Description and Physical Characteristics
The star Antares, also known as Alpha Scorpii (α Scorpii or α Sco), is a class M red supergiant belonging to the Scorpius constellation. Its name derives from the ancient Greek words "Ant-Ares" meaning the "rival of Mars". Since it lies in the ecliptic - the path the Sun, the Moon and the planets trace on the celestial sphere - it could be easily mistaken for Mars due to its color and size resemblance to the red planet.
Despite its relatively small mass, the size of this supergiant is enormous, and the average density is considerably low. Another characteristic is that it pulsates irregularly causing its apparent magnitude to vary considerably over the years (variable star). Regarding its luminosity, it is classified as either the 15th or 16th brightest star in the sky. This actually depends on whether we regard the two brighter stars in the Capella quadruple system as one or not. It is 10,000 times brighter than our Sun in the visual spectrum, however since most of its energy is radiated in the infrared, its bolometric luminosity is almost 65,000 times that of the Sun.
Surface temperature: ~ 3,500°K
Spectral type: M1
Apparent magnitude: 0.9 - 1.8 (variable star)
Distance: ~ 600 ly (light-years)
Luminosity: ~ 10,000 times the luminosity of the Sun
Mass: 15-18 times the mass of the Sun
Radius: ~ 800 times the radius of the Sun
Radial velocity: - 1.4 km/s