|Astronomical designation||Alpha Scorpii|
|Right ascension||16h 29m 24s|
|Declination||-26o 25′ 55|
|Type of object||Supergiant star|
|Magnitude||Apparent Mag: 0.9~1.8, Average: 1.09|
Absolute Mag: −5.28
|Distance from Earth||~600 ly|
|Radial Velocity||−3.4 km/s|
|Proper Motion||RA: −10.16 mas/yr|
Dec.: −23.21 mas/yr
|Parallax||5.40 ± 1.68 mas|
Antares, also known as Alpha Scorpii is a binary system that consists of a red supergiant and its hot, blue companion star located in the constellation Scorpius. Antares is easily seen in the night sky as the fifteenth brightest star, known since ancient times.
Antares in Culture and History
The name Antares is a derivative of the Ancient Greek Αντάρης, meaning "(holds) against Ares (Mars)" because like Mars, the star appears with a reddish hue in the sky. It is this distinct color that made Antares well known to ancient cultures.
In Ancient Egypt, many temples are aligned in such a way that the light from Antares plays a role in the temple ceremonies. The Persians referred to Antares as Satevis and it was referenced in their culture to as far back as 3000 B.C. as one of the four royal stars. In ancient India the star was called Jyeshtha, and the Arabs called it Ķalb al Άķrab, or the "Scorpion's heart",which is translated from the ancient Greek Καρδια Σκορπιου Kardia Scorpiou.
Antares was also seen as one of the four archangel stars, or the four keys of heaven. Antares represented Oriel, the Watcher of the West. Along with Fomalhaut (Gabriel), Watcher of the South, Regulus (Raphael), Watcher of the North, and Aldebaran (Michel), Watcher of the East.
The Antares system is actually a binary star system even though the unaided eye sees only the primary star. The system itself is estimated to be some 600 light years from Earth; despite this distance Antares still has an average apparent luminosity of 1.09. However Antares is a variable star and thus its luminousity ranges from 0.9 to 1.8 over a period of years.
The primary star, Antares (also called Antares A), is a class M1.5Iab-b supergiant. The star is so large, that its diameter was calculated using its parallax, and angular diameter, which lead to a radius of 822 ±80 that of our Sun. If the star was at the center of our solar system, it would extend to between the orbits of Mars and Jupiter. Despite Antares’ size, it contains only 15 to 18 times the mass of the sun; giving Antares a very low average density. Its visual luminosity is some 10,000 times that of the sun, with an absolute luminosity of 60,000 times, much of which is in the infrared. Like all M class stars, its surface is relativity cool in comparison to other stars, at 3600K.
Antares B, the companion star, is a blue star of spectral type B2.5V. Although much dimmer then it’s giant companion, Antares B is still 170 times as luminous as our Sun. By itself the star could be seen by the unaided eye, but because of the glare of its neighbor, a small telescope is required to resolve the star at all. It is estimated that the two stars are some 550AUs from each other, taking 878 years to complete an mutual orbit, but their orbit is still poorly understood.
- Richard Hinckley Allen, Star-names and their meanings (1936), p. 365.
- Dr Eric Morse, The Living Stars, p.56 ISBN 978-0944256022