Octans

Octans
Constellation
Abbreviation Oct
Genitive Octantis
Pronunciation /ˈɒktænz/, genitive /ɒkˈtæntɪs/
Symbolism the Octant
Right ascension 22h
Declination −90°
Quadrant SQ4
Area 291 sq. deg. (50th)
Main stars 3
Bayer/Flamsteed
stars		 27
Stars with planets 3
Stars brighter than 3.00m 0
Stars within 10.00 pc (32.62 ly) 1
Brightest star ν Oct (3.73m)
Messier objects none
Meteor showers none
Bordering
constellations		 Tucana
Indus
Pavo
Apus
Chamaeleon
Mensa
Hydrus
Visible at latitudes between +0° and −90°.
Best visible at 21:00 (9 p.m.) during the month of October.
Circumpolar.

Octans /ˈɒktænz/ is a faint constellation located in the deep southern sky. Its name is Latin for the eighth part of a circle, but it is named after the octant, a navigational instrument. The constellation was devised by French astronomer Nicolas Louis de Lacaille in 1752, and it remains one of the 88 modern constellations.

History and mythology

Octans was one of 14 constellations created by Nicolas Louis de Lacaille during his expedition to the Cape of Good Hope, and was originally named "l’Octans de Reflexion", French for “the reflecting octant”. It was part of his catalogue of the southern sky, the Coelum Australe Stelliferum, which was published posthumously in 1763. In Europe, it became more widely known as Octans Hadleianus, in honor of English mathematician John Hadley, who invented the octant in 1730. There is no real mythology related to Octans, partially due to its faintness and relative recentness, but mostly because of its extreme southerly latitude.[1]

Notable features

The constellation Octans as it can be seen by the naked eye.

Stars

Octans is a very faint constellation; its brightest member is Nu Octantis, a spectral class K1 III giant star with an apparent magnitude 3.73 .

Sigma Octantis, the southern pole star, is a magnitude 5.4 star just over 1 degree away from the true South Celestial Pole. Its relative faintness means that it is not practical for navigation.[2] Conveniently for navigators, there are other, much easier methods for locating the southern celestial pole.

For example, the constellation Crux, the Southern Cross, currently points toward the South Celestial Pole, if one draws a line from Gamma Crucis to Alpha Crucis. Another method includes an asterism made up of Sigma, Chi, Tau, and Upsilon Octantis, which form a distinctive trapezoid shape.

In addition to having the current southern pole star of Earth, Octans also contains the southern pole star of the planet Saturn, which is the magnitude 4.3 Delta Octantis.

Namesakes

USS Octans (AF-26) was a stores ship used by the United States Navy during World War II.

References

Citations
  1. ↑ Staal 1988, p. 257.
  2. ↑ Staal 1988, p. 258.
References

  • Ridpath, Ian; Tirion, Wil (2017), Stars and Planets Guide, Princeton University Press, ISBN 978-0-691-17788-5
  • Staal, Julius D.W. (1988), The New Patterns in the Sky: Myths and Legends of the Stars, The McDonald and Woodward Publishing Company, ISBN 0-939923-04-1

Coordinates: 22h 00m 00s, −90° 00′ 00″

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