Astronomy Chapter 9 – The Milky Way Galaxy.docx - Astronomy...

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Astronomy Chapter 9 – The Milky Way Galaxy -Herschels attempted to gauge true shape of star system by counting stars in 683 different directions in the skyThe Size of the Milky WayCepheid Variable Stars– variable stars with pulsation periods of 1 to 60 days and whose period of variation is related to their luminosity Harlow Shapley– collaborated Cepheid variable stars to find the distance to globular clusters-Showed our galaxy is much larger than the region we can see easily and that the Sun is not at the centre Instability Strip– region of the H-R diagram in which stars are unstable to pulsation -Intersects the main sequence in the region of A and F stars and extends to G and early K bright super giantsDelta Cephei – Distance: 887ly, Radius: 44.5 R (sun), Mass: 4.5 M (sun)Period-Luminosity Relation– relation between period of pulsation and intrinsic brightness among Cepheid variable stars The Disk Component– consists of all matter confined to the plane of the galaxySpiral Arms:-

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Term
Winter
Professor
ArthurRead

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