Is Uranus Colder Than Neptune

Curious Kids: What is the coldest planet in the solar system?

(Paradigm credit: NASA images/Shutterstock)

This article was originally published at The Chat. (opens in new tab) The publication contributed the article to Space.com's Skillful Voices: Op-Ed & Insights .

Brad Gibson (opens in new tab) , Director of the E.A. Milne Centre for Astrophysics and Head of the Department of Physics and Mathematics, University of Hull

What is the coldest planet in the Solar Organisation? — Sejal, aged seven, Bangalore, India

The planets in our solar system are heated by the sun. Here on Earth, we are about 100 million miles away from the sun — a altitude that provides the perfect temperature for life.

You might think, so, that the coldest planet in the solar system would be Neptune, as it is the furthest abroad from the dominicus's warmth. Neptune is an incredible three billion miles away from the sun.

Notwithstanding, the coldest planet is not Neptune, but Uranus — even though Uranus is a billion miles closer to the sun than Neptune. Uranus holds the record for the coldest temperature e'er measured in the solar system: a very chilly minus 371 degrees Fahrenheit (minus 224 degrees Celsius), according to NASA (opens in new tab) . The temperature on Neptune is even so very cold (opens in new tab), of course — commonly effectually minus 353 degrees F (minus 214 degrees C) — but Uranus beats that.

Related: 25 weird and wild solar organization facts

A composite image of Uranus shows both X-ray emissions and infrared emissions against an optical view of the planet. — A Hubble Space Telescope view showing Uranus surrounded past its 4 major rings and x of its 17 known satellites. (Image credit: Ten-ray: NASA/CXO/University College London/Westward. Dunn et al; Optical (HRC): Westward.M. Keck Observatory); Optical (VLT/HRC): ESO/VLT/Kirill Feigelman)

Knocked sideways

The reason why Uranus is so cold is naught to do with its altitude from the sunday. Billions of years ago, something big crashed into Uranus (opens in new tab) with so much strength that information technology tipped the planet over onto its side. Uranus still rolls around the lord's day on its side today. The affect of the crash too let some of the heat that was trapped inside Uranus escape.

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Curious Kids is a series by The Conversation that gives children the gamble to have their questions about the world answered by experts. If yous accept a question you lot'd like an skillful to answer, send it to curiouskids@theconversation.com . We won't be able to reply every question, only we'll exercise our very all-time. (Image credit: The Conversation)

The heat inside planets is left over from when they were formed. Planets are made when smaller chunks of rock blast together, building the full planet piece past piece over many millions of years. Every time these rocks boom together, the planet gains a little more heat. If yous clap your hands together for a long time they will starting time to feel hot — the same thing happens with planets.

Neptune wasn't hit by a huge asteroid like Uranus was, so it has been able to hold on to more than of its oestrus.

You might also be surprised to learn that the closest planet to the sunday, Mercury, can also exist extremely cold. While the side of Mercury facing the sun is more than 750 degrees F (400 degrees C), the side facing away from the sun is nearly minus 328 degrees F (minus 200 degrees C).

The reason for this is that Mercury does not accept whatever atmosphere (opens in new tab), dissimilar Globe. An atmosphere like ours acts like a blanket, holding heat in and spreading it all around. Because information technology does not have this blanket, the front side and the back side of Mercury can take very dissimilar temperatures.

Measuring temperatures in space

For some nearby planets similar Mars, nosotros can send probes to study the atmosphere directly from the planet'southward surface. However, we haven't been able to practise this for afar planets such as Neptune and Uranus.

Instead, we have to work out how cold they are by measuring their temperature from here on Earth. Nosotros do this past studying the light from the planet, which can tell us the types of atoms and molecules which make upward the planet'due south atmosphere. This information lets united states of america know exactly what the temperature of the planet is: the atoms and molecules deed as a kind of temperature "fingerprint" for the planet.

While these planets in our solar system are incredibly cold, there are even chillier places in the universe. The coldest of all is the Boomerang Nebula (opens in new tab), a cloud of dust and gas xxx million billion miles away from us. In that location, the temperature reaches minus 457 degrees F (minus 272 degrees C).

Nix in the universe can be colder than minus 459 degrees F (minus 273 degrees C), because at that temperature the tiny particles and atoms that everything is made of basically cease moving, and once that happens information technology's impossible to get colder. This temperature is known as absolute zero (opens in new tab). This means it is unlikely that nosotros will ever observe anywhere in the Universe colder than the Boomerang Nebula.

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