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Betelguese is truly a star.
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This extremely bright supergiant is famous for its variable fading and brightening
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and distinctive presence as a red star amongst a sky of twinkling gold.
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It has secured a name for itself in numerous myths, stories, and recorded observations the world over.
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But lately, Betelguese has been catching our attention for another reason.
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Long considered one of the brightest stars in the night sky, it has begun to dramatically fade then brighten again
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for reasons we can't quite pin down.
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And it's caused some people to wonder if it's about to explode.
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Despite being roughly 643 light years away,
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Betelguese is nearly impossible to miss.
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For starters, it's MASSIVE; so big that if it were at the center of our Solar System, it would engulf all the planets up to Jupiter.
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Its diameter is roughly 1,000 times that of our Sun!
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To find it, just look at the Orion constellation.
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If Orion is “The Hunter” with his iconic three-star belt, then Betelguese is the hunter's left shoulder.
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If you're in the Northern Hemisphere during the first few days of January, you can see Betelguese rising in the east just after sunset.
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All other times, this star is easy to spot no matter where you're located in the world!
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Especially September through March.
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Some of the earliest known records of Betelguese come from China in the 1st century BCE.
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These records describe Betelgeuse as being yellow… which is strange, because just a few years later, in 150 CE,
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the Egyptian astronomer Ptolemy described Betelguese as red.
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This indicates that Betelguse rapidly underwent a stellar phase change sometime between the time these two records were made,
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evolving to become the red giant that it is today.
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Betelguese's propensity for fading and brightening over a multi-year cycle also seems to have caught people's attention.
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In western Aboriginal Australian oral tradition, Betelguese represents the 'fire magic' used by a love-struck hunter to reach the object of his affection.
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Unfortunately, the fire magic's tendency to flicker out ultimately causes him to fail.
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While Sir John Herschel continues to be recognized as the first to notice Betelguese's variable brightness,
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it's clear that people living before the 19th century also recognized what was going on.
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But recently, Betelguese has us all confused.
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Typically, its apparent magnitude averages 0.5.
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That's just how we measure a star's brightness as seen from Earth.
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That apparent magnitude drops and rises according to short cycles that last a few hundred days,
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as well as a longer cyclic variation that lasts every 5 years or so.
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But starting in late 2019, Betelguese began dimming and brightening in a way that was inconsistent with its normal cycles.
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By mid-February 2020, it had lost more than 2/3rds of its brilliance,
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becoming the faintest it's been in at least a century!
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And just a few months later, Betelguese had returned to its normal self.
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Betelguese is a red supergiant, meaning that it's nearing the end of its life.
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We know that it's only a matter of time before it explodes as a supernova—but when?
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That's the mystery.
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Well, I'm super excited to be talking about this star with you guys… because it just so happens that I've devoted six years to solving this very question.
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My research focus is supernovae, so figuring out when Betelguese will explode has been a burning question of mine for quite some time now.
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I started studying Betelgeuse by running stellar evolution simulations to model how massive stars live and die.
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By running hundreds of models and comparing them to observations made in the field,
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my team and I determined that it'll likely be another 100,000 years or so before Betelgeuse explodes as a supernova.
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So, if it's not going to explode soon… why is it acting so erratic?
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Well, there are a few compelling theories.
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It could be there was a cloud of gas and dust obscuring its light.
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Massive stars like Betelgeuse undergo violent eruptions as they get older,
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to the point where they eject matter from their surface.
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To us, that literally looks like Betelgeuse is burping up shells of matter,
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which obscure the star from our point of view.
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Another contributing factor to these violent eruptions are unstable regions within the star.
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Here, temperature and density wildly fluctuate.
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All of these characteristics point to the fact that Betelguese is probably still burning helium and is nowhere near the end of its life.
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Because the fact is, if Betelgeuse were preparing to explode, we'd expect it to be getting brighter instead of dimmer.
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But there is something that my team and I noticed during our research that totally caught us off guard:
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Betelguese is rotating REALLY fast.
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Like, 150 times faster than we'd expect for a star of its size!
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So, what gives?
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Well, to explain it's observed rotational velocity, we think it may have actually gobbled up another star.
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The idea is that when Betelguese ballooned to a red supergiant, it took a nearby star with it,
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absorbing that star's rotational velocity angular momentum and started spinning faster as a result.
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While we continue to monitor Betelgeuse's behavior and watch for any indication of what its future holds,
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we can be certain that its striking presence in the night sky will continue to hold our interest.
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For the time being, anyway.
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And whenever Betelguese does explode as a supernova, we can look forward to an amazing light show.
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It'll shine as bright as the moon for weeks on end; so bright that it will be visible during the day!
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I'm Sarafina Nance and this is Seeker Constellations.
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Thanks so much for watching this season of Constellations, I had such a blast!
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If there's another astronomy topic that you'd like to see us cover, let us know in the comments.
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Thanks for watching!
