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Betelgeuse: All the supernova questions and answers from astronomers

“I think about Betelgeuse all the time.”

Originally Published: 
ALMA (ESO/NAOJ/NRAO)/E. O'Gorman/P. Kervella

Betelgeuse, a red giant star in the constellation Orion, has been under the close watch of astronomers since December, 2019, when its once-bright light started mysteriously dimming. Was Betelgeuse going to explode? Was Betelgeuse just dimming? What type of star was Betelgeuse? Wait, how do you even pronounce Betelgeuse? Here's what scientists know so far about this changing star 642.5 light years from Earth.

The European Southern Observatory (ESO) released this image of the changing star on Friday, February 14, 2020, the first image since news of its dimming was announced in December.

It's a startling side-by-side comparison that clearly shows a less bright Betelgeuse:

Betelgeuse, before and after the star started to lose its signature brightness.

ESO/M. Montargès et al.

Although the star’s dimming is apparent to the naked eye, the ESO’s Very Large Telescope (located in Chile's Atacama desert) captured Betelgeuse in December, 2019 and compared it to a previous image taken in January, 2019. The two show Betelgeuse’s dimming light and reveal a different shape to the star as well. In the new image, Betelgeuse looks a little ... deformed. Its previously round shape now looks more oblong.

Betelgeuse supernova?

Betelgeuse is currently at around 36 percent of its normal brightness, but scientists aren’t quite sure whether the star is nearing the end of its life, and may soon explode in a supernova. On the other hand, this stellar activity could just be part of this mischievous star’s regular cycle.

The bottom line is that astronomers don't have enough data yet to definitively know if it is going to blow, but its steady brightness over the past ten days indicates it may not explode.

To get to the bottom of this stellar saga, Inverse went to the experts and laid down all the details around this strange phenomenon.

Betelgeuse dimming.

The news of Betelgeuse's possible death broke in December, 2019 — and the world gasped, scientists included. Edward Guinan, an astrophysics professor at Villanova University, was watching the news on CNN when the anchor announced that a burst of gravitational waves had been detected from around the constellation Orion on January 14, 2020.

“I immediately jumped out of bed,” Guinan tells Inverse.

“I immediately jumped out of bed"

Guinan is all too aware of the star's meteoric rise in the public consciousness. After all, it was his initial observations that sparked the hype around the star's seemingly impending demise.

Guinan began observing Betelgeuse in 1981 — long before it was cool. It was a practical decision, he says: It is a bright, nearby star in the prominent constellation of Orion. But despite his long admiration of the star, Guinan admits that he had been getting ready to give up on Betelgeuse.

“It’s been 25 years, we were getting tired of it,” Guinan says. “Let’s give it one more year before we stop observing it.”

As if on cue, things started to get interesting. In November 2019, the star began to dim. At first, Guinan didn’t think it was unusual — the star often varies in brightness. But this time, it was different — rather than continue varying in luminosity, the star's brightness kept decreasing.

“It didn’t stop, it just kept going,” Guinan says. “Whenever we thought it’s near the end, it can’t go anymore, it would go more.”

The recent image obtained by ESO also showed the clouds of dust surrounding Betelgeuse.

ESO/P. Kervella/M. Montargès et al., Acknowledgement: Eric Pantin

Guinan and his colleagues reported the dip in Betelgeuse’s brightness on The Astronomer’s Telegram on December 8, 2019. To find out what was going on, they also put out a call for other astronomers to start observing the star as well.

Astronomers worldwide answered, and so began the growing consensus that Betelgeuse wasn't just acting strange — it was on the verge of exploding.

What happens if Betelgeuse explodes?

As a star nears the end of its life, it runs out of fuel and essentially collapses under its own gravity. The death of a giant star results in a massive explosion witnessed across galaxies, a supernova.

Astronomers have only been able to observe supernovae faint stars in distant galaxies. Because of the distance, these supernovae are only detected long after the star has exploded. But Betelgeuse is right here in our neck of cosmic woods — being this close to the star means that scientists could observe the entire process from start to finish in unprecedented detail.

An artist's depiction of what Betelgeuse would look like if it were go to supernova.

ESO, L. Calcada

“We’ll have a front-row seat observation to what happens when a star becomes a supernova,” Guinan says.

The problem is knowing when that might happen. Astronomers aren’t exactly sure what happens before a star goes supernova, so it’s hard to predict whether Betelgeuse will explode tomorrow -- or 100,000 years from now. When Betelgeuse explodes remain a cosmic mystery.

“We’ll have a front-row seat"

“No one has ever really seen a star before it became supernova, or measured it for weeks or months before it happened,” Guinan says. “There’s no precedence, there are no clues.”

Scientists still aren't sure whether this is part of the star’s irregular behavior or if Betelgeuse is about to give us the show of a lifetime.

"It’s not something you get to see very often"

“There’s a very, very, very low chance that it would blow up, but if it does -- then it would completely change my life,” Andy Howell, staff scientist at Las Cumbres Observatory Global Telescope Network, tells Inverse. “It’s like a lottery ticket ... very low probability but life-changing.”

If Betelgeuse were to explode, the star will appear super bright once more— in fact, it's going to appear brighter than it's ever been.

The exploding star would reach peak brightness after a week or so, becoming as bright as the full Moon in the night sky and casting a shadow on Earth.

The detonation would also be visible during the daytime, similar to how Venus looks in twilight. Its light would last for a few months, before it plateauing and eventually completely fading from our vision over the course of a year or two.

Aside from the awe-inspiring sight of a star visible during the day, it would be an incredible learning opportunity for scientists around the world. An astronomical event of this size would make everyone hyper-aware of astronomy and the intricate science behind our stars, Howell says.

Observing a supernova in real time would also provide insight into some of the still-unexplored physics behind the stellar explosions, he says.

“People have been trying to simulate supernova for decades,” Howell says. “But in the simulators, they haven’t been blowing up.”

Because our knowledge of these events is incomplete, astronomers think they are likely still missing a piece of the puzzle behind what causes a star to explode.

What type of star is Betelgeuse?

Betelgeuse was already pretty popular even before all this talk of its imminent death. A quick look at its vital statistics demonstrates why.

How do you pronounce Betelgeuse?

Betelgeuse -- pronounced "beetle-juice," by the way -- is a red supergiant star located 642.5 light years away in the constellation Orion. It is a variant star, meaning that it varies in brightness in a range between +0.0 and +1.3, but it is consistently one of the brightest stars in our sky.

Due to its brightness, Betelgeuse can be observed using small telescopes and is a favorite among amateur astronomers.

Betelgeuse is so big that if it were in our Solar System, it would engulf Mercury, Venus, Earth, Mars, and Jupiter.


Irene Pease, president of the Amateur Astronomers Association of New York, has been observing Betelgeuse for over a decade. She was able to notice the star dimming by just looking up at it at night.

"It definitely looks different"

“Just looking up in the sky, I can tell,” Pease tells Inverse. “It definitely looks different.”

When news of the star’s dimming broke out, celebrity astrophysicist Neil deGrasse Tyson called on amateur astronomers everywhere to keep their telescopes on Betelgeuse and monitor its brightness, the New York Times reported.

Since there are more amateur astronomers than professionals in the world, there’s a better chance that they would see it first, Pease says. Even if the star doesn’t go supernova, Pease still encourages people to go out and observe it for themselves.

“It’s definitely a novelty because we don’t really know what’s gonna happen so it’s kind of exciting,” Pease says. “It’s not something you get to see very often, seeing a prominent star change its brightness.”

The conversation around Betelgeuse going supernova has made astronomy accessible to more people. The star even has its own fake Twitter account, which tweets out updates such as, “I install one dimmer switch in my dining room and the entire galaxy loses its shit.”


“You call it hype, but it’s my life,” Howell says. “I think about Betelgeuse all the time.”

He is not alone — Guinan, so close to giving up on Betelgeuse, has renewed passion for the star. “It’s a star I’ve grown quite fond of,” Guinan says. “I’ve been observing it for close to 30 years and I always know what it’s gonna do, until now.”

“I think about Betelgeuse all the time.”

Guinan started drafting a paper on the dimming of Betelgeuse, but he was not quite sure what the conclusion of the paper would be.

If the star starts regaining its brightness, then the dimming was part of its variant nature. “This is a small sample of its life, it may have done this in the past and no one noticed it,” he says.

But should it continue to decrease in brightness, then it may be a sign that it really is getting ready to go supernova. And if it does, both amateur stargazers and astronomers will be thrilled.

Either way, Betelgeuse's dimming event is a thrill all on its own, even if some are hoping that it ends in a massive explosion that will forever alter our skies.

“When you look up at the sky, you always take a couple of seconds to wish upon a star,” Howell says. “I’m always wishing for Betelgeuse to blow up.”

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