About the image. Drawn as a huge red-orange supergiant with a mottled surface, and a small blue-white companion far to one side. The colours follow the two stars' temperatures and the large surface cells follow interferometer images; the exact pattern of the cells, the haze around the star and the view are imagined, and the companion's distance is not to scale.
Antares is the red star at the heart of the constellation Scorpius, one of the brightest in the sky. It is a red supergiant about 680 times wider than the Sun, about 550 light-years away. Put in the Sun’s place, it would reach out past the orbit of Mars into the asteroid belt. Its name means “rival to Ares”, the Greek Mars, because of its colour.
A surface you can map
Antares is so large and close that telescopes can see it as a disc and follow what happens across it. In 2017 Ohnaka and colleagues used ESO’s Very Large Telescope Interferometer to make the first map of how material moves across the face of a star other than the Sun. Clumps of gas were rising and falling at up to about 20 kilometres per second, too violently for the boiling of the star’s outer layers alone to explain. Its turbulent atmosphere reaches out to about 1.7 times the star’s radius.
In 2025 Pilate and colleagues made the first images of its surface from the polarisation of its light. They found a few enormous convection cells, the largest about 30% of the star’s radius, each lasting for months.
A lukewarm atmosphere
In 2020 O’Gorman and colleagues looked at Antares with the ALMA and VLA radio telescopes. Its chromosphere, the layer above the visible surface, reaches 2.5 times the star’s radius, where the Sun’s reaches only a two-hundredth of its own. It was cooler than expected. Its temperature rises from 2 700 K (2 430 °C) at 1.35 times the star’s radius to a peak of about 3 800 K (3 530 °C), then falls to 1 650 K (1 380 °C) at more than eleven times the star’s radius. The 2017 infrared study, though, had found gas at 5 000 to 8 000 K (7 730 °C) at similar heights. The two measurements do not yet fit together. One possibility is that the hot gas is there but fills only a small part of the space.
The blue companion
Antares has a companion, Antares B, a hot blue-white star of about 6.7 Suns and 18 200 K (17 930 °C), seen 2.6 to 2.9 arcseconds from the supergiant. Estimates of its orbit range from 880 to 2 562 years. It was first reported in 1819 by Johann Tobias Bürg, as the Moon passed in front of Antares. The blue star sits inside the wind blowing off the red one and lights it up: radio images show the glow, and a small nebula of glowing, ionised gas around it is probably its work. Through telescopes it is often described as green, which is probably a contrast effect next to the red giant.
The Moon is covering Antares again now. A series of 68 lunar occultations began in August 2023 and runs until August 2028.
Its end
Like Betelgeuse, Antares will end as a supernova. A 2022 study by Neuhäuser and colleagues puts the time left at about 1.0 to 1.4 million years.
How hot is it?
Earth (average)288 K · 15 °C
Water boils373 K · 100 °C
Venus surface737 K · 464 °C
Iron melts1 811 K · 1 540 °C
Sun's surface5 772 K · 5 500 °C
Antares3 660 K · 3 390 °C
Antares: surface temperature. Logarithmic scale from 100 K to 10 000 K. Reference values: NASA, IAU.
How long to get there?
Antares is about 550 light-years away.
Light299 792 km/s550 years
Breakthrough Starshotplanned light sail, 20% of light speed2 750 years
Parker Solar Probefastest spacecraft so far, 192 km/s858 779 years
Voyager 1leaving the Solar System, 17 km/s9.7 million years
At Voyager 1's speed the trip would take about 121 239 human lifetimes of 80 years. Bars are on a logarithmic scale. Speeds: NASA, Breakthrough Initiatives.
Gallery
A huge red-orange star with a mottled surface of bright and dark cells fills the left of the picture, and far off at the upper right shines a small blue-white star, an impression of Antares and its companion. AI-generated painting.The glowing red surface of a giant star curving across the bottom of the picture, with thin spikes of gas rising from it, under a black sky where a small blue-white star shines, an impression of the view close to Antares. AI-generated painting.Antares, 3D artist's impression, rendered from the interactive model.Antares, 3D artist's impression, from another angle, rendered from the interactive model.Antares, 3D artist's impression, close-up, rendered from the interactive model.
Timeline
1819Johann Tobias Bürg reports a companion as the Moon passes in front of Antares.
1921Its diameter is measured with an interferometer.
2017ESO's interferometer maps the motion of gas across its surface, a first for a star other than the Sun.
2020Radio telescopes find a cooler than expected chromosphere reaching 2.5 times its radius.
2023A series of 68 lunar occultations begins, running until August 2028.
2025The first images of its surface from polarised light show convection cells lasting months.
Questions people ask
How big is Antares compared to the Sun?
About 680 times wider. Put in the Sun's place, it would reach past the orbit of Mars into the asteroid belt.
When will Antares explode as a supernova?
A 2022 study puts the time left at about 1.0 to 1.4 million years.
Does Antares have a companion star?
Yes. Antares B is a hot blue-white star of about 6.7 solar masses, seen 2.6 to 2.9 arcseconds from the supergiant. Its orbit has been estimated at 880 to 2 562 years.