2021-10-17 天文距离单位 | Parsec （三）

Parsec:

1 parsec (pc) = distance d when angle is 1 arcsecond =  3.086 10km = 3.26 ly

Distances to the closest stars can be determined through measurement of their trigonometric parallax.  The parsec was defined to be the distance at which 1AU(perpendicular to the line of sight) subtends an angle of 1 arcsecond:

Using the Earth’s orbit as a baseline, the distance (in parsecs) to a star can be calculated using: d = 1/p where p is measured in arcseconds.

【4】

Note:

1 AU = 1.5 x 10^11 m = 1.5 x 10^8 km

1 light year = 9.5 * 10^12 km

T(Sun light to earth in vacuum) = 1 AU / C = 1.5 x 10^11 m / (3 x 10^8 m/s) = 500 s = 8 minutes 20 second

相关阅读 & Reference 文献：

[1].2021-03-02 《天体物理学》|绪论|宇宙概观|太阳系

[2]. Oxford Dictionary of English (British English). Copyright © 2010, 2017 by Oxford University Press.

[3]. 譯典通英漢雙向字典

[4]. https://astronomy.swin.edu.au/cosmos/P/Parsec

以上。