Measuring Distance to Stars Very difficult! Astronomers have developed methods of determining stellar distances.

 Parallax (most basic way to measure star distance) • Slight shift of apparent position of a star due to the orbital motion of Earth (determined from photographs) * Nearest stars have largest angles; distant stars are too small to measure.

 Variable Stars (stars may fluctuate in brightness) • Cepheid Variable: varies in brightness at a measureable interval Nova - explosively increases in brightness (sudden change). Who cares? Figure 6: pg. 705 Images of a Nova Taken 2 Months Apart, shows the decrease in brightness that follows a nova flare-up.