Hacker News Reader

It's amazing, yes, and at the same time, it makes perfect sense.

(Somewhat) similar mechanisms are at work whether you're pulling together stars into a galaxy, hydrogen gas into a solar system or water towards the drain of your bath tub - a pull towards the center, the centripetal force, slight variations producing "artifacts".

View on HN

Well, I would not call these two mechanisms similar, though the artifacts may be similar. I wonder if in fact the spirals are similar, for that matter if mathematicians even have terminology for different types of spirals.

The spirals shown in the paper do look like idealised spirals of very young galaxies, shortly after the bar phase. I wonder, other than spirals, what other artifacts such processes might cause.

Imagine an accretian disk undergoing fusion in spiral-shaped filaments!

Also, galaxy spirals are very much an open question. Galaxies don’t rotate the way you’d expect from the matter you see, and it’s the main reason we hypothesize the existence of dark matter. Unless dark matter is the reason the Oort Cloud develops spiral arms, I’d wager the mechanisms are quite different.

> Galaxies don’t rotate the way you’d expect from the matter you see

In what way?

Given the stars' angular velocity, they should fly out away from the galactic center, but they stay confined to their disc.

Reply on news.ycombinator.com