PCS 181 Lecture Notes - Lecture 8: Henrietta Swan Leavitt, Proper Motion, Minute And Second Of Arc
15 Dec 2017
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Astronomy week 8 (week 7 is in phone ) march 11-12. Period-luminosity curve for cepheid variable stars- a cephied variable star grows larger and brightens. The time span cycle occurs over a timespan of days. Henrietta leavitt produced a plot versus nagnitutude. Cepheids can be used as farther distant indicators to other galaxies. A cephied varies in brightness we use an average absolute magnitude. We can observe the period of a distant cepheid and find its average absolute magnitude on the period-lumodity curve (of leavitt) A cepheid in another galaxy has an average apparent magnitutde of 15 and a period of. Recall that radial velocity (vr) is the component of the stars velocity along our line of sight. Proper motion (weird looking u)- is the star"s angular displacement perpendicular to (across) our line of sight. Is measured in arcseconds per year ( /year) = seconds of arc per year.
