Russian telescope considered the darkening of Betelgeuse in detail

astronomers using the 2.5-meter telescope of the Caucasus Mountain Observatory of the Sternberg astronomical Institute has been able to see the movement of dust clouds above the red giant Betelgeuse in a few months. One of these clouds, most likely, and caused a record decline in the magnitude of the star at the end of 2019 – beginning of 2020, it is reported on the website of the Observatory. Preprint published on the portal arXiv.org.

Red supergiant Betelgeuse is considered to be ninth on the brightness of a star in the sky and is at a distance of 600-700 light-years from Earth in the constellation of Orion. Estimate the mass of stars vary and range from 9.5 to 20 solar masses, and its dimensions are enormous — the scale of the Solar system boundary of Betelgeuse would reach the orbit of Mars or Jupiter, depending on the distance from it.

The age of the star is about eight million years, in its interior already concluded nuclear reaction “burning” of hydrogen and helium and are reactions involving heavier elements such as carbon. As soon as the kernel starts the reaction with the formation of iron (it will most likely be not more than ten thousand years), the balance in the star is broken, happens the gravitational collapse of a kernel and Betelgeuse will explode as a supernova of type II.

Betelgeuse is classified as a semiregular variable star, fluctuating brilliance was first noticed in the 19th century. In the period from November 2019-March 2020 Betelgeuse was a record deep low its luster in the entire history of photoelectron observations. Its apparent magnitude has fallen from 0.6 to 1.6. This could mean that Betelgeuse is in the final stage of its evolution and is preparing to explode. In April 2020, its brightness returned to normal values, which meant that the supernova will not take place.

There were two versions to explain such a sharp fall in the brilliance of Betelgeuse: a sharp cooling of the surface due to strong pulsations and convective processes, and extensive dust emissions in the direction of the earth observer. Earlier analysis of spectroscopic observations of the star showed that the temperature of the photosphere of the star changed during the minimum of the glitter slightly, which is bad due to the influence of convective processes. The reason of falling of brightness was called the cloud of gas and particles resulting from possible ejection from the star, such has happened in 2009.

In the period from 27 Oct 2019 to 24 April 2020 the star followed by then astronomers, led by Boris Safonov, who used the 2.5-meter telescope at Caucasian mountain Observatory of the Sternberg astronomical Institute. Observations were conducted at wavelengths of 465, 550, 625 and 880 nanometers by the method of differential speckle polarimetry, which provided information on the distribution of polarized flux with a diffraction resolution of 0.05 arc seconds, thanks to what scientists saw base dust in the wind.

On the pictures visible the inner part of the inhomogeneous atmosphere of Betelgeuse. Emerging and disappearing dark areas are dust clouds above convective cells. One of such clouds is likely, and caused a record drop of glitter star, and start darkening the southern halfand then this part of the star was unusually bright, indicating that increasing the number of scattering dust in this area.

Why Betelgeuse dim and soon it will explode, you can read in our article “Clock is ticking”.

Alexander Voytyuk

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