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Chapter_22_Dark_matterx_dark_energy_x_Universe_summary -...

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Chapter Summaries Chapter 22: Dark Matter, Dark Energy, Fate of Universe (don’t forget to find definitions at the end of the book, in the glossary and draw pictures!!!!!) 1. Dark Matter: An undetected form of mass that emits little or no light but whose existence we infer from its gravitational influence 2. Dark Energy: An unknown form of energy that seems to be the source of a repulsive force causing the expansion of the universe to accelerate 3. Contents of the Universe Normal” Matter: ~ 4.4% Normal Matter inside stars: ~ 0.6% Normal Matter outside stars: ~ 3.8% Dark Matter: ~ 23% Dark Energy ~ 73% 4. Rotation curves and their meaning (Spiral galaxies all tend to have flat rotation curves, indicating large amounts of dark matter) 5. Broadening of spectral lines in elliptical galaxies tells us how fast the stars are orbiting, indication these galaxies contain dark matter. 6. The mass found from galactic motions in a cluster is about 50 times larger than the mass in
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Unformatted text preview: larger than the mass in stars! indicating lots of dark matter a) Clusters contain large amounts of X-ray emitting hot gas b) Temperature of hot gas (particle motions) tells us cluster mass: 85% dark matter 13% hot gas 2% stars 7. Ways to measure or get indication of dark matter a) measure velocity of cluster galaxies b) measure temperature of its hot gas c) gravitational lensing 8. Dark Matter is more than likely made of WIMPS: Weakly Interacting Massive Particles: mysterious neutrino-like particles 9. The gravity of dark matter seems to be what drew gas together into protogalactic clouds, initiating the process of galaxy formation 10. Galaxies appear to be distributed in gigantic chains and sheets that surround great voids 11. Fate of Universe depends on the amount of dark matter. a) Brightness of distant white-dwarf supernovae tells us how much universe has expanded since they exploded b) Accelerating universe is best fit to supernova data...
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