Black holes are dark,
matter-devouring balls of gravity.
Most of them are so far away
that we don't need to worry about them.
But not this one.
This enormous black hole sits
right outside our Solar System.
More specifically,
1,600 light-years away from us.
Now, that might sound like a huge distance.
But it's way closer than
any other black hole on record.
What's worse,
we didn't know about it until now.
Despite Gaia BH1 being 10 times
more massive than our Sun,
we couldn't see it.
Scientists usually discover these monstrosities
by spotting the gas that a black hole feeds on.
These hungry giants
are called feeding black holes.
Only Gaia BH1
isn't anything like that.
This black hole is dormant.
It hides in the darkness,
patiently waiting for the galaxy
to throw it some cosmic matter to feast on.
But there's one thing that gave away Gaia's presence.
You see,
most star systems in the Universe are binary.
That means that they have not one,
but two stars orbiting each other.
Our black hole neighbor
is also part of a binary star system.
Except instead of two stars,
this system has one star
and one black hole.
Yeah, Gaia BH1 was disguising itself as a star.
But even though this monstrosity
doesn't feed on any gas or matter yet,
it still couldn't help but jiggle its star counterpart a little.
Yeah, good try, Gaia,
but we still caught you.
Out there in space,
there are black holes
a lot scarier than Gaia BH1.
And some are so bizarre
that they shouldn't even exist.
A team of scientists discovered
an unbelievable black hole
and gave it the melodic name
LB-1.
The weird thing about this black hole
is that it’s just too massive to be true.
OK, let's get some facts straight.
We know of two types of black holes.
Stellar black holes are
what massive stars become when they die.
They are everywhere in the Universe.
Even in our Milky Way galaxy,
there could be as many as
one billion of them lurking around.
These beasts can be between
10 and 24 times as massive as our Sun.
The other type of black holes
are supermassive ones.
These enormities
sit at the center of almost every galaxy,
including our own.
We don't really know how they form,
but we do know that they are unimaginably gigantic.
Billions of times more massive than our Sun.
But LB-1 doesn't fit either of these types.
At 70 solar masses,
it's too enormous to be a stellar black hole,
yet it's too tiny to be a supermassive one.
Scientists were scratching their heads
trying to explain this phenomenon.
Some theorized that it might not be a single black hole,
but two black holes orbiting each other.
Others guessed that
LB-1 was born of a gigantic star
that was still in the middle of becoming a black hole.
Well, the answer was simpler than we thought.
LB-1 isn't a black hole at all.
It's an optical illusion caused by
two rare stars orbiting each other.
It's a unique star system to stargaze.
But when scientists said they found an improbable black hole,
well, they were wrong.
But, please, how could you blame them?
It's pretty hard to study an object
15,000 light-years away.
Mistakes happen.
The good news is that LB-1
didn’t upend our understanding of black holes after all.
Now, that doesn't mean that black holes can't blow your mind.
Remember the one at the center of the Milky Way?
Yeah, it's called Sagittarius A*
and it's as massive as 4.5 million Suns.
But there's always a bigger fish in the Universe.
Sagittarius A* might be the most
massive monster lurking in our galaxy,
but it's not even close
to some of the really big players out there.
This black hole is devouring matter
10 billion light-years away from us.
It’s as bright as 140 trillion Suns,
so bright that it outshines its own galaxy.
And its mass?
Yeah, 66 billion times that of our Sun.
Yeah, that’s right, 66 billion.
TON 618 is horrifyingly big.
When scientists discovered it,
they began to wonder if
even more massive black holes were possible.
Of course, the name 'supermassive'
wouldn't do bigger black holes any justice.
So astronomers came up with
a cool name for them too.
Stupendously Large Black Holes, or SLABs.
Yeah, and then, they found one.
Move over, TON 618,
there's a new gargantuan black hole in town.
This stupendously large monstrosity
sits at the center of Phoenix A galaxy
around 8.5 billion light-years away from us.
It's almost impossible to imagine
how enormous this thing is.
Scientists think it has a mass
of 100 billion Suns.
That's more massive than
some galaxies out there.
And it won’t stop growing.
The event horizon of this black hole
at the center of Phoenix A is unimaginably huge, too.
It has a diameter of about 100 times
the distance between the Sun and Pluto.
If you jumped on SpaceX Starship
and tried to fly across this black hole,
it would take you 2,500 years to complete that journey.
Yeah, we're lucky this monstrous SLAB
is so far away from us
that we don't have to worry about it
swallowing our Solar System whole.
But there are two more supermassive black holes
very close to Earth.
And they're on a collision course with each other.
OK, when I say very close to Earth,
I mean
500 million light-years away from us.
But, still,
closer than a lot of the other scary things out there.
Seriously though,
we don't know what exactly happens
when two supermassive black holes collide.
We've never observed a full merger of supermassive giants.
Scientists think that
they'll dance around each other for about 200 million years
before finally becoming one.
But this would be a violent marriage.
As the black holes spiral together,
they'll send enormous gravitational waves through space.
Waves so big
that we will be able to detect them
from our planetary neighborhood.
But that's not the scary part.
Mergers like that happen all the time.
And right now,
the Milky Way is on a collision course
with the Andromeda galaxy.
When our two galaxies become one,
what will happen to the supermassive black holes at their centers?
Will they merge too?
Would an event like this tear
tear everything in its vicinity to shreds?
Yeah, I bet that’s what keeps astronomers up at night.
Yeah, our galaxy is doomed.
But how exactly will this world-ending scenario go down?
You know what,
I'll leave that story for another WHAT IF.