The stable climate of KELT-9b

Even among the most irradiated gas giants, so-called ultra-hot Jupiters, KELT-9b stands out as hottest planet thus far discovered with a dayside temperature of over 4500 K. At these extreme irradiation levels, we expect an increase in heat redistribution efficiency and low Bond albedo owed to extended atmosphere molecular hydrogen dissociation occurring on planetary dayside. We present new photometric observations KELT-9 system throughout 4 full orbits 9 separate occultations obtained by 30 cm space telescope CHEOPS. The CHEOPS bandpass, located at optical wavelengths, captures peak thermal emission spectrum KELT-9b. In this work simultaneously analyse phase curves along public from TESS Spitzer infer joint constraints curve variation, gravity-darkened transits, occultation depth three bandpasses, well derive 2D maps different depths. find day-night ~0.3 which confirms expectations enhanced energy transfer nightside due recombination hydrogen. also calculate consistent zero. no evidence variability brightness planet, excluding greater than 1%