A Neptune-size planet with a clear atmosphere is shown crossing in front of its star in this artist's depiction.

(NASA/JPL-Caltech)

Astronomers have made a huge discovery– a planet, outside our solar system that has clear skies and water vapor.

The planet is called HAT-P-11b, and it is located 120 light-years away in the constellation Cygnus, according to NASA. It was discovered by astronomers using three NASA space telescopes: Hubble, Spitzer and Kepler, the report added.

"This discovery is a significant milepost on the road to eventually analyzing the atmospheric composition of smaller, rocky planets more like Earth," said John Grunsfeld, assistant administrator of NASA's Science Mission Directorate, in the NASA report. "Such achievements are only possible today with the combined capabilities of these unique and powerful observatories."

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Finding exoplanetsisn't an easy task, even with advancing technology, and investigating the composition of one's atmosphere is even more difficult. As the Los Angeles Times notes, scientists must wait for the planet to move in front of the star it's orbiting, which gives them a chance to study the starlight. Then, as the report adds, if there's water in the slim, gassy shell around the exoplanet, it can absorb specific wavelengths of the light, alerting scientists that it has the chemical properties they're looking for.

Exoplanets with thick cloud layers absorb light, according to Ars Technica, so scientists need cloudless conditionsto allow light to pass through the atmosphere. Then, they can study the composition of the planet.

HAT-P-11b is roughly the size of Neptune, and it's the smallest exoplanetfrom which scientists have been able to find molecules of any kind, NASA added.

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"The work we are doing now is important for future studies of super-Earths and even smaller planets, because we want to be able to pick out in advance the planets with clear atmospheres that will let us detect molecules," study co-author Heather Knutson of the California Institute of Technology in Pasadena told NASA.

Since scientists began searching for planets outside our solar system, they have confirmed the discovery of 1,516 exoplanets, according to the Exoplanet Orbit Database.

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