• Question: What percentage of the Milky Way is made up of stars ?

    Asked by shasow15 to Colm, Eoin, Joseph, Lauren, Stephen on 14 Nov 2013.
    • Photo: Stephen Scully

      Stephen Scully answered on 14 Nov 2013:

      Considering that most of the universe is Dark matter and dark energy. I can only assume the same for the galaxy. Stars I would think is a couple of percent at most.

    • Photo: Eoin O Colgain

      Eoin O Colgain answered on 15 Nov 2013:

      The Milky Way is a spiral galaxy and it rotates.

      Interestingly, the rotation of spiral galaxies cannot be explained only through luminous matter (stars). The rotation curves of spiral galaxies tell us that there must also be dark matter. By this reasoning there is also dark matter in the Milky Way and various experiments are now looking for it.

    • Photo: Joseph Roche

      Joseph Roche answered on 15 Nov 2013:

      The Milky Way is the stars. So 100% I guess.

    • Photo: colm bracken

      colm bracken answered on 19 Nov 2013:

      I think you mean how much of the space in the Milky Way is made up of stars? This is a tough question, but I would try a guess at some really small number like 0.0000000001%. The reason for my tiny guess is because space within our galaxy is mostly empty. Consider our Sun which is about 1,391,000 kilometers across, and then consider that the nearest star to us in any direction is 4.3 light years away, or 40670000000000 kilometers. So the percentage of the Suns diameter to the distance between stars (roughly) is:
      1,391,000 / 40670000000000 x 100 / 1 = 0.00000342%.
      However this is a linear result. For a volume percentage (since space is three dimensional) the result would have about three times as many zeros. In fact my initial guess was probably a bit too big???

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