Term
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Definition
| the extremely bright center of a distant galaxy, thought to be powered by a massive black hole |
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Term
| What evidence suggests that small galaxies in our Local Group have undergone two or more starbursts in the past? |
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Definition
| We see small galaxies in which many stars have one age and many others have another age that is billions of years older. |
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Term
| Why should galaxy collisions have been more common in the past than they are today? |
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Definition
| Galaxies were closer together in the past because the universe was smaller. |
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Term
| We can study how galaxies evolve because ______. |
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Definition
| The farther away we look, the further back in time we see. |
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Term
| According to the theory that active galactic nuclei are powered by supermassive black holes, the source of energy that supplies the power is _____. |
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Definition
| gravitational potential energy released by matter that is falling toward the black hole. |
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Term
| The most active galactic nuclei are usually found at large distances from us; relatively few nearby galaxies have active galactic nuclei. What does this imply? |
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Definition
| Active galactic nuclei tend to become less active as they age. |
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Term
| The relationship between the masses of central black hole and the bulge masses of galaxies implies that: |
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Definition
| Galaxy formation and supermassive black hole formation must be related somehow. |
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Term
| Which of the following is not a strong argument for the theory that some large elliptical galaxies formed as the result of galaxy collisions? |
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Definition
| Galaxy collisions are common and most galaxies in the universe are elliptical. |
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Term
| Hot gas erupting into intergalactic space from a large superbubble is called a ____________. |
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Definition
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Term
| The most luminous objects in the universe are ____________. |
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Definition
| quasars|QSOs|quasi-stellar objects |
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