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how does the movement of stars compare to the movement of planets
Actually, the seasonal movement of the Earth around the Sun causes nearby stars to shift apparent position. This is called parallax, and it is the only direct means of measuring the distance to objects outside our solar system. This indeed makes the apparent positions of nearby stars wobble back and forth, though the variations are small and require careful observation and measurement.One more note about the difference between the apparent position of stars vs. planets is that a planet can appear to change the direction it's going and then go backwards and then forwards again. As far as I know a star can't do this, except for maybe the tiny wobble of a binary star which wouln't have been observed by the naked eye.
Yes, each galaxy exerts gravitational force on every other galaxy in the local group, just like the supermassive black hole in the center of our own galaxy that causes the stars to orbit around it. Also, a cluster of galaxies can be gravitationally attracted to other galaxy clusters, which causes it to move across space if space isn't expanding too fast.What causes the local group to move? I mean, in a galaxy there's a black hole in the center that causes the stars to orbit around it, but in a cluster of galaxies, is there anything that can cause them to move so fast?
Ok thanks for clarifying. Haha I was under the impression that the galaxies didn't move...Yes, each galaxy exerts gravitational force on every other galaxy in the local group, just like the supermassive black hole in the center of our own galaxy that causes the stars to orbit around it. Also, a cluster of galaxies can be gravitationally attracted to other galaxy clusters, which causes it to move across space if space isn't expanding too fast.