Antares

Antares is a red supergiant of spectral type M1.5Iab-Ib at magnitude 0.96 (slightly variable), the brightest star in Scorpius. Located about 550 light-years from Earth, it has a diameter roughly 680 times the Sun's — if placed at the Sun's position, its surface would extend beyond the orbit of Mars. Antares has a blue-white companion (Antares B, magnitude 5.5) orbiting at a projected separation of about 2.5 arcseconds.

Antares is the fiery red heart of Scorpius, unmistakable during summer evenings. Its deep red-orange color is obvious to the naked eye and is often compared to Mars — hence the name 'rival of Mars.' The companion Antares B is a challenging but rewarding target in a 6-inch or larger telescope at high magnification; it appears greenish by contrast. Best observed June through August.

The name Antares means 'rival of Ares' (Mars) in Greek, because its red color and brightness often mimic the planet. It was one of the four Royal Stars of ancient Persia, marking the autumnal equinox around 3000 BC. In many cultures it represents a heart — the heart of the Scorpion in Western astronomy, and the Fire Star in Chinese astronomy.