Betelgeuse Turns 2.5x Darker

A team of astronomers led by Bill Dent at the University of Manchester has observed the inner atmosphere of Betelgeuse, one of the closest red supergiants to Earth, using the Atacama Large Millimeter Array (ALMA). The observation has revealed that Betelgeuse's atmosphere is becoming spotty and asymmetric.

The team used ALMA's ability to detect wavelengths in the range of 0.6–1.4 mm to make the observation, which was made possible by using the longest possible baseline at the ALMA facility to maximize the resolution of their images. This is the first time ALMA has been pointed specifically at Betelgeuse since 2015, before the star's dramatic dimming in 2020, known as the Great Dimming, when it suddenly became around 2.5 times fainter.

The results of the observation, which will be published in Astronomy & Astrophysics, could ultimately reveal deeper insights into the dramatic changes taking place at Betelgeuse as it approaches the end of its life. Betelgeuse is a significant object of study for astronomers, as it is one of the closest red supergiants to Earth and is expected to eventually explode as a supernova.

## What changed The observation is significant because it provides new information about the changes taking place at Betelgeuse's surface and inner atmosphere. In the past few years, the aging star has been changing rapidly, and the Great Dimming has left many questions about the underlying causes of these changes. The team suspected that the changes could be connected to the Great Dimming, but needed clearer observations to confirm their theories.

## Why it matters The study of Betelgeuse is important because it can provide insights into the life cycle of red supergiants, which are stars that will eventually explode as supernovae. As Betelgeuse approaches the end of its life, it is undergoing significant changes, including the formation of bright spots and patches in its atmosphere. The observation of these changes can help astronomers understand the processes that occur in the final stages of a star's life.

The ALMA facility, which is made up of 66 radio telescopes in the Atacama Desert in Chile, has played a crucial role in the observation of Betelgeuse. The facility's ability to detect wavelengths in the range of 0.6–1.4 mm has allowed astronomers to study the inner atmosphere of Betelgeuse in unprecedented detail.