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What is a Black Hole?
Space
What is a black hole? How do they form? What are they made of? Black holes have long fascinated the imagination yet challenged discovery. Their extreme gravity, so strong light cannot escape, make them exceptionally difficult to see.
Transcript
What is a black hole?
Imagine a place in space where gravity is so strong that nothing, not even light, can escape its clutches.
It's a region of the universe where space has collapsed in on itself to a point that has zero size.
It's called the singularity.
It's a point in space where the matter of an object has been crushed basically out of existence.
But the mass remains.
The mass of an object is a way to describe how much stuff like atoms, molecules, and particles are in it.
So it's gone, but still there.
And its gravitational field affects everything around it.
And because not even light can escape, we call it a black hole.
You might be thinking, how do we know black holes exist if we can't see them?
Astronomers notice stars behaving in strange ways, orbiting around invisible companions.
They often suspected a black hole's powerful gravity must be doing some stealthy influencing by observing the effects of a black hole's gravity on nearby objects.
They can learn a lot about these hidden cosmic giants.
This shows the swirling hot gas that is getting sucked into the black hole.
It's called the accretion disk.
If you are in space, your eyes limit what you can see.
So scientific artists make animations like this to help us have an idea of what it looks like.
There are a couple ways astronomers think black holes are created.
One way is when a star more massive than our sun runs out of fuel and explodes as a supernova.
One of the possible results of this explosion is a black hole.
The core of the star collapses, and much of the mass of that star collapses down into nothing.
A singularity, that's where all of the crushed mass is.
Black holes that are created when a star dies are known as stellar sized black holes.
Another type is called a supermassive black hole that scientists
think form when black holes collide and merge into a bigger one.
Kind of like when you combine small pieces of clay.
Scientists believe there may be a supermassive black hole at the center of every galaxy.
We know there is one at the center of our galaxy, the Milky Way.
American astronomer Andrea Ghez was awarded the Nobel Prize in Physics when she discovered it.
After 25 years of research.
It is called Sagittarius A-Star and is about 26,000 light years from Earth.
A team of scientists using radio telescopes from all over the world created an image of those radio waves, translated into something the human eye can see.
Since we can't see a black hole, black holes are made of two components the singularity and what is called the event horizon.
To learn more about the event horizon, let's ask Doctor Joe Pash with the US National Science Foundation.
He's an astronomer who studies black hole formation.
Doctor Pesch, can you explain what the event horizon is?
What we call a black hole is the singularity surrounded by the event horizon?
The event horizon can be thought of as the last orbit, outside of which material can escape the black hole, the singularity, and inside of which material falls into the singularity.
So the event horizon is a, a shield around the the singularity.
And in, in the universe, it's a three dimensional structure.
So it looks like a sphere.
And so you had the you have the singularity, and then the event horizon surrounds.
It looks like a, ultra black sphere.
Now, if that black hole is rotating and when they rotate, they typically rotate very rapidly.
Large percentages of the of the speed of light.
you might get an oblong structure, of, of the event horizon.
So it's no longer spherical and, and like a globe, but it might be more elongated like a, like a football, perhaps.
So once matter crosses over a black hole's event horizon, a sort of boundary line, it is trapped within that gravitational field and cannot return to the outside universe.
The size of its event horizon depends on the mass of the black hole.
The more massive it is, the larger its event horizon is.
Black holes are invisible yet powerful, shaping the cosmic dance of stars and galaxies.
While they may sound like something out of a science fiction story.
Black holes are very real, adding a touch of cosmic magic to our ever expanding universe.
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