A dark star is a hypothetical type of star that may have existed early in the universe long before conventional stars were able to form and thrive. High concentrations of neutralino dark matter within them would generate heat via annihilation reactions between the dark matter particles. This heat would prevent the star from collapsing into the relatively compact and dense size of modern stars and therefore prevent nuclear fusion between the normal matter atoms inside from being initiated. A dark star is predicted to be an enormous cloud of molecular hydrogen and helium ranging between 1 and 960 astronomical units (AU) in radius with a surface temperature reaching upwards of 10000K..