About Exoplanets

An exoplanet is a planet orbiting a star other than our Sun. Using a wide variety of methods, astronomers have discovered more than 3,700 exoplanets to date. We now know that our galaxy likely hosts more planets than stars, including perhaps more than 10 billion potentially habitable worlds.

Of particular interest are planets that may orbit in their star’s habitable zone, the distance from a star where temperatures allow liquid water to persist on a planet’s surface, given a suitable atmosphere. As we currently understand, water is necessary for life, however, this definition is confined to our understanding of current and past life on Earth and the environments present on other planets. As researchers learn more and discover new environments in which life can sustain itself, the requirements for life on other planets may be redefined.

We find exoplanets a number of ways, but the most successful to date is the transit method. A transit occurs when a planet’s orbit carries it directly in front of its parent star as viewed from the observer’s perspective. This results in a temporary and periodic drop in the star’s brightness. Thousands of exoplanets have been discovered through this method, largely thanks to NASA’s Kepler mission, and thousands of additional candidates await confirmation.

Other NASA missions play a key role in detecting exoplanets. The Transiting Exoplanet Survey Satellite, which launched in April 2018, will monitor 200,000 of the brightest dwarf stars for transiting exoplanets. Future missions like the James Webb Space Telescope will be able to study these discovered planets in greater detail, helping determine their composition. In addition, transit observations can be used to study the dynamics of planetary systems, such as planet-planet interactions.

SEEC researchers are leveraging work across disciplines to better understand exoplanets. Areas like planet-star interactions, planetary formation, and even study of the Earth itself enable researchers to develop tools to learn more about how exoplanets evolve, and what ingredients are necessary to support life.

Learn more at

NASA logo Goddard Space Flight Center


NASA Official : Ravi Kopparapu
Media Contact : Claire Saravia
Web Curator : Lori J. Tyahla