Alex Knapp summarizes the news:
NASA has announced that its Kepler telescope has uncovered a new solar system about 500 light years away, currently dubbed Kepler 186. Circling that star are five planets, and the outermost planet, Kepler-186f, is about the size of Earth and within the star’s habitable zone. “The discovery of Kepler-186f is a significant step toward finding worlds like our planet Earth,” NASA’s Paul Hertz said in a statement. The star Kepler 186 is a “red dwarf” star, about half the size and mass of our own Sun. It’s about 500 light years away from Earth, near the constellation Cygnus in the night sky. The planet itself orbits its sun once every 130 days.
Adrienne LaFrance provides more details:
Kepler-186f is about 10 percent larger than Earth and it orbits a sun that is cooler, dimmer, and about half the size of our own. The effects of gravity would be “slightly” more apparent there, so “you would feel heavier,” Meadows said. Our cousin avoids many of the problems that reduce the likelihood of life on other Earth-like planets. Some are too big, too cold, too gaseous, or have gravity problems that scorch oceans. So far, Kepler-186f appears almost to be a Goldilocks — not too big, not too far from its star, maybe just right.
Phil Plait calls this “potentially the most Earth-like planet we’ve yet found”
I say potentially because honestly we don’t know all that much about it besides its size and distance from its star (and its year—it takes 130 days to orbit the star once). The next things we’d need to know about it are the mass, what its atmosphere is like, and the surface temperature. The gravity of the planet depends on its mass, and in many ways the atmosphere depends on the gravity. Unfortunately, we don’t know either, and we’re unlikely to. The techniques used to find planet masses aren’t up to the task for this planet—the star is too dim to get reliable data. The same is true for any air the planet might have as well. And without that, we don’t really know its surface temperature.
Joseph Stromberg explains what comes next:
This is more of a stepping stone in the search for earth-like planets and extraterrestrial life than a destination. Because the star is so far away, we can’t really tell if it has an atmosphere or learn much more about it, and definitely can’t visit it.
So astronomers like Barclay and the hundreds of others looking for exoplanets will use this as evidence that earth-sized planets can form in their star’s habitable zones, and search for others closer to us. The discovery is particularly exciting because the majority of stars in our galaxy are red dwarves like Kepler-186, so there may be many more exoplanets similar to this one out there.
(Image: Artist’s concept depicts Kepler-186f, the first validated Earth-size planet to orbit a distant star in the habitable zone. By NASA Ames/SETI Institute/JPL-Caltech.)
The Dish 