Upsilon Andromedae B - Physical Characteristics

Physical Characteristics

Given the planet's high mass, it is likely that Upsilon Andromedae b is a gas giant with no solid surface. Since the planet has only been detected indirectly, properties such as its radius and composition are unknown.

The Spitzer Space Telescope measured the planet temperature, and found that the difference between the two sides of Upsilon Andromedae b of about 1,400 degrees Celsius, ranging from minus 20 to 230 degrees to about 1,400 to 1,650 degrees Celsius. The temperature difference has led to speculation that Upsilon Andromedae b is tidal locked with the same side always facing Upsilon Andromedae A.

Sudarsky had, on the assumption that the planet is similar to Jupiter in composition and that its environment is close to chemical equilibrium, predicted Upsilon Andromedae b to have reflective clouds of silicates and iron in its upper atmosphere. The cloud deck instead absorbs the sun's radiation; between that and the hot, high pressure gas surrounding the mantle, exists a stratosphere of cooler gas. The outer shell of dark, opaque, hot cloud is assumed to consist of vanadium and titanium oxides ("pM planets"), but other compounds like tholins cannot be ruled out as of yet.

The planet has possibly, trough unlikely,one or more moons. Due to great size of the planet,the moons can be as large as Mars. A moon so great in size would have enough gravity to keep an atmosphere.The distance of the planet from Upsilon Andromedae A is too small to make liquid water possible. However, as the composition of its atmosphere is unknown,it may have gases that block some of the sunlight and thus cool down the moon.If it is so, it may host extraterrestrial life and/or be habitable for humans.

The planet (with 51 Pegasi b) is deemed a candidate for direct imaging by Planetpol.