Astronomers have created the most detailed map of the atmosphere of the red supergiant Antares. It turned out that the temperature of the chromosphere of the star is much lower than previously estimated. Article describing the observations was published in Astronomy & Astrophysics.
Red supergiants are very large and relatively cool star, which pass to the final stage of evolution. They have exhausted the reserves of hydrogen in the core, expanded and began to drop the shell into the surrounding space. If in place of the Sun was such a star, the outer layers of its atmosphere would reach far beyond the orbit of Mars. Coming from red giants powerful winds blown the heavy elements into space, while a scientist is not completely clarified the mechanism of occurrence of these winds, and the study of the atmosphere of stars such as Antares, can help to answer this question.
Antares is the brightest star in the constellation Scorpius and one of the brightest stars in the night sky. It is located 600 light years from Earth, and its mass greater than the sun about 12 times. In the visible range of electromagnetic radiation, its diameter larger than the diameter of our sun is about 700 times, however, the radio observations showed that the boundaries of its atmosphere even more.
Eamon O’gorman (Eamon O’gorman) from the Dublin Institute of advanced studies, together with colleagues studied Antares in the millimeter and centimeter range using the interferometers, ALMA and the VLA. Observatory ALMA watched Antares near its surface (photosphere), while the VLA interferometer have investigated the outer atmospheric layers of the star.
Radio telescopes measured the temperature of the greater part of gas and plasma in the atmosphere of Antares. Averaged over the disk, the gas temperature was equal to 2700 Kelvin 1.35 radii of stars (0,35 radius above the photosphere), reached a peak of 3800 Kelvin radius of 2.5, and then gradually decreased up to 1650 Calvin 11.6 stellar radius.
The greatest attention of astronomers was attracted by the chromosphere of the star — the outer shell of the star, which heats up the magnetic fields and shock waves. Chromosphere stars is still poorly understood, and astronomers for the first time managed to observe it in the radio. It turned out that it was much colder than was shown by the past observations in the optical and UV range, which can be attributed to their sensitivity only to very hot gas and plasma. The temperature of the chromosphere Antares was equal to about 3.5 thousand degrees Celsius. For comparison, the chromosphere of the Sun is heated to 20 thousand degrees Celsius.