When a star burns out, what is the compostition of what's left? Is it carbon, etc?

Answer 1

Like everyone said it depends on size and mass of stars. Low mass stars burn quickly and whats left over is a white dwarf. It is mostly a helium ash core.

High mass stars eventually go out with a bang - called a supernova and depending on how many solar masses of material is left (or something like that) you can end up wither either a black hole or a nebulla. High denisty areas of nebulla is where new star formation occurs.

Answer 2

All stars begin life as almost pure hydrogen, with a tiny fraction of heavier elements present. The star ignites when hydrogen to helium fusion begins. When the hydrogen becomes exhausted the star will collapse creating the pressure and temper needed to start helium fusion, which yields heavier elements like carbon. Some small stars burn out at the helium fusion stage because they haven't the mass to burn the heavy elements. These remnants of red dwarf stars are mostly carbon.

Calculations predict that our own Sun will end in a carbon red dwarf.

More massive stars will blow off most of their mass in a nova explosion, the remnant in those cases will be either a black hole or a neutron star. Neutron stars are composed of degenerate matter in which the protons and electrons of normal matter have been crushed together to form neutrons. This material, sometimes called neutronium, has no chemical properties at all, and is unlike any kind of matter we are familiar with. It's just very heavy stuff.

Answer 3

It'll depend on the size & mass of the star. If it's been manufacturing helium, and isn't massive enough to undergo the Carbon flash, then a core of helium will be the only thing left. Other, more massive stars will continue to burn material into heavier elements, and (as you'd expect) the heavier the element, the closer to the core it'll be - so you'd get a burnt-out star with layers of materials (provided the star's collapse and explosion didn't scatter everything.)

Answer 4

It depends on the size of the star. After a trillion years, a red dwarf will leave behind a helium core. Sun-sized stars will burn down to carbon-oxygen white dwarfs. As the remnant cools, the carbon crystallizes, creating a core of ultra-dense diamond. Slightly larger stars leave behind oxygen-neon-magnesium white dwarfs. The outer envelopes of white dwarfs is mostly blown away during their red giant phase, which the smallest red dwarfs will not experience. More massive stars can fuse heavier elements, up to and including iron, but they collapse into neutron stars in which all semblance of atomic species has been eliminated.

Answer 5

I kinda like your question, and the other answers too. I looked into the iron sun thing, it sounds like a real minority opinion.

Sounds like what is left after a star burns out depends on the initial size of the star, and I put some references below. In the case of our sun it seems too small to burn past the carbon it produces in its fusion reaction.

Answer 6

Depends on the size. It could be a neutron star, in which all the atomic particles are crushed together to make what amounts to a single huge atomic nucleus, or a black hole, or a white dwarf (which is mostly iron).

Answer 7

It's core can comprise of anything from helium up to the atomic weight of iron but it stops there. To fuse iron atoms it takes energy to do that and not energy released being a by product.

Interesting website here that claims the sun is mostly iron
http://www.spaceflightnow.com/news/n0201/10ironsun/

Answer 8

I know at least some of it is iron, that's what it all degrades too ultimately.