A nebula is made of dust (elements heavier than He and H) and gas (H and He).

Stars are made when nebulae's collapse and hydrogen begins to fuse. 99% of nebula material goes into making the star. The left-over 0.01 of debris creates planets.

Does 99% of nebula material that makes the star only consist of gas (He/H) and the 0.01% is the dust which makes the planets?

Question Clarification:

Are the constituents of the 99% of mass that makes the star and the 0.01% mass that makes the planets the same?


  • Does both the 99% and 0.01% compose of mainly He/H and a small portion of metals (meaning the star contains heavier elements like Si and Fe etc before fusion?)
  • is 99% of the nebula composed of He/H, which collapses to form the star, and 0.01% consists of heavier elements that make the planets?
  • 1
    $\begingroup$ A small portion of the star are metals (elements heavier than He and H). The star's percentage of metals, along with its mass, determine its fate when it dies. $\endgroup$ Commented Jun 27, 2016 at 19:46
  • $\begingroup$ But are the small portion of metals in a star from fusion or the initial nebula it self? What I mean is the 99% of nebula that makes up a star, mainly He/H and a small portion of heavier elements (meaning the star has heavy elements like iron before fusion), or is it just He/H that creates the sun while the small portion of metals creates the planetary bodies? $\endgroup$
    – G. Gip
    Commented Jun 28, 2016 at 11:05
  • $\begingroup$ The ones that allow its fate to vary are from the initial nebula itself. And its more of a combination. The metals form planets, but a small percentage of the stars is also metals from the initial nebula. $\endgroup$ Commented Jun 28, 2016 at 15:21

1 Answer 1


The very first stars to form indeed consisted essentially only of hydrogen and helium. When stars die, they leave behind them more massive atoms, as you say. These heavier elements are too incorporated in newer stars when they form. This results in stars which start out with a lower portion of hydrogen and helium, thus making them somewhat less effective; see for example this question and answer. The Sun, for instance, is a so-called third generation star, which means that it is made up of materials which have already been used at least twice since the Big Bang, and thus naturally contains heavier elements it has not produced itself.

  • $\begingroup$ Metallicity (anything but hydrogen, helium, and lithium are metals to astronomers) makes a star more effective rather than less effective. That tiny bit of waste has but a tiny effect on fusion but it has a very large effect on how a star transfers heat from the core to the surface. $\endgroup$ Commented Jun 28, 2016 at 15:20
  • $\begingroup$ By calling it a third generation star, I think you are misunderstanding what Rob Jeffries was saying. All he said was that the material has been produced by at least two stars — it is likely that billions preceded the Sun. $\endgroup$ Commented Jun 28, 2016 at 15:28
  • $\begingroup$ @DavidHammen If anything, it makes the star more opaque and hinders radiation pressure from escaping. No idea why you call that "more effective". $\endgroup$ Commented Jun 28, 2016 at 15:31
  • $\begingroup$ @SirCumference You are right, I'll change my answer. $\endgroup$ Commented Jun 28, 2016 at 16:30

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .