Antares: Supergiant Star Rivaling Mars

Star Walk
6 min readMar 4, 2024
© Vito Technology, Inc.

Antares is the massive ruby-red heart of Scorpius in the night sky. Here you’ll learn about its rivalry with Mars, its immense size, and other features. And, with the help of the astronomy app Star Walk 2, you will easily locate the star in the sky.

Antares — key star facts

  • Official name: Antares, α Scorpii, Alpha Scorpii
  • Alternative names: Cor Scorpii, Kalb al Akrab, Scorpion’s Heart, Vespertilio
  • Catalog designations: 21 Scorpii, HD 148478, SAO 184415, HIP 80763
  • Constellation: Scorpius
  • Star type: class M1.5Iab-Ib red supergiant
  • Right ascension: 16 h 29 m 24.46 s
  • Declination: −26° 25′ 55.21″
  • Apparent magnitude: from 0.6 to 1.6
  • Mass: ≈ 12 solar masses
  • Luminosity: 2,754 L
  • Radius: ≈ 680 solar radius
  • Surface temperature: 3,500 K
  • Distance from the Earth: ≈ 550 light-years
  • Rotation period: unknown

How big is Antares?

Antares is one of the largest known stars. It is about 700 times larger in diameter than the Sun. It’s also about 10,000 times brighter, although its surface temperature is quite low (about 1.5 times cooler than that of the Sun) — all because of the star’s enormous size. Antares is so large that if it were in the position of our Sun, it would extend beyond the orbit of Mars, and the star’s chromosphere would extend past Jupiter.

Antares is really large. If it took the Sun’s place, it would extend even further than the orbit of Mars. © Vito Technology, Inc.

Antares color & brightness

Antares is classified as a spectral type M1.5Iab-Ib star. “M1.5” here signifies a temperature of around 3,400˚C. The stars of this temperature appear orange-red. “Lab” is the designation of an intermediate-size luminous supergiant, “Ib” being a less luminous supergiant. Antares is between these designations.

Antares is a variable star, with its visual magnitude changing irregularly from 0.6 to 1.6. It’s the brightest star in the constellation Scorpius and the 15th-brightest star in the whole night sky.

The name Antares is of Greek origin and literally means “rival of Ares”, that is, rival of Mars. The star is very similar in brightness and color to the Red Planet. And because of its proximity to the ecliptic, Antares occasionally meets Mars in the sky, making the celestial objects appear together like twin brothers.

Where is Antares in the sky?

Antares is located in the “heart” of the constellation Scorpius. In the Northern Hemisphere, the star is visible south of 63° north latitude. In the Southern Hemisphere, Antares rises high in the sky and is circumpolar from about 63° south latitude.

How to find Antares?

Antares is surrounded by mostly 2nd and 3rd-magnitude stars, so there are no bright stars around to help you navigate. However, if you’re in the Southern Hemisphere, you might spot the constellation Scorpius itself, as it’s large and distinct. You can also navigate by the Moon or planets when they’re near Antares. Read on to find out the upcoming Antares conjunction dates.

Another easy way to find Antares is to use the Star Walk 2 app. Simply search for the star, and follow the arrow on the screen to locate Antares in the sky above you. The app is available for free, but you can subscribe for additional features.

Use the astronomy app Star Walk 2 to easily find Antares in your sky. © Vito Technology, Inc.

When to see Antares?

As a part of the zodiac constellation Scorpius, Antares is visible only during specific months when the constellation is not obscured by the Sun. This period extends from May through August, with the optimal viewing time in mid-July.

Below is the list of upcoming celestial events featuring Antares. You can also find these events through the Star Walk 2 calendar, where you can enable alerts and see how these objects will appear in the sky from your location on the specified dates.

March 30: Lunar occultation of Antares

On March 30, from 12:57 to 17:20 GMT (from 8:57 a.m. to 1:20 p.m. EDT), the lunar occultation of Antares will take place. Unfortunately, it will only be visible over the Pacific Ocean (in Oceania, Federated States of Micronesia, Kingman Reef, and Palmyra Atoll).

The rest of the world will see Antares close to the 76% illuminated Moon, separated by 0°18′. The conjunction will take place at 14:24 GMT.

April 26: Lunar occultation of Antares

On April 26, from 18:36 to 22:55 GMT (2:36–6:55 p.m. EDT), the lunar occultation of Antares will be visible over Asia and Africa. During this time, the star will disappear behind the 92% illuminated Moon.

The rest of the world will see Antares in the sky at a distance of 0°18′ from the Moon. The conjunction will occur at 20:00 GMT.

May 24: Lunar occultation of Antares

On May 24, from 01:11 to 05:24 GMT (from May 23, 9:11 p.m. to May 24, 01:24 a.m. EDT), the lunar occultation of Antares will be visible over North and South America, Western Africa, and Middle Africa. During this time, the star will disappear behind the almost Full Moon.

The rest of the world will see Antares in the sky at a distance of 0°24′ from the Moon. The conjunction will occur at 02:31 GMT.

More facts about Antares

The life cycle of Antares

Antares is a red supergiant, which means it is in the final stages of its life cycle. One day it will run out of fuel and collapse, possibly causing a supernova that we could see from the Earth. We don’t know exactly when it will happen — it could be tomorrow or millions of years from now. But when it does, it’s going to be an amazing show in the sky!

Want to know more about the life of stars? Here is our fun infographic — check it out!

Antares B: the lesser-known companion

Antares is, in fact, a binary star system, consisting of the red supergiant Antares A and the blue-white main sequence star Antares B. Antares B, situated approximately 2.5 arc seconds west of Antares A, was first observed in 1819 by astronomer Johann Tobias Bürg when Antares A was obscured by the Moon.

Antares B shines with a magnitude of 5.5 and has a blue-white hue, though it appears greenish due to the influence of orange-red Antares A. To catch a glimpse of Antares B, you’ll need a telescope with an aperture of 8 inches and a magnification of 200x.

Antares name in different cultures

Different cultures have different names for the star and its constellation. We already know the Greek name, which means “rival of Ares”. In ancient China, Antares was called the Fire Star and was part of a dragon constellation. In Hawaiian stories, the constellation represents a fishing hook used by the hero Maui to lift the islands out of the sea. Antares (Lehua Kona) sits just above the point of the hook. In addition, both the Arabic and Latin names for the star translate to “heart of the scorpion”.

Antares, the rival of Mars: Conclusion

Antares is a bright orange-red star in the constellation Scorpius. It’s best seen from the Southern Hemisphere, but can also be spotted in the Northern Hemisphere. To easily locate Antares, try the free Star Walk 2 app or observe it near the Moon or planets.

Wishing you clear skies and happy stargazing!

Text Credit: Vito Technology, Inc.



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