Johann Bode's depiction of Antlia as a double-cylinder air pump
The French astronomerNicolas-Louis de Lacaille first described the constellation in French asla Machine Pneumatique (the Pneumatic Machine) in 1751–52,[4][5] commemorating theair pump invented by the French physicistDenis Papin.[6] De Lacaille had observed and catalogued almost 10,000 southern stars during a two-year stay at theCape of Good Hope, devising fourteen new constellations in uncharted regions of theSouthern Celestial Hemisphere not visible from Europe. He named all but one in honour of instruments that symbolised theAge of Enlightenment.[a][7] Lacaille depicted Antlia as a single-cylinder vacuum pump used in Papin's initial experiments, while German astronomerJohann Bode chose the more advanced double-cylinder version.[6] LacailleLatinised the name toAntlia pneumatica on his 1763 chart. English astronomerJohn Herschel proposed shrinking the name to one word in 1844, noting that Lacaille himself had abbreviated his constellations thus on occasion.[8] This was universally adopted.[9] TheInternational Astronomical Union adopted it as one of the88 modern constellations in 1922.[10]
Although visible to theAncient Greeks, Antlia's stars were too faint to have been commonly recognised as a figurative object, or part of one, in ancient asterisms.[6] The stars that now comprise Antlia are in a zone of the sky associated with the asterism/old constellationArgo Navis, the ship,the Argo, of the Argonauts, in its latter centuries. This, due to its immense size, was split into hull, poop deck and sails by Lacaille in 1763.[11][12] Ridpath reports that due to their faintness, the stars of Antlia did not make up part of the classical depiction of Argo Navis.[13]
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, andTheta Antliae were incorporated into the celestial temple, which also contained stars from modernPyxis.[6]
Covering 238.9 square degrees and hence 0.579% of the sky, Antlia ranks 62nd of the88 modern constellations by area.[14] Its position in theSouthern Celestial Hemisphere means that the wholeconstellation is visible to observers south of49°N.[14][b]Hydra the sea snake runs along the length of its northern border, whilePyxis the compass,Vela the sails, andCentaurus the centaur line it to the west, south and east respectively. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union, is "Ant".[10] The official constellation boundaries, as set by Belgian astronomerEugène Delporte in 1930,[c] are defined by a polygon with an east side, south side and ten other sides (facing the two other cardinal compass points) (illustrated in infobox at top-right). In theequatorial coordinate system, theright ascension coordinates of these borders lie between09h 26.5m and11h 05.6m, while thedeclination coordinates are between −24.54° and −40.42°.[2]
Lacaille gave nine starsBayer designations, labelling them Alpha through to Theta, combining two stars next to each other as Zeta. Gould later added a tenth,Iota Antliae. Beta and Gamma Antliae (nowHR 4339 andHD 90156) ended up in the neighbouring constellation Hydra once the constellation boundaries were delineated in 1930.[16] Within the constellation's borders, there are 42 stars brighter than or equal toapparent magnitude 6.5.[d][14]The constellation's two brightest stars—Alpha andEpsilon Antliae—shine with a reddish tinge.[18] Alpha is an orangegiant ofspectral typeK4III that is a suspectedvariable star, ranging betweenapparent magnitudes 4.22 and 4.29.[19] It is located 320 ± 10light-years away from Earth.[20] Estimated to be shining with around 480 to 555 times theluminosity of the Sun, it is most likely an ageing star that is brightening and on its way to becoming aMira variable star, having converted all its core fuel into carbon.[21] Located 590 ± 30 light-years from Earth,[22] Epsilon Antliae is an evolved orange giant star of spectral type K3 IIIa, that has swollen to have a diameter about 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] It is 202 ± 2 light-years distant.[27]
Located near Alpha isDelta Antliae, abinary star, 450 ± 10 light-years distant from Earth.[28] The primary is ablue-white main sequence star of spectral typeB9.5V and magnitude 5.6, and the secondary is ayellow-white main sequence star of spectral typeF9Ve and magnitude 9.6.[29]Zeta Antliae is a wide opticaldouble star. The brighter star—Zeta1 Antliae—is 410 ± 40 light-years distant and has a magnitude of 5.74,[30] though it is a true binary star system composed of twowhite main sequence stars of magnitudes 6.20 and 7.01 that are separated by 8.042arcseconds.[31] The fainter star—Zeta2 Antliae—is 386 ± 5 light-years distant[32] and of magnitude 5.9.[33]Eta Antliae is another double composed of a yellow white star of spectral type F1V and magnitude 5.31, with a companion of magnitude 11.3.[31]Theta Antliae is likewise double, most likely composed of anA-type main sequence star and a yellow giant.[34]S Antliae is aneclipsing binary star system that varies in apparent magnitude from 6.27 to 6.83 over a period of 15.6 hours.[35] The system is classed as aW Ursae Majoris variable—the primary is hotter than the secondary and the drop in magnitude is caused by the latter passing in front of the former. Calculating the properties of the component stars from the orbital period indicates that the primary star has a mass 1.94 times and a diameter 2.026 times that of the Sun, and the secondary has a mass 0.76 times and a diameter 1.322 times that of the Sun.[36] The two stars have similarluminosity andspectral type as they have acommon envelope and share stellar material.[37] The system is thought to be around 5–6 billion years old. The two stars will eventually merge to form a single fast-spinning star.[36]
T Antliae is ayellow-white supergiant of spectral type F6Iab andClassical Cepheid variable ranging between magnitude 8.88 and 9.82 over 5.9 days.[38]U Antliae is a redC-typecarbon star and is anirregular variable that ranges between magnitudes 5.27 and 6.04.[39] At 910 ± 50 light-years distant,[40] it is around 5819 times as luminous as the Sun.[24]BF Antliae is aDelta Scuti variable that varies by 0.01 of a magnitude.[41]HR 4049, also known as AG Antliae, is an unusual hot variable ageing star of spectral type B9.5Ib-II. It is undergoing intense loss of mass[42] and is a unique variable that does not belong to any class of known variable star, ranging between magnitudes 5.29 and 5.83 with a period of 429 days.[43] It is around 6000 light-years away from Earth.[44]UX Antliae is anR Coronae Borealis variable with a baseline apparent magnitude of around 11.85, with irregular dimmings down to below magnitude 18.0.[45] A luminous and remote star, it is asupergiant with a spectrum resembling that of a yellow-white F-type star but it has almost no hydrogen.[46]
A composite image of NGC 2997
HD 93083 is an orange dwarf star of spectral type K3V that is smaller and cooler than the Sun. It has a planet that was discovered by theradial velocity method with theHARPS spectrograph in 2005. About as massive as Saturn, the planet orbits its star with a period of 143 days at a mean distance of 0.477 AU.[47]WASP-66 is a sunlike star of spectral type F4V. A planet with 2.3 times the mass of Jupiter orbits it every 4 days, discovered by the transit method in 2012.[48]DEN 1048-3956 is abrown dwarf of spectral type M8 located around 13 light-years distant from Earth. At magnitude 17 it is much too faint to be seen with the unaided eye. It has a surface temperature of about 2500 K. Two powerfulflares lasting 4–5 minutes each were detected in 2002.[49]2MASS 0939-2448 is a system of two cool and faint brown dwarfs, probably with effective temperatures of about 500 and 700 K and masses of about 25 and 40 times that of Jupiter, though it is also possible that both objects have temperatures of 600 K and 30 Jupiter masses.[50]
GalaxyESO 376-16 is located nearly 23 million light-years from Earth.[51]
Antlia contains many faint galaxies,[52] the brightest of which isNGC 2997 at magnitude 10.6.[53] It is a loosely wound face-onspiral galaxy of typeSc. Though nondescript in most amateur telescopes, it presents bright clusters of young stars and many dark dust lanes in photographs.[33] Discovered in 1997, theAntlia Dwarf is a 14.8mdwarf spheroidal galaxy that belongs to theLocal Group of galaxies.[54] In 2018 the discovery was announced of a very lowsurface brightness galaxy near Epsilon Antliae,Antlia 2, which is a satellite galaxy of the Milky Way.[55]
TheAntlia Cluster, also known as Abell S0636, is acluster of galaxies located in theHydra–Centaurus Supercluster. It is the third nearest to theLocal Group after theVirgo Cluster and theFornax Cluster.[56] The cluster's distance from earth is 40.5 to 40.9 Mpc (132.1 to 133.4 Mly)[57] Located in the southeastern corner of the constellation, it boasts the giant elliptical galaxiesNGC 3268 andNGC 3258 as the main members of a southern and northern subgroup respectively, and contains around 234 galaxies in total.[52]
^Although parts of the constellation technically rise above the horizon to observers between the 49°N and65°N, stars within a few degrees of the horizon are to all intents and purposes unobservable.[14]
^Delporte had proposed standardising the constellation boundaries to the International Astronomical Union, who had agreed and gave him the lead role[15]
^Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.[17]
^Leggett, Sandy K.; Cushing, Michael C.; Saumon, Didier; Marley, Mark S.; Roellig, Thomas L.; Warren, Stephen J.; Burningham, Ben; Jones, Hugh R. A.; Kirkpatrick, J. Davy; Lodieu, Nicolas; Lucas, Philip W.; Mainzer, Amy K.; Martín, Eduardo L.; McCaughrean, Mark J.; Pinfield, David J.; Sloan, Gregory C.; Smart, Richard L.; Tamura, Motohide; Van Cleve, Jeffrey E. (2009). "The Physical Properties of Four ~600 K T Dwarfs".The Astrophysical Journal.695 (2):1517–1526.arXiv:0901.4093.Bibcode:2009ApJ...695.1517L.doi:10.1088/0004-637X/695/2/1517.S2CID44050900.
^abStreicher, Magda (2010). "Deepsky Delights: Antlia, the Machine Pneumatique".Monthly Notes of the Astronomical Society of Southern Africa.69 (5–6):107–12.Bibcode:2010MNSSA..69..107S.
Ridpath, Ian (2017),Stars and Planets Guide, Princeton University Press,ISBN978-0-691-17788-5
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.Bibcode:2003lslm.book.....W.ISBN978-0-939923-78-6.
