Octans was one of 14 constellations created by French astronomerNicolas Louis de Lacaille during his expedition to theCape of Good Hope, and was originally namedl’Octans de Reflexion (“the reflecting octant”) in 1752, after he had observed and catalogued almost 10,000 southern stars during a two-year stay at theCape of Good Hope. He devised fourteen new constellations in uncharted regions of theSouthern Celestial Hemisphere not visible from Europe. All but one honoured instruments that symbolised theAge of Enlightenment.[a][3]
It was part of his catalogue of the southern sky, theCoelum Australe Stelliferum, which was published posthumously in 1763. In Europe, it became more widely known asOctans Hadleianus, in honor ofEnglish mathematicianJohn 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.[4]
The constellation Octans as it can be seen by thenaked eye.
Lacaille gave 22 starsBayer designations Alpha through Upsilon in 1756, but omitted Omicron and Xi, and labelled three stars as Gamma and two stars as Mu and Pi. In 1879,Benjamin Gould added Xi, Phi, Chi, Psi, and Omega, as they were bright enough and their closeness to the south celestial pole warranted their names. Charles Rumker added Omicron Octantis, which was noted to be the southern pole star at the time, but this is now generally unused in some atlases.[3]
Octans is a generally inconspicuous constellation with only one star brighter than magnitude 4.
Beta Octantis is the second brightest star in the constellation.
Polaris Australis (Sigma Octantis), the southernpole 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.[6]
BQ Octantis is a fainter, magnitude 6.82 star located much closer to the South Pole (at less than a degree) than Sigma.
In addition to having the current southern pole star of Earth, Octans also contains the southern pole star of the planetSaturn, which is the magnitude 4.3Delta Octantis.
At least four star systems are known to have planets.Mu2 Octantis is a binary star system, the brighter component of which has a planet.Nu Octantis A also has a planet orbiting.HD 142022 is a binary system, a component of which is a sunlike star with a massive planet with an orbital period of 1928 ± 46 days.HD 212301 is a yellow-white main sequence star with ahot jupiter that completes an orbit every 2.2 days.
^abcWagman, Morton (2003).Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, Virginia: The McDonald & Woodward Publishing Company. pp. 6–7.ISBN978-0-939923-78-6.
^Cooper, Tim (2003). "Presidential address: Amateur Observations – Successes and Opportunities".Monthly Notes of the Astronomical Society of Southern Africa.62:234–240.Bibcode:2003MNSSA..62..234C.
References
Ridpath, Ian; Tirion, Wil (2017),Stars and Planets Guide, Princeton University Press,ISBN978-0-691-17788-5
Staal, Julius D.W. (1988),The New Patterns in the Sky: Myths and Legends of the Stars, The McDonald and Woodward Publishing Company,ISBN0-939923-04-1
