Antlia

Antlia

Antlia
Constellation
Antlia
Abbreviation Ant
Genitive Antliae
Pronunciation , genitive
Symbolism the Air Pump[1]
Right ascension 09h 27m 05.1837s–11h 05m 55.0471s[2]
Declination −24.5425186°–−40.4246216°[2]
Family La Caille
Area 239 sq. deg. (62nd)
Main stars 3
Bayer/Flamsteed
stars
9
Stars with planets 2
Stars brighter than 3.00m 0
Stars within 10.00 pc (32.62 ly) 2
Brightest star α Ant (4.25m)
Nearest star DEN 1048-3956[3]
(13.17 ly, 4.04 pc)
Messier objects 0
Meteor showers None
Bordering
constellations
Hydra
Pyxis
Vela
Centaurus
Visible at latitudes between +45° and −90°.
Best visible at 21:00 (9 p.m.) during the month of April.

Antlia (; from Ancient Greek ἀντλία) is a constellation in the southern sky. Its name means "pump" and it specifically represents an air pump. The constellation was created in the 18th century from an undesignated region of sky, so the stars comprising Antlia are faint. The brightest star is Alpha Antliae is an orange giant that is a suspected variable star, ranging between apparent magnitudes 4.22 and 4.29. NGC 2997, a spiral galaxy, and the Antlia Dwarf Galaxy lie within Antlia's borders.

History

Johann Bode's depiction of Antlia.

The French astronomer Nicolas Louis de Lacaille first described the constellation in French as la Machine Pneumatique (the Pneumatic Pump) in 1751–52,[4][5] commemorating the air pump invented by the French physicist Denis Papin.[6] He had observed and catalogued almost 10,000 southern stars during a two-year stay at the Cape of Good Hope, devising fourteen new constellations in uncharted regions of the Southern Celestial Hemisphere not visible from Europe. All but one honoured instruments that symbolised the Age of Enlightenment.[1][7] Lacaille Latinised the name to Antlia pneumatica on his 1763 chart. John Herschel proposed shrinking the name to one word, which was universally taken up.[8]

Though Antlia was technically visible to ancient Greek astronomers, its stars were too faint to have been included in any constellations.[6] Because of this, its main stars have no particular pattern and it is devoid of bright deep-sky objects.[9] Lacaille and Johann Bode each depicted Antlia differently, as either the single-cylinder vacuum pump used in Papin's initial experiments, or the more advanced double-cylinder version.[6] The International Astronomical Union subsequently adopted it as one of the 88 modern constellations. There is no mythology attached to Antlia as Lacaille discontinued the tradition of giving names from mythology to constellations and instead chose names mostly from scientific instruments.[6]

According to some, the most prominent stars that now comprise Antlia were once included within the ancient constellation Argo Navis, the Ship of the Argonauts, which due to its immense size was split into several smaller constellations by Lacaille in 1763.[10][11] However, given the faintness and obscurity of its stars, most authorities do not believe that the ancient Greeks included Antlia as part of their classical depiction of Argo Navis.[12]

In non-Western astronomy

Chinese astronomers were able to view what is modern Antlia from their latitudes, and incorporated its stars into two different constellations. Several stars in the southern part of Antlia were a portion of "Dong'ou", which represented an area in southern China.[6] Furthermore, Epsilon, Eta, and Theta Antliae were incorporated into the celestial temple, which also contained stars from modern Pyxis.[6]

Characteristics

Covering 238.9 square degrees and hence 0.579% of the sky, Antlia ranks 62nd of the 88 modern constellations by area.[13] Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 49°N.[13][2] It is bordered by Hydra the sea snake to the north, Pyxis the compass to the west, Vela the sails to the south, and Centaurus the centaur to the east. This group of constellations is prominent in the southern sky in late winter and spring. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'Ant'.[14] The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of twelve segments (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between 09h 26.5m and 11h 05.6m, while the declination coordinates are between -24.54° and -40.42°.[2]

Notable features

The constellation Antlia as it can be seen by the naked eye.

Stars

Lacaille gave nine stars Bayer designations, labelling them Alpha through to Theta, including two stars next to each other as Zeta. Gould later added a tenth, Iota Antliae. Beta and Gamma Antliae (now HR 4339 and HD 90156) ended up in the neighbouring constellation Hydra once the constellation boundaries were delineated in 1930.[15] Within the constellation's borders, there are 42 stars brighter than or equal to apparent magnitude 6.5.[3][13]

The constellation's brightest star,[9] Alpha Antliae is an orange giant of spectral type K4III that is a suspected variable star, ranging between apparent magnitudes 4.22 and 4.29.[17] It is located 370 ± 20 light-years away from Earth.[18] Estimated to be shining with around 480 to 555 times the luminosity of the Sun, it is most likely an ageing star that is brightening and on its way to becoming a Mira variable star, having converted all its core fuel into carbon.[19] Located near Alpha is Delta Antliae, a binary star , 430 ± 30 light-years distant from Earth.[18] The primary is a blue-white main sequence star of spectral type B9.5V and magnitude 5.6 and the secondary is an yellow-white main sequence star of spectral type F9Ve and magnitude 9.6.[20]

Zeta Antliae is a wide optical double star. The brighter star—Zeta1 Antliae—is 410 ± 40 light-years distant and has a magnitude of 5.74,[18] though it is a true binary star system composed of two white main sequence stars of magnitudes 6.20 and 7.01 that are separated by 8.042 arcseconds.[21] The fainter star—Zeta2 Antliae—is 380 ± 20 light-years distant[18] and of magnitude 5.9.[22] Eta Antliae is another double composed of an F-type main sequence star of spectral type and magnitude 5.22, with a companion of magnitude 11.3. Theta Antliae is likewise double, composed of an A-type main sequence star and yellow giant.

Located 710 ± 40 light-years from Earth,[18] Epsilon Antliae is an evolved orange giant star of spectral type K3 IIIa, that has swollen to have a diameter around 69 times that of the Sun,[23] and a luminosity of around 1279 Suns.[24] It is slightly variable.[25] At the other end of Antlia, Iota Antliae is likewise an orange giant of spectral type K1 III.[26]

T Antliae is a yellow-white supergiant of spectral type F6Iab and Classical Cepheid variable ranging between magnitude 8.88 and 9.82 over 5.9 days.[27] U Antliae is a red C-type carbon star and is an irregular variable that ranges between magnitudes 5.27 and 6.04.[28] Around 900 light-years distant, it is around 5819 times as luminous as the Sun.[24]

HR 4049, also known as AG Antliae, is an unusual hot variable ageing star of spectral type B9.5Ib-II. It is undergoing intense mass-loss[29] and is a unique variable, ranging between magnitudes 5.29 and 5.83 with a period of 429 days[30] UX Antliae is an R Coronae Borealis variable with a baseline apparent magnitude of around 11.85, with irregular dimmings down to below magnitude 18.0.[31] A luminous and remote star, it is a supergiant with a spectrum resembling that of a yellow-white F-type star but it has almost no hydrogen.[32]

DEN 1048-3956 is a brown dwarf located around 13 light-years distant from Earth. At magnitude 17 it is much too faint to be seen with the unaided eye.

Deep-sky objects

A composite image of NGC 2997.

Because it occupies a part of the celestial sphere that faces away from the Milky Way, Antlia contains very few deep-sky objects. It contains no globular clusters, no planetary nebulae, and no open clusters. However, it does contain several galaxies.

NGC 2997 is a loose face-on spiral galaxy of type Sc.[22] It is the brightest galaxy in Antlia at an integrated magnitude of 10.6.[9] Though nondescript in most amateur telescopes, it presents bright clusters of young stars and many dark dust lanes in photographs.[22]

The Antlia Dwarf, a 14.8m dwarf spheroidal galaxy that belongs to our Local Group of galaxies. It was discovered only as recently as 1997.[33]

The Antlia Cluster, also known as Abell S0636, is a cluster of galaxies located in the Hydra-Centaurus Supercluster. It is the third nearest to our Local Group after the Virgo Cluster and Fornax Cluster.[34] The cluster's distance from earth is 40.5 Mpc (132.1 Mly) to 40.9 Mpc (133.4 Mly)[35] Located in the southeastern corner of the constellation, it boasts the giant elliptical galaxies NGC 3268 and NGC 3258 as the main members of a southern and northern subgroup respectively.[36]

Notes

  1. ^ The exception is Mensa, named for the Table Mountain. The other thirteen (alongside Antlia) are Caelum, Circinus, Fornax, Horologium, Microscopium, Norma, Octans, Pictor, Pyxis, Reticulum, Sculptor and Telescopium.[7]
  2. ^ While parts of the constellation technically rise above the horizon to observers between the 49°N and 65°N, stars within a few degrees of the horizon are to all intents and purposes unobservable.[13]
  3. ^ Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.[16]

References

Citations
  1. ^
  2. ^ a b c
  3. ^
  4. ^
  5. ^
  6. ^ a b c d e f
  7. ^ a b Wagman 2003, pp. 5-6.
  8. ^ Wagman 2003, p. 25.
  9. ^ a b c Moore & Tirion 1997
  10. ^ Peter Birren (2002) Objects in the Heavens, pp. 9, 45 (ISBN 155369662X).
  11. ^ Thomas William Webb (Dover Publications 1962) Celestial objects for common telescopes, Volume 2, p. 36.
  12. ^ Ian Ridpath (2002) Stars and Planets, pp, 65, 122. (ISBN 0-7894-8988-0)
  13. ^ a b c d
  14. ^
  15. ^ Wagman 2003, p. 29.
  16. ^
  17. ^
  18. ^ a b c d e
  19. ^
  20. ^
  21. ^
  22. ^ a b c Ridpath 2001, pp. 74–76
  23. ^
  24. ^ a b
  25. ^
  26. ^
  27. ^
  28. ^
  29. ^
  30. ^
  31. ^
  32. ^
  33. ^
  34. ^
  35. ^
  36. ^
References