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| the theory that the massive black hole in our galaxy sends compression waves thru the galaxy and creates new spiral arms |
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| material between stars gas and dust |
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| hydrogen spin flip –radio waves |
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| 90 percent of matter in galaxy |
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| particles shot out by supernova |
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| carbon and silicate dust between stars |
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| bluish from dust reflection |
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| prime areas for formation |
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| 20% of all galaxies –lots of dust and gas—normal most abundant of spirals |
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| 80% of all galaxies—most are dwarfs the super large ones eat others |
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| each type of galaxy has certain absolute magnitude |
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| galaxies are not alone but in clusters |
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| 1 to 100 days –yardsticks to other galaxies |
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| how we use Cepheid’s to measure distance |
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| homogeneous and isotropic |
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| all bodies are moving away –further the faster |
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| time since the beginning of universe |
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| colliding galaxies—main reason |
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| quasi stellar objects –small energetic cores of early galaxies |
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| makes up 60 percent of dark matter |
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Definition
| stars do not slow down as they go around the galaxy because of dark matter |
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| galaxies orbit each other faster because of dark matter |
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| light is bent by galaxies more than it should because of dark matter |
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| massive compact halo objects –may be dark matter |
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| normal matter about 10 percent |
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| weakly interacting particles –may be dark matter |
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| clusters of galaxies and clusters of cluster called super clusters |
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| matter needed to open or close the universe |
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| high critical density so universe stops expansion and recollapses |
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| flat universe—this what we think it is—barely expanding |
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| that which dominates the baryonic materials in our universe |
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| universe expands out rapidly |
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| grand unification of all forces |
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| time at beginning that universe expanded quickly |
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| Cosmic microwave background— |
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| left over of early hot universe –3K now |
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| why is night sky dark—cannot have infinite size and infinite number of stars |
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| area around a star that life can exist |
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| probabilities of life that communicates in universe |
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