Astronomy 1021 Study Guide - Milky Way, Spiral Galaxy, Stellar Population

• School: Western University
• Department: Astronomy
• Course: Astronomy 1021
• Professor: Stacey Hallman

Document Summary

Cepheid variable stars: variable stars with pulsation periods of 1 to 60 days whose period of variation is related to their luminosity. Instability strip: the region of the h-r diagram in which stars are unstable to pulsation. A star evolving through this strip becomes a variable star. Period-luminosity relation: the relation between period of pulsation ad intrinsic brightness among cepheid variable stars. Proper motion: the rate at which a star moves across the sky, measured in seconds of arc per year. Calibrate: to make observations of reference objects, checks on instrument performance, calculations of unit conversions, and so on, needed to completely understand measurements of unknown quantities. Disk component: all material confined to the plane of the galaxy. Spiral arms: long spiral pattern of bright stars, star clusters, gas, and dust. Spiral arms extend from the center to the edge of the disk of spiral galaxies.