Melted Away

A newly discovered gas planet, orbiting a distant star, is approximately the size of Neptune — but it's so close to the red dwarf it orbits that it's literally boiling away.

"This is the smoking gun that planets can lose a significant fraction of their entire mass," Johns Hopkins planetary scientist David Sing, who helped find the exoplanet, said in a news release. He added that it's "losing more of its mass than any other planet we seen so far; in only a few billion years from now, half of the planet may be gone."

Nature Is Metal

The planet, which is called GJ 3470b and described in a new paper in the journal Astronomy & Astrophysics, is what's known as a "hot Neptune." That means that it's a gas giant, like our own solar system's Neptune or Jupiter, but it's far closer to its host star than either of those planets.

GJ 3470b is so close to its star, in fact, that it's boiling away into space. To make matters worse, it's not a very heavy planet, meaning that its gravitational pull on its own atmosphere is comparatively weak.

Mysteries of the Cosmos

The rapidly vanishing GJ 3470b could provide an important clue about the nature of gas planets outside our solar system. Though the Kepler mission has found many smaller "mini-Neptunes" sprinkled throughout the galaxy, hot Neptunes are rare. The new theory: we're not finding as many hot Neptunes because, like GJ 3470b, they tend to boil away into mini-Neptunes.

"It's one of the most extreme examples of a planet undergoing a major mass-loss over its lifetime," University of Geneva astronomer Vincent Bourrier, another researcher on the hot Neptune project, said in the same news release. "This sizable mass loss has major consequences for its evolution, and it impacts our understanding of the origin and fate of the population of exoplanets close to their stars."

READ MORE: Astronomers Have Detected a Planet That's Actually Evaporating Away at Record Speed [Science Alert]

More on hot Neptunes: Researchers Found a Treasure Trove of Planets Hiding in Dust

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