NASA's Kepler mission, whose goal is to search for and study habitable planets, has identified a rather tiny planet of significance recently: Kepler-37b is smallest planet we know of outside our solar system orbiting around a star similar to our sun.
Kepler-37b is so so small, in fact, that it's barely bigger than our own moon. With a size approximately one-third of our planet Earth's, the planet is smaller than Mercury, our solar system's smallest and closest planet to the sun. Kepler-37b is located in the constellation Lyra, some 210 light-years away, making it an incredibly hard planet to detect.
"Even Kepler can only detect such a tiny world around the brightest stars it observes," said NASA's Jack Lissauer from the Ames Research Center in Moffett Field, Calif. said.
"The fact we've discovered tiny Kepler-37b suggests such little planets are common, and more planetary wonders await as we continue to gather and analyze additional data."
Kepler-37b is believed to have no atmosphere, and is not a candidate for an Earth-like or habitable planet - after all, it orbits its star at a distance closer than Mercury does around our sun, and it is estimated to be a smoldering 800 degrees Fahrenheit on the surface. The planet's parent star is in the same class as our sun, although it isn't as large or hot.
"We uncovered a planet smaller than any in our solar system orbiting one of the few stars that is both bright and quiet, where signal detection was possible," said lead author of the study Thomas Barclay said. "This discovery shows close-in planets can be smaller, as well as much larger, than planets orbiting our sun."
The Kepler data also turned up two other planets in the same star system, Kepler-37c, which is slightly smaller than Earth, and Kepler-37d, a planet twice the size of Earth.
You can read the full published study here, in the journal Nature.