Free Astronomy Magazine September-October 2025

46 ASTRO PUBLISHING sidered young by astronomy stan- dards, it’s late in its life. Located in the shoulder of the constellation Orion, people have observed Betel- geuse with the naked eye for millen- nia, noticing that the star changes in brightness over time. Astronomers established that Betelgeuse has a main period of variability of around 400 days and a more extended sec- ondary period of around six years. In 2019 and 2020, there was a steep decrease in Betelgeuse’s brightness — an event referred to as the ‘Great by NOIRLab Josie Fenske Long-predicted companion of Betelgeuse discovered B etelgeuse is one of the bright- est stars in the night sky, and the closest red supergiant to Earth. It has an enormous volume, spanning a radius around 700 times that of the Sun. Despite only being ten million years old, which is con-