Antares

Article By:

McAlister, Harold A. Center for High Angular Resolution Astronomy, Georgia State University, Atlanta, Georgia.

Last reviewed:October 2019

DOI:https://doi.org/10.1036/1097-8542.038100

α Scorpii, a cool supergiant star of spectral type M1Ib, whose red color stands out in the midsummer sky. With an effective temperature of approximately 6000°F (3600 K), Antares resembles Betelgeuse, the brightest of the red supergiants, and would fill the solar system beyond the orbit of Mars if it replaced the Sun. Antares has a distance of 185 parsecs (600 light-years) from the Sun, and its angular diameter of about 0.045 arc-second has been measured by interferometric and lunar occultation methods. Red supergiants of this type originate as stars with mass at least 20 times that of the Sun. Such stars quickly evolve through successive stages of thermonuclear fusion of heavier and heavier elements in their cores with lighter elements undergoing fusion in concentric shells surrounding the hot core. Eventually, the core builds up with iron, the most tightly bound of all atomic nuclei. The fusion of iron nuclei absorbs rather than releases energy, and the supergiant star implodes in a type II supernova explosion. This fate is likely for Antares in less than a million years. Prior to this dramatic event, Antares will have shed up to 50% of its mass through a stellar wind of material blown away from the star into the surrounding interstellar medium. See also: Betelgeuse; Scorpius; Spectral type; Stellar evolution; Supergiant star; Supernova

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