PHY 110 Chapter Notes - Chapter 14: Virgo Cluster, Light Curve, Protogalaxy
13 Apr 2017
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Chapter 14: when galaxies were first discovered, it was not clear that they lie far beyond the milky. Way until their variable stars were carefully observed: hubble proved that the spiral nebulae are far beyond the milky way a. i. Took a picture of the andromeda nebula and discovered several. Begin my carefully measuring the variations in apparent brightness of a cepheid varuabke, then recording the results in the form of a plot of brightness versus time, or light curve a. ii. 1. a. Gives the variable star"s period and average brightness a. ii. 2. Given the star"s period, the astronomer then uses the period-luminosity relation to find the cepheid"s average luminosity a. ii. 3. Knowing the apparent brightness and luminosity, you can use the inverse square law to calculate distance a. iii. Irregulars, irr: spiral galaxies: stellar birthplaces c. i. Spiral arms contain young, hot, blue stars and glowing hydrogen gas regions, indicating ongoing star formation c. ii. New stars that form in spiral galaxies are population i star c. iii.
