Can somebody explain accretion of galaxies?

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Can somebody explain accretion of galaxies?

In: Physics

2 Answers

Anonymous 0 Comments

Not really, the process of galaxy formation is not well understood.

We know that most of the big ones have supermassive black holes in the center, but it’s unclear if those came first or even how such a gargantuan object can gather so much mass over such a relatively short period of time.

We also know that many large galaxies appear to exert significantly more gravitational force than their observable matter would suggest, implying there’s an unknown “dark matter” providing additional mass and assisting formation and stability.

What this dark matter is, when and how the black holes formed, and how quickly the galaxy structure accumulates is still an active debate.

Anonymous 0 Comments

Short answer: In a cloud of randomly moving particles (whether those particles are dust or stars, it doesn’t matter), there is an average center of mass (where gravity will try to pull everything) and an average angular momentum around that center of mass. Since the particles can bump into each other (or in the case of stars, gravitationally attract each other in a way that mimics friction), all motion except for that average rotational speed eventually gets canceled out, flattening the mass into a disk. Gravity pulls things inwards, and due to conservation of angular momentum, the more things get pulled inwards, the faster they spin and the more they can resist being pulled inwards. Eventually, everything stabilizes into a spinning disk.