied Mathematics, Russian Academy of Sciences, Moscow, RussiaIn spite of numerous studies, the main question of how the planetary system of the Sunhas been formed remains still open.Large‐scale gravitational instability of the proto‐planet solar disk might be a physicalprocess that leads to the formation of planets. However in the scientific society there is nocommon opinion concerning this question. Some researches consider the proto‐planet diskin the gas phase to be stable [1, 2]. Other researchers keep the opposite point of view [3, 4].Thus, Pavlyuchenko and Friedman have found [4] existence of the gravitational ring‐shapedinstabilities in the proto‐planet solar disk, which can lead under specific conditions to theformation of the solar planetary system. In calculations, they used a flat disk model withsufficiently small thickness.The purpose of the present paper is to study large‐scale gravitational instabilities at theinitial stage of the proto‐planet solar disk evolution. The problem of the proto‐planet diskevolution in the general formulation is extremely difficult. In order to simplify this problemand make the treatment of the results obtained possibly unambiguous, several assumptionsare employed. The medium of the disk is considered to be single‐phase and ideal. Of allphysical processes, which occur in the proto‐planet disk, we leave only basic ones thatinfluence the gravitational stability of the disk: gas‐dynamic processes, the Sun gravitationalfield, and the disk own gravitational field. The initial state of the proto‐planet solar disk isset up in accordance with the analytical solution by Roche [5, 6].In this formulation, the proto‐planet disk has the form of a slim torus, whose internalpart becomes narrow, if we go towards to the center. Strong gravitational field of the Sundraws the gaseous medium of the proto‐planet disk to the center, and due to this effect thedensity of the gaseous medium reaches maximum values near the internal edge of the disk.This creates significant density gradients.The problem of the proto‐planet solar disk evolution is solved numerically. A numericaltwo‐dimensional axisymmetric gasdynamic model, which accounts both the gravitational31