Hey Kromp, whatcha doing?
I’m looking for a BLACK HOLE!
I heard there’s a black hole out there that
sucks everything into it.
Well, yeah, there are lots of black holes.
Not anywhere close to us, though.
But yes, lots of black holes all throughout
the universe.
I’m going to be ready for that black hole.
I’ll tell it to go away.
I’ll scare it away because I’m a MONSTER!
Kromp... do you know what a black hole IS?
Yes... but I want to hear YOU tell it.
OK.
A black hole is a place in space that is very
dense.
It has immense gravity
Nothing can escape, not even light
That’s why we call it a BLACK hole
Well I’m going to stay here and keep watch.
We can’t see a black hole, Kromp.
It’s invisible.
Wait a minute.
They’re invisible?
Then how do we know they’re even out there?
We have giant telescopes and special tools
out in space to help us find black holes.
What good are telescopes if you can’t SEE
a black hole, huh?
We look at what the black hole does to things around it.
The gravity of the black hole 
pulls on everything around it.
So we look at things CLOSE to black holes and
see how they move around.
Ohh.
You mean things look different around a black
hole?
Exactly.
That sounds indirect at best.
I think it’s incredibly clever.
Show a little appreciation for the science,
Kromp.
No, you’re right, froggy woggy.
Good job, astronomer-scientist people, good job.
Yeah!
It's amazing that they figured all this out
about something you can't even see!
So, froggy...Where do Black Holes come from?
Sometimes when a really big star dies, it forms a black hole.
Stars die?
I thought stars were big burning balls of gas.
I didn't know they were alive.
How sad.
It's just a figure of speech, Kromp.
I'm talking about when  stars run out of energy.
The matter that’s left behind collapses on itself
and there’s a gigantic explosion.
Oooh, exciting.
Everything left over from the explosion collapses
into the tiniest point.
It's infinitely small.
That's pretty small!
We call that tiny point with a lot of mass
squeezed into it a SINGULARITY.
It has enormous gravity that can pull things
in towards it.
Wait a minute.
You keep talking about gravity.
What does gravity have to do with black holes?
I thought we had gravity here on Earth.
We do have gravity on Earth.
Everything that has mass has gravity.
The Earth, the moon, the sun, even you, Kromp.
I do??!
Just a little, because you’re not very big.
I’m bigger than you, froggy woggy.
Yeah!
That means you have a little bit more gravity
than me!
Everything that has mass warps the fabric
of space a little bit.
The more mass, the more warping.
So
the Moon orbits the Earth because of gravity.
Because The Earth is massive and so it pulls
the moon towards it.
Yeah!
Same with how the Earth orbits the Sun.
The Sun is so massive, it warps the fabric
of space, so its gravity naturally pulls on
the Earth and all the planets.
OK, that makes sense.
But I thought you said the black hole was tiny.
The very center of the black hole is infinitely small.
But it has a TON of mass.
Imagine something with WAY more mass than
our sun, squeezed into the tiniest point.
That’s a LOT of gravity!.
If you anything gets close, it’s going to
get sucked in.
How close can you get?
We draw an imaginary circle (well, really a sphere) around a black hole.
Inside that sphere, the gravity is
too strong for anything to escape.
Even light.
We call this sphere the EVENT HORIZON.
Well, how big is that circle? I mean sphere?
That seems like pretty important safety information, froggy woggy.
The more mass the black hole has, the bigger the danger zone.
Some black holes are small.
Some are huge!
There’s one kind of black hole called a
STELLAR black hole.
That has the mass of around a dozen of our Suns.
Oh, pretty big.
That’s nothing.
Have you heard of a SUPERMASSIVE BLACK HOLE?
No, what’s that?
Like, two dozen suns?
A supermassive black hole has the mass of
MILLIONS and MILLIONS of our SUNS!
Scientists think there’s a supermassive
black hole in the middle of every galaxy.
We call the supermassive black hole in the
middle of the Milky Way Galaxy Sagittarius
A.
The Milky Way Galaxy!
But that’s OUR galaxy.
Yeah.
So.
So aren’t we in danger?
No, Kromp, we’re really far away from the
center of our galaxy.
Anyway, nothing outside of the event horizon
is going to get pulled in to the black hole.
Here’s a picture of the galaxy and everything is still there.
I don’t see any black hole.
No, remember Kromp - we’re not going to
actually SEE the black hole.
But we can see how things behave around it.
But really, froggy.
Tell me.
What do black holes look like?
We can’t take a regular picture, because
light doesn’t escape a black hole.
When we look at something, or take a picture
of something, we’re looking at the light
that bounces off of that thing.
Well, light doesn’t bounce off of a black
hole.
It gets sucked up by the black hole!
THAT'S IT. I'm just going to hold my breath until you tell me what a black hole looks like.
arrghhh. Kromp!!
OK. Listen!
There is this huge telescope, called the Event Horizon Telescope, that's specially made
for looking at Black Holes.
{huge breath} Now you're talking!
It's actually made up of
lots of parts all over the world.
Put together, it’s like a telescope the
size of the Earth!
It’s a radio telescope.
Like, a radio that plays all the top hits?
Well, it detects radio waves instead of light.
You’re losing me, Froggy.
There are different kinds of radiation, Kromp.
Energy that radiates off of things.
There’s visible light rays that we can see with our eyes, but there’s also x rays, gamma rays, infrared rays,
radio waves…
Oh, yeah, I’ve heard of some of those things.
So the Event Horizon Telescope is LISTENING
to the black hole?
Yeah! Sort of.
Astronomers use the radio signals to paint
a picture of what’s going on around the
black hole.
But what about the black hole itself?
The black hole doesn’t have a surface.
It’s just a region in space, and we can’t
see past its boundary.
OK Kromp. Are you ready?
Here's the first picture from the 
Event Horizon Telescope.
So what am I looking at, here?
There’s a disk of gas and dust around a
black hole.
We call that an accretion disk.
It spirals around and around the black hole, and because
of friction it heats up and glows!
It gives off various kinds of radiation.
And that’s what the telescopes are picking
up!
Is the black part the black hole?
Well, it’s sort of like the shadow of the
black hole.
This is what happens because light is bent
by the enormous gravity of the black hole.
Huh, it doesn’t look very big.
It’s 6.5 BILLION times the size of our sun.
Oh, not bad, not bad.
So where is this black hole?
This is the black hole at the center of the
huge galaxy called Messier 87.
It’s 55 million light years away.
So we’re pretty safe, huh.
Yeah, that’s pretty far away.
But what about OUR supermassive black hole
in the center of OUR galaxy?
I think it probably looks a lot like this,
Kromp.
Okay, froggy woggy.
I’ll stay here and keep watch.
Leonard sighs.
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