The 149.6 million kilometer distance between the Earth and the Sun provides an ideal temperature for life. However, the temperature of the planets in the Solar System is not only related to their distance from the hot star. So, for example, Neptune is the most distant planet in our system – from it to the Sun 4.5 billion kilometers. But at the same time, Uranus, which is closer to the Sun by 1.7 billion kilometers, is the coldest planet in the solar system.
Uranus has a minimum temperature of minus 224 °C. Neptune’s is minus 214 °C.
What’s the cause?
Planets form over millions of years from rocky objects colliding with each other. Each collision heats up the forming planet. If you clap your hands for a long time, they start to heat up – the same thing happens to planets. So heat builds up in their interior.
Billions of years ago, something huge slammed into Uranus with such force that it tilted the planet on its side. As a result of the violent impact, some of the internal heat escaped. Neptune has not experienced such severe collisions, so it was able to retain most of its heat.
Interestingly, Mercury, the closest planet to the Sun, also gets extremely cold. While the Sun-facing side of Mercury has a temperature of 400 °C, on the other side it drops to minus 200 °C. The reason for these temperature contrasts is that, unlike Earth, Mercury has no atmosphere, which acts like a blanket, trapping heat and spreading it around.
How do they measure the temperature of planets?
To study the atmospheres of nearby planets such as Mars, we can send probes. However, in the case of distant worlds such as Neptune and Uranus, this is not possible. Scientists determine their temperatures by analyzing a planet’s light, which contains data on “temperature markers” – the types of atoms and molecules in its atmosphere.
