The siriometer is an obsolete astronomical unit of length, defined to be equal to one million astronomical units (au). [1] [2] One siriometer is approximately 149.6 petametres; 4.848 parsecs; 15.81 light-years. The distance from Earth to the star Sirius is then approximately 0.54 siriometers. [3]
The unit was proposed in 1911 by Carl V. L. Charlier, [3] who worked on stellar statistics. [4] Charlier originally used the symbol 'sir' [1] but the symbol 'Sm' has also seen use. [5]
The siriometer never gained widespread usage. Frank Dyson (the Astronomer Royal) objected to the name siriometer, because "it suggests a machine for measuring". [6] The first General Assembly of the International Astronomical Union in 1922 adopted the parsec as the standard unit of stellar distances, [7] which simplified the definition of absolute magnitude. [3] Use of the siriometer seems to have disappeared from the astronomical literature by c. 1930. [3] Modern professional astronomers use the parsec as their primary unit for distances larger than the Solar System.
Further reading
- Arenou, Frédéric. "The origin of the parsec". Paris Observatory. Retrieved 18 May 2018.
References
- ^ a b Charlier, C. V. L. (1921). Lectures on Stellar Statistics. Bibcode: 1921lss..book.....C.
-
^
Charlier, C. V. L. (May 1913).
"An Investigation on the Motion of the Stars". Monthly Notices of the Royal Astronomical Society. 73 (7): 486–492.
Bibcode:
1913MNRAS..73..486C.
doi:
10.1093/mnras/73.7.486.
I have used ... the term "Siriometer" for denoting a distance equal to a million times the mean distance of the Sun from the Earth.
- ^ a b c d Beech, Martin (2008). "The reluctant parsec and the overlooked light-year". The Observatory. 128: 489. Bibcode: 2008Obs...128..489B.
- ^ "Astronomy in Sweden 1860-1940". www.astro.uu.se. Retrieved 2021-02-28.
- ^ "units". nrc-cnrc.github.io. Retrieved 2023-03-31.
- ^ "Meeting of the Royal Astronomical Society. Friday, 1913 March 14". The Observatory. 36 (460): 160. April 1913. Bibcode: 1913Obs....36..160.
- ^ Malmquist, K. G. (1925). "On the units of distance in stellar astronomy". The Observatory. 48: 142. Bibcode: 1925Obs....48..142M.
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