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First Earth-Size Planet in 'Habitable Zone'
04.17.2014
artist conception of planet Kepler-186f
Kepler-186f, the first Earth-size Planet in the Habitable Zone of Another Star
Credit: NASA Ames/SETI Institute/JPL-Caltech
The artist's concept depicts Kepler-186f, the first validated Earth-size planet to orbit a distant star in the habitable zone. The size of Kepler-186f is known to be less than ten percent larger than Earth, but its mass, density and composition are not known. Previous research suggests that a planet the size of Kepler-186f is likely to be rocky. Prior to this discovery, the "record holder" for the most "Earth-like" planet went to Kepler-62f, which is 40 percent larger than the size of Earth and orbits in its star's habitable zone.
Kepler-186f orbits its star once every 130 days and receives one-third the energy that Earth does from the sun, placing it near the outer edge of the habitable zone. If you could stand on the surface of Kepler-186f, the brightness of its star at high noon would appear as bright as our sun is about an hour before sunset on Earth.
The artistic concept of Kepler-186f is the result of scientists and artists collaborating to imagine the appearance of these distant worlds.

Recording of Press Conference: http://www.ustream.tv/recorded/46348063 (55 min, including Q&A)

Discovery paper: An Earth-Sized Planet in the Habitable Zone of a Cool Star by Elisa V. Quintana, Thomas Barclay, Jason F. Rowe, et al, Science Magazine.

Get the Press Kit

Watch Hangout session at SETI Institute with Jill Tarter, Elisa Quintana, Tom Barclay, and Jason Rowe. (38 min)

PBS News Hour interview with Tom Barclay. April 17, 2014 at 6:39 PM EDT

Science Magazine Article: "Almost-Earth Tantalizes Astronomers With Promise of Worlds to Come", April 18, 2014

See NASA RELEASE: 14-111.

Excerpts:

Using NASA's Kepler Space Telescope, astronomers have discovered the first Earth-size planet orbiting a star in the "habitable zone" -- the range of distance from a star where liquid water might pool on the surface of an orbiting planet. The discovery of Kepler-186f confirms that planets the size of Earth exist in the habitable zone of stars other than our sun.

While planets have previously been found in the habitable zone, they are all at least 40 percent larger in size than Earth and understanding their makeup is challenging. Kepler-186f is more reminiscent of Earth.

"The discovery of Kepler-186f is a significant step toward finding worlds like our planet Earth," said Paul Hertz, NASA's Astrophysics Division director at the agency's headquarters in Washington. "Future NASA missions, like the Transiting Exoplanet Survey Satellite and the James Webb Space Telescope, will discover the nearest rocky exoplanets and determine their composition and atmospheric conditions, continuing humankind's quest to find truly Earth-like worlds."

diagram of Kepler-186 system

Kepler-186 and the Solar System
Credit: NASA Ames/SETI Institute/JPL-Caltech
See full caption. Excerpt: The diagram compares the planets of our inner solar system to Kepler-186.... The five planets of Kepler-186 orbit an M dwarf, a star that is half the size and mass of the sun.
Kepler-186f orbits its star once every 130 days, receiving one- third the heat energy that Earth does from the sun. This places the planet near the outer edge of the habitable zone.
The inner four companion planets each measure less than fifty percent the size of Earth. Kepler-186b, Kepler-186c, Kepler-186d and Kepler-186, orbit every 4, 7, 13 and 22 days, respectively, making them very hot and inhospitable for life as we know it....
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The Kepler-186 System Fly-through

movie of Kepler-186 system

Higher res version
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Credit: NASA Ames/SETI Institute/JPL-Caltech

This artist's movie illustrates Kepler-186, a five-planet system located about 500 light-years from Earth in the constellation Cygnus, from an overhead view. The green circular band depicts the habitable zone—a range of distances from a star where liquid water might pool on the planet's surface.
The blue streak shown in the habitable zone depicts the orbital path of Kepler-186f -- the first validated habitable-zone, Earth-size planet around another star. Kepler-186f orbits its star once every 130 days and receives one-third the energy that Earth does from the sun, placing it near the outer edge of the habitable zone.
Zooming in, the four yellow streaks depict the orbital paths of the inner companion planets. They whiz around the host star once every 4, 7, 13 and 22 days, respectively, making them very hot and inhospitable for life as we know it. The four companion planets each measure less than 1.5 times the size of Earth.
At the center of the system is a star that is half the size and mass of the sun. Called an M dwarf, this star-type emits light in the infrared and has an amber-like glow compared to our sun.
Continuing passed the star and inner planets is Kepler-186f. Kepler-186f is less than ten percent larger than Earth in size, but its mass, composition and density are not known. While scientists don't know the density of the planet, previous research suggests that a planet the size of Kepler-186f is likely to be rocky.


diagram showing habitable zone status of known exoplanets as of April 2014


Habitable zone exoplanets as of April 2014
"Stellar flux" on the x-axis is essentially how much of the star's energy the planet is receiving. Source: Press Kit Presentation

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