Astronomers have constructed the first detailed image of the surface of the star Antares, a red supergiant in the constellation Scorpio. In addition, the first map of the velocities of matter in the stellar atmosphere was obtained - earlier such maps were built only for the Sun. Researchers have discovered unexpectedly large turbulent regions in the Antares gas shell. The article was published in the journal Nature.
Red supergiants are massive and very large stars that have left the main sequence and are in an advanced stage of evolution. At this stage of their life, stars "swell" and develop a complex, multicomponent atmosphere. For example, it is known that there are bright spots in the gas envelope of red supergiants, and also that within three stellar radii the hot chromosphere (5-8 thousand kelvin) and cold gas (<3500 kelvin) coexist. The dynamics of the complex atmosphere of these stars has already been studied using ultraviolet and optical spectroscopy, but this provides only general information. In the new work, another method was applied - measuring the velocities of the movement of matter in a gas envelope using spectrograms, images of the spectrum of a celestial body.
A team of researchers led by Keiichi Ohnaka from Northern Catholic University used the Very Lagre Telescope (VLT) interferometer at the Paranal Observatory for this purpose. It is a complex of four separate 8.2-meter and four auxiliary 1.8-meter telescopes combined into one system. Together they form a virtual telescope with an equivalent mirror diameter of up to 200 meters. This method allows you to see details of a much smaller angular size than is possible with each of the telescopes separately.
Using the AMBER instrument, which operates in the near-infrared range, astronomers have obtained individual images of the Antares surface. Comparing the images, the researchers calculated the difference in the speeds of atmospheric gas at different points in the atmosphere and the average speed of movement of matter over its entire surface. The result is a map of the relative velocities of atmospheric gas throughout the entire Antares disk - the first such map ever produced for the Sun.
The researchers found low-density turbulent gas at much greater than predicted distances from the center of the star. They concluded that these gas movements cannot be caused by convection, that is, large-scale movements of matter when energy is transferred from the core of a star to its outer atmosphere, as is the case in many stars. Probably, another mechanism, still unknown to science, is involved in this process. The image taken by astronomers is not the first image of a star's surface. Not so long ago, scientists using the ALMA telescope obtained the most detailed image of another red supergiant, the star Betelgeuse.
Christina Ulasovich