Astronomy notes - Astronomy 120 Dave Meyer Office Hours -...

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Astronomy 120 Dave Meyer Office Hours - MWF 12:30-1:30 Review Monday 7-8 Tech Lecture Room 3 September 26 Go to an observing session - each Wednesday at Dearborn Blackboard has practice pop quizzes and practice midterms April 13, 2029 No class Wednesday before Thanksgiving The universe is huge 93 million miles to sun 1 astronomical unit (AU) = 1.5 x 10^8 km, 150 million km It takes light 8 minutes to travel from sun to earth, distance is called 8 light-minutes The universe we see is the universe of the past September 28 Moon is 1 light-second away Mars is 4 light-minutes away when closest to Earth, 20 light-minutes when furthest Pluto is 5 light-hours Distance to nearest star (Alpha Centauri) is 4.3 light years Molecular clouds look cool when reflecting light They are where stars are formed Ex. Eagle Nebula, Horsehead Nebula, Cat’s Eye Nebula (Star dying) Stars twinkle because of the atmosphere In 5 billion years, sun will have burned up all its hydrogen, it will become a Red Giant and it will have expanded close to Earth Milky way galaxy have about 200 billion stars, 100,000 light-years across We live in the suburbs of the Milky Way, 28,000 light-years from the center Universe contains many other galaxies like the Milky Way Virgo cluster of galaxies is the nearest cluster of galaxies, we live in the “local group” cluster of galaxies October 1 Hubble saw that the universe is expanding over time Balloon analogy – universe expands and galaxies spread apart but stay the same size Shows that the universe had a beginning – big bang Can almost see the big bang part of the universe Space was bright everywhere for the first 300,000 years Big bang left off tons of radiation, can see it in your tv, maps showing high radiation spots
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Almost all astronomers believe big bang theory to be true “Dark energy” is what is driving the universe It may be expanding almost as fast as the speed of light M87 is an enormous galaxy with black hole in the middle How do we obtain information about the universe? Study of the light that the objects in the universe emit and absorb Meteorites can be studied and you can use elemental composition etc to see how the universe was formed Some meteorites have come from the moon and mars from when asteroids have hit them and sent pieces flying Cosmic rays are high energy charged particles that smash into earth (electrons, protons, nuclei etc) Cosmic rays can cause cancer or mutations They can come from the sun or supernova explosions deep in the universe Neutrinos are elusive, very fast, low mass particles that are produced by the sun due to nuclear reactions and trillions upon trillions come down to earth They are hard to detect Gravitational waves have never been detected but if two enormous objects interacted their gravitational fields would interact and cause gravitational waves
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This note was uploaded on 04/07/2008 for the course ASTRON 120 taught by Professor Meyer during the Fall '07 term at Northwestern.

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Astronomy notes - Astronomy 120 Dave Meyer Office Hours -...

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