Spectroscopy gives information about how fast or slow an object is moving, and helps astronomers figure out how far away it is. An object moving toward us shows lines in its spectrum that are blueshifted, or shifted to the blue end of the spectrum. If it moves away from us, then the lines are redshifted —shifted toward the red end of the spectrum. The term redshift is often used to indicate an object’s distance, say a redshift of 0.5. Astronomers notate that as z = 0.5.
