Scientists have discovered a new exoplanet that is of a very rare variety called a “hot Neptune.” The new exoplanet is dubbed Gliese 3470b, and the big thing about this exoplanet is that it is losing its atmosphere at an incredible rate. Hot Neptunes are exceedingly rare, and scientists have long wondered why this is.
This rapidly vanishing exoplanet has led to a new hypothesis that says perhaps the reason hot Neptunes are so rarely discovered is that they evaporate away and turn into one of the most commonly discovered exoplanets dubbed mini-Neptunes. For those curious about what exactly a hot Neptune is, this is a giant planet around the size and mass of Neptune or Uranus that is much, much closer to its host star than the Earth is to the Sun.
That proximity to the host star means that the atmospheric temperature on a hot Neptune planet is in the area of 1,700-degrees Fahrenheit. Gliese 3470b isn’t the first exoplanet discovered that is bleeding its atmosphere, but it is doing it the fastest. Scientists say that Gliese 3470b is losing its atmosphere at 100 times the speed that another evaporating exoplanet, Gliese 436b, is losing its atmosphere at.
If the evaporation of 3470b continues at this rate, scientists say it could end up as a mini-Neptune or a super-Earth in only a few billion years. That is rapid on a galactic timescale. Half the planet could be gone over the next few billion years.
The team plans to continue the study of 3470b using the James Webb Space Telescope set to launch in 2021. The star the exoplanet orbits is much hotter and more turbulent than the star 436b orbits accounting for the faster evaporation compared to the other exoplanet.