Chapter_20_Galaxies_and_Cosmology_summary - within it 4...

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Chapter Summaries Chapter 20: Galaxies and Cosmology (don’t forget to find definitions at the end of the book, in the glossary and draw pictures!!!!!) 1. Hubble’s deepest Field image shows a great variety of galaxies. (billions of light-years away) 2. Galaxy types: Spiral (both disk and spheroidal components) Barred Spiral Lenticular (has a disk like a spiral galaxy but much less dusty gas) (intermediate between spiral and elliptical) Elliptical (all spheroidal component, no disk component) (older star population) Irregular (ongoing star formation) 3. Measuring distances to galaxies: 1. Determine size of solar system using radar 2. Parallax: Determine distances of stars out to a few hundred light-years using parallax 3. Apparent brightness of star cluster’s main sequence tells us its distance (Knowing a star cluster’s distance, we can determine the luminosity of each type of star
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Unformatted text preview: within it) 4. Cepheid variable stars are very luminous standard candles and they obey a strict period-luminosity relationship. A standard candle is an object whose luminosity we can determine without measuring its distance 5. Apparent brightness of white-dwarf supernova tells us the distance to its galaxy (up to 10 billion light-years) 6. Tully-Fisher Relation Entire galaxies can also be used as standard candles because galaxy luminosity is related to rotation speed 7. Hubble’s Law: a. Hubble measured the distance to nearby galaxies using Cepheid variables as standard candles b. Hubble found that the spectral features of virtually all galaxies are redshifted ⇒ They’re all moving away from us c. Hubble found that the further away a galaxy is, the faster it is receding from us! Chapter Summaries 8. Ionization nebulae (also known as emission nebulae): active star formation regions...
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This note was uploaded on 09/08/2010 for the course ASTR 101 at San Jose State.

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Chapter_20_Galaxies_and_Cosmology_summary - within it 4...

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