It's almost as old as the Universe,
and as massive as 34 billion Suns.
It eats stars for breakfast.
And now it's about to consume ours.
Behold, the great and powerful black hole
with the catchy name J2157.
If it came close enough to our Solar System,
Black holes are scary enough.
They form when big stars
explode in a supernova,
and then collapse in on themselves.
The most common black holes, 
the stellar ones, are only
16 km (10 mi) in diameter.
But they have the mass of a star,
at least ten times more massive
than our Sun, crammed in them.
All that mass compressed
into such a small diameter
makes black holes extremely dense.
If you came too close to a black hole's vicinity,
beyond its event horizon,
its extreme gravitational pull
would turn you into a spaghetti noodle.
But there are black holes so massive
that they make stellar black
holes look featherlight.
These are called supermassive black holes.
These monstrosities lurk
at the centers of galaxies,
and take up space roughly
the size of our Solar System.
But most of them don't even get close
to the size of black hole J2157.
J2157 is the fastest-growing black hole
in the known Universe.
And it's the second largest one.
Its event horizon has a radius
of 670 astronomical units,
which is comparable to the distance
between the Sun and
Neptune multiplied by 22.
If that's not scary enough,
J2157 holds the title of the
hungriest black hole we know.
To stay in good shape, it gobbles up matter
at a rate of about one Sun per day.
Now, take this monstrosity
and bring it closer to our Solar System.
You can imagine how that would play out.
If J2157 could replace the
supermassive black hole
that sits at the center of our Milky Way galaxy,
to us on Earth, it would look
ten times brighter than the full Moon. 
That's because of its
incredibly large accretion disk,
the matter the black hole
collected on its way to us.
And because it always needs
to be the center of attention,
the monstrous black hole
would outshine most of the stars in the sky.
If a black hole under 100
million masses of our Sun
entered our Solar System,
it wouldn't swallow the Sun in one go.
It would gradually start
pulling matter from our star,
until all that's left of it would be a cloud of gas.
In that case, you could expect
lethal amounts of cosmic
radiation headed toward the Earth.
But that's not how J2157
likes to deal with things.
A black hole of that size and mass
would devour the Sun in a moment.
But losing the Sun would be
the least of our problems.
Our planet could be torn apart
by the tidal forces from the
black hole consuming our Sun.
Or, it could be bombarded with
an unthinkable amount of cosmic radiation.
Or, it would disappear into
the black hole's event horizon,
along with the rest of the Solar System.
Either way, you wouldn't get out of this alive.
But no matter how big and scary J2157 is,
remember that it sits at a safe distance
of 12.5 billion light-years away from us.
I'd say we're pretty safe here. 
If you ever plan to visit a black hole,
you'll need to look into some survival tips.
And we have a new show
for you about just that,
to help you survive whatever awaits you.
