text: Indeed some do as stated above, usually due to the accretion forces of a supermassive black hole, like the 200,000 solar mass one at the center of our galaxy, or the 2,000,000 solar mass one at the center of galaxy M87. Surrounding them are dead stars in the form of dwarves, or even some very ancient population II stars.\n\nA few things that were incorrectly stated, are that galactic rotation CAN be measured, but it is immensely slow (we are talking one rotation across maybe a couple hundred million years or so, for small galaxies).  Considering that our average-sized milky way is 35,000 light years across, travelling linearly down the center, it would take our sun (going 60,000 km/h) 630,000,000 years to reach the other side. Since it is travelling circularly, it would take something closer to a billion or so years. Likely our solar system has completed about one or two "galactic years," but it is a slow, slow process.\n\nFurthermore, not all galaxies rotate, however. Newer galaxies, such as clusters, have no center point nor supermassive black hole, so they are for the most part stationary in terms of rotation.\n\nThe blackhole at the center of our galaxy, as I state above, is closer to 200,000 times the mass of our sun, not the giant underestimation of 1000 times as stated above.\n\nAnd despite what is says below there isn't a "blackhole at the center of our universe." They are the centroids of galaxies, not the universe. There is no central, universal rotation point as such. Also the explanation below fails to explain why galaxies are denser in their centers - and even then some aren't. Yet the user still complains about other answers' inaccuracies...