Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

Wikipedia says,

A Black hole grows by absorbing everything nearby, during its life-cycle. By absorbing other stars, objects, and by merging with other black-holes, they could form Super massive Black-holes

  • When two black-holes come to merge, don't they rotate with an increasing angular velocity as they come closer and closer (what causes the difference of it from a neutron star. I mean who's POWERFUL..?)

And also, it says,

Inside of the event horizon, all paths bring the particle closer to the center of the black hole.

  • What happens to the objects that are absorbed into a black-hole? Which state they really are now..? They would've already been on plasma during their accretion spin. Would they be on the surface (deposited) or would they still be attracted and moved towards the center..? If so, then the surface of black-hole couldn't be a SOLID...

Is this question really ambiguous? (Sorry, But please comment if I've asked wrong...)

share|improve this question
add comment

1 Answer

up vote 2 down vote accepted

An object isn't necessarily heated to a plasma when it falls into a black hole. With quasars matter spirals down towards the event horizon so both it's speed and density increases, but this doesn't heat it directly. It's because matter interacts with the other matter around the event horizon that you get collisions and heating and the spectacular X-ray emission.

By contrast the black hole at the centre of our galaxy is thought to be fairly quiet because it's already gobbled up all the matter in it's vicinity. If you jumped into it you'd probably make it through the event horizon unharmed and it would only be near the singularity that tidal forces squished you.

You need to bear in mind that once matter has passed the event horizon it's fall to the singularity is very quick, so there isn't very much matter within the event horizon that hasn't already fallen into the singularity. What happens to the matter at the singularity no-one knows.

Response to comment: my point is that an acretion disk isn't a feature of all black holes. Accretion disks only form where a black hole is actively swallowing matter. Also accretion disks will form around any heavy object. Arguably Saturn's rings are a form of accretion disk with the matter in them eventually falling into Saturn.

My other point is that for matter falling into a black hole nothing special happens when it crosses the event horizon. If you were falling into a black hole then you wouldn't be able to detect when you had crossed the event horizon. So if you had been heated up by friction in an accretion disk before you hit the event horizon you'd be in pretty much the same state after you'd crossed it.

The state you're in, whether it's plasma or not, is dependant on how much you got heated up as you fell through the accretion disk (if an accretion disk is present) and is not anything specifically related to the presence of an event horizon.

share|improve this answer
Sorry. But, could you please elaborate your answer for my first question to provide a better understanding. Why do you say "not necessarily heated to plasma"... While spinning in the accretion, don't friction heat the objects to plasma? –  Waffle's Crazy Peanut Aug 30 '12 at 0:23
add comment

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.