Lupus, meanings “the wolf” in Latin, is one of the original 48 constellations catalogued by the Greek astronomer Ptolemy of Alexandria around 150 AD. It is a southern hemisphere constellation found between Centaurus and Scorpius, whose brightest star is Alpha Lupi, a blue-white giant located 460 light years away that shines with an apparent visual magnitude of 2.30.
Lupus, the 46th largest constellation in the sky, can be seen by observers situated between +35° and -90° of latitude, although it is best seen in June. The constellations bordering Lupus include Centaurus, Circinus, Hydra, Libra, Norma and Scorpius.
Lupus is part of the Hercules family of constellations, together with Aquila, Ara, Centaurus, Corona Australis, Corvus, Crater, Crux, Cygnus, Hercules, Hydra, Lyra, Ophiuchus, Sagitta, Scutum, Sextans, Serpens, Triangulum Australe and Vulpecula.
The constellation of Lupus started out as a star-pattern (asterism) in the constellation of Centaurus, and to the ancients represented an animal that was being hunted or killed by a centaur. The impaled animal is seen as facing towards the nearby constellation of Ara (“The Altar”), which served as a shrine for the sacrifice. It is likely that the Greeks loosely based their version on a myth from the Babylonians, who associated the constellation with the Mad Dog, a mythical carnivorous human hybrid creature that could have been part dog, lion or wolf.
In the 3rd century BC, the ancient Greek astronomer Hipparchus separated it from Centaurus and renamed the new constellation Therium, meaning wild animal, and by around 150 AD, Ptolemy had entered it in his astronomical treatise called Almagest. The Romans subsequently chose to call it Bestia, meaning “the beast,” and the constellation continued to not have any one animal associated with it until the Renaissance when the Latin translation of Ptolemy’s work refined the animal’s identification to being a wolf, and so called it Lupus.
– Alpha Lupi, the brightest star in Lupus, is a blue-white giant star (B1.5III) with a visual magnitude of 2.30, although being a Beta Cephei variable it experiences random variations in its brightness by about 0.03. Alpha Lupi is around 460 light years away from Earth, has a mass ten times greater than the Sun, and is also around 25,000 brighter.
– Beta Lupi, the constellation’s second brightest star, is also a blue-white giant (B2 III) found 383 light years distant. It is around 25 million years old, has 8 solar masses, and shines with a visual magnitude of 2.68, making it visible to the naked eye. Beta Lupi lies close to the remnants of SN 1006, a supernova explosion that in 1006 AD could be seen during the daytime, and was described as a “guest star”.
– Gamma Lupi, the third brightest star in the constellation, is a blue-white subgiant (B2 IV) that is around 420 light years from our solar system. It is, in fact, a close binary system that has a combined visual magnitude of 2.77.
Other stars of interest in Lupus includes the blue-white subgiants Delta Lupi, Eta Lupi, Iota Lupi, 114 G. Lupi, and Tau Lupi; the yellow stars Zeta Lupi, 1 Lupi and RU Lupi; as well as the red giant star Phi-1 Lupi.
Notable Deep Sky Objects
Lupus contains no Messier objects, but it does have a number of notable deep-sky objects:
– NGC 5986 is a globular cluster that is located 2.5 degrees west-northwest of the star Eta Lupi. It is around 33,900 light years from Earth, shines with a visual magnitude of 7.52, and is worth mentioning because it has two really bright A-F classified stars that are probably in their final stage of evolution.
Other notable objects in the constellation includes the globular clusters NGC 5822, NGC 5824, NGC 5927. Lupus also contains the large open cluster NGC 5822; as well as the Retina Nebula (IC 4406), which is a multi-colored donut-shaped planetary nebula found 2,000 light years away.