According to scientists, the surface of Neptune is one of the coldest places in the Solar System. At its surface, where the clouds of the planet touch space, the temperature of Neptune can dip down to 55 Kelvin. That’s -218 degrees Celsius.
The average temperature of Neptune is 73 K (-200 Celsius). But one strange anomaly is the planet’s south pole, which is 10 degrees warmer than the rest of planet. This “hot spot” occurs because Neptune’s south pole is currently exposed to the Sun. As Neptune continues its journey around the Sun, the position of the poles will reverse. Then the northern pole will become the warmer one, and the south pole will cool down.
If you could travel down into Neptune, temperatures would increase dramatically. Like all the planets, the temperature of Neptune’s interior is much hotter than its outside. The temperature of the core of Neptune is 7000 degrees Celsius, which is comparable to the surface of the Sun.
The huge temperature differences between Neptune’s center and its surface create huge wind storms. The winds on Neptune have been measured as high as 2,100 km/hour, which makes them the fastest in the Solar System.
Want to compare Neptune’s temperature to other objects in the Solar System? Pluto’s temperature will only get down to 33 Kelvin, which is even colder than Neptune. But Pluto isn’t a planet, so it can’t be the coldest planet in the Solar System.
We have written many articles about Neptune on Universe Today. Here’s an article about how the temperatures inside Neptune could get to the point that liquid oceans of water might exist.
We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune.