- 72 degree(s) Kelvin
- Not Applicable ()
The coldest planet in the solar system is Neptune, which has an average surface temperature of 72°K (-201.15°C; -330.07°F). For gas giants such as Neptune, which don't have a solid surface, this measurement is taken from the level of the atmosphere where the pressure is at 1 bar (100 kPA; the same as surface atmospheric pressure on Earth).
Although Neptune is 1.62 billion km (1 billion mi) farther from the Sun than Uranus, the inner of these two planets is only marginally warmer. Due to Uranus's mysteriously cool planetary core, the mean surface temperature is only 76°K (-197.15°C; -322.87°F). The surface of Uranus also has cold spots, where the temperature drops even lower, reaching just 49°K (-224°C; -371°F) – the coldest measured atmospheric temperature on any planet.