# 秒差距本文重定向自 秒差距

1秒差距指的是从太阳至某一天体间，具有1视差的长度（非等比例绘制）

1 pc相当于
米制SI）单位   3.0857×1016
~31拍米
英制美制单位   1.9174×1013 mi
天文单位系统   2.0626×105 au
3.26156 ly

2015年8月，国际天文学联合会通过B2决议文，将绝对星等热星等英语bolometric magnitude进行标准定义，也包含将秒差距定义为一个精确值，即648000π天文单位，或大约3.08567758149137×1016米（基于2012年国际天文学联合会对于天文单位的精确国际单位制定义）。此定义对应于众多当代天文学文献中对于秒差距的小角度定义。

## 基础定义

### 计算秒差距的值

${\displaystyle \mathrm {\tan 1''} ={\frac {\mathrm {ES} }{\mathrm {SD} }}}$

${\displaystyle \mathrm {SD} \approx {\frac {\mathrm {ES} }{1''}}={\frac {1\,{\mbox{AU}}}{{\frac {1}{60\times 60}}\times {\frac {\pi }{180}}}}={\frac {648\,000}{\pi }}\,{\mbox{AU}}\approx 206\,264.81\,{\mbox{AU}}}$

 1秒差距 ≈ 206264.806247096天文单位 ≈ 3.085677581×1016米 ≈ 19.173511577兆英里 ≈ 3.261563777光年

## 注脚

1. ^ 对于此计算方式，其误差值约为10亿分之一（1×10−9）。

## 参考文献

1. ^ Cosmic Distance Scales - The Milky Way. [24 September 2014]. （原始内容存档于2015-08-10）.
2. ^ Benedict, G. F.; 等. Astrometric Stability and Precision of Fine Guidance Sensor #3: The Parallax and Proper Motion of Proxima Centauri (PDF). Proceedings of the HST Calibration Workshop: 380–384. [11 July 2007]. （原始内容存档 (PDF)于2016-09-09）.
3. ^ Dyson, F. W. Stars, Distribution and drift of, The distribution in space of the stars in Carrington's Circumpolar Catalogue. Monthly Notices of the Royal Astronomical Society. March 1913, 73: 334–342. Bibcode:1913MNRAS..73..334D. doi:10.1093/mnras/73.5.334. There is a need for a name for this unit of distance. Mr. Charlier has suggested Siriometer ... Professor Turner suggests parsec, which may be taken as an abbreviated form of 'a distance corresponding to a parallax of one second'.
4. ^ Cox, Arthur N. (编). Allen's Astrophysical Quantities 4th. New York: AIP Press / Springer. 2000. Bibcode:2000asqu.book.....C. ISBN 0387987460.
5. ^ Binney, James; Tremaine, Scott. Galactic Dynamics 2nd. Princeton, NJ: Princeton University Press. 2008. Bibcode:2008gady.book.....B. ISBN 978-0-691-13026-2.
6. ^ International Astronomical Union (编), RESOLUTION B2 on the re-definition of the astronomical unit of length (PDF), RESOLUTION B2, Beijing: International Astronomical Union, 31 August 2012 [2017-11-01], （原始内容存档 (PDF)于2013-08-16）, The XXVIII General Assembly of International Astronomical Union recommends [adopted] that the astronomical unit be redefined to be a conventional unit of length equal to exactly 149597870700 米, in agreement with the value adopted in IAU 2009 Resolution B2