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.
Emil, an avid astronomy writer, formerly owned and ran nightskyinfo.com, making the universe more comprehensible for his readers. He has recently handed over its reins to Tom Urbain from starlust.org, ensuring that his legacy of simplifying the stars continues to enlighten and inspire.