自行[Proper Motion] - 达人(其实～我是卧底，来自外星)

2005/06/16 | 自行[Proper Motion]
类别(¤〖天文〗) | 评论(0) | 阅读(30) | 发表于 21:38: The velocity of a star relative to the sun can be broken down into perpendicular components: the radial velocity and transverse velocity. The transverse velocity results in a change of angular position, which can be measured in arc seconds per year. This is called the proper motion of the star, denoted . If the star is located at a distance d, then the transverse velocity v will b
(1)

where the factor 206265 converts from arc seconds per year to radians per year.
When d is expressed in terms of the star's parallax p, i.e.,
(2)

where A is one astronomical unit and p is measured in arc seconds,
(3)

Finally, if A is expressed in kilometers and the year is expressed in seconds the expression becomes
(4)

km/s.; 0