What Is a Black Hole?

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A black hole is a region in space where gravity pulls so strongly that nothing can escape it — not even light, which is why it appears completely black. It forms when a very massive star runs out of fuel and collapses, squeezing an enormous amount of matter into a tiny space and making gravity there incredibly intense.

Gravity is the invisible pull that keeps your feet on the ground and the Moon orbiting Earth; the heavier and more tightly packed an object is, the stronger its pull. A black hole takes this to the extreme. Surrounding every black hole is an invisible boundary called the event horizon — the point of no return. Anything that crosses it can never come back out, but anything staying outside is safe.

Learners discover that black holes come in different sizes, from small ones to a giant supermassive black hole at the centre of our Milky Way galaxy. Importantly, black holes do not roam around 'sucking up' everything — you must get very close for the pull to trap you, and the nearest black hole is extremely far from Earth.

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Frequently asked questions

Why is a black hole black?
It is black because its gravity is so strong that light cannot escape from it. Since no light comes out, our eyes and telescopes see only darkness where the black hole is.
How is a black hole made?
A black hole often forms when a very large star runs out of fuel and can no longer hold itself up. The star collapses, squeezing all its matter into an extremely small space, which creates gravity strong enough to trap light.
Could a black hole swallow the Earth?
No. The nearest black hole is extremely far away, and a black hole does not 'suck up' everything around it. You would have to get very close, past its event horizon, to be pulled in — and nothing near Earth is close to a black hole.
What is the event horizon?
The event horizon is the invisible edge around a black hole, sometimes called the point of no return. If something stays outside it, it is safe; if it crosses inside, it can never escape.
Are all black holes the same size?
No, black holes come in different sizes. Some are relatively small, while supermassive ones are gigantic — a huge black hole sits at the centre of our Milky Way galaxy.

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