• Question: Why is the Milky way very thin but very wide?

    Asked by to Nick, Alan on 17 Mar 2014. This question was also asked by .
    • Photo: Alan Fitzsimmons

      Alan Fitzsimmons answered on 17 Mar 2014:

      It’s flat and wide because its slowly spinning. When the Milky way first formed it would have been a more blobby cloud of gas. The gravity of the gas makes it all collapse in on itself, but because it was slowly rotating, this stopped all the gas falling into the centre. It’s like a fairground swing ride, when you spin on one you feel an outward force, and this resists gravity.

      The amazing thing is the at the Milky Way spins really slowly at the edge, about once every 250 million years! But even that is enough to keep the thin, flat disk of stars and gad falling into the centre.

    • Photo: Nick Wright

      Nick Wright answered on 18 Mar 2014:

      We think that when galaxies like the Milky Way formed they form from a giant cloud of gas that collapses down into a disk-like shape, all the time spinning round and round. So gravity makes the cloud of gas become very thing, but the rotation of the galaxy makes it very wide and stops it completely collapsing down into a point.

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