Also, the orbits of stars around the galactic centre are very similar to the orbits of planets around stars-the spiral arms are just a kind of pressure wave caused by complicated interactions, individual stars follow normal orbits ( they are slightly different because the mass of the galaxy isn't dominated by the centre like that of a solar system is, but that isn't very important, it just affects the numbers a little ) .-- talk ) 00 : 17, 13 March 2010 ( UTC)
