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Kepler-138 b Facts: Mars-Size Exoplanet Smaller Than Earth (Infographic)

Facts about planet Kepler-138b
By studying data from the Kepler probe, scientists have found a planet about the size of Mars, about 200 light-years away from Earth.
(Image: © By Karl Tate, Infographics Artist)

Although most of the planet candidates cataloged by NASA's Kepler space telescope have diameters in the range of 2 to 4 times that of the Earth, little Kepler-138 b is only about the size and mass of Mars.

Full Story: Alien Planet Is Smaller Than Earth and Surprisingly Light

Kepler-138 b is one of three planets orbiting the red dwarf star Kepler-138, which is located 200 light-years from Earth in the constellation Lyra. The gravity of Kepler-138's three planets pulls them into slightly different positions than they would occupy otherwise. This enables scientists to calculate the mass of the planets.

The innermost planet is Kepler-138 b, which has a density about the same as the rocky planet Mars. The middle planet, Kepler-138 c, has a density about the same as Earth, and the outermost planet (Kepler-138 d) is less than half as dense, indicating a large proportion of light materials such as water and hydrogen. [The Smallest Known Alien Planets in Pictures]

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