A small and rather inconspicuous southern constellation representing the altar on which Centaurus the centaur sacrificed Lupus the wolf. It is visible at latitudes between +25° and -90°, and best visible during the month of July.
Abbreviation: Ara Genitive: Arae English name: The altar
Notable Stars in Ara
Alpha Arae – A spectroscopic binary located approximately 242 light years from Earth.
Beta Arae – The brightest star of the constellation, shining at magnitude 2.8. Beta is a supergiant star, with a luminosity of about 4600 times that of the Sun.
Gamma Arae – A double star located approximately 1140 light years from Earth. The brightest component has a magnitude of 3.5 and the companion is 10th magnitude, 18 arcseconds away. Gamma was found to be a binary system in 1835, when John Herschel observed it with his telescope.
R Arae – The only variable star in the constellation of any interest for amateur astronomers. Its magnitude ranges from 6 to 7.1 in a period of 4.4 days.
Notable Deep Sky Objects in Ara
NGC 6193 – A large open star cluster located eight degrees west of Alpha Arae. Binoculars will show about 30 stars, the brightest of which shining at 6th magnitude.
NGC 6208 – An elusive open star cluster located 1.5 degrees west of the 4th-magnitude star Epsilon1 Arae. It is best seen at low power, appearing as an irregular glow to the southeast of an 8th-magnitude star.
NGC 6397 – One of the closest globular clusters, located approximately 7200 light years from Earth. It is a bright object visible even with the naked eye on clear nights. Binoculars or a small telescope show it as a misty patch with a diameter close to 20 arcminutes.