• Question: What are black holes.

    Asked by peter296 to Simon, Rosemary, Roisin, Jean on 28 Apr 2020.
    • Photo: Simon Spichak

      Simon Spichak answered on 28 Apr 2020:

      From our current understanding of space, a black hole is very strange indeed. They are thought to form when a star begins to run out of fuel, since it isn’t burning it’s fuel it becomes heavier and heavier. This star becomes really heavy as its mass keeps increasing! Now with an increase in mass, the star exerts more and more gravity until it reaches a point where the gravity is so strong that it collapses inwards upon itself! When it collapses inwards, it becomes a very small point in space with a very, very strong gravitational pull. In fact, it’s so strong that once light, or anything else for that matter, gets close enough to the black hole – it cannot escape! It is literally so dense that it stops light from escaping! Now if we have an object approach close to a black hole, such as a basketball or a loaf of bread, it is sucked in. A process called spaghettification occurs where an object is stretched apart (kind of like spaghetti) as it falls into the black hole. We don’t know exactly what happens at this point but its fascinating! Thanks for the wonderful question!

Comments

  • Photo: peter296

    peter296 commented on :

    Thank you

  • Photo: Ollie

    Ollie commented on :

    Sorry @Simon Spichak, I disagree with some of your explanation.

    Those funny laws of physics dictate there is conservation of energy during whatever process, so a star cannot make extra mass out of nothing!
    It could gain mass when it is leaching material off a nearby star, but not when it is on its own. In fact, when a star starts running out of fuel it will expand and starts ejecting material and so it will actually become lighter. But when there is no more fuel left for the star to burn there will be no more outward pressure and the star will start to collapse under its own weight. What happens then is that the star becomes denser, not heavier. So all that mass of the big star gets compressed into a tiny area of space, like the size of a tennis ball or even smaller and gravity gets so strong that it turns into a black hole.
    That’s what a black hole is essentially: an enormous amount of mass packed in such a tiny area of space that is so dense that gravity becomes strong enough to trap even light!