NGTS-6b: an ultrashort period hot-Jupiter orbiting an old K dwarf

We report the discovery of a new ultra-short period hot Jupiter from the Next Generation Transit Survey. NGTS-6b orbits its star with a period of 21.17 h, and has a mass and radius of 1.330+0.024−0.028MJ and 1.271+0.197−0.188RJ respectively, returning a planetary bulk density of 0.805+0.498−0.283 g cm−3. Conforming to the currently known small population of ultra-short period hot Jupiters, the planet appears to orbit a metal-rich star ([Fe/H]=+0.11 ± 0.09 dex). Photoevaporation models suggest the planet should have lost 5% of its gaseous atmosphere over the course of the 9.6 Gyrs of evolution of the system. NGTS-6b adds to the small, but growing list of ultra-short period gas giant planets, and will help us to understand the dominant formation and evolutionary mechanisms that govern this population.