Japanese researchers say observation of a distant exoplanet in the center of the Milky Way suggests the "super-Earth" likely has a water-rich atmosphere.

Super-Earths are exoplanets orbiting a star outside of the solar system with a mass and radius larger than Earth's but smaller than those of ice giants in our system such as Uranus or Neptune.

Scientists say they are still are still studying their properties to determine whether such worlds are more like a "large Earth" or a "small Neptune."

The Japanese research team of astronomers and planetary scientists focused their efforts on investigating the atmospheric features of one super-Earth, GJ 1214 b, located 40 light years from Earth in the center of our Milky Way galaxy, the National Astronomical Observatory of Japan reported Wednesday.

Planets are thought to develop in a disk of dense gas surrounding a newly formed star, and while the element hydrogen is a major component of such a protoplanetary disk, water ice is abundant in an outer region beyond a so-called "snow line."

Scientists say if they can determine the major atmospheric component of a super-Earth they can then infer the planet's birthplace and formation history.

Initial results of the study of GJ 1214 b indicate it is likely to have a water-rich atmosphere, the researchers said.