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Constellation on the celestial equator From Wikipedia, the free encyclopedia
Sextans is a faint, minor constellation on the celestial equator which was introduced in 1687 by Polish astronomer Johannes Hevelius. Its name is Latin for the astronomical sextant, an instrument that Hevelius made frequent use of in his observations.
Constellation | |
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Abbreviation | Sex |
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Genitive | Sextantis, Sextansis |
Pronunciation | /ˈsɛkstənz/, genitive /sɛksˈtæntɪs/ |
Symbolism | the Sextant |
Right ascension | 09h 41m 04.8653s–10h 51m 30.2447s[1] |
Declination | 6.4327669°–−11.6621428°[1] |
Quadrant | SQ2 |
Area | 314 sq. deg. (47th) |
Main stars | 3 |
Bayer/Flamsteed stars | 28 |
Stars with planets | 5 |
Stars brighter than 3.00m | 0 |
Stars within 10.00 pc (32.62 ly) | 5 |
Brightest star | α Sex (4.49m) |
Messier objects | 0 |
Meteor showers | Sextantids |
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. |
Sextans is a medium sized constellation bordering Leo to the north, touching on Hydra to the southwest, and Crater to the southeast. The recommended three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Sex".[2] The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a square. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 09h 41m and 10h 51m , while the declination coordinates are between +6.43° and −11.7°.[3] Since it is close to the ecliptic plane, the Moon and planets regularly cross the constellation, especially its northeastern corner.[citation needed]
John Flamsteed labeled 41 stars for the constellation.[4] Francis Baily intended to give Bayer designations to some of the stars but because none of them were above magnitude 4.5, he left them unlettered.[4] Rather, it was Benjamin Apthorp Gould who lettered some of the stars. He labeled the five brightest stars using Greek letters Alpha (α) to Epsilon (ε) in his Uranometria Argentina.[4] All together, there are 38 stars that are brighter than or equal to apparent magnitude 6.5.[lower-alpha 1][6]
Sextans contains a few notable multiple star systems within its boundaries.
35 Sextantis is a triple star system consisting of two evolved K-type giants of equal mass, with both stars being twice as massive as the Sun.[16] The secondary is itself a single-lined spectroscopic binary consisting of a 0.58 M☉ companion and itself.[16] The system is located approximately 700 light years away.[17][18] The outer pair has a separation of 6.8" and both stars take roughly 23,000 years to orbit each other while the B subsystem takes 1,528 days to circle each other in a relatively eccentric orbit.[19]
There are a few notable variable stars, including 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.
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.[21]
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.[22]
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.[23][24]