NATS 1745 Lecture Notes - Lecture 18: Parsec, Globular Cluster, Andrea M. Ghez
13 Mar 2016
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Document Summary
Understanding the structure of our galaxy, the milky way distances to stars: parallax, inverse square law. Models of herschel, kapetyn variable stars: eclipsing, pulsating - cepheid variable stars. Work of henrietta leavitt: period-luminosity relation fro cepheids. Work of harold shapley: using cepheids to get distances to globular clusters; mapping the scale and structure of our. Multi-wavelength observations: using infrared, radio observations to discover central supermassive black hole discovery of dark matter using doppler shift. Variable stars----brightness fluctuates: regular variables ---- have an even period o. Irregular variables ---- uneven variability (some peaks together, some further apart) Key: finding distances to stars: difficult, variety of ways. Herschel 1785 tried to determine size and shape of galaxy: presumed: all stars have same brightness absolute or intrinsic brightness, all stars are uniformly arranged around the sky o. 2 main problems: stars all don"t have the same brightness, there is inter-stellar gas/dust which obscures distant stars. Geometric method for getting distances (saw last term)
