Hot Super Neptune Burns with Mystery

A hot super Neptune seen by astronomers shouldn’t exist — but there it is, as TESS looks on.

The exoplanet LTT 9779b is far more massive than our own world, and the world is nearly five times larger. Temperatures on its surface put Venus — the hottest planet in our solar system — to shame. This exoplanet, discovered just last year, is so extreme it should not exist — at least not for long.

Hot Neptunes are — theoretically — worlds the size of Neptune or slightly larger than Neptune, orbiting close to their parent stars. However, such planets were thought to be unstable, as the atmospheres would be driven off by heat from the local star.

“This planet is so intensely irradiated by its star that its temperature is over 3,000 degrees Fahrenheit and its atmosphere could have evaporated entirely. Yet, our Spitzer observations show us its atmosphere via the infrared light the planet emits,” Ian Crossfield, assistant professor of physics and astronomy at the University of Kansas stated.

Much like the more-familiar hot Jupiters, hot Neptunes are highly gaseous worlds, but they are not nearly as massive as their larger cousins.

Roughly 30 times more massive than Earth, LTT 9779 b orbits six times closer to its parent star as the Earth does from the Sun. The star at the center of this…