ASTR 1210 Study Guide - Final Guide: Spiral Galaxy, Protogalaxy, Angular Momentum
18 Feb 2016
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Galaxies were seen before people knew what they were: people found galaxies about 200 years ago, charles messier saw them as balls of light, william herschel. He couldn"t photograph galaxies, but he drew what he thought he saw. He drew blobs of stuff pretty much. He drew galaxies w/ nuclei, disks, etc: it was only around 1900 when people realized these were outside our galaxy. To know that the nebulae were island universes outside our galaxy, we had to know how far they were away so they weren"t mistaken for gases inside our galaxy. Really big w/ hydrogen shell and inert core. They measure the oscillations (periods b/t 3 and 300 days) Period is connected w/ intrinsic luminosity: higher the period, higher the intrinsic, the more massive stars have a longer luminosity period and produce more energy. You can see them in our galaxy, but also in very distance galaxies.
