Assume we have a gridded cube of $10^{57}$ hydrogen atoms, with all atoms 1mm apart from other atoms. This 'cube cloud' is in an area of space that would otherwise be at zero g, were it not for the huge grid of atoms of course.

1) Would this cloud collapse into a star?

2) If it did start to collapse, what would be the primary driver - residual electromagnetic forces or gravitational forces? Or do both contribute, but at different stages of the collapse?

3) If it wouldn't collapse, what would cause it to collapse? A smaller grid? One atom offset near the centre of the grid? A mix of different kinds of atoms? A few ions?

  • 3
    $\begingroup$ EM forces should mostly contribute to forming molecular hydrogen. Otherwise, given some time gravity should do its work. Your cube, by the way, is a light year across. $\endgroup$ – LLlAMnYP Jan 23 '16 at 14:34
  • $\begingroup$ It's dynamical. With the simpliest model : the shell theorem says that there is a net force from any dot of the grid to the center of gravity. There are also 6 other forces due to the lack of sphericity and the heat negative pression. The whole stuff will collapse if the gravity is stronger. But while it collapses, the heat increases until an equilibrium. Residual EM interactions may help to break the latter , I don't know ... The equations are more explicit but it's better to wait an expert to get a normalized answer $\endgroup$ – user46925 Jan 23 '16 at 14:45
  • $\begingroup$ For 1, what does the Jeans criteria tell you? $\endgroup$ – Kyle Kanos Jan 23 '16 at 15:02
  • $\begingroup$ considering we are talking about a cube a cube, would this microscopic effect play out on the macroscopic? - physics.stackexchange.com/q/231114 $\endgroup$ – Amphibio Jan 23 '16 at 16:23
  • $\begingroup$ That's a bit under a solar mass, and you've proposed a density (1 billion atoms per cubic meter) much higher than that observed in a typical nebula, so you are likely to get some kind of compact body, but the dynamics of nebular collapse are complicated, and I won't venter a guess as to how much mass will be lost. $\endgroup$ – dmckee --- ex-moderator kitten Jan 23 '16 at 17:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.