Origin of Circumstellar Dust Clouds and Formation of Planetary Systems

我研究了不同质量恒星周围行星系统的形成，得到了以下结果。通过扩展京都关于行星形成的理论，我已经证明了海王星是在太阳系的年龄内形成的，这是以前的理论无法得出的。通过将这一理论应用于太阳以外的恒星，我调查了什么样的恒星可能有行星。因为形成行星所需的时间是离恒星距离的递增函数，所以在恒星寿命内形成行星的区域有一个外部边界。由于寿命较短，质量较大的恒星的外部边界离恒星较近。由于温度很高，恒星附近不存在固体物质，所以行星形成的区域有一个内部边界。大质量恒星的内部边界更远，因为它的光度更高。因此，对于质量更大的恒星，行星可能形成的区域更小)，而对于质量超过约10米的恒星，行星可能形成的区域就会消失。关于贝塔皮托里斯尘埃盘中的密度分布，有两种相互矛盾的断言，n(伽马)α伽马^-3和n(伽马)α伽马^-1，其中伽马是离恒星的距离，而尘埃的大小在任何地方都是相同的。只有当尘埃的前向散射比引起黄道光的星际尘埃强得多时，才能通过单位体积的散射截面的分布来再现沿圆盘中面的观测到的表面亮度分布，该分布由指数u=3.6-4.3的幂定律i(*)α^^；；u^u来近似。另外，nsigma nsigmaα伽马分布可以再现观测到的表面亮度，是一个合适的分布。

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.