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What’s a Black Hole?

Le 04/09/2019

A black hole is formed when a massive star dies and collapses down into a very compact object.

It’s called a Black Hole because it’s invisible in space; it gives off no rays of light.

Its force of gravity is so great that nothing can ever escape: neither matter nor light.

But how does a black hole trap light?

When you throw a ball into the air, it always ends up falling back down because of gravity which attracts it to the center of our planet.

To escape Earth’s gravity, you would have to throw the ball at a speed of over 40,000 km an hour.

The more massive a star is, the more speed you need to escape its gravity.

A black hole is so massive that to escape from it, you’d have to go faster than the speed of light.

And as nothing can go faster than the speed of light, even light itself can’t escape.

Because black holes are invisible, astronomers have to use clever tricks to observe them.

They detected a black hole in the middle of our galaxy by observing stars orbiting around an invisible object.

In other galaxies, their presence is betrayed by huge jets of matter.

To spot them, astronomers therefore look at what’s happening around black holes and they learn a bit more about their size, the density and how they behave. Smart!