The Record Fall In Betelgeuse Brightness Was Explained By The Cooling Of The Photosphere
Astronomers have proposed a new explanation for the record-breaking fall in the brightness of the red giant Betelgeuse in late 2019-early 2020. In their opinion, this is due to processes in the outer layers of the star, such as the formation of huge spots or a general drop in the temperature of the photosphere, and can not be explained by the influence of dust clouds. The article is available in the Astrophysical Journal.
The red supergiant Betelgeuse is located 600-700 light-years from Earth in the constellation of Orion. The mass of a star is between 9.5 and 20 times the mass of the Sun. If it is placed in the center of the Solar system, the Betelgeuse boundary will reach the orbit of Mars or even Jupiter. The star is about eight million years old, and it is believed that in the next ten thousand years, the core will collapse gravitationally, and Betelgeuse will explode as a type II supernova.
In the period from November 2019 to March 2020, Betelgeuse passed the record-deep minimum of its brilliance in the history of photoelectronic observations. Its apparent magnitude dropped from 0.6 to 1.6. It was Assumed that this indicates that the star is ready to explode, but in April 2020, its brightness was restored. A hypothesis was put forward, confirmed by observations, that the supergiant's dimming is due to external causes — dust clouds.
A group of astronomers led by Thavisha Dharmawardena from the max Planck Institute of astronomy put forward a different version. Scientists analyzed data from observations of the star obtained between 2007 and 2020 using the APEX radio telescope and the JCMT infrared telescope. It turned out that the dimming of Betelgeuse was also observed in the submillimeter wavelength range — the luminosity of the star decreased by 20 percent.
Such results, according to the authors, can not be explained by dust, which practically does not absorb radiation in the submillimeter range. Numerical simulations show that the main contribution to the star's dimming must have been made by processes in its photosphere, such as the formation of huge spots covering about half of the star's visible disk, which are about 400 Kelvin colder than the rest of the photosphere. Alternative ideas suggest a General decrease in the temperature of the Betelgeuse photosphere by about 200 Kelvin, or a decrease in the radius of the star by about 10 percent.
However, as noted by astrophysicist Sergey Lamzin from the Moscow State University, the influence of dust on the brightness of the star can not be completely excluded. "Betelgeuse vibrations are not spherical-symmetrical. Because of this, an inhomogeneous distribution of the temperature of the star's photosphere occurs, accompanied by the outflow of matter from the overlying layers with different intensities. Where the stellar wind is more powerful, more dust is formed, which leads to the observed asymmetry of the dust envelope of the star as a whole," Lamzin said.
How soon Betelgeuse will explode and why it will happen can be found out from our material "the Clock is ticking."