This artist's illustration gives an impression of how common planets are around the stars in the Milky Way galaxy. The planets, their orbits, and their host stars are all vastly magnified compared to their real separations. A six-year search that surveyed millions of stars using the microlensing technique concluded that planets around stars are the rule rather than the exception. The average number of planets per star is greater than one. Image credit: NASA/ESA/ESO

Astrophysicist Lisa Kaltenegger is the director of the Carl Sagan Institute at Cornell University.

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In this talk, held at the American Museum of Natural History, she explains the different methods astronomers use to detect exoplanets orbiting distant stars, what these planets would need to support life, and how Earth and its range of species might serve as a Rosetta Stone—a key to detecting the existence of extraterrestrial life.