Astronomers using the Hubble Space Telescope have discovered a planet roughly the size of Neptune, evaporating at a rate 100 times faster than a previously identified exoplanet of similar size.
The research findings were published in the Journal of Astronomy & Astrophysics, advance astronomers’ knowledge about how planets evolve.
A hot Neptune is pretty much what it sounds like. A giant planet, around the size and mass of Neptune or Uranus, but much, much closer to its host star – closer than the distance between Earth and the Sun. Therefore, it’s also hotter, with an atmospheric temperature of around 927 degrees Celsius (1,700 Fahrenheit). There are other Neptune-ish planets out there, but they’re generally found orbiting much farther from their star.
The star-hugging, extremely hot exoplanets discovered so far seem to fall into two opposite groups. There’s the so-called “hot Super-Earths,” which are a little bit bigger than our home planet, and way up the other end of the scale we have the “hot Jupiters.” Logic says there should also be plenty of medium-sized “hot Neptunes” that are around the size of our local ice giant Neptune but are scorching hot because they’re extremely close to their parent star.
The speed and distance at which planets orbit their respective blazing stars can determine each planet’s fate – whether the planet remains a longstanding part of its solar system or evaporates into the universe’s dark graveyard. Planets such as “super” Earths and “hot” Jupiters orbit more closely to their stars and are therefore hotter, causing the outermost layer of their atmospheres to be blown away.
Researchers hypothesize that these Neptunes get stripped of their atmospheres and ultimately become smaller planets. GJ 3470b is 96 light-years away and circles a red dwarf star in the general direction of the constellation Cancer. Hubble found that exoplanet GJ 3470b had lost significantly more mass and had a noticeably smaller exosphere than the first Neptune-sized exoplanet studied, GJ 436b, due to its lower density and receipt of a stronger radiation blast from its host star.
Vincent Bourrier, lead researcher on the study said, “I think this is the first case where this is so dramatic in terms of planetary evolution” and further added “It’s one of the most extreme examples of a planet undergoing a major mass-loss over its lifetime. 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.”