Astronomy Notes 4 14 16 PDF

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Notes from Descriptive Astronomy PHYS 1455...

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Chapter 15: Galaxies and Cosmology The sun's position in the Milky Way (in the disk, 2/3 of the way out from the center). It takes 230 million years for the Sun to go around the Milky Way once. Overall shape and regions (Bulge, Disk, Halo) of the Milky Way Distinctive features of the regions, for example: Halo – contains Globular clusters, is spherical in shape, contains pop. II stars and very little interstellar gas and dust Galactic disk – flattened shape, spiral arms, both pop I and pop II stars, interstellar gas, dust, and pop I stars associated with spiral arms. Bulge - Center of the galaxy, football shape, pop II stars, little gas and dust, supermassive black hole at the center. Shapely methods of determining the size and position of the center of the Milky Way.  Used globular clusters and variable stars in the halo Density wave theory for spiral arm formation.  Spiral arms are traffic jams in Dallas Self propagating star formation for spiral arm formation.  Definitions and properties of Pop. I, Pop. II,  Pop 1: contain young bright blue bright stars (interstellar gas and dust)  Pop 2: older stars yellows and reds not a lot of gas and dust Three major types of Galaxies in the Hubble Classification scheme: Elliptical, Spiral/Barred Spiral, Irregular.  Be able to identify Galaxy types by properties. Review of causes of the different galaxy types Clusters – Rich clusters, poor clusters, local group, Virgo cluster. Know the 'rungs' in the distance ladder. Big Bang Video Links Part 1 http://www.youtube.com/watch?v=0FPUutjtqfw&feature=related Part 2 http://www.youtube.com/watch?v=8RHfUFljTmw&feature=related Outline of the Big Bang Theory 1 Planck Epoch – A mystery partly because we lack a quantum theory of gravity. 2 The Grand Unification Epoch – Forces except gravity are unified 3 The inflationary Epoch – Universe expands rapidly smaller than a proton to bigger than a melon – Supported experimentally 4 Electroweak epoch – Weak and electromagnetic forces act as one. 5 The Quark, Hadron and Lepton Epoch – What we think of a “normal” elementary particle form and survive. 6 Photons, Nucleosynthesis and the Cosmic Background Radiation – Atoms form (Hydrogen and

Helium) and Cosmic Background radiation ‘ decouples ‘ from matter 7 Dark Ages- Atoms exists but stars don’t.’ “Modern” Era =Stars form – Quantum fluctuations at the time of inflation determines the distribution of matter in the universe. Denser areas are where stars will form. Gravity is the major large-scale force  

Supermassive blackhole in the middle of the Galaxy (Galaxies)...