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Top Ten Facts About Jupiter
10. Jupiter is the largest planet in our solar system.
The four outer planets (Jupiter, Saturn, Uranus and Neptune) are called jovian planets, which means Jupiter-like. They are called such because of their massive sizes. Jupiter is by far the largest; all of the other planets combined would fit inside it!
The planets in our solar system have a vast range of compositions—Jupiter and Saturn are gas giants, while Uranus and Neptune are ice giants. By contrast, the inner planets are composed largely of rock and metal.
So why are the outer and inner planets so different? The answer lies in condensation, determined by where each formed. At the beginning of our solar system, there was a lot of debris everywhere—rock, ice, metal, etc. The pieces would smash into each other, growing ever larger. This process is called accretion, and is similar to using a large ball of Play-Doh to pick up other smaller pieces—thereby increasing the size of the original ball.
The inner, or terrestrial, planets formed near the Sun. There, temperatures are more suitable for the formation of rock and metal; so that's what was there, smashing into each other.
Much farther from the Sun, where the jovian planets formed, temperatures were more conducive to the condensation of gases and ice. Again, that material is simply what was there—through the process of accretion, it built up to the formation of the planets we now know.
Interestingly, Stepinski and Valageas (of the Lunar Planetary Institute and Saclay Nuclear Research Centre, respectively) have developed a model and conducted experiments which have led them to say that "some initial conditions lead to all solids being lost to the star." That means there should be planetless stars. However, they stated that there were also conditions which led to "a radial distribution of solid material"—like in our own solar system.
9.Gravity on Jupiter is more than double what we experience on Earth.
The force of gravity that we are used to feeling here on the surface of Earth is 9.8 m/s^2. At surface-level on Jupiter, the force of gravity is 23.1 m/s^2—about 2 1/3 times as strong as ours!
Weight is a measure of gravity's pull on something, so it can change based on location. The factors affecting gravity are mass and distance. On Earth, we experience the gravity that we do because of how far we are from the center of the Earth and the amount of mass that it's composed of.
On Jupiter, surface-level is MUCH farther from the center than it is here—but gravity is still much stronger because of its incredible amount of mass. Someone weighing 100 pounds on Earth would weigh about 236 pounds on Jupiter!
8. Jupiter's average temperature is -170 degrees Fahrenheit.
The Earth is situated approximately 93 million miles from the Sun. Jupiter is over five times farther from the Sun! (The image above is obviously not to scale). Understandably, it's much colder that far away from the Sun's warmth.
Though the average temperature at the surface-level is -170 degrees Fahrenheit, other parts of Jupiter can be colder or much hotter than that. In the clouds, for example, temperatures range from -190 to 26 degrees Fahrenheit, depending on composition.
What's interesting, considering that Jupiter is so incredibly cold, is that its core is believed to be exceptionally hot. It is thought to be around 43,000 degrees Fahrenheit. If correct, that makes the core of Jupiter over four times hotter than the surface of the Sun!
7. Jupiter is composed of the same material as stars.
Our Sun is made mainly of hydrogen and helium. So is Jupiter! According to NASA, "Jupiter would have become a star if it were about 80 times bigger."
Jupiter's atmosphere is composed almost exclusively of hydrogen and helium, with trace amounts of other things like methane and ammonia. Much is still unknown about the composition of Jupiter itself, which is why Juno is on its way to study it (see fact 1, below).
In addition to distance from the Sun, atmospheric makeup can be a factor in determining a planet's temperature. See the figure at the right, noting that Mercury is over twice as cold as Venus, though also nearly twice as close to the Sun. The difference is that Mercury has very little atmosphere, whereas the atmosphere on Venus is very thick. That helps Venus to lock in heat, while much of Mercury's escapes.
6. A year for Jupiter lasts about 12 Earth years.
Since Jupiter is more than five times farther from the Sun than Earth is, it has to cover much more distance to complete a full revolution around the Sun. It's the same principle behind staggering the starting line for runners in a track event. If all the runners started in a straight line instead, the runner in the inside lane would have the shortest distance run. The distance to be run would increase more and more as you approach the outermost lane.
Also the farther a planet is from the Sun, the slower it travels in its orbit. That's because distance is a major factor in determining gravitational force (back up to fact 9 if you've forgotten!). The closer a planet is to the Sun, the more quickly it speeds along its orbit. For Jupiter, the orbital speed is about 13.07 kilometers per second! That sounds like a lot (and it is), but Earth travels at 30 kilometers per second--about 2.3 times as fast as Jupiter.
5. Jupiter is the fastest spinning planet in our solar system.
Though its year is much longer than ours, its day is less than half the length of an Earth day—only about 10 hours! That's especially incredible considering how large it is.
Jupiter's speedy spinning creates monstrous wind and storms. Wind on Jupiter can reach over 400 miles per hour! Considering that, it's a bit easier to understand the magnitude of the storms Jupiter experiences—most notably, the Great Red Spot.
4. Jupiter's Great Red Spot is a storm 2-3 times the size of Earth.
The Great Red Spot is a terrifyingly enormous storm that's been raging for over 300 years. We know that Schwabe, an amateur astronomer from Germany, made record of it in 1831, but it may be the same as Cassini's "Permanent Spot," discovered in 1665.
When it comes to this storm, scientists have more questions than answers. According to the Encyclopedia Britannica, "an exact theory that explains both its source of energy and its stability remains to be developed." For now, it persists as something of a mystery.
3. Jupiter has 67 named moons and a small ring system.
Though Saturn is the planet most famous for them, ALL of the jovian planets have ring systems. Jupiter's ring system is composed of three primary components, known as the Halo, Gossamer, and Main rings.
Jupiter also has 67 named moons. The largest four are pictured above: Io, Europa, Ganymede, and Callisto. They are known as the Galilean moons, after the Italian astronomer who discovered them: Galileo (pictured below). Though they're all moons of the same planet, they are vastly different.
Io is a little larger than Earth's moon. It may have its own magnetic field, and it's the only moon known to have active volcanoes. It's actually the most volcanically active body in the entire solar system!
Contrast that with Europa. It's completely covered in ice; it has very visible cracks all over it (visible in the image above—Europa is the moon on the top left). Beneath the ice astronomers believe there may be an ocean. If so, it could potentially be harboring life even as you read this! The possibility of life (or at least a habitable environment) on Europa is so compelling that a NASA mission, Europa Clipper, is being planned to investigate it. This mission will launch sometime in the 2020s and will complete a series of flybys to study the moon.
Ganymede is a giant—it's even bigger than the planet Mercury, and easily the largest moon in the solar system. It's the only moon that astronomers know to have its own magnetic field, just as they suspect Io might.
The most cratered body in the solar system is Callisto. Like Europa, astronomers believe Callisto may have an ocean deep beneath its icy surface.
2. Jupiter was named for the Roman king of the Gods.
In Roman mythology, Jupiter ruled over all the other gods. He was also the god of the sky. The planet Jupiter's name is very appropriate, considering that it is the largest of all our planets and it's famous for its stripes or banding, which are clouds in its atmosphere.
It is also appropriate because Jupiter (among many, many other ancient gods) was known for abducting goddesses and mortals. Jupiter's moons are named for these individuals. Marilyn Morgan, of the NASA Jet Propulsion Laboratory, notes that these names are "an appropriate choice since the moons of Jupiter are indeed caught in its gravitational pull."
Because he wanted to hide his mischievous doings, Jupiter is said to have surrounded himself in a shroud of clouds. The only one who could see through them was his wife: Juno.
1. Juno is a current mission by NASA to learn more about Jupiter.
Juno is a very exciting mission, which arrived at the planet in July 2016. Its goals are to study Jupiter's clouds, gravitational field, planetary composition, the aurorae caused by its strong magnetic field, and several other things as well. It is in a polar orbit, which allows us to characterize the planet's perplexing poles.
So many things about Jupiter remain shrouded in mystery, but hopefully Juno will allow us to see past the obscurity.
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