Scientists Detect and Analyze A Hot Neptune Rapidly Losing Its Atmosphere

It has only been a couple decades since scientists have been able to study planets outside our solar system.  Called “exoplanets,” these extra-solar entities are not only potential ideas for another Earth—should we need one—but they also tell us a lot about our own planet and the whole of our solar system.

And, of course, the more we explore, the more we find, and the more we find, the more we learn.  Today, scientists are talking about a strange mystery they have found in a planet orbiting close to its star.  About the size of our Neptune, this planet—known as Gliese 3470b—is orbiting a very young—and very active—red dwarf star about 97 light years from Earth. It is not the discovery of this planet, however, that is so mysterious, necessarily; rather it is its relationship to its star.

You see, apparently, the radiation streaming from this red dwarf star is actually stripping away this “Hot Neptune’s” upper atmosphere. And this erosion is happening far more quickly and dramatically than scientists would have otherwise assessed; and at this rate, the planet won’t be this size for much longer.

Of course, we have to remember that our understanding of “time” is very different when talking about the life of a planet.  In terms of Gliese 3470b, the planet has lost between 4 and 35 percent of its total mass over the last 2 billion years. To put this into perspective, Gliese 436b is another planet we know of that is losing its atmosphere, but Gliese 3470b is experiencing atmosphere loss at 100 times the rate of Gliese 436b.

“Hot Neptunes” are pretty rare—far less common than “Hot Jupiters”—because they do not have the appropriate gravity to contain their atmosphere against their host star’s solar wind.  In terms of our Mars, for example, it is theorized that coronal mass ejection events and other types of solar storms are responsible for some of its atmosphere loss.

And Gliese 3470b orbits its star at just a fraction of the distance that the Milky Way’s Mercury orbits our yellow sun.  So, we can also theorize that as a smaller gas giant, it could eventually transform into another of the many super-Earths we have been finding pretty frequently in our hunt for another habitable planet.

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