A hot Jupiter is a giant exoplanet with a short orbital period and strong stellar irradiance, typically orbiting much closer to its star than Mercury orbits the Sun. Large radius and short orbital period make these bodies favourable for exoplanet transit photometry; large mass and small orbital separation also increase the stellar radial-velocity semi-amplitude.
Strong external heating makes an exoplanet atmosphere very different from that of Jupiter. Tidal locking can maintain nearly permanent illuminated and dark hemispheres, creating a large driving force for day-night heat redistribution. HD 209458 b illustrates transit spectroscopy, while HD 189733 b illustrates an exoplanet thermal phase curve. Their proximity to their stars also motivates planetary migration models: present orbital location need not be the location of formation.
New to topics? Read the docs here!