The Star That Exploded At the Dawn of Time

sciencehabit writes To probe the dawn of time, astronomers usually peer far away; but now they've made a notable discovery close to home. An ancient star a mere thousand light-years from Earth bears chemical elements that may have been forged by the death of a star that was both extremely massive and one of the first to arise after the big bang. If confirmed, the finding means that some of the universe's first stars were so massive they died in exceptionally violent explosions that altered the growth of early galaxies.

Re:Why can't hydrogen cool?

[tysonedwards]

It's deceptive. At this point in time, the universe was quite small relatively speaking. As such, the density of those materials was still sufficiently high that the materials were in a persistent plasma state even though they weren't a "star", however fusion was still taking place converting Hydrogen to Helium. At this point, we're talking about all matter in the Universe occupying something not much larger than the Milky Way after all, maybe a little larger considering that we're talking about very, very fast expansion of the universe and the difference of a second amounts to a light year or so of growth. As the Universe continued to expand outwards and the material became less dense, it allowed for the material to actually split apart from one giant clump of hydrogen, helium and lithium and begin to actually get some empty space. As that empty space formed, then this plasmatic cloud could coalesce into the first stars. As long as there was these plasma clouds and not "empty space", then yes, there was "nothing" yet in which the material could *cool* into.

Re:Why can't hydrogen cool?

[ShanghaiBill]

I appreciate your explanation, but honestly, what you say makes no sense. To be blunt, I don't think you know what you are talking about. You say that the Universe was the size of the Milky Way, and expanding by a light year per second. Since the Milky Way is only 120,000 light years across, if the Universe was really expanding that quickly, it would be bigger than the Milky Way in ONE DAY. You also say that hydrogen fusion was occurring, but according to this graph [wikipedia.org], fusion stopped three minutes after the big bang. There is nothing that you say that would only apply to H-He-Li and would not apply to heavier elements.

I found the following explanation here [harvard.edu]:

Hydrogen and helium are, by far, the most abundant elements in interstellar clouds. However, these elements are very poor coolants because they cannot be collisionally induced to emit photons at the low gas temperatures characteristic of molecular clouds. Two decades of theoretical studies have consistently predicted that a large fraction of the total cooling is borne by a few other atoms and molecules, notably gaseous water (HO), carbon monoxide (CO), molecular oxygen (O), and atomic carbon (C).