Sextans is a medium sized constellation borderingLeo to the north, touching onHydra to the southwest, andCrater 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 astronomerEugène Delporte in 1930, are defined by a square. In theequatorial coordinate system, theright ascension coordinates of these borders lie between09h 41m and10h 51m, while thedeclination 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.[4]
The constellation Sextans as it can be seen by the naked eye
John Flamsteed labeled 41 stars for the constellation.[5]Francis Baily intended to giveBayer designations to some of the stars but because none of them were above magnitude 4.5, he left them unlettered.[5] Rather, it wasBenjamin Apthorp Gould who lettered some of the stars. He labeled the five brightest stars usingGreek letters Alpha (α) to Epsilon (ε) in hisUranometria Argentina.[5] All together, there are 38 stars that are brighter than or equal to apparent magnitude 6.5.[a][7]
γ Sextantis is the second brightest star in the constellation with an apparent magnitude of 5.05. It is abinary star consisting of twoA-type main-sequence stars with classes of A1 V and A4 V respectively.[11] The stars take 77.55 years to circle each other in an eccentric orbit[12] and the system is located 280±10 light-years away from the Solar System.[9] The separation of the stars is four-tenths of anarcsecond,[12] making it difficult to observe without the use of a telescope with an aperture of 30 cm.
Sextans contains a few notable multiple star systems within its boundaries.
35 Sextantis is a triple star system consisting of two evolvedK-type giants of equal mass, with both stars being twice as massive as the Sun.[17] The secondary is itself a single-linedspectroscopic binary consisting of a 0.58 M☉ companion and itself.[17] The system is located approximately 700 light years away.[18][19] 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 relativelyeccentric orbit.[20]
^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,VA: The McDonald & Woodward Publishing Company. p. 290.ISBN978-0-939923-78-6.
^abHeintz, W. D. (March 1982), "Orbits of 16 visual binaries",Astronomy and Astrophysics Supplement Series,47:569–573,Bibcode:1982A&AS...47..569H.
^Crawford, D. L.; et al. (1971), "Four-color, H-beta, and UBV photometry for bright B-type stars in the northern hemisphere",The Astronomical Journal,76: 1058,Bibcode:1971AJ.....76.1058C,doi:10.1086/111220.
^Mathys, G.; et al. (March 1986), "Photometric variability of some early-type stars",Astronomy and Astrophysics Supplement Series,63 (3):403–416,Bibcode:1986A&AS...63..403M.
^Kholopov, P. N.; et al. (April 1989), "The 69th Name-List of Variable Stars",Information Bulletin on Variable Stars,3323 (3323): 1,Bibcode:1989IBVS.3323....1K.
