What is a black hole?
We’re not used to thinking of
gravity
affecting
light,
but
massive objects can “pull” on
beams of light.
Astronomers
have observed this phenomenon
when massive galaxies pass in
front of distant bright objects,
called quasars. As gravity pulls
on the light and deflects it, we
Heavy objects (in this case a galaxy) can “pull” on light
see several “false” images of the quasar around the galaxy.
Black holes are the densest objects known to exist in the universe. In fact, they’re so
dense that their gravity prevents anything from escaping them if it gets too close, even
light, which is how black holes get their name.
Supernovas form black holes
To become a black hole, matter must be squeezed together with extreme forces! In nature,
this can occur when big stars run out of fuel and explode in a supernova explosion. Stars
make energy by fusing elements together and making heavier ones. Young stars are mostly
made up of hydrogen, which they fuse to form helium. When most of
the hydrogen in the core has been converted to helium, a new nuclear
reaction begins that converts the helium to carbon.
This process
continues converting the carbon to oxygen to silicon to iron. If you
could slice a very old star in half, it may look (sort of) like this:
A big old star
Even though the star is huge and heavy, its radiation keeps it from collapsing on itself.
However, nuclear fusion stops at iron. So if the star makes a big enough iron core, there’s
nothing to keep it from collapsing on itself.
When that happens, the outer layers fall
inwards and “bounce” off the iron in a massive explosion. If the star is heavy enough, the
remnants of the explosion is a black hole.
So what happens in and around a black hole?
Far away from a black hole, you wouldn’t feel any different. It’s a
misconception that black holes suck everything everywhere into
them like a giant cosmic vacuum. They, just like any other massive
object in the solar system, pull on you gently with their gravity.
Things only feel different when you get close enough.
When you stand on Earth, gravity at your feet is a little stronger
than at your head, because they’re closer – you just don’t feel it
very much.
Near a black hole, these tidal forces are much
stronger; in fact, the difference is large enough to pull a person
apart!
So if you were to fall towards a black hole, you would
unfortunately die before making it all the way in.
If you were to get very close (past a point of no return called the event horizon), you would
never be able to escape. It is past this point that not even light can escape. Of course,
since not even light can escape, nobody knows what’s “inside” the black hole.