Betelgeuse: Facts & Size

Instructor: Katie Chamberlain

Katie has a PhD in Microbiology and has experience preparing online education content in Biology and Earth Science.

You don't need a super-giant brain to learn about this red supergiant star. Betelgeuse, of the Orion constellation, won't be around forever, so play it safe and learn about it now.


There are many types of stars: movie stars, throwing stars, gold stars and, of course, the stars in the sky. One of the more famous stars is Betelgeuse (which is pronounced 'beetle juice'), or Alpha Orionis. Betelgeuse is partly famous because of its interesting name, and partly famous because of its location in the recognizable constellation Orion.

This is the constellation Orion. Betelguese is the reddish star in the upper left.
The Constellation Orion

Orion, the hunter, is easily recognized by the line of three stars which forms his belt. To the upper left of the belt is the star Betelgeuse, which represents the hunter's raised arm. The name Betelgeuse is a sloppy translation from the Arabic words for 'hand of the giant.' It was also the source of inspiration for Michael Keaton's character name in the movie 'Beetlejuice.'

Betelgeuse is a red supergiant star located approximately 520 light years from Earth. Red supergiants are a rare type of star - only 200 have been identified in our galaxy. This classification tells us quite a few things about Betelgeuse's age, size, appearance, and eventual demise.


During the main sequence life of a star, gravity causes hydrogen to fuse to form helium in the star's core. However, when the hydrogen runs out and the helium accumulates, the game changes. Large stars like Betelgeuse will swell to a massive size, hence their supergiant status.

Larger stars tend to burn their hydrogen more quickly and, thus, have shorter lifespans. For example, Betelgeuse is at the end of its life, even though it is only about ten million years old. Our sun is still in its prime at nearly five billion years old.

Appearance and Size

Betelgeuse is the second brightest star in Orion, and one of the ten brightest stars in the entire sky. It is typically described as having a ruddy red appearance, which is particularly evident when comparing it to the blue glow of Rigel (the lower right star of Orion).

Although Betelgeuse is actually cooler than our sun, it is about 10,000 times brighter. Its brightness can vary slightly due to changes in its size, but it is easily visible in the Southern sky during the winter months to observers in the Northern hemisphere.

Betelgeuse photographed by the Hubble telescope.
Betelgeuse photographed by the Hubble telescope

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