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Jay Wacker1 (professor of physics at the SLAC National Accelerator Laboratory) stated:

The first stars (known as Pop III) were made out of hydrogen and helium. They had no planets.

Why couldn't they have had gas planets?

[1] Requires login at LinkedIn

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This question is more extensively referenced and cited than most answers on the site. – Andrew Nov 14 '11 at 20:57
up vote 8 down vote accepted

The earliest stars did not have planets primarily due to a lack of metals. Metals in this sense is an element (with some extra properties that are not relevant in this context) heavier than helium. The very article that you linked to references this. This leads to the following:

  1. Stars without metals tend to not last very long. Metals in a star act to slow down the reaction speed of the fusion. Without metals, the stars quickly get to a state where they will explode. Short time scales do not allow for enough time to form planets.
  2. Metals seem to be the initial building block of planets. This wikipedia article discusses the current leading theories for rocky and gas planets. Basically, they both start with a rock forming that's big enough, leading to a chain effect which ends up to be a planet. Rocks can't form from hydrogen and helium, making planet formation difficult.
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(The Wikipedia link is a redirect. Where did you get the link? On Wikipedia itself?) – Peter Mortensen Nov 15 '11 at 9:13
If metals are initial building blocks, how could the (Pop III) stars form in the first place? – Peter Mortensen Nov 15 '11 at 9:15
@PeterMortensen: Yes, I did get it from wikipedia, oddly enough. Hmmm... As far as being the initial building blocks, they are only the blocks for smaller objects. Stars form from a different mechanism, which is hard to form smaller objects like planets. – PearsonArtPhoto Nov 15 '11 at 14:10
@Pearsonartphoto: I still don't know... Couldn't there be some 'failed stars'? – Count Zero Jan 6 '12 at 23:19
@CountZero: there definitely are 'falied stars' out there: – Jerry Schirmer Jun 9 '12 at 16:09

Several answers occurred to me.

  1. Timescale. Pop III stars only last a few million years. This article, which is billed as as evidence for a much shorter timescale of planetary formation than previously thought, still quotes 10 million years (caveat: for terrestrial planets, but I didn't find a source right off the bat for gas giants). However, if I'm wrong there, there's always these other answers:

  2. In continuation of the discussion of How can a Population III star be so massive? the metallicity may be a factor. The original stars had virtually no metals, which made their cool down much, much less efficient. For the same reason that you can get larger stars that way, perhaps there won't be much material left over for planet formation?

  3. The upper layers of very large, fluffy stars are barely gravitationally bound, and they have enormous stellar winds. Maybe such massive winds and/or the enormous luminosity of a Pop III star either prevent planets from forming in the first place, or ablate embryonic planets into oblivion?

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I'm not sure there is a reason for not also having pop III stars with low mass. Metallicity increases opacity, which greatly affects the high mass stars. Does it also make it hard for low mass (say the mass of the sun) to form? Stars below 2-3 solar masses should last at least a billion years. – Omega Centauri Nov 18 '11 at 23:16
The slow-cooling, quasi-static contraction mechanism responsible for the existence of really huge stars is just as plausible a reason for a corresponding suppression of the formation of small stars. Unless there's a study by a specialist that contradicts me... – Andrew Nov 23 '11 at 19:18

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