Anyone who watches the sky regularly may be familiar with the constellation Orion the Hunter. It is one of the few constellations that actually looks like what it should look like, rather than an abstract resemblance. One prominent star is Betelgeuse, which has dimmed lower in 2020 than at any time in history. A team of astronomers studied this phenomenon and obtained impressive results.

Betelgeuse is a red supergiant star located almost 650 light-years from Earth. If the Earth, with a radius of 617 million kilometers, were in the position of the Sun, it would be buried deep in the layers of its orbit. It is also a variable star, meaning it also varies its light output, and in Betelgeuse’s case this variation is semi-regular, i.e. regular, with a few bumps along the way!

Its variability is related to a pulsation in the radius of the star occurring over a period of about 400 days, but there is a longer period of variability of about 2100 days of uncertain origin, possibly related to changes in convective flow. In 2020, Betelgeuse dimmed to a never-before-seen level in what has since been called the “great eclipse.”

Its visual brightness, or magnitude, fell by 1.6, but its dimming did not appear consistent across the star’s sphere; The southern hemisphere was much darker than the northern hemisphere, and many theories have been put forward to explain this phenomenon. The most popular among these are the large star spots or dust cloud formations above the photosphere.

A recently published article Astronomy and Astrophysics A group of astronomers led by Daniel Jadlowski is investigating the Great Eclipse event using 15 years of data from the STELLA robotic telescope. The STELLA system consists of two robotic telescopes in Spain combined with a high-resolution spectrograph and a wide-field camera.

This data allowed the team to examine Betelgeuse’s photosphere (visible layer) in incredible detail. They were able to obtain valuable information about radial vibrations, shock waves, and how they travel through the photosphere.

Five different layers of the photosphere were identified using the tomographic technique, a method in which images are created from a series of projections. The analysis showed that changes in the innermost photospheric layer, known as C1, were consistent with the time scales of changes in visual magnitude. Shock waves passing through the layers were also found to largely correspond to brightness fluctuations.

Data on the origin of the 2020 Great Eclipse showed two powerful shock waves in the photosphere; The first of these probably caused a massive flow of material that caused entire layers to fall. When the fall reached its maximum speed, a second, stronger shock wave was generated, leading to a significant flow of material. Due to the different layers of the photosphere, these events did not occur simultaneously in all layers, and Betelgeuse’s resettlement was not possible until early 2022.