Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: acecharly on 28/08/2012 10:51:56

Title: If a blackhole lost mass, would it swell up?
Post by: acecharly on 28/08/2012 10:51:56

If a blackhole were to lose enough mass that it droped below the chandrasekhar limit, would it suddenly expand like it suddenly shrunk when it went above the limit?

Any thoughts

Cheers Ace

Title: Re: blackhole question
Post by: imatfaal on 28/08/2012 16:00:45

Ace - No.  The limits are specifically for stars - above and one thing happens, below and something else.  They are based on the characteristics of stars and don't hold for black holes or neutron stars.  An aging star at a certain temperature, size, fuel-left etc has various things that can happen to it - and we can estimate that very well by just the mass; but once the star has proceeded down one course the density/compostion change is often so extreme that the path is irreversible. 

Title: Re: If a blackhole lost mass, would it swell up?
Post by: evan_au on 30/08/2012 10:46:59

Once a star becomes a neutron star, the gravity becomes so much more intense that it stays a neutron star.

Once a neutron star becomes a black hole, the gravity becomes so much more intense that it stays a black hole.

There is a theoretical mechanism called Hawking radiation that allows a black hole to evaporate, but it has the biggest impact on very small black holes (eg with a mass less than a gram, not ones with the mass of a star). http://en.wikipedia.org/wiki/Micro_black_hole

Title: Re: If a blackhole lost mass, would it swell up?
Post by: Soul Surfer on 01/09/2012 19:00:50

A stellar mass black hole can loose mass if it is placed in a very cold place much colder than the current temperature of the cosmic microwave background radiation so it will not start to loose mass by radiation until the universe gets a lot colder than it is now.  However as it radiates away its mass it will get smaller and hotter over trillions of trillions of years and finally go out with a small bang about as bright as a big solar flare.