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