•System
 seen “edge-on”
 •Stars pass in front of each other
 •Brightness
 drops when either is hidden
 •
 •Used
 to measure:
 –size
 of stars (relative to orbit)
 –relative
 “surface brightness”
 •area
 hidden is same for both eclipses
 •drop
 bigger when hotter star hidden
 –tells
 us system is edge on
 •useful
 for spectroscopic binaries