The Antlia Constellation

The Antlia Constellation.

Antlia is a small, faint constellation located in the southern skies. Its name is an ancient Greek word for “the pump,” originally named Antlia Pneumatica, to commemorate the invention of the air pump, which it represents Antlia (see above cover illustration of Antlia Constellation which is below the Felis Constellation or the Cat at the bottom right). It was created and catalogued by the French astronomer Abbé Nicolas Louis de Lacaille in the 18th century, along with 13 other constellations (Caelum, Circinus, Fornax, Horologium, Mensa, Microscopium, Norma, Octans, Pictor, Reticulum, Sculptor, and Telescopium) introduced by Lacaille to fill the void in some faint regions in the southern sky. Lacaille’s constellations are mostly named after scientific instruments and there are no myths attached to them. Antlia is one of the smaller constellations in the sky (62nd in size), occupying an area of 239 square degrees. It is located in the second quadrant of the southern hemisphere and can be seen at latitudes between +45° and -90°, right ascension 10h 7m and declination -33degrees 21’, with April at around 9.00pm as its best viewing month and time. The neighbouring constellations are Centaurus, Hydra, Pyxis, and Vela.

It does not have any stars brighter than magnitude 3.00. The brightest star is Alpha Antliae, a fourth magnitude star Its apparent magnitude varies between 4.22 and 4.29. It is located approximately 365 light years away, and is classified as a K4III-type orange giant. It is suspected to be a variable star, estimated to be shining with around 480 to 555 times the luminosity of the Sun. Its age is estimated to be about a billion years, so the next evolutionary stage it will reach is Mira-type variable before it turns into a white dwarf. The nearest star in Antlia, DEN 1048−3956, is a brown dwarf only 13.15 light years distant from Earth. Antlia has two stars with known planets, HD 93083 (spectral class K2V) and WASP-66 (F4V). The constellation does not contain any Messier objects.

Notable deep sky objects in Antlia include the Antlia Dwarf Galaxy (PGC 29194), the Antlia Cluster of Galaxies (Abell S0636), and the unbarred spiral galaxy NGC 2997 (ESO 434-G 35, PGC 27978). The Antlia Dwarf is a dwarf spheroidal galaxy located about 4.3 million light years from Earth. It is a very faint object, with an apparent magnitude of 16.2. The galaxy was not discovered until 1997. The Antlia Dwarf lies on the outer rim of the Local Group of galaxies, possibly even beyond it, and there is evidence suggesting that it is tidally interacting with another small galaxy, NGC 3109, in the Hydra constellation.

The Antlia Cluster is a cluster of galaxies within the Hydra–Centaurus Supercluster which, in turn, is the closest neighbour to the Virgo Supercluster, in which the Milky Way Galaxy is located. The cluster is the third closest to our Local Group, with only the Fornax Cluster and Virgo Cluster lying closer. The Antlia Cluster does not have a single brightest cluster galaxy and is therefore classified as a Bautz-Morgan type III cluster, which is a rather rare type of galaxy cluster. The Cluster contains about 234 galaxies and is dominated by two massive elliptical galaxies, NGC 3258 and NGC 3268. The northern subgroup of galaxies inside the cluster gravitates around NGC 3268, while the southern subgroup is centred on NGC 3258. Each of the two giant elliptical galaxies contains several thousand globular clusters. Most galaxies in the Antlia Cluster are early type galaxies, and dwarf elliptical galaxies are the most common galaxy type. The Antlia Cluster is located between 32.58 and 32.71 million light years from Earth. In spite of being relatively close by, it has not been sufficiently investigated. Members of the Antlia Cluster include the elliptical galaxy NGC 3260, lenticular galaxies NGC 3269 and NGC 3267, the spiral galaxy NGC 3281, and the barred spiral NGC 3271, which is the brightest spiral galaxy in the cluster.

NGC 2997 is an unbarred spiral galaxy in Antlia, located approximately 24.8 million light years away. It is a grand design galaxy, which is to say the kind of spiral galaxy with clearly defined spiral arms that extend around it. Only ten percent of spiral galaxies are grand design spirals. What makes NGC 2997 particularly notable is the chain of hot giant clouds of ionized hydrogen surrounding the galaxy’s nucleus. It is the brightest galaxy in the NGC 2997 group, a group of galaxies, approximately 24.8 million light-years distant, belonging to the Local Supercluster.

Antlia also contains the spiral galaxies NGC 3244 and IC 2560 and the interacting pair IC 2545. NGC 3244 is a spiral galaxy about 100 million light years distant. It has a visual magnitude of 12.89 and an apparent size of 2’ x 1.5’. The galaxy was discovered by John

Herschel on April 22, 1835. On June 2010, a supernova was discovered in NGC 3244. Designated SN 2010ev, it reached a magnitude of about 14 and was the third brightest supernova discovered that year. IC 2560 is another spiral galaxy in Antlia. It has an apparent magnitude of 13.31 and lies at an approximate distance of 110 million light years from Earth. The galaxy occupies an area 2.79’ x 1.06’ in size. IC 2545 is a pair of interacting galaxies located at a distance of 450 million light years from Earth. The galaxies have a visual magnitude of 14.27 and an apparent size of 0.6’ x 0.4’. They were discovered by the American astronomer DeLisle Stewart on May 1, 1900.

HD 93083 b is an extrasolar planet orbiting the star HD 93083 in the constellation. It is probably much less massive than Jupiter, although only the minimum mass is known. The planet’s mean distance from the star is about half that of Earth, and the orbit is slightly eccentric. This planet is another discovery by the HARPS search team. Credits: Constellation Guide, Wikipedia.