In Search of Missing Worlds, Hubble Finds a Fast Evaporating Exoplanet

A few years ago astronomers using NASA's Hubble Space Telescope found that one of the warmest known Neptunes (GJ 436b) is losing its atmosphere. The planet isn't expected to evaporate away, but hotter Neptunes might not have been so lucky.

Now, astronomers have used Hubble to nab a second "very warm" Neptune (GJ 3470b) that is losing its atmosphere at a rate 100 times faster than that of GJ 436b. Both planets reside about 3.7 million miles from their star. That's one-tenth the distance between our solar system's innermost planet, Mercury, and the Sun.

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Credits: NASA, ESA and A. Feild (STScI)

This graphic plots exoplanets based on their size and distance from their star.

Each dot represents an exoplanet. Planets the size of Jupiter (located at the top of the graphic) and planets the size of Earth and so-called super-Earths (at the bottom) are found both close to and far from their star.

But planets the size of Neptune (in the middle of the plot) are scarce close to their star.

This so-called desert of hot Neptunes shows that such alien worlds are rare, or, they were plentiful at one time, but have since disappeared.

The detection that GJ 3470b, a warm Neptune at the border of the desert, is fast losing its atmosphere suggests that hotter Neptunes may have eroded down to smaller, rocky super-Earths.

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Astronomers discovered very warm-Neptune (GJ 3470b) that is losing its atmosphere 100 times more rapidly unlike any other alike exoplanet previously identified