Sparkling near the heart of the constellation Scorpius lies ruby-red Antares, the 15th-brightest star in the night sky. Like its bloated cousin Betelgeuse, Antares is a red supergiant nearing the end of its life. These enormous yet relatively cold stars sport strong stellar winds that fire heavy elements like carbon and nitrogen into space, providing many of the building blocks for life as we know it.
Exactly how these winds are cast off has largely remained a mystery — but it might not stay that way for long. Thanks to both the Atacama Large Millimeter/submillimeter Array (ALMA) and the National Science Foundation’s Karl G. Jansky Very Large Array (VLA), astronomers have peered deep within the atmosphere of Antares, and the insights their observations reveal help bring them one step closer to solving the mystery of superpowered winds from supergiant stars.
A new puzzle piece found
The two radio telescopes revealed that Antares is even larger than we previously believed. In visible light, the star is about 700 times larger than the Sun. But when ALMA and VLA looked at it in radio light, they saw that the star’s chromosphere — the second of a star’s three main atmospheric layers — extended out some 2.5 times the star’s radius. For comparison, the Sun’s chromosphere extends only 1/200 of its radius.