  We report the discovery of WASP-103b, a new ultra-short-period planet (P=22.2
hr) transiting a 12.1 V-magnitude F8-type main-sequence star (1.22+-0.04 Msun,
1.44-0.03+0.05 Rsun, Teff = 6110+-160 K). WASP-103b is significantly more
massive (1.49+-0.09 Mjup) and larger (1.53-0.07+0.05 Rjup) than Jupiter. Its
large size and extreme irradiation (around 9 10^9 erg/s/cm^2) make it an
exquisite target for a thorough atmospheric characterization with existing
facilities. Furthermore, its orbital distance is less than 20% larger than its
Roche radius, meaning that it might be significantly distorted by tides and
might experience mass loss through Roche-lobe overflow. It thus represents a
new key object for understanding the last stage of the tidal evolution of hot
Jupiters.
