Hey there, star friends.
I am Trace.
And this week, I've been hearing so much
about Orion's most famous star, Betelgeuse.
Betelgeuse, Betel-- no, I'm just kidding.
I'm not looking to call up stripey Batman.
Astronomers are excited because the 10th brightest
star in the sky is acting super weird.
So I called up my friend Sarafina,
who studies this stuff.
And then I popped across the Bay to have a chat with her.
Is this star going to explode, Sarafina.
I want it to.
I just want--
[MUSIC PLAYING]
Thank you.
Thank you so much for tuning into Uno Dos of Trace
this week.
I am Trace.
This is a really fun episode all about Betelgeuse.
And even if you already think you know what's going on,
there is way more to this story than you think.
The nerd media or "nerdia" is covering this
like they always do, with each site
taking little bits of all the different parts of the story.
Little bits.
So I'm going to do what I do best
and gather everything all into one place, just for you.
So stick around, and you'll get to know
how we know anything about stars,
what exactly Betelgeuse is and why it's interesting,
plus the latest news and, importantly, why you
should care about this at all.
So let's kick into it.
This is a really great story because you can actually
be a part of it.
Just go outside tonight and look at Orion.
It looks like this.
Orion is a lot of people's favorite constellation.
It is so easy to find.
Just look for the three stars of Orion's belt.
If you're in the Northern Hemisphere, look southwest.
If you're in the Southern Hemisphere, look northwest.
It's right there, only in the winter.
It's on the other side of the Sun in the summer.
It's really hard to spot.
If you look closely at Orion's right shoulder,
that is Betelgeuse.
And astronomers all over the planet, maybe even the galaxy,
are interested in this little reddish
dot because it is about to go supernova.
Vocab update-- astronomers don't actually say "going supernova."
I didn't know that.
They actually say "explode into a supernova,"
just so we all know.
I've got to check myself.
Speaking of astronomers, again, I
called up my friend Sarafina Nance to ask her
all about Betelgeuse, because that's what she studies.
So I'm here with Sarafina.
Hi.
Can you tell everyone what you do?
So I am an astrophysics grad student at UC Berkeley,
studying supernova and cosmology.
That sounds fun.
Yeah, it's great.
I love it.
I was so excited when I saw that it was trending on Twitter
and people are excited about it, because I literally
spent my entire undergrad studying
Betelgeuse and modeling it.
So it's like, great.
I know about this.
This is awesome.
So it's been a lot of fun.
It's been really exciting to actually walk outside and see
with the naked eye that Betelgeuse looks a lot dimmer
than it normally looks.
Typically, it's shining very red, very bright, whereas
right now, it just looks like any other star.
And so the question is, why is it doing that?
Does that mean that it could explode soon?
OK.
Fingers crossed.
Yeah.
So we really want it to explode.
I want it to explode.
I think it is going to look amazing from Earth
whenever that happens.
So it'll look like a shining bright light,
as bright as the Moon, in our day and nighttime sky.
And it'll fade over the course of a few months.
So we'll be able to see the explosion and kind of watch
it change with time, which would be absolutely amazing.
Betelgeuse is about 600 light-years from Earth.
It actually got its name from an ancient Arabic phrase,
"ibt al-jauza," meaning "hand of the central one,"
an ancient constellation of a female warrior
that was up in the sky.
And Europeans actually replaced that constellation
with Orion, the hunter.
Now, we call it "Betelgeuse," and it was the 10th brightest
star in the sky in 2019.
It was the 10th brightest star.
You hear that?
"Was"-- because now, it's dimming,
which many astronomers think it might be on the way
to exploding into a supernova.
Note that vocab update, fam, although in all honesty,
it probably won't explode any time soon.
It might, but come on.
It's not probably going to do it.
But it might, but it's not going to do it.
Our stellar models are forecasting,
I guess, that it's not going to explode for another 100,000
years.
That absolutely could be wrong, and don't hold me to that.
Like usual, with any bit of science news, which
is why I love what I do, there is
so much more to this than just a giant explosion.
Hey, if it explodes tomorrow, I will throw a party.
Oh my god.
I will be in tears.
It'd be amazing.
But I think the cool part is that we
get to very closely study a star as it
nears the end of its life.
And we get to try to unpack some of these interesting theories
that we have for what goes on in the interior of a star
when it's impossible to probe the inside of a star.
So we get to use these really interesting techniques to try
to understand what's going on.
But first, a bit of background--
Betelgeuse is a red giant star.
It used to be a main sequence star, just like our Sun.
But it burned through all its hydrogen
fuel, which our Sun's going to do some day.
This is a normal bit of the lifecycle of a star.
And when it does this, it will explode into a supernova.
So I asked Sarafina, can you just walk
through us what happens in a supernova,
because here's my assumption.
A star's just chilling.
And then all of a sudden, it's all like, boom.
That's basically it.
Is it more than that?
Yeah.
So there are two main types of supernovae.
The first is when there are actually two stars,
and one star either accumulates matter from another star
or the stars completely merge.
And in that scenario, the stars ignite nuclear fusion,
which is basically the fuel process of making fuel
on the star, and explode the star.
For that scenario, you need what's
called a "degenerate star."
So that's typically called a "white dwarf"
in astronomy terms.
In the other scenario, you have a massive star that
runs out of fuel and explodes.
What happens is stars undergo nuclear fusion
throughout their lifetime.
And that's basically how stars shine.
The star fuses hydrogen, and then it fuses helium.
And then it fuses carbon, nitrogen, oxygen,
heavier and heavier elements, until it gets to iron.
And you need a really massive star
to be able to get to that point.
And once it reaches iron, it can no longer hike up temperatures
enough to fuse it.
And so what happens is the outer regions
of the star start to collapse, and the temperature
gets hyped up in the interior of a star.
You reignite nuclear fusion, and it explodes
the outer parts of the star.
And so what you have left is either
a black hole, a neutron star, or, in some cases,
you actually completely explode the star.
The reason our Sun hasn't exploded into a supernova
is because the gravity of all the mass in the star
is balanced with the rate of nuclear fusion.
Red giant stars like Betelgeuse, they're older.
And like our expert said, that tips the balance,
causing it to swell into this red giant.
BT-dubs, again, someday, this is going
to happen to our Sun, which is actually
kind of exciting, right?
Red supergiants like Betelgeuse are really big, about 950 times
larger than our Sun.
When our Sun goes red giant, if it does,
the outside of the star will be equal to the orbit of Mars.
We will be inside of our Sun's atmosphere.
We're going to be long gone by then,
so it kind of doesn't matter for us.
But isn't that cool?
The red indicates the stars are cooler than hotter white stars,
with nuclear fusion happening all
throughout their atmospheres.
Even though it is cooler, it's still really bright,
more than a million times brighter than our Sun.
I mean, it was.
The thing that's kind of strange about Betelgeuse
is it's so bright, you would think, OK,
that makes it easy to study.
Yeah.
But that brightness actually kind of saturates observations,
kind of like if you take a photo and it's over-exposed.
That makes it actually quite hard
to observe it in a really well-defined way.
In order to try to understand some
of what's going on beneath the stellar interior,
we basically have to use both models and observations
to try to match them up and see what's happening.
And of course, it's not quite as bright
as it used to be now that it's dimming
and brightening and dimming again,
which it's done for a long time.
This massive star is out there changing constantly.
I don't look at the sky close enough to notice.
But astronomers, they do.
Betelgeuse is a variable star.
A lot of massive stars have periodic variability,
where they basically contract and expand on a periodic basis
that we're able to measure and anticipate.
Betelgeuse is also a semi-variable.
So it has periods that are more random,
and there's a variety of factors that can contribute to that.
The thing that's weird right now is
that it has been dimming more than we've previously seen
and more than we would probably anticipate.
And so some of the theories are that Betelgeuse
has regions of convective instabilities, which basically
means if you picture some blobs, there
are blobs floating and collapsing within the star.
And those blobs carry energy to the outer regions of the star
and can make the star contract and expand.
So maybe those convective cells have
something to do with its changing luminosity.
Another option is that perhaps there
was some mass ejected from the star
and is at a distance in front of the star
that's actually obscuring the light.
And so that's the dimming that we're seeing
is the dust is actually shrouding the star.
And we know that massive stars like Betelgeuse
undergo periods of violent interrupted mass loss.
So it's not surprising that there's some crazy stuff going
on on the inner parts of the star
that we're seeing on the outer parts.
But the question is why.
What's the physics behind that?
Another theory is that there are regions of magnetic instability
within the star.
So the core could be rotating, and that rotating core
can actually cause magnetic fields.
And similar to our Sun, those magnetic fields
can transport energy from the surface of the star into space.
So a lot of theories for what's going
on in the interior of a star, and it's
very not well-constrained as to what it actually is
and why it's doing what it's doing.
Whoa.
Yeah.
So we don't really know that much.
So all this is to say it might just explode.
One day, you'll go outside.
And instead of a star, there'll be a giant bright blob
in the sky, as bright as the full Moon
and visible during the day.
The original mass of the star that
is Betelgeuse is thought to be around 20 solar masses--
so 20 times mass of our Sun.
Right.
But right now, it's a red supergiant.
So it's expanded to be really, really, really large.
We think that it will likely form a neutron star.
Cool.
Yes.
I love neutron stars.
Very, very cool.
They're super awesome.
Yes.
Betelgeuse is probably going to form
what's called a "type 2p supernova," which
are what I study, actually.
Shut the front door.
I know.
So cool.
I know.
So what we think is the light is going to get really bright.
And then it'll fade and sort of plateau
for about 50 to 100 days.
And at the end of those 100 days, it'll start to drop off.
And we think that it plateaus because the explosion runs
into the circumstellar medium of the star.
So the circumstellar media are basically regions outside
of the star that are formed from these eruptive mass loss events
that the star undergoes at the last throes of its lifetime.
And so--
So it's throwing stuff off.
It's basically burping--
It's shedding mass left and right.
Yes.
It's getting messy.
That's right.
And so when it explodes, it's going
to run into that sort of dust.
And light is going to get trapped.
And so that's why it plateaus.
We know this because supernovae, they
explode in our field of view about once a century.
They're not common, but they're not
exactly uncommon compared to everything
that could happen up in the universe.
For example, the Crab Nebula, that used to be a star.
It exploded into a supernova, and we're
seeing the remnants of it.
We know all this because of the light coming off the star.
You might think of light as a simple thing, just brightness
or energy.
But it's not nothing.
We can learn a lot just by looking
at the light coming off a star.
And astronomers call that light "spectra."
Yeah.
That's a vocab word.
Well done.
[LAUGHTER]
Supernova expert in training.
In terms of using telescopes, we do two things, mainly.
One of them is collect data and make light curves out of it.
And so the light curve is basically
measuring the brightness over time.
So for a supernova, you can imagine the star explodes.
So it gets really bright, and then it fades over time.
And then the other tool that we use is the spectra.
So we collect the light in our telescope.
And then we're able to break it into its constituent parts
by using what's called a "spectrograph."
So in layman's terms, it's kind of like a prism.
So you shine a light through a prism,
and you get different colors out of it.
That's basically what we do with a spectrograph.
And from spectrographs, from spectra,
we can learn a lot about the physical characteristics
of a star.
We can learn how fast it's rotating, how far
away the galaxy is, what the composition of the star is
and what the atmosphere is, the mass of the star,
the radius of the star.
It's really incredible what we're actually
able to learn from the light from a star.
And I think, taking a step back, just about astronomy,
that's one of the coolest things is these things are
in the middle of space.
We can't touch them.
We can't measure them.
We can't weigh them.
So how do we actually learn about what's going on?
And light is our biggest tool.
That's cool.
Yeah.
I think that's something that is very hard to realize
and explain to people is light is
all we can use to actually learn these things.
And we can learn so much about the star from light.
But from an observational perspective,
that's what we'd use.
And then we also run a bunch of stellar simulations using code.
And we're able to model stars and try
to make them look like the observed characteristics
of a star like Betelgeuse.
This news is actually still updating and ongoing.
I didn't get to talk to Sarafina about this
because honestly, it just happened.
But we detected gravitational waves
coming from the direction of Betelgeuse, as well.
And for a hot second, astronomers
thought that that meant the star might be exploding.
But it was just hype.
Most astronomers have not revised
their within-100,000-year mark, which I have to say is somewhat
disappointing.
But what happens when these things explode, right?
When a star goes supernova, when it explodes into a supernova,
what happens to all the stuff that might be orbiting?
Let's say we've got a couple hot Jupiters, maybe
some moons, some sexy asteroids out there, maybe
some Oort cloud situation.
What's going on?
What happens to all that stuff?
Do we get rogue planets?
Are we talking like full Alderaan, like this is gone?
What happens?
So this is a great question.
It varies from case to case.
But some of the really exotic things in space
can actually be traced back to a supernova exploding and pushing
away stuff in its vicinity.
So there will be stars--
I actually tweeted about it earlier,
because I was so excited to learn--
You should follow her on Twitter.
Thanks.
But they're called "hyper-velocity stars."
Picture the first scenario of supernovae that I talked about,
where you have two stars.
One star accumulates matter from the other star, explodes.
The second star survives the explosion.
But it's so close that the shockwave from the supernova
basically throws it out, flings it out of the system,
and it gets to speed along through space
at a rate of 1,500 to 2,000 kilometers a second.
It is going so fast.
Sometimes, it can get expelled from the solar system,
the galaxy, even.
And these are basically rogue stars kind
of traveling through space.
Cool.
Very cool.
So I would imagine the same thing happens to planets.
So the thing I really wanted to know
is, when this star explodes into a supernova,
whenever that happens, is it just going to be gone?
Orion's going to have no shoulder.
Yeah.
It's going to look very different, very, very
different.
Well, that's the sky for you.
But that means you have to go outside and look every night
to see if it's still there.
True.
That's cool.
Yeah.
I like that idea.
So after all this, do you want to see what it'll look like?
Do you actually want to see what it'll
look like, because somebody made an animation.
I know I wanted to see.
So that's why I was so happy to have CuriosityStream
as a supporter for this video, because they have
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And they actually covered this exact topic,
which is amazing, right?
This is from that show, Cosmic Front.
It explores Magellanic Clouds, black holes, asteroids,
and other phenomena in the universe.
It is awesome.
CuriosityStream is where you go to learn
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They have thousands of documentaries, short and long.
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You name it, they got it.
Again, join CuriosityStream with my link,
curiositystream.com/trace, with the promo code "trace,"
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It's only $2.99 a month after that.
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In the end, our sky is not just one thing.
It's not static.
It's not a fabric with pinholes shining through.
It's a dynamic and changing ecosystem,
the same as any we would find here on Earth.
Betelgeuse is over 600 light-years away,
meaning it's not even dimming right now.
It was actually dimming during the late Middle Ages
over 600 years ago, and we're just seeing it now.
This happened long before most Western Europeans even
knew there was another continent on this planet,
and we're all talking about it today.
Betelgeuse could have exploded already,
and we won't even know until the light from it gets to us.
Maybe that won't happen till the 27th century, which
is hundreds of years further in the future than most
of the Star Trek shows.
Now that you know so much about this one massive red
supergiant, think about the stories
that are out there for every other star in the sky.
What could they be hiding?
Cool, right?
Thank you so much for watching Uno Dose of Trace this week.
I am Trace.
Again, I really hope that you learned something
from this video.
I know I did.
Welcome, new subscribers.
I love you all.
Hello.
Thanks for watching my battery video.
Thanks again to Sarafina Nance for coming on the video.
You can find her at @starstrickenSF
either on Twitter or Instagram.
She's going to talk to you about space and astronomy,
but also BRCA genes and breast cancer research
and mastectomies.
She is amazing.
Go learn something.
Follow her.
You can follow me, too.
I'm at @tracedominguez literally everywhere on the internet.
Thanks so much for watching.
Thanks to the patrons, and I will see you in the future.