Kepler-13Ab Artist’s Concept

This illustration shows the seething hot planet Kepler-13Ab that circles very close to its host star, Kepler-13A. Seen in the background is the star's binary companion, Kepler-13B, and the third member of the multiple-star system is the orange dwarf star Kepler-13C.

The alien world, called a "hot Jupiter," is actually six times more massive than Jupiter. Unlike chilly Jupiter, this exoplanet is one of the hottest known of the hot Jupiters, with a dayside temperature of nearly 5,000 degrees Fahrenheit. Another difference between Jupiter and Kepler-13Ab is that the exoplanet is so close to its star that it is tidally locked. One side keeps a permanent face to the star, and the other side is perpetually dark.

On the colder nighttime side, titanium oxide gas changes to titanium dioxide. The planet's immense gravity pulls the titanium dioxide deeper into the atmosphere, where it precipitates as snow. Hubble observations of the planet's atmospheric temperature profile represent the first time astronomers have detected this precipitation process, called a "cold trap," on an exoplanet. Without titanium oxide gas to absorb incoming starlight on the daytime side, the atmospheric temperature grows colder with increasing altitude. Normally, titanium oxide in the atmospheres of hot Jupiters absorbs light and reradiates it as heat, making the atmosphere grow warmer at higher altitudes. The Kepler-13 system is 1,730 light-years from Earth.

The research teams consists of Thomas Beatty, Ming Zhao, Jason Wright, and Ronald Gilliland (Pennsylvania State University, University Park), Nikku Madhusudhan (University of Cambridge, U.K.), Angelos Tsiaras (University College London, U.K.), and Avi Shporer and Heather Knutson (California Institute of Technology, Pasadena, California).