Destination: Kepler-186f
Mode of Transportation: Pending

Kepler-186f, First Earth-Sized Planet in Extra-Solar Habitable Zone Image Credit: NASA Ames/SETI Institute/JPL-Caltech

Science fiction stories abound with distant colonies on Earth-like worlds. But the existence of those planets has been speculation (and reasonable minds can disagree about how warranted such speculation is). But now, while the starships remain speculation, the existence of an Earth-sized world in a distant “habitable zone” is confirmed, thanks to astronomers using NASA’s Kepler Space Telescope.

For those unfamiliar, the “habitable zone” is 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.

Previous discoveries of planets in stellar habitable zones have been too big–at least 40 percent larger than Earth and a difficult place to get around. Don’t even think about trying push ups or chin ups. Even riding a bike might be a challenge.

But Kepler-186f is more reminiscent of Earth.

According to Paul Hertz, NASA’s Astrophysics Division director at the agency’s headquarters in Washington:

“The discovery of Kepler-186f is a significant step toward finding worlds like our planet Earth. 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.”

Not that there isn’t still a lot of room for speculation. Although the size of Kepler-186f is known, its mass and composition are not. Previous research, however, suggests that a planet the size of Kepler-186f is likely to be rocky. That’s a good start. But, according to Thomas Barclay, research scientist at the Bay Area Environmental Research Institute at Ames, and co-author of the paper disclosing the discovery:

“Being in the habitable zone does not mean we know this planet is habitable. The temperature on the planet is strongly dependent on what kind of atmosphere the planet has. Kepler-186f can be thought of as an Earth-cousin rather than an Earth-twin. It has many properties that resemble Earth.”

So maybe now is the time to buy land–while the prices are cheap because of uncertainty.

But don’t pack your bags just yet. Kepler-186f resides in the constellation Cignus, orbiting a red dwarf star in the Kepler-186 system, about 500 light-years from Earth. We haven’t quite perfected a mode of transportation that would get us there in a lifetime–or even scores of lifetimes–and that would not corrode or otherwise fail to entropy long before reaching the destination.

But maybe soon. In the meantime, if you are making plans, plan for a 130-day year, and plan for cold weather. Kepler-186f receives about one-third the energy from its star that Earth gets from the sun, placing it nearer the outer edge of the habitable zone. On the surface of Kepler-186f, the brightness of its star at high noon is only as bright as our sun appears to us about an hour before sunset.

The four companion planets, inside the orbit of Kepler-186f (named, for now, Kepler-186b, c, d and e–okay, okay, the marketing folks need to work on that), whiz around the red dwarf every four, seven, 13, and 22 days, respectively, making them too hot for life as we know it. Maybe good sources of minerals?

The diagram compares the planets of our inner solar system to Kepler-186, a five-planet star system about 500 light-years from Earth in the constellation Cygnus. The five planets of Kepler-186 orbit an M dwarf, a star that is is half the size and mass of the sun. [Click link below for more.] Image Credit: NASA Ames/SETI Institute/JPL-Caltech

Overall, this is an astounding find, and we can expect more discoveries of the same type. For more information about the Kepler mission, visit the Kepler Mission Site.

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