Characteristics
55 Cancri b is a gas giant with no solid surface. The atmospheric transit has demonstrated 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.
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