hydrogen in the upper atmosphere. That transit is so tangential, that properties such as its radius, density, and temperature are unknown. Assuming a composition similar to that of Jupiter and that its environment is close to chemical equilibrium, 55 Cancri b's upper atmosphere is predicted to be cloudless with a spectrum dominated by alkali metal absorption. The atmosphere's transit indicates that it is slowly evaporating under the sun's heat. The evaporation is slower than that for previously studied (hotter) hot Jupiters. The planet is unlikely to have large moons, since tidal forces would either eject them from orbit or destroy them on short timescales relative to the age of the system. See also Appearance of extrasolar planets Cancer (Chinese astronomy) Lists of exoplanets Gliese 1132 b, Rocky exoplanet with a confirmed atmosphere. Mu Arae c, At constellation Ara Planetary system References External links 55 Cancri Cancer (constellation) Exoplanets discovered in 1996 Giant planets Exoplanets detected by radial velocity Transiting exoplanets Exoplanets with proper names Galileo Galilei Hot Jupiters