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Nuradnan
2004-Jan-22, 09:23 AM
The first stage is nebula, right? Then, by condensation, nebula becomes star. There is thermonuclear fusion reaction there, right?

The first stage of fusion is two hydrogen atoms fused, become a helium atom. Helium atom is heavier than hydrogen atom. But a helium atom is slightly lighter than two hydrogen atom. There is a mass defect. So, is it true that nebula mass is greater than star' s?

Let us continue. Star evolves. Finally, it may becomes Black Hole. If star is lighter than nebula, is Black Hole is lighter than star :unsure: ?

GOURDHEAD
2004-Jan-22, 09:43 PM
The black hole is less massive than the initial mass of its progenitor star for a number of reasons. During its life the star via stellar wind expels the equivalent of several jovian mases. The supernova explosion just prior to the formation of the black hole will expel several Sol masses out into the universe to be used by the star forming processes leading, probably, to folk like us. Also, billions of kilograms of mass will have been converted to photons and radiated away during the star's life.

Matthew
2004-Jan-23, 12:55 AM
Though a black hole can also later absorb matter to become heavier than its mass as a star, but only if there is mass around for it to absorb.

lazserus
2004-Jan-23, 05:20 PM
On top of that, a nebula is normally nursery for birthing stars. Nebulae are normally span minimally a few hundred light-years. Nebula mass will always be greater than star mass.

Tiny
2004-Jan-23, 06:07 PM
Comparing to the masss of BH and Nebulae, I think Black Hole has the most powerful mass - not even light - can escape.

GOURDHEAD
2004-Jan-23, 10:56 PM
The black hole has the greater density and, therefore, usually a stronger gravitational field at a given distance from its center of mass as compared to either the cloud or the star.

Matthew
2004-Jan-24, 05:52 AM
Comparing to the masss of BH and Nebulae, I think Black Hole has the most powerful mass - not even light - can escape.

Thats just because of density, a stellar size black hole has much less mass than a nebula. So infact a nebula has a bigger gravitational field than a black hole, when looking at a still reasonbly strong gravitational effect). But when you are close to a black hole the gravitational field is much more powerful because of the density of the matter which is much higher than in a nebula. But when you get further away, the gravity of the nebula will be stronger because it has a greater mass.

Tiny
2004-Jan-24, 07:32 AM
What happen when u put a Black Hole in a middle of the Nebula gas?

Matthew
2004-Jan-27, 01:44 AM
Well I suppose it would suck up the gas nearby, which would increase its mass so it could suck up mass from further away, ect, ect. Until it absorbed the entire nebula, or most of it. And so it would be a massive, maybe even a supermassive black hole.

Tiny
2004-Jan-27, 01:56 AM
What about both of the BH and NG has the same amout of mass and density? What will happen?

GOURDHEAD
2004-Jan-27, 01:34 PM
What about both of the BH and NG has the same amout of mass and density? What will happen?

Assumptions are important. For a black hole and a large cloud of the same mass separated by 10 times the radius (or largest dimension if not spherical) of the cloud, first the mutual attraction will draw them together. Then since the black hole occupies a smaller volume of more severely warped spacetime, it will first come into contact with a much smaller portion of the mass of the cloud which it will consume and continue to do so until the cloud is consumed or until they are separated by their relative velocities due to initial conditions.

GOURDHEAD
2004-Jan-27, 01:57 PM
I forgot to mention that assuming that the BH and the NG have the same density is beyond my comprehension!!