Scientists have spotted a giant cloud of hydrogen gas escaping from a Neptune-sized planet.

The exoplanet GJ436 is about 23 times more massive than Earth and orbits its host star in only three days, the University of Geneva reported. It has an atmosphere that leaves behind a trail of hydrogen as the planet moves across its orbit.

"This cloud is very spectacular; it's as if, after carrying the planet's atmosphere at a high temperature, causing the hydrogen to evaporate, the radiation of the star was too weak to blow away the cloud that accumulated around the planet," said David Ehrenreich, an astrophysicist with UNIGE.

The cloud is essentially made up of carbon and absorbs ultraviolet light given off by nearby stars. The phenomenon is invisible from Earth because this ultraviolet light is blocked by the atmosphere, but scientists were able to get a glimpse

"When you're searching in the visible region you only see the shadow of a planet whose size is equivalent to four times that of Earth like Neptune. But if the sensitive eye is pointed toward the Hubble ultra violet light, the planet is transformed into a veritable monster, far bigger than the star," Ehrenreich said.

The evaporation could help explain the disappearance of atmospheres belonging to rocky exoplanets that orbit extremely close to their blazing hot stars. The findings could also help aid the search for habitable planets in our universe.

 "[This is because] hydrogen from the ocean water that evaporate on slightly hotter terrestrial planets than the Earth could be detected" said Vincent Bourrier, the second author of these results.

The findings could also have implications for our own atmosphere, and could help predict what Earth will look like in three or four billion years when the Sun inevitably becomes a Red Giant. The researchers now believe our planet could transform into a massive comet resembling GJ436b.

The findings were published in a recent edition of the journal Nature.