Shapley used the period

Shapley used the period -...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Shapley used the period-luminosity relation to estimate distances. First, he  collected all the available data on Cepheid stars, from his own  observations and from other astronomers including Leavitt. The distance  to some of the nearer Cepheids had been measured, and thus Shapley  could figure out their absolute magnitudes. The only physics he needed  was the simple rule that brightness decreases with the square of the  distance. Then Shapley graphed period versus absolute magnitude. [The period-luminosity curve is] based upon more than 230 stars,  and, except for zero-point uncertainty [the uncertainty in the  distance measured by other methods to the nearer Cepheids], is  probably correct within one or two hundredths of a magnitude.                                          —Harlow Shapley Shapley made the reasonable assumption  that Cepheids in 
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/15/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.

Ask a homework question - tutors are online