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Super Earth-size Planet Confirmed Around Bright F6 Subgiant Star
December 2, 2011

A research team led by Steve Howell, NASA Ames Research Center, has announced the discovery of an exoplanet orbiting one of the brightest stars in the Kepler field of view.

Coined Kepler-21b, the planet is approximately 1.6 times the radius of Earth and nearly ten times the mass of Earth. Circling its host star every 2.8 days, Kepler-21b orbits at a distance of six million km – nearly ten times closer than Mercury orbits the sun. The surface temperature is calculated to be 2,960 Fahrenheit. While this temperature is nowhere near the habitable zone in which liquid water might be found, the planet's size is approaching that of Earth.

The parent star, HD 179070, a little hotter and brighter than the sun, is 352 light years away. Somewhat similar to the sun, the parent star has a mass of 1.3 solar masses, is larger at 1.9 solar radii, and its age, based on stellar models, is 2.84 billion years- younger than the sun's 4.6 billion years. Although Kepler-21b is pretty small and very far away, unable to be seen with the naked eye, the parent star can easily be seen with binoculars or a small telescope.

This incredibly sensitive and difficult detection required the collaboration of over 65 astronomers with both space and multiple ground-based telescopes to confirm the newest member of the Kepler family.

To read the press release from the National Optical Astronomy Observatory visit:

To learn more about the discovery, please see the details table at:

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Page Last Updated: July 28th, 2013
Page Editor: NASA Administrator