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Updated April 25, 2017 By Wanda Starr
The order of planets from hottest to coldest is almost in order of its proximity to the sun, because the sun is the primary heat source. However, another factor that effects a planet’s atmospheric temperature is the gases that make up the atmosphere. Gases like carbon dioxide cause a greenhouse effect trapping heat in.
Venus' atmosphere consists of carbon dioxide and nitrogen, with clouds of sulfuric acid droplets.The greenhouse gases in Venus’ atmosphere trap heat and make it so hot that you can melt lead. In fact, any of NASA's exploratory spacecraft that has landed on Venus has only been able to last for a few hours. With atmospheric temperatures of 864 degrees Fahrenheit, the second planet is the hottest.
In photos of Mars, you can see the ice in the atmosphere. Due to its tilt, Mars has seasons like Earth. In the winter, it can go as low as -125 degrees Fahrenheit. The current temperatures and atmospheric conditions make it impossible for water to last very long on the planet – making it doubtful that life exists on Mars. However, scientists have found evidence that water once existed on the planet.
On parts of Earth, it can get as cold as -126 degrees Fahrenheit, similar to Mars’ coldest temperatures.
As the planet closest to the sun, you might expect Mercury to be one of the hottest planets and it is. It is also one of the coldest. Because Mercury doesn’t have an atmosphere, the side of the planet that faces the sun can reach temperatures of 800 degrees, but on the side that faces away from the sun and its lowest temperature can drop to -290 degrees Fahrenheit.
Known for its rings made of ice chunks and rock, Saturn's lowest temperatures can get to -288 degrees Fahrenheit. If you weigh 100 pounds on Earth, you will weigh approximately 107 pounds on Saturn. The atmosphere is made primarily of helium and hydrogen
The biggest planet in our solar system contains a system of moons and rings that make it like a minisystem. Jupiter has 50 moons – four large moons and 46 smaller moons. The massive planet can get as cold as -234 degrees Fahrenheit. Like Saturn and Uranus, the atmosphere is made up of hydrogen and helium.
With a temperature of -357 degrees Fahrenheit, Uranus is the coldest planet in the solar system. The atmosphere is made up of methane, hydrogen and helium – the methane giving it its green look. Most of the mass of Uranus is made up of water, methane and ammonia ice.
Since Pluto was classified as a dwarf planet in 2006, Neptune became the farthest planet from the sun. It is no surprise that, 30 times farther from the sun than Earth, Neptune is one of the coldest planets. It has a temperature of -214 degrees Fahrenheit. The atmosphere, similar to Uranus, consists of hydrogen, helium and methane. Scientists believe that another unknown gas exists in the atmosphere, because it appears to be a bright blue, as opposed to the Uranus’ blue-green that comes from the methane.
First the quick facts: Our Solar System has eight “official” planets which orbit the Sun. Here are the planets listed in order of their distance from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. An easy mnemonic for remembering the order is “My Very Educated Mother Just Served Us Noodles.” If you add in the dwarf planets, Ceres is located in the asteroid belt between Mars and Jupiter, while the remaining dwarf planets are in the outer Solar System and in order from the Sun are Pluto, Haumea, Makemake, and Eris. There is, as yet, a bit of indecision about the Trans-Neptunian Objects known as Orcus, Quaoar, 2007 O10, and Sedna and their inclusion in the dwarf planet category. A mnemonic for this list would be “My Very Educated Mother Could Just Serve Us Noodles, Pie, Ham, Muffins, and Eggs” (and Steak, if Sedna is included.) You can find more tricks for remembering the order of the planets at our detailed article here. Now, let’s look at a few details including the definition of a planet and a dwarf planet, as well as details about each of the planets in our Solar System. Artistic impression of the Solar System, with all known terrestrial planets, as giants, and dwarf planets. Credit: NASAWhat is a Planet?In 2006, the International Astronomical Union (IAU) decided on the definition of a planet. The definition states that in our Solar System, a planet is a celestial body which:
This means that Pluto, which was considered to be the farthest planet since its discovery in 1930, now is classified as a dwarf planet. The change in the definition came after the discovery three bodies that were all similar to Pluto in terms of size and orbit, (Quaoar in 2002, Sedna in 2003, and Eris in 2005). With advances in equipment and techniques, astronomers knew that more objects like Pluto would very likely be discovered, and so the number of planets in our Solar System would start growing quickly. It soon became clear that either they all had to be called planets or Pluto and bodies like it would have to be reclassified.
With much controversy then and since, Pluto was reclassified as a dwarf planet in 2006. This also reclassified the asteroid Ceres as a dwarf planet, too, and so the first five recognized dwarf planets are Ceres, Pluto, Eris, Makemake and Haumea. Scientists believe there may be dozens more dwarf planets awaiting discovery. Later, in 2008, the IAU announced the subcategory of dwarf planets with trans-Neptunian orbits would be known as “plutoids.” Said the IAU, “Plutoids are celestial bodies in orbit around the Sun at a distance greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighborhood around their orbit.” This subcategory includes Ceres, Pluto, Haumea, Makemake, and Eris. The Planets in our Solar System:Having covered the basics of definition and classification, let’s get talking about those celestial bodies in our Solar System that are still classified as planets (sorry Pluto!). Here is a brief look at the eight planets in our Solar System. Included are quick facts and links so you can find out more about each planet. Mercury: Mercury is also the smallest planet in our Solar System, and is also smaller than its largest moon (Ganymede, which orbits Jupiter). And being equivalent in size to 0.38 Earths, it is just slightly larger than the Earth’s own Moon. But this may have something to do with its incredible density, being composed primarily of rock and iron ore. Here are the planetary facts:
Venus: And due to its thick atmosphere and proximity to the Sun, it is the Solar Systems hottest planet, with temperatures reaching up to a scorching 735 K (462 °C). To put that in perspective, that’s over four and a half times the amount of heat needed to evaporate water, and about twice as much needed to turn tin into molten metal (231.9 °C)!
Earth: Whether it is gravity (g), distance (measured in AUs), diameter, mass, density or volume, the units are either expressed in terms of Earth’s own values (with Earth having a value of 1) or in terms of equivalencies – i.e. 0.89 times the size of Earth. Here’s a rundown of the kinds of
Mars: The same holds true for surface features. Like Earth, Mars has many familiar surface features, which include volcanoes, valleys, deserts, and polar ice caps. But beyond these, Mars and Earth have little in common. The Martian atmosphere is too thin and the planet too far from our Sun to sustain warm temperatures, which average 210 K (-63 ºC) and fluctuate considerably.
Jupiter: Jupiter’s atmosphere is the most intense in the Solar System. In fact, the combination of incredibly high pressure and coriolis forces produces the most violent storms ever witnessed. Wind speeds of 100 m/s (360 km/h) are common and can reach as high as 620 km/h (385 mph). In addition, Jupiter experiences auroras that are both more intense than Earth’s, and which never stop.
Saturn:
Uranus: Uranus is also the coldest planet in our Solar System, making the term “ice” seem very appropriate! What’s more, its system of moons experience a very odd seasonal cycle, owing to the fact that they orbit Neptune’s equator, and Neptune orbits with its north pole facing directly towards the Sun. This causes all of its moons to experience 42 year periods of day and night.
Neptune: Due to its extreme distance from our Sun, Neptune cannot be seen with the naked eye, and only one mission has ever flown close enough to get detailed images of it. Nevertheless, what we know about it indicates that it is similar in many respects to Uranus, consisting of gases, ices, methane ice (which gives its color), and has a series of moons and faint rings.
Now you know! And if you find yourself unable to remember all the planets in their proper order, just repeat the words, “My Very Educated Mother Just Served Us Noodles.” Of course, the Pie, Ham, Muffins and Eggs are optional, as are any additional courses that might be added in the coming years! We have many great articles on the Solar System and the planets here at Universe Today. Here is a rundown of the Inner Planets, the Outer Planets, a description of Terrestrial Planets, the Dwarf Planets, and Why Pluto is no Longer a Planet?. Astronomy Cast also has some cool episodes about the Solar System. Here’s Episode 68: Pluto and the Icy Outer Planets, Episode 306: Accretion Discs, and Episode 159: Planet X. |