One of the most wondrous aspects of space is an astronomer could look out into its vast reaches - spanning millions of years - and one day see something no one else has.

Dubbed GJ 436b, an exoplanet about the size of Neptune was observed orbiting a red dwarf star with a massive gas trail. According to Space.com, it is the first time a planet has even been spotted with the defining characteristic of a comet.

Their work published in the journal Nature, the astronomers spotted the planet with NASA's Hubble Telescope and the Chandra X-ray Observatory.

"This cloud of hydrogen is very spectacular!" study lead author David Ehrenreich, of the Observatory at the University of Geneva in Switzerland, said in a press release. "Although the evaporation rate doesn't threaten the planet right now, we know that the star, a faint red dwarf, was more active in the past. This means that the planet's atmosphere evaporated faster during its first billion years of existence. Overall, we estimate that it may have lost up to 10 percent of its atmosphere."

GJ 436b is 22 times as massive as the Earth and its gas trail stretched behind it for millions of miles, the astronomers found. Ehrenreich told Space.com the exoplanet "is 33 times closer to its star than Earth is to the sun, and 13 times closer than Mercury."

Located 33 light years from Earth in the Leo constellation, GJ 436b was classified a "warm Neptune," meaning it resembles the planet Neptune in size, but orbits its star at a short distance. The gas tail is mostly made up of hydrogen, the researchers found, and it is slowly depleting the planet's atmosphere, but slow enough to outlast its host star.

"In order to be really hydrogen-poor and helium-rich, the atmosphere of GJ 436b should have represented a very small fraction of the planet['s] initial mass, around one-thousandth," Ehrenreich told Space.com. "In such a case, the whole atmosphere would have been gone today, which as we measure is not the case.

"We're going to study one such object in the course of next year with Hubble, and have proposed to observe several more."