A team of astronomers, led by Keiichi Ohnaka, of the Universidad Católica del Norte in Chile, used the ESO’s Very Large Telescope Interferometer (VLTI) at the Paranal Observatory in Chile to capture an image of Antares that reveals surface details! This is the best image of the surface and atmosphere of any star other than the Sun.
Antares is a bright star in Scorpius that shines with a strong red tint. It is a large red supergiant in the later stage of its life and is expected to become a supernova in a few thousand years. It is located nearly 620 light-years from Earth with a mass and diameter of 12 times and 700 times that of our sun, respectively.
The team also made the first map of the velocities of material in the atmosphere of a star, other than the Sun, revealing unexpected turbulence in Antares’s extended atmosphere. In stars like our sun, convection flows of superheated gases bubble up from near the stars’ cores to the surface. But convection cannot explain Antares’ strange atmosphere, and the researchers conclude that, for the atmospheres of red supergiants, there must be another—as yet unknown—process that drives the motion of material. This process might help explain how stars like Antares lose mass so quickly in the final phase of their evolution.
Ohnaka is hopeful that the observational techniques demonstrated on Antares may be applied to other stars to see how their atmospheres are structured, perhaps revealing the mystery that drives these turbulent motions.
The VLTI consists of up to four telescopes—8.2 m “unit” telescopes and smaller 1.8m “auxiliary” telescopes – that combine light using interferometry to create a “virtual” telescope 200 m wide. Very high angular resolution can therefore be attained, allowing the surface of Antares to be studied in detail.