Tiniest planet ever discovered by Nasa outside our solar system

NASA's Kepler space telescope detected the smallest planet yet found around a star similar to the Sun in a new planetary system.

The planets are located in a system called Kepler-37, about 210 light-years from Earth in the constellation Lyra.

The smallest planet, Kepler-37b, is slightly larger than our Moon, measuring about one-third the size of Earth. It is smaller than Mercury, which made its detection a challenge.

The Moon-size planet and its two companion planets were found by scientists with NASA's Kepler mission to find Earth-sized planets in or near the "habitable zone," the region in a planetary system where liquid water might exist on the surface of an orbiting planet.

However, while the star in Kepler-37 may be similar to our Sun, the system appears quite unlike the solar system in which we live.

Astronomers think Kepler-37b does not have an atmosphere and cannot support life as we know it. The tiny planet almost certainly is rocky in composition.

Kepler-37c, the closer neighbouring planet, is slightly smaller than Venus, measuring almost three-quarters the size of Earth. Kepler-37d, the farther planet, is twice the size of Earth.

"Even Kepler can only detect such a tiny world around the brightest stars it observes," said Jack Lissauer, a planetary scientist at NASA's Ames Research Center in Moffett Field, California.

"The fact we've discovered tiny Kepler-37b suggests such little planets are common,

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