Antares

Antares is a red supergiant of spectral type M1.5Iab-Ib and the brightest star in Scorpius at magnitude 0.96. Located about 550 light-years from Earth, it is roughly 680 times the diameter of the Sun — if placed at the center of our solar system, it would engulf the orbit of Mars. Antares is about 10,000 times more luminous than the Sun in visible light, though its total luminosity including infrared is about 75,000 times solar. It has a hot blue companion, Antares B (magnitude 5.5), orbiting at about 550 AU.

Antares is the fiery red heart of the Scorpion, easily identified at the center of Scorpius in summer skies. Its deep red-orange color is striking and deepens noticeably through binoculars. The companion Antares B (magnitude 5.5, spectral type B2.5) lies about 2.7 arcseconds away and appears green by contrast — one of the most beautiful and challenging color-contrast doubles in the sky, requiring at least a 150mm telescope and steady seeing. Nearby is the magnificent globular cluster M4. Best observed from May through August.

The name Antares means 'rival of Ares (Mars)' in Greek, referring to its similarity in color and brightness to the planet Mars, which occasionally passes near it in the sky. It was another of the four Royal Stars of ancient Persia, where it marked the autumnal equinox around 3000 BC. Aboriginal Australians saw it as a key star in their songlines and creation stories.