August 27th, 2017
A map of activity on the surface and in the atmosphere of the star Antares by a team of astronomers is the most detailed ever created for a star other than the Sun. The red supergiant is located in the constellation Scorpius and is in its end stages. It will eventually die in a supernova explosion.
While Antares likely started its life with about 15 times the mass of our Sun, it is now shedding mass and is estimated to have lost about three solar masses. Its current diameter is approximately 700 times that of the Sun.
Researchers led by Keiichi Ohnaka of the Universidad Catolico del Norte in Chile used the European Southern Observatory’s (ESO) Very Large Telescope Interferometer (VLTI) at Paranal Observatory to map the surface of the luminous, low-density star and measure the speed at which surface material is moving.
The VLTI is an instrument composed of several telescopes that create the equivalent of a single large telescope with a mirror boasting a diameter up to 656 feet (200 meters). It combines the light from as many as four telescopes, including either the 26.9-foot (8.2-meter) Unit Telescopes or the 5.9-foot (1.8-meter) Auxiliary Telescopes, enabling scientists to view the star in incredible detail.
Using three Auxiliary Telescopes along with the near-infrared AMBER instrument, astronomers imaged several locales on Antares’ surface in various infrared wavelengths to measure the speed at which gases are moving in these different regions and across the entire star. The technique yielded the most detailed map of surface activity by atmospheric gases on any star besides our Sun.
Ohnaka said a central goal of the study is to determine how stars like Antares lose so much mass at the end of their lives.
“The VLTI is the only facility that can directly measure the gas motions in the extended atmosphere of Antares – a crucial step towards clarifying this problem. The next challenge is to identify what’s driving the turbulent motions,” Ohnaka said.
Low-density gas was discovered extending much further from the star than the researchers expected, leading them to conclude it was brought there by a process other than convection, which involves the transfer of energy from a star’s core to its outer atmosphere. Just what that process is remains unknown.
Other stars of various types will need to be studied using the technique astronomers used to map Antares in the same degree of detail for scientists to determine what that process is, Ohnaka said.
“Our work brings stellar astrophysics to a new dimension and opens an entirely new window to observe stars,” Ohnaka said.
Ohnaka is lead author of a paper on the study published in the journal Nature.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.