Professor Geoffrey Marcy is one of the leaders in the hunt for extrasolar planets. He is head of the Center for Integrative Planetary Science at UC Berkeley. According to the Center, the first terrestrial planet was recently discovered orbiting GJ 876, a star about 15 light years away. The planet, called Gleise 876 d, was discovered by E. Rivera and his team and announced in 2005.

Temperature on Gleise 876 d is listed at a balmy 642 Kelvin (695 Fahrenheit) in The Guide to Extrasolar Planets. Scientists are still searching for a more Earth-like planet that has more moderate temperatures.

The scientists who work on the Automated Planet Finder Telescope are driven by a deep, fascinating question: “Are other Earth-like planets common?”  The answer for now is mysterious: “No one knows.”  Details on the specific technology to be used are sketchy, but as of 2008 the goal was to automate the search for terrestrial planets by using a computerized telescope to scan stars within 100 light years of Earth. The telescope will include a spectrograph for the type of light analysis used in the search for extrasolar planets. The telescope will be fully automated.

The Kepler mission, launched in March, 2009, is also looking for Earth-like exoplanets. It has a tremendous capacity for collecting information: In only 10 days it took pictures of over 52,000 stars! Basically, the Kepler Telescope is a photometer that senses slight changes in light from a star. When an extrasolar planet passes in front of a star, some of the light from the star is blocked. The Kepler Telescope can sense the change in light emission.

The NASA/JPL Space Interferometry Mission is a project to launch a space-based interferometry telescope to be used in the search for extrasolar planets. It will utilize data from the Kepler mission.

NASA’s Terrestrial Planet Finder Mission is another mission that is currently in the planning phase.