Astronomy:Sextans

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Short description: Constellation on the celestial equator


Sextans
Constellation
Sextans
AbbreviationSex
GenitiveSextantis, Sextansis
Pronunciation/ˈsɛkstənz/,
genitive /sɛksˈtæntɪs/
Symbolismthe Sextant
Right ascension 09h 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.

Sextans is a faint, minor equatorial constellation 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.

Notable features

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. Altogether, there are 38 stars that are brighter than or equal to apparent magnitude 6.5.[lower-alpha 1][3] 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]

Because it is close to the ecliptic plane, the Moon and planets regularly cross the constellation, especially its northeastern corner.

Stars

The constellation Sextans as it can be seen by the naked eye


Bright Stars

  • Alpha Sextantis is an ageing A-type star of spectral class A0 III[5] located 280±20 light-years away[6] from the Solar System. At the age of 385 million years,[7] it is exhausting hydrogen at its core and leaving the main sequence.
  • γ Sextantis is the second brightest star in the constellation with an apparent magnitude of 5.05. It is a binary star consisting of two A-type main-sequence stars with classes of A1 V and A4 V respectively.[8] The stars take 77.55 years to circle each other in an eccentric orbit[9] and the system is located 280±10 light-years away from the Solar System.[6] The separation of the stars is four-tenths of an arcsecond,[9] making it difficult to observe without the use of a telescope with an aperture of 30 cm.
  • β Sextantis is slightly fainter at magnitude 5.07;[10] it is said to be 364±10 light-years distant.[11] Beta Sextantis is a B-type main-sequence star of spectral class B6 V and it has been used as a standard in the MK spectral classification system.[12] It is suspected to be a Alpha2 Canum Venaticorum variable with a period of 15.4 days.[13]

Multiple Star Systems

  • 35 Sextantis is a triples star system consisting of two evolved K-type giants of equal mass, with both stars being twice as massive as the Sun.[14] The secondary is itself a single-lined spectroscopic binary consisting of a 0.58 M☉ companion and itself.[14] The system is located approximately 700 light years away.[15][16] 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.[17]


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.

COSMOS project

  • COSMOS-Gr30 is a particularly dense region in space that contains 10 individual galaxies[18]

  • 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.[19]

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.[20]

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.[21][22]

Depictions of the constellation

  • The constellation Sextans as depicted in Johann Doppelmayr's Atlas Coelestis, c. 1730 (Plate 19, Southern Celestial Hemisphere).

  • Sextans and other constellations seen around Hydra. From Urania's Mirror (1825)

See also

  • Sextans (Chinese astronomy)

References

  1. ↑ 1.0 1.1 IAU, The Constellations, Sextans.
  2. ↑ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y. 
  3. ↑ Ridpath, Ian. "Constellations: Lacerta–Vulpecula". Star Tales. Self-published. http://www.ianridpath.com/constellations2.html. 
  4. ↑ 4.0 4.1 4.2 Wagman, 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. pp. 290. ISBN 978-0-939923-78-6. 
  5. ↑ Cowley, A.; Cowley, C.; Jaschek, M.; Jaschek, C. (April 1969). "A study of the bright stars. I. A catalogue of spectral classifications.". The Astronomical Journal 74: 375. doi:10.1086/110819. ISSN 0004-6256. Bibcode: 1969AJ.....74..375C. 
  6. ↑ 6.0 6.1 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  7. ↑ Monier, Richard; Bowman, Dominic M.; Lebreton, Yveline; Deal, Morgan (2023). "The Unexpected Optical and Ultraviolet Variability of the Standard Star α Sex (HD 87887)". The Astronomical Journal 166 (2): 73. doi:10.3847/1538-3881/acdee4. Bibcode: 2023AJ....166...73M. 
  8. ↑ Edwards, T. W. (April 1976), "MK classification for visual binary components", Astronomical Journal 81: 245–249, doi:10.1086/111879, Bibcode: 1976AJ.....81..245E. 
  9. ↑ 9.0 9.1 Heintz, W. D. (March 1982), "Orbits of 16 visual binaries", Astronomy and Astrophysics Supplement Series 47: 569–573, Bibcode: 1982A&AS...47..569H. 
  10. ↑ 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, doi:10.1086/111220, Bibcode: 1971AJ.....76.1058C. 
  11. ↑ Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  12. ↑ 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. 
  13. ↑ 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. 
  14. ↑ 14.0 14.1 Tokovinin, A. (September 11, 2008). "Comparative statistics and origin of triple and quadruple stars". Monthly Notices of the Royal Astronomical Society 389 (2): 925–938. doi:10.1111/j.1365-2966.2008.13613.x. Bibcode: 2008MNRAS.389..925T. 
  15. ↑ Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  16. ↑ Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  17. ↑ Tokovinin, A. A.; Gorynya, N. A. (April 2007). "New spectroscopic components in multiple systems. V.". Astronomy & Astrophysics 465 (1): 257–261. doi:10.1051/0004-6361:20066888. ISSN 0004-6361. Bibcode: 2007A&A...465..257T. 
  18. ↑ "A gigantic cosmic bubble". https://www.eso.org/public/images/potw1746a/. 
  19. ↑ Levy 2005, p. 178.
  20. ↑ Wang, Tao; Elbaz, David; Daddi, Emanuele; Finoguenov, Alexis; Liu, Daizhong; Schrieber, Corenin; Martin, Sergio; Strazzullo, Veronica et al. (2016). "Discovery of a galaxy cluster with a violently starbursting core at z=2.506". The Astrophysical Journal 828 (1): 56. doi:10.3847/0004-637X/828/1/56. Bibcode: 2016ApJ...828...56W. 
  21. ↑ 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. doi:10.1088/0004-637x/808/2/139. Bibcode: 2015ApJ...808..139S. 
  22. ↑ Overbye, Dennis (17 June 2015). "Astronomers Report Finding Earliest Stars That Enriched Cosmos". New York Times. https://www.nytimes.com/2015/06/18/science/space/astronomers-report-finding-earliest-stars-that-enriched-cosmos.html. 

Notes

  1. ↑ Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban–rural transition night skies.[2]

External links

Coordinates: Sky map 10h 00m 00s, +00° 00′ 00″



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