Sextans

Sextans is a minor equatorial constellation which was introduced in 1687 by Johannes Hevelius. Its name is Latin for the astronomical sextant, an instrument that Hevelius made frequent use of in his observations.

This article is about the constellation. For the ancient Roman coin, see sextans (coin). For the Sextans dwarf galaxy, see Sextans Dwarf Spheroidal.
Sextans
Constellation
Sextans
List of stars in Sextans
AbbreviationSex
GenitiveSextantis, Sextansis
Pronunciation/ˈsɛkstənz/,
genitive /sɛksˈtæntɪs/
Symbolismthe Sextant
Right ascension09h 41m 04.8653s–10h 51m 30.2447s[1]
Declination6.4327669°–−11.6621428°[1]
QuadrantSQ2
Area314 sq. deg. (47th)
Main stars3
Bayer/Flamsteed
stars		28
Stars with planets5
Stars brighter than 3.00m0
Stars within 10.00 pc (32.62 ly)5
Brightest starα Sex (4.49m)
Messier objects0
Meteor showersSextantids
Bordering
constellations		Leo
Hydra
Crater
Visible at latitudes between +80° and −90°.
Best visible at 21:00 (9 p.m.) during the month of April.

Notable features
See also: List of stars in Sextans
The constellation Sextans as depicted in Johann Doppelmayr's Atlas Coelestis, c. 1730 (Plate 19, Southern Celestial Hemisphere).

Sextans as a constellation covers a rather dim, sparse region of the sky. It has only one star above the fifth magnitude, namely α Sextantis at 4.49m. The constellation contains a few double stars, including γ, 35, and 40 Sextantis. There are a few notable variable stars, including β, 25, 23 Sextantis, and LHS 292. NGC 3115, an edge-on lenticular galaxy, is the only noteworthy deep-sky object. It also lies near the ecliptic, which causes the Moon, and some of the planets to occasionally pass through it for brief periods of time.

The constellation is the location of the field studied by the COSMOS project, undertaken by the Hubble Space Telescope.

COSMOS project
  • COSMOS-Gr30 is a particularly dense region in space that contains 10 individual galaxies
    COSMOS-Gr30 is a particularly dense region in space that contains 10 individual galaxies[2]
  • Cosmos Redshift 7, brightest galaxy in the early universe, is located in the constellation Sextans (artist concept)
    Cosmos Redshift 7, brightest galaxy in the early universe, is located in the constellation Sextans (artist concept)

Sextans B is a fairly bright dwarf irregular galaxy at magnitude 6.6, 4.3 million light-years from Earth. It is part of the Local Group of galaxies.[3]

CL J1001+0220 is as of 2016 the most distant-known galaxy cluster at redshift z=2.506, 11.1 billion light-years from Earth.[4]

In June 2015, astronomers reported evidence for population III stars in the Cosmos Redshift 7 galaxy (at z = 6.60) found in Sextans. Such stars are likely to have existed in the very early universe (i.e., at high redshift), and may have started the production of chemical elements heavier than hydrogen that are needed for the later formation of planets and life as we know it.[5][6]


Depictions of the constellation
  • The constellation Sextans as it can be seen by the naked eye
    The constellation Sextans as it can be seen by the naked eye
  • Sextans and other constellations seen around Hydra. From Urania's Mirror (1825)
    Sextans and other constellations seen around Hydra. From Urania's Mirror (1825)

See also

References
  1. IAU, The Constellations, Sextans.
  2. "A gigantic cosmic bubble". www.eso.org. Retrieved 13 November 2017.
  3. Levy 2005, p. 178.
  4. Wang, Tao; Elbaz, David; Daddi, Emanuele; Finoguenov, Alexis; Liu, Daizhong; Schrieber, Corenin; Martin, Sergio; Strazzullo, Veronica; Valentino, Francesco; van Der Burg, Remco; Zanella, Anita; Cisela, Laure; Gobat, Raphael; Le Brun, Amandine; Pannella, Maurilio; Sargent, Mark; Shu, Xinwen; Tan, Qinghua; Cappelluti, Nico; Li, Xanxia (2016). "Discovery of a galaxy cluster with a violently starbursting core at z=2.506". The Astrophysical Journal. 828 (1): 56. arXiv:1604.07404. Bibcode:2016ApJ...828...56W. doi:10.3847/0004-637X/828/1/56. S2CID 8771287.
  5. Sobral, David; Matthee, Jorryt; Darvish, Behnam; Schaerer, Daniel; Mobasher, Bahram; Röttgering, Huub J. A.; Santos, Sérgio; Hemmati, Shoubaneh (4 June 2015). "Evidence For POPIII-Like Stellar Populations In The Most Luminous LYMAN-α Emitters At The Epoch Of Re-Ionisation: Spectroscopic Confirmation". The Astrophysical Journal. 808 (2): 139. arXiv:1504.01734. Bibcode:2015ApJ...808..139S. doi:10.1088/0004-637x/808/2/139. S2CID 18471887.
  6. Overbye, Dennis (17 June 2015). "Astronomers Report Finding Earliest Stars That Enriched Cosmos". New York Times. Retrieved 17 June 2015.
  • "Sextans". The Constellations. International Astronomical Union.
  • Levy, David H. (2005). Deep Sky Objects. Prometheus Books. ISBN 1-59102-361-0.
  • Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0-00-725120-9. Princeton University Press, Princeton. ISBN 978-0-691-13556-4.
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