Origin of Circumstellar Dust Clouds and Formation of Planetary Systems

我研究了围绕不同质量恒星的行星系统的形成，并得到了以下结果。通过扩展行星形成的京都理论，我证明了海王星在太阳系的年龄内形成，这是以前的理论无法推导出来的。通过将这个理论应用于太阳以外的恒星，我研究了什么样的恒星可以有行星。因为形成行星所需的时间是与星星距离的递增函数，所以在恒星寿命内行星形成的区域有一个外边界。质量更大的星星的外边界更靠近星星，因为它的寿命更短。由于温度很高，固体物质不能在星星附近存在，所以行星形成的区域有一个内边界。大质量星星的内边界更远，因为它的光度更高。因此，行星可能形成的区域对于质量更大的恒星来说更小，而对于质量超过10 M <] SY. sun的恒星来说，它会消失。[）.3.关于β星尘盘的密度分布，有两种相互矛盾的说法，n（gamma）alpha gamma^<-3>和n（gamma）alpha gamma^<-1>，其中gamma是到星星的距离，而尘埃的大小被假设为到处都是一样的。沿着星盘中平面观测到的表面亮度分布沿着可以用指数μ = 3.6-4.3的幂律I（*）alpha *^近似<mu>，只有当尘埃的前向散射比产生黄道光的行星际尘埃强得多时，才可以用每单位体积的散射截面分布nsigma nsigma alpha gamma^来再现<-1>。否则，分布nsigma nsigma alpha gamma<1-mu>可以再现观察到的表面亮度，并且是适当的分布。

I have investigated the formation of planetary systems around stars of various masses and obtained the following results.1. By extending the Kyoto theory on planet formation I have shown that Neptune forms within the age of the Solar System, which the previous theories could not derive.2. By applying this theory to stars other than the Sun I investigated what kind of stars can have planets. Because the time needed to form a planet is an increasing function of the distance from the star, there is an outer boundary to the region where planets form within the stellar lifetime. The outer boundary for a more massive star is closer to the star because of the shorter life. Because the temperature is high and solid material cannot exist near the star, there is an inner boundary to the region where planets form. The inner boundary is farther for a massive star because of the higher luminosity. Therefore the region where planets may form is smaller for more massive stars) and it disappears for stars more massive than about 10M<]SY.sun.[).3. There have been two conflicting assertions on the density distribution in the beta Pictoris dust disk, n(gamma) alpha gamma^<-3> and n(gamma) alpha gamma^<-1>, where gamma is the distance from the star and the size of dust has been assumed the same everywhere. The observed surface brightness distribution along the midplane of the disk, which is approximated by a power law I(*) alpha *^<mu> with the index mu = 3.6-4.3, can be reproduced by the distribution of the scattering cross section per unit volume nsigma nsigma alpha gamma^<-1> only if the dust is much more strongly forward-scattering than the interplanetary dust which is responsible for the zodiacal light. Otherwise the distribution nsigma nsigma alpha gamma^<1-mu> can reproduce the observed surface brightness and is an appropriate distribution.