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Galaxies, Dark Matter and the Universe
Galaxies are gravitationally bound systems of stars, planets, gas, and dark matter, existing in three major types: elliptical, spiral, and irregular. The Milky Way, our galaxy, contains 200 to 400 billion stars and is part of the Local Group, which will eventually merge into a supergalaxy. Dark matter, which does not emit light and is difficult to detect, is thought to comprise five times more mass than all ordinary matter combined.
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Galaxies, Dark Matter and the Universe
- 1. GALAXIES:! Island ! "Universes"! Stephen Perrenod, Ph.D.
- 2. What is aGalaxy? Gravitationally bound ! system of:! ! Stars! Planets! Gas! Dust! ! "Dark Matter" (mostly!)
- 3. 3 Major Typesof Galaxies Elliptical - M87! ! Spiral - M101! ! Irregular - NGC1427A Image credit: X-ray: NASA/CXC/SAO; Optical: Detlef Hartmann; Infrared: NASA/ JPL-Caltech
- 4. Our Galaxy: TheMilky Way 200 to 400 Billion Stars! ! A Spiral Shape! ! Size 100,000+ light-year Diameter ! (Only 1000 thickness)! ! Sun distance to center, 27,000 light-years! ! Rotates once per 240 million years Portion of # Milky Way NGC 6744
- 5. Milky Way! Schematic Bar, Spiral Arms &! You are Here!
- 6. Our Neighbor: AndromedaGalaxy Distance - 2.5 Million light-years ! ! Size - 220,000 light-years! ! Will collide with us in ~4 Billion years! M31
- 7. Andromeda Attacks! Lotsof time to prepare..
- 8. The Magellanic Clouds Southern Hemisphere objects, visible to the naked eye! ! About 200,000 light-years away! ! Large Magellanic Cloud is 14,000 light-years in size! ! Small Magellanic Cloud size is 7,000 light-years
- 9. The Local Group Our neighborhood!! ! 10 million light-years across! ! Will coalesce eventually into one Supergalaxy! !
- 10. Rich Cluster ofGalaxies ~ 1000 galaxies bound together! ! Along with dark matter and gas! ! High gravitational potential heats gas to 100 million degrees! ! X-ray emission Abell 2218
- 11. Stellar Factories Galaxiesare Huge! ! They are old ~ 13 billion years! ! They are factories for star formation and planet formation Orion # Nebula
- 12. Why Galaxies? Galaxiesexist so that multiple generations of stars can be created! ! Stars exist to create elements for, and provide heat and light to, planets! ! Planets exist as friendly abodes for life:! Including You!
- 13. Dark Matter Ourgalaxy is mostly made of mysterious "Dark Matter"! ! Not stars or light-emitting gas, but gravitational effects seen! ! All galaxies and clusters of galaxies are like this! ! Harvard computer simulation
- 14. What does "DarkMatter" mean? Simply, matter that is hard to detect because it doesn't emit light! ! But it has mass, so has gravitational effects! ! Thought to be some kind of new, unknown matter Abell 1689
- 15. Ways to DetectDark Matter's Gravitational Effects Galaxy rotation curves! ! Clusters of galaxies, X-ray emission! ! Gravitational lensing
- 16. How Much DMis there? 5 times as much as all ordinary matter!
- 17. What is itcomposed of? We don't know!! ! NOT candidates: faint stars, black holes, dust, planets, lumps of coal! ! Candidates are all hypothetical new particles!! ! WIMPs (LSP - neutralinos)! Axions! Sterile neutrinos
- 18. Thank you! Cosmologyblog:# darkmatterdarkenergy.com