KELT-2Ab is an extrasolar planet that orbits the starKELT-2A approximately 440 light-years away in the constellation of Auriga.[1] It was discovered by the KELT-North survey via the transit method - so both its mass and radius are known quite precisely - in a paper led by Thomas Beatty. As of its discovery KELT-2Ab is the fifth-brightest transiting Hot Jupiter known that has a well constrained mass. This makes the KELT-2A system a promising target for future space- and ground-based follow-up observations to learn about the planet's atmosphere.[3]
The water vapour was detected in planetary atmosphere in 2018.[4]
^Piskorz, Danielle; Buzard, Cam; Line, Michael R.; Knutson, Heather A.; Benneke, Björn; Crockett, Nathan R.; Lockwood, Alexandra C.; Blake, Geoffrey A.; Barman, Travis S.; Bender, Chad F.; Deming, Drake; Johnson, John A. (2018), "Ground- and Space-based Detection of the Thermal Emission Spectrum of the Transiting Hot Jupiter KELT-2Ab", The Astronomical Journal, 156 (3): 133, arXiv:1809.05615, Bibcode:2018AJ....156..133P, doi:10.3847/1538-3881/aad781, S2CID119033501