The researchers used cosmological simulations to recreate the first 700 million years of cosmic history, focusing on the formation of a single dwarf galaxy. In their virtual galaxy, waves of stars were born in short, explosive bursts as cold gas clouds collapsed inside a dark matter halo. Instead of a single starburst episode followed by a steady drizzle of star formation as Garcia expected, there were two major rounds of stellar birth. Whole swarms of stars flared to life like Christmas tree lights.<\/p>\n
\u201cThe early Universe was an incredibly crowded place,\u201d Garcia said. \u201cGas clouds were denser, stars formed faster, and in those environments, it\u2019s natural for gravity to gather stars into these tightly bound systems.\u201d<\/p>\n
Those clusters started out scattered around the galaxy but fell in toward the center like water swirling down a drain. Once there, they merged to create one megacluster, called a nuclear star cluster (so named because it lies at the nucleus of the galaxy). The young galactic heart shone with the light of a million suns and may have set the stage for a supermassive black hole to form.<\/p>\n<\/p>\n
\n A simulation of the formation of the super-dense star clusters.<\/p>\n
A seemingly simple tweak was needed to make the simulation more precise than previous ones. \u201cMost simulations simplify things to make calculations more practical, but then you sacrifice realism,\u201d Garcia said. \u201cWe used an improved model that allowed star formation to vary depending on local conditions rather than just go at a constant rate like with previous models.\u201d<\/p>\n