The Short Life of an Active Galax1

The Short Life of - and active galaxies can last for only a few billion years at most Quasars tend to be found at great distances from us there are

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The Short Life of an Active Galaxy Galaxy nuclei do not remain active for billions of years. Eventually, the gas fuel runs out in the accretion disk. The disk's gas can be replenished if some stars in the galaxy wander too close to the central black hole and get stretched apart by the black hole's strong gravity. Select the link below to show a spiral galaxy turning into a quasar when some material is dumped onto the supermassive black hole at the center. It is a mpeg movie, so you will need to have a mpeg viewer. Quasar movie from the Space Telescope Science Institute Also, galaxy mergers and collisions will keep the gas and stars in the central part of active galaxies sufficiently stirred up so some of that material will become part of the accretion disk. The expansion of the universe decreases the rate at which interactions will happen. Because the frequency of galaxy close encounters decreases over time as the universe expands, the quasars
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Unformatted text preview: and active galaxies can last for only a few billion years at most. Quasars tend to be found at great distances from us; there are no nearby quasars. When we look at quasars, we see them as they were billions of years ago. The number of them increases at greater distances, so that must mean they were more common long ago. The number of quasars peaks at a time when the universe was about 20% of its current age. Back then the galaxies were closer together and collisions were more common than today. Also, the galaxies had more gas that had not been incorporated into stars yet. The number of quasars was hundreds of times greater than the time closer to the present. At very great distances the number of quasars drops off. The light from the most distant quasars are from a time in the universe before most of the galaxies had formed, so fewer quasars could be created....
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This note was uploaded on 12/15/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.

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