Both bottom-up and top-down galaxy formation theories revolve around gravity and its collapsing effects on gas in early galaxies. Bottom-up theories propose that this gas collapsed and compressed into clumps the size of a million suns. These smaller clumps (cosmically speaking) then got together to form enormous galaxies, like the Milky Way.
What can NASA teach us about Earth?
Answered by NASA (National Aeronautics and Space Administration)
Are all stars the same?
Answered by Craig C. Freudenrich and Science Channel
What are solar flares?
Answered by Science Channel