Upsilon Andromedae b

Ownership: UCP
System: Upsilon Andromedae
Type: Gas giant
Orbit distance: 0.059 AU
Orbit time: 4.6 days
Temperature: 1400 K
Location: Alpha Quadrant

This giant planet circling very close to its sun is always as hot as fire on one side, and potentially as cold as ice on the other. The planet has a giant hot spot in the hemisphere that faces the star Upsilon Andromedae. If you were moving across the planet from the night side to the day side, the temperature jump would be equivalent to leaping into a volcano.

The planet is tidally locked to its star, which means it is rotating slowly enough that the same side always faces the star. However, since this planet is made of gas, its outer atmosphere could be circulating much faster than its interior.

The temperature difference between the two sides of Upsilon Andromedae b is extreme -- about 1,400 degrees C. Such a large temperature difference indicates the planet's atmosphere absorbs and reradiates sunlight so fast that gas circling around it cools off quickly.