Antares, the red heart of Scorpius

Antares is the reddish star at the heart of Scorpius, a red supergiant about 700 times the Sun's diameter. Its name compares it to Mars, and it is easy to see why.

Where is it from where I am?

How to spot it: The reddish star at the heart of the Scorpion's curve. Source (opens in a new tab)

What you are looking at

ESO (opens in a new tab) describes Antares as a huge, comparatively cool red supergiant late in its life, about 700 times the Sun's diameter and about 12 times its mass, having already shed some three solar masses of material, and on its way to becoming a supernova.

Like Mars

The name is Greek and means "like Mars" (opens in a new tab), for its reddish-orange colour; it is often translated "rival of Mars". Its Arabic name, qalb al-'aqrab, means the scorpion's heart. Ptolemy, who named very few stars, named this one.

The best view of a star's surface

In 2017 astronomers using ESO's Very Large Telescope Interferometer made the most detailed image (opens in a new tab) yet of any star but the Sun, and the first map of how the gas in another star's atmosphere moves. They found turbulent, thin gas much further out than expected, and movements that convection alone cannot explain.

A cluster next door

Close to Antares in the sky is Messier 4 (opens in a new tab), the nearest globular cluster to Earth at about 5,500 light-years, a ball of more than 100,000 old stars. A small telescope finds it.

In another tradition

In Vedic astrology Antares is the star of Jyeshtha, "the eldest".

Where on Earth, and when

It rises from anywhere south of about 64°N.

South of about 64°S, it never sets.

It climbs at least 20° high, the finder's threshold for a suggestion, from anywhere south of about 44°N.

It is highest in the evening sky, at about 9 p.m. local time, in mid-July, from either hemisphere, wherever it rises. With daylight saving time, that is nearer 10 p.m. on the clock.

Worked out by this site from the Bright Star Catalogue, for a flat, clear horizon. Hills, buildings, haze and city light all cut into this; the air also lifts objects near the horizon by about half a degree. For your own place and night, use the sky finder.