Space · The stars

Black holes

Not even light gets out

Only spacecraft can see it

Black holes — A black hole surrounded by the gas falling onto it: that gas heats up and glows before it disappears.

The numbers

What it is: A region nothing gets out ofNot even light
The border: The event horizonPast it there is no way back
Can you see it?: No, only its effects
Where they come from: The collapse of very big masses

To get an idea

If the Sun became a black hole of the same mass, the planets would keep going around just as they do now.

It cannot be seen directly: it is found by the way it bends orbits and by the glow of the gas falling in.

Fun facts

These are not in the book: there was no room on paper.

A black hole is not observed directly: only its effect on what is around it can be detected.
The gas falling onto it heats up enormously and glows before disappearing past the border.
Many are born from the collapse of enormous stars at the end of their lives.
At the center there would be a singularity, a point whose nature is still unknown.
At the center of almost every galaxy, ours included, there is a gigantic black hole.

Test yourself

The first question is the one printed under the QR code, with the answer the book did not give. The other four only exist here.

Question 1 of 5★ is the one from your book

What is a black hole?

Question 2 of 5

Does a black hole suck in everything that passes nearby?

Question 3 of 5

What is its border called?

Question 4 of 5

How do we know they are there?

Question 5 of 5

How are many black holes born?

Riddles

Nobody can see me, because I let nothing out: not even the fastest thing there is. You find me only by watching how my neighbors behave. What am I?

Everyone thinks I suck things in like a vacuum cleaner, but it is not true: from far away I pull exactly like any other weight. It is up close that I become hard to handle. What am I?

Around me there is a line made of nothing that cannot be seen, but whoever crosses it never comes back. What am I?

Try it yourself

Activity 1

Stretch a sheet between two people and put a heavy ball on it: a dip forms. Then roll a marble nearby and watch how it curves.

Activity 2

Imagine the Sun replaced by a black hole of the same mass: the Earth would keep exactly the same orbit, only in the dark. The cold would be the problem, not being sucked in.

The words

singularity: The point at the center of a black hole, where known laws stop working.

Sources: Wikidata (Q589), Wikipedia (Buco nero).