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Hubble Law

# Hubble Law - cluster The Hubble Law applies for only the...

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Hubble Law The galaxy (a) astronomers see the other galaxies moving away from them and their home galaxy appears to be at rest. Now jump to galaxy (c). To the astronomers on galaxy (c), galaxy (a) is moving away at 1,540 kilometers/second and galaxy (b) is moving away at 770 kilometers/second. Their home galaxy (c) appears to be at rest. You can use similar reasoning to show that everybody will also get the same numerical value for the Hubble constant. The figure above also illustrates another point about the expansion. Notice that the sizes of the dots and the size of the threesome group at center-top do not change. The galaxies themselves do not expand and the galaxies inside a cluster do not expand away from each other. On small size scales, the internal gravity of a galaxy or galaxy cluster prevents the expansion inside the galaxy or galaxy

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Unformatted text preview: cluster. The Hubble Law applies for only the very large distances. Another example of how everyone will see the same Hubble Law is given in the figure below. Each of the galaxies in the figure is 100 million parsecs (about 300 million light years) apart from each other and the Hubble constant is set to 75 km/sec/Mpc here. If you choose galaxy C to be your home galaxy, then you will see galaxies B and D moving at 7,500 kilometers/second away from you because they are at a distance of 100 megaparsecs from you. Galaxies A and E are 100 megaparsecs from their closest neighbors, so they are moving away from them at 7,500 kilometers/second and 15,000 kilometers/second away from galaxy C since they are each 200 megaparsecs from galaxy C. What would the galaxy speeds be if you chose galaxy D or galaxy E as your home galaxy?...
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Hubble Law - cluster The Hubble Law applies for only the...

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