Sextans

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Sextans
Constellation
Sextans IAU.svg
List of stars in Sextans
AbbreviationSex
Genitive Sextantis, Sextansis
Pronunciation /ˈsɛkstənz/ ,
genitive /sɛksˈtæntɪs/
Symbolismthe Sextant
Right ascension 09h 41m 04.8653s–10h 51m 30.2447s [1]
Declination 6.4327669°–−11.6621428° [1]
QuadrantSQ2
Area 314 sq. deg. (47th)
Main stars 3
Bayer/Flamsteed
stars		28
Stars with planets 5
Stars brighter than 3.00m0
Stars within 10.00 pc (32.62 ly)5
Brightest star α Sex  (4.49 m )
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 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.

Contents

Characteristics

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 ]

Notable features

Stars

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

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] Altogether, there are 38 stars that are brighter than or equal to apparent magnitude 6.5. [lower-alpha 1] [6]

Bright stars

Multiple star systems

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.

COSMOS project

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]

Depictions of the constellation

See also

Related Research Articles

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<span class="mw-page-title-main">Apus</span> Constellation in the southern celestial hemisphere

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<span class="mw-page-title-main">Fornax</span> Constellation in the southern celestial hemisphere

Fornax is a constellation in the southern celestial hemisphere, partly ringed by the celestial river Eridanus. Its name is Latin for furnace. It was named by French astronomer Nicolas Louis de Lacaille in 1756. Fornax is one of the 88 modern constellations.

<span class="mw-page-title-main">Microscopium</span> Minor constellation in the southern celestial hemisphere

Microscopium is a minor constellation in the southern celestial hemisphere, one of twelve created in the 18th century by French astronomer Nicolas-Louis de Lacaille and one of several depicting scientific instruments. The name is a Latinised form of the Greek word for microscope. Its stars are faint and hardly visible from most of the non-tropical Northern Hemisphere.

<span class="mw-page-title-main">Piscis Austrinus</span> Constellation in the southern celestial hemisphere

Piscis Austrinus is a constellation in the southern celestial hemisphere. The name is Latin for "the southern fish", in contrast with the larger constellation Pisces, which represents a pair of fish. Before the 20th century, it was also known as Piscis Notius. Piscis Austrinus was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. The stars of the modern constellation Grus once formed the "tail" of Piscis Austrinus. In 1597, Petrus Plancius carved out a separate constellation and named it after the crane.

<span class="mw-page-title-main">Crater (constellation)</span> Constellation in the southern celestial hemisphere

Crater is a small constellation in the southern celestial hemisphere. Its name is the latinization of the Greek krater, a type of cup used to water down wine. One of the 48 constellations listed by the second-century astronomer Ptolemy, it depicts a cup that has been associated with the god Apollo and is perched on the back of Hydra the water snake.

<span class="mw-page-title-main">Horologium (constellation)</span> Constellation in the southern celestial hemisphere

Horologium is a constellation of six stars faintly visible in the southern celestial hemisphere. It was first described by the French astronomer Nicolas-Louis de Lacaille in 1756 and visualized by him as a clock with a pendulum and a second hand. In 1922 the constellation was redefined by the International Astronomical Union (IAU) as a region of the celestial sphere containing Lacaille's stars, and has since been an IAU designated constellation. Horologium's associated region is wholly visible to observers south of 23°N.

<span class="mw-page-title-main">Alpha Sextantis</span> Star in the constellation Sextans

Alpha Sextantis is the brightest star in the equatorial constellation of Sextans. It is visible to the naked eye on a dark night with an apparent visual magnitude of 4.49. The distance to this star, as determined from parallax measurements, is around 280 light years. This is considered an informal "equator star", as it lies less than a quarter of a degree south of the celestial equator. In 1900, it was 7 minutes of arc north of the equator. As a result of a shift in the Earth's axial tilt, it crossed over to the southern hemisphere in December 1923.

Beta Sextantis, Latinized from β Sextantis, is a variable star in the equatorial constellation of Sextans. With an apparent visual magnitude of 5.07, it is faintly visible to the naked eye on a dark night. According to the Bortle scale, it can be viewed from brighter lit suburban skies. The distance to this star, based upon an annual parallax shift of 8.96 mas, is around 364 light years.

Epsilon Sextantis, Latinized from ε Sextantis, is a solitary, yellow-white hued star in the equatorial constellation of Sextans. With an apparent visual magnitude of 5.24, it is faintly visible to the naked eye on a dark night. The distance to this star, based upon an annual parallax shift of 16.86 mas, is about 193 light years. It is drifting further away from the Sun with a radial velocity of +15 km/s.

HD 7853 is a double star in the constellation Andromeda. With an apparent magnitude of 6.46, it can barely be seen with the naked eye even on the best of nights. The system is located approximately 130 parsecs (420 ly) distant, and the brighter star is an Am star, meaning that it has unusual metallic absorption lines. The spectral classification of kA5hF1mF2 means that it would have a spectral class of A5 if it were based solely on the calcium K line, F2 if based on the lines of other metals, and F1 if based on the hydrogen absorption lines. The two components are six arc-seconds apart and the secondary is three magnitudes fainter than the primary.

<span class="mw-page-title-main">S Monocerotis</span> Star in the constellation Monoceros

S Monocerotis, also known as 15 Monocerotis, is a massive multiple and variable star system located in the constellation Monoceros. It is the brightest star in the Christmas Tree open cluster in the area catalogued as NGC 2264.

<span class="mw-page-title-main">1 Camelopardalis</span> Double star system in the constellation Camelopardalis

1 Camelopardalis is a double star system in the constellation Camelopardalis. Its combined apparent magnitude is 5.56 and it is approximately 800 parsecs (2,600 ly) away.

HD 85951, formally named Felis, is a solitary orange hued star in the constellation Hydra. It has an apparent magnitude of 4.94, making it faintly visible to the naked eye under ideal conditions. Based on parallax measurements, the object is about 570 light-years away from the Sun and is receding with a heliocentric radial velocity of 50 km/s.

<span class="mw-page-title-main">Eta Pavonis</span> Star in the Pavo constellation

Eta Pavonis, a name latinized from η Pavonis, is a single star in the southern constellation of Pavo, positioned near the western constellation border next to Ara. It has an orange hue and is visible to the naked eye with an apparent visual magnitude of 3.61. Based on parallax, this object is located at a distance of approximately 350 light-years (108 pc) from the Sun. It has an absolute magnitude of −1.56, and is drifting closer with a radial velocity of −7.6 km/s.

<span class="mw-page-title-main">18 Sextantis</span> K-type giant star in the constellation Sextans

18 Sextantis, or simply 18 Sex, is a solitary star located in the southern constellation Sextans. It is faintly visible to the naked eye as an orange-hued point of light with an apparent magnitude of 5.62. Gaia DR3 parallax measurements imply a distance of 558 light-years and it is slowly receding with a poorly constrained heliocentric radial velocity of approximately 0.2 km/s. At its current distance, 18 Sex's brightness is diminished with an interstellar extinction of two-tenths of a magnitude and it has an absolute magnitude of −0.16.

<span class="mw-page-title-main">HD 84607</span> F-type subgiant; Sextans

HD 84607 is a solitary star located in the equatorial constellation Sextans. It is faintly visible to the naked eye as a yellowish-white hued point of light with an apparent magnitude of 5.64. The object is located relatively close at a distance of 250 light-years based on Gaia DR3 parallax measurements, but it is receding with a heliocentric radial velocity of 7.8 km/s. At its current distance, HD 84607's brightness is diminished by an interstellar extinction of 0.18 magnitudes and it has an absolute magnitude +1.12.

<span class="mw-page-title-main">19 Sextantis</span> K-type giant star; Sextans

19 Sextantis, or simply 19 Sex, is a solitary star located in the equatorial constellation Sextans. It is faintly visible to the naked eye as an orange-hued point of light with an apparent magnitude of 5.78. Gaia DR3 parallax measurements imply a distance of 516 light-years and it is currently receding with a heliocentric radial velocity of 31.8 km/s. At its current distance, 19 Sex's brightness is diminished by an interstellar extinction of 0.17 magnitudes.

<span class="mw-page-title-main">35 Sextantis</span> Triple star system in Sextans

35 Sextantis, or simply 35 Sex, is a triple star system located in the equatorial constellation Sextans. The primary has an apparent magnitude of 6.09, making it barely visible to the naked eye, even under ideal conditions. The companion has an apparent magnitude of 7.01, making it readily visible in binoculars, but not to the naked eye. The system is located relatively far at a distance of approximately 700 light-years but it is drifting closer with a combined heliocentric radial velocity of −2.18 km/s.

<span class="mw-page-title-main">25 Sextantis</span> Alpha2 Canum Venactiorum variable.

25 Sextantis, or simply 25 Sex, is a star located in the equatorial constellation Sextans; it also bears the variable star designation SS Sextantis. With an average apparent magnitude of 5.97, 25 Sex is barely visible to the naked eye, even under ideal conditions. Gaia DR3 parallax measurements imply a distance of 345 light-years, and it is currently drifting away with a heliocentric radial velocity of approximately 23 km/s. At its current distance, 25 Sex's average brightness is diminished by an interstellar extinction of 0.17 magnitudes and it has an absolute magnitude of +0.86.

References

  1. 1 2 IAU, The Constellations, Sextans.
  2. ↑ Russell, Henry Norris (1922). "The new international symbols for the constellations". Popular Astronomy . Vol. 30. p. 469. Bibcode:1922PA.....30..469R.
  3. ↑ "International Astronomical Union | IAU". www.iau.org.
  4. 1 2 3 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. p. 290. ISBN   978-0-939923-78-6.
  5. ↑ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope . Sky Publishing Corporation. Retrieved 4 March 2016.
  6. ↑ Ridpath, Ian. "Constellations: Lacerta–Vulpecula". Star Tales. Self-published. Retrieved 4 March 2016.
  7. ↑ 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. Bibcode:1969AJ.....74..375C. doi: 10.1086/110819 . ISSN   0004-6256. S2CID   121555804.
  8. 1 2 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv: 0708.1752 , Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID   18759600.
  9. ↑ 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. arXiv: 2306.08551 . Bibcode:2023AJ....166...73M. doi: 10.3847/1538-3881/acdee4 .
  10. ↑ Edwards, T. W. (April 1976), "MK classification for visual binary components", Astronomical Journal, 81: 245–249, Bibcode:1976AJ.....81..245E, doi:10.1086/111879.
  11. 1 2 Heintz, W. D. (March 1982), "Orbits of 16 visual binaries", Astronomy and Astrophysics Supplement Series, 47: 569–573, Bibcode:1982A&AS...47..569H.
  12. ↑ 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.
  13. ↑ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics . 616. A1. arXiv: 1804.09365 . Bibcode: 2018A&A...616A...1G . doi: 10.1051/0004-6361/201833051 . Gaia DR2 record for this source at VizieR .
  14. ↑ 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.
  15. ↑ 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.
  16. 1 2 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. arXiv: 0806.3263 . Bibcode:2008MNRAS.389..925T. doi: 10.1111/j.1365-2966.2008.13613.x .
  17. ↑ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR .
  18. ↑ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR .
  19. ↑ Tokovinin, A. A.; Gorynya, N. A. (April 2007). "New spectroscopic components in multiple systems. V." Astronomy & Astrophysics. 465 (1): 257–261. Bibcode:2007A&A...465..257T. doi: 10.1051/0004-6361:20066888 . ISSN   0004-6361. S2CID   34100030.
  20. ↑ "A gigantic cosmic bubble". www.eso.org. Retrieved 13 November 2017.
  21. ↑ Levy 2005, p. 178.
  22. ↑ 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.
  23. ↑ 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.
  24. ↑ Overbye, Dennis (17 June 2015). "Astronomers Report Finding Earliest Stars That Enriched Cosmos". New York Times . Retrieved 17 June 2015.

Notes

  1. ↑ Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban–rural transition night skies. [5]
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