According to NASA, "One of Hubble's key duties was to help astronomers determine a precise age for the universe. The telescope helped astronomers accomplish that goal, narrowing the universe's age to 13 to 14 billion years old, an accuracy of about 10 percent. Astronomers made observations of Cepheid variable stars [pictured above]pulsating stars used to measure vast distancesin the Virgo and other clusters to establish the expansion rate and the universe's age."