Astronomers Reveal Just How Big Supergiant Star Antares Really Is

A team of astronomers has created an updated map of the star known as Antares, which accurately shows just how massive the red supergiant really is.

Antares is a massive star that lies in the constellation of Scorpius. It is the brightest star in the constellation and the 15th brightest in Earth’s night sky. Initial observations on the red supergiant revealed that it is about 12 times more massive than the Sun.

Recently, astronomers released a new study on Antares, which was published in the journal Astronomy and Astrophysics. As part of the study, the authors created an updated map that accurately shows the star’s massive size.

The astronomers were able to create the star using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile and the Karl G. Jansky Very Large Array (VLA) of the National Science Foundation in New Mexico.

Through the data collected by ALMA and the VLA, the astronomers were able to create a radio map of the massive star’s atmosphere. According to the astronomers, the star has a diameter that’s about 700 times larger than that of the Sun. This is dwarfed by its massive chromosphere, which is a gaseous layer that forms the outer atmosphere and the corona.

As noted by the astronomers, Antares’ chromosphere is about 2.5 times the red supergiant’s radius. To put its size into perspective, the Sun’s chromosphere is only about 0.5% of its radius.

Aside from its size, the astronomers were also able to measure the temperature of Antares’ chromosphere. According to their study, the readings taken by ALMA and the VLA indicated that the chromosphere’s temperature is cooler compared to previous observations.

The astronomers stated that the temperature of Antares’ chromosphere is about 6,400 degrees Fahrenheit, which is significantly cooler than that of the Sun’s at 36,032 degrees Fahrenheit.

“We found that the chromosphere is 'lukewarm' rather than hot, in stellar temperatures,” Eamon O’Gorman of the Dublin Institute for Advanced Studies and lead author of the study said in a statement.

“The difference can be explained because our radio measurements are a sensitive thermometer for most of the gas and plasma in the star's atmosphere, whereas past optical and ultraviolet observations were only sensitive to very hot gas and plasma,” he continued.