Betelgeuse is a star nearing the end of its life. Because it is creating heavier and heavier elements in its core that could be used for stars after it dies, a NASA story once dubbed the red giant a workaholic.
The star is a famous one among amateur astronomers not only for its size and brightness, but also because it is part of Orion, a bright winter constellation in the Northern Hemisphere.
Professional astronomers also keep a close eye on the star, as it is notoriously variable: its diameter changes from anywhere between 550 to 920 times the sun’s diameter. In 2013, astronomers said Betelgeuse is likely to crash into a “cosmic wall” of interstellar dust in a few thousand years.
Ancient astronomers would have easily spotted Betelgeuse because of its size and relatively close distance from Earth: it is about 600 light-years away. It is the 12th brightest star in the night sky.