The Search for Exoplanets: What Astronomers Know

Learn about the exciting mission of exoplanetary science - the study of planets orbiting stars beyond the Sun. Review the eight planets in our solar system, which provide a baseline for understanding the more than 1,000 worlds recently discovered in our region of the Milky Way galaxy.

Given the extreme faintness of a planet relative to the star it orbits, how can astronomers possibly find it? Learn about direct and indirect methods of detection. As an example of the indirect method, discover why a planet causes a star's position to change, providing a strategy for locating exoplanets without seeing them.

Explore two other indirect approaches for finding exoplanets: first, by measuring the Doppler shift in the color of a star due to the pull of an unseen orbiting planet; and second, by measuring the tiny drop in the brightness of a star as a planet transits in front of it.

Chart the history of exoplanet hunting - from a famous false signal in the 1960s, through ambiguous discoveries in the 1980s, to the big breakthrough in the 1990s, when dozens of exoplanets turned up. Astronomers were stunned to find planets unlike anything in the solar system.

Investigate 51 Pegasi b, the first planet detected around a Sun-like star, which shocked astronomers by being roughly the size of Jupiter but in an orbit much closer to its star than Mercury is to the Sun. Probe the strange characteristics of these "hot Jupiters," which have turned up around many stars.

The standard theory of planet formation is based on our solar system. But does this view require revision based on the existence of misplaced giant planets - hot Jupiters circling close to their parent stars? Compare competing theories that try to resolve this conflict.