ASTRON 1F03 Quiz: Measuring the Milky way
12 Apr 2016
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Intrinsic variables: stars whose luminosity varies in a regular way. The variability of these stars comes from a dynamic balance between gravity and pressure they have large oscillations around stability. The upper plot is for an rr lyrae star. All such stars have essentially the same luminosity curve with periods from 0. 5 to 1 day. The lower plot is cepheid variable; cepheid periods range from about 1 to 100 days. The utility of these stars comes from their period-luminosity relationship. This allows us to measure the distances to these stars. Many rr lyrae stars are found in globular clusters. These clusters are not all in the plane of the galaxy, so they are not obscured by dust and can be measured. This yields a much more accurate picture of the extent of our galaxy and our place within it. We have now expanded our cosmic distance ladder one more step.
