Is the Star Betelgeuse About to Experience a Supernova?

Since October 2019, Betelgeuse has dimmed to its lowest brightness in the last 50 years.
Marcia Wendorf

Ask someone who doesn't know much about the constellations, and they will probably tell you they know just one — Orion.

Located on the celestial equator, the abstract projection out into space of Earth's equator, Orion is a prominent constellation that is visible in the Northern Hemisphere from November to February, and is generally visible between the latitudes of 85° and -75°.

Named for a hunter in Greek mythology, Orion is anchored by its two brightest stars: blue-white Rigel (Beta Orionis) which appears in the lower right,  in the left foot of the hunter; and orange-red Betelgeuse (Alpha Orionis) which appears towards the upper left, in the hunter's right shoulder.


The name Betelgeuse is Arabic for "the armpit of Orion." Ask a group of astronomy-aware grade-school-age children what their favorite star is and they'll likely gleefully yell "Betelgeuse", most likely because the name sounds like a squashed bug.

Betelgeuse is a red supergiant star that is about 1,400 times larger than our Sun. If it were placed in the Sun's position in our solar system, Betelgeuse would extend past the orbit of Mars, and possibly even that of Jupiter.

Betelgeuse is also a variable star, which means that its brightness waxes and wanes, but it has been dimming since October 2019. Betelgeuse normally varies in brightness, having a period of approximately 420 days, plus or minus 15 days, but on December 8, 2019, it was announced that Betelgeuse has reached its dimmest point in the last 50 years. It is so dim that the difference is noticeable when looking at Orion with the naked eye.

A big blow out and then no more

Betelgeuse's extreme dimness could be a precursor to its exploding into a supernova in the not too distant future. The star would then be lost to us forever.

Supernovas happen when a star runs out of its hydrogen fuel, and some of its mass flows into its core. When the core becomes so heavy that it can't stand up to its own gravitational force, the core collapses and a supernova occurs.

If Betelgeuse explodes, the light from that explosion will be strong enough to be visible on Earth during the daytime, and it will outshine the Moon at night. The brightest planet in our solar system as seen from Earth is Venus, which has an apparent magnitude of -4.4. Should Betelgeuse explode, it would have an apparent magnitude of -12.4!

If Betelgeuse does explode, it could become either a neutron star or a black hole. To become a black hole, the material left over by the supernova explosion would have to equal more than 3 solar masses.

Any material expelled by Betelgeuse could go on to form other star systems and planets, in the same way, that the Sun and our solar system were formed by material expelled by supernovas in other stars.

It is even possible that Betelgeuse has already exploded, since it is 642 light-years away from Earth. That means that whatever appears to be happening with Betelgeuse, actually happened in the year 1377.

The last time a supernova occured in our Milky Way Galaxy was in 1604, when Kepler's Star exploded into a supernova. Light from that explosion was visible during the day for more than 3 weeks. Betelgeuse is at least 10 times closer to the Earth than Kepler's Star, and it is much larger.

Kepler's Star supernova
Kepler's Star supernova Source: NASA/Wikimedia Commons

In 1988, director Tim Burton named his fantasy film, which starred Winona Ryder, Michael Keaton, Alec Baldwin, and Geena Davis, Beetlejuice after the star because the character "Beetlejuice" is the doorman of the underworld. The studio, Warner Bros, hated the title and begged Burton to change it, but he refused.

Physics teacher Dr. David Boyce tweeted about Betelgeuse: "Whatever happens it will be worth watching. A supernova within our galaxy is a once in a lifetime spectacle."

Orion without Betelgeuse
Orion without Betelgeuse Source: Marcia Wendorf

However, the night sky will be a lot lonelier without red Betelgeuse to keep the hunter Orion company.

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