A body intermediate to stars and galaxies

[Loren Booda]

Out of the primordial hydrogen, what were the largest star and smallest galaxy that eventually formed?

 

[turbo]

Who can say? According to the BB model, the largest star formed from primordial materials (it is assumed that the BB created more than just Hydrogen, by the way) is LONG since gone, and the smallest galaxy ( if it still exists) is undetectable due to low luminosity.

 

[Chronos]

Enormous primordial stars [>200 solar masses] are thought to have been very abundant. Large numbers of early supernova are needed to explain reionization, primordial metallicity and create the black hole seeds responsible for quasars. These behemoths would only last around 100 million years before detonating. The earliest large structures were probably globular clusters. They apparently play a role in galaxy formation.

 

[hellfire]

Apart from these big primordial population III stars, I do not see how larger objects could actually have formed. Immediately after decoupling, the Jeans mass is about 10⁵ solar masses (the mass of globular clusters, as Chronos mentioned). This structures will be the first protogalactic clouds, which will merge and cluster. However, the formation of a massive body (assuming you had that in mind) on such a scale is actually not possible, since it takes place isothermal collapse of the cloud, which leads the Jeans mass to decrease (density increase), and produces fragmentation into smaller clouds. When the cooling of the cloud is not longer possible, the temperature does not longer remain constant and this process is stopped, leading to the formation of stars.