WHAT CAME FIRST: GALAXIES OR BLACK_HOLES?

WHAT CAME FIRST: GALAXIES OR BLACK_HOLES?

Astronomers have developed two models for how the large scale structure of the Universe came together: 

(1) the top_down_model and 

(2) the bottom_up_model

In the top-down model (i.e. one big event that leads to the structure we see today), an entire_galactic_supercluster formed all at once out of a huge cloud of primordial hydrogen leftover from the Big_Bang. A supercluster’s worth of stars. 

As the cloud came together, it spun up, kicking out smaller spirals and dwarf galaxies. These could have combined later on to form the more complex structure we see today. The supermassive black holes would have formed as the dense cores of these galaxies as they came together. 

The assumption made is that a single cloud of gas and dust forming multiple stars systems within it. Over time, the stars matured and drifted away from each other. 

In the bottom-up model (i.e. small parts coming together forming what we see today), pockets of gas and dust collected together into larger and larger masses, eventually forming dwarf galaxies and even the clusters and superclusters we see today. The supermassive black holes at the heart of galaxies were grown from collisions and mergers between black holes over eons. 

This is the concept of how pieces of dust attracting one another into larger and larger grains finally formed the planet-sized objects, over millions of years. 

Shortly after the Big Bang, the entire Universe was incredibly dense. But it wasn’t the same #density everywhere. Tiny quantum fluctuations in density at the beginning evolved over billions of years of expansion into the galactic superclusters we see today.