Which of the nine planets is called the coldest planet?

Among the nine planets, Pluto is the coldest.

The surface temperature of Pluto is about MINUS 230 degrees Celsius, which is several times higher than the familiar MINUS temperature. Such extreme temperatures make Pluto an extremely cold environment. In fact, the surface temperature of Pluto is enough to solidify and freeze almost all substances, including gases and liquids. This is a very unsuitable environment for life forms.

Due to the influence of low temperature, Pluto's atmosphere is thin and scarce. Pluto has only a very thin atmosphere, mainly composed of nitrogen and methane. This thin atmosphere can't carry and protect a lot of gas and water molecules, which leads to the dry and barren surface of Pluto. This dry environment makes there almost no water on Pluto, and neither liquid water nor gaseous water can exist there.

Pluto orbital period:

Pluto's orbital period is about 248 years, which means it takes Pluto a long time to revolve around the sun. This long orbital period directly affects the climate and weather changes of Pluto.

There is a special * * vibration relationship between Pluto's orbital period and planetary rotation period, that is, 3: 2 * * * vibration. This means that Pluto's rotation period is half its orbital period plus one hour. This special * * * vibration relationship will cause the seasonal change of Pluto's surface to be very violent.

In a season of Pluto, its southern hemisphere will face extreme low temperature and darkness, while the northern hemisphere will usher in a relatively warm and bright season. This seasonal change has an important influence on the climate and geological activities on the surface of Pluto.

Reference to the above content: Baidu Encyclopedia-Pluto