• Question: If gravity keeps celestial bodies like planets and stars spherical, then why are galaxies a spiral or disc shape?

    Asked by Dracomagic to Anne, Beth, COLFlight, Jon, Tom on 7 Oct 2015.
    • Photo: Columbus Flight Directors

      Columbus Flight Directors answered on 7 Oct 2015:

      Hi Dracomagic, this is a very interesting question of which I don’t know for sure the answer. Actually I think nobody know the answer for sure, there are theories about it and astronomers are still studying the subject.

      What I can say is that there is a big difference between celestial bodies and galaxies (or even Solar systems): the celestial bodies are very dense aggregates of mass, while in galaxies and solar systems the different celestial bodies are extremely far one from the other. So what I can guess is that gravity plays a different role between the two.

      Did you see that very nice recent video that shows to scale how far are the planets in our Solar system?
      Here it is: https://www.youtube.com/watch?v=zR3Igc3Rhfg