Jupiter is the largest planet in the solar system. It’s so large that all of the other planets in the solar system could fit inside it. If we really paid attention to the sky, we’d do nothing but freak out that there’s a giant, terrifying, stormy orb of pressure and gas up there. Mental Floss spoke about Jupiter with an expert: Barry Mauk, the lead investigator of the JEDI instrument on the Juno spacecraft, which entered Jupiter’s orbit on July 4, 2016 to conduct the most in-depth scientific analysis of the planet ever. Mauk is a principal staff physicist at the Johns Hopkins UniversityApplied Physics Laboratory, which built JEDI. Here’s what you need to know about Jupiter.
1. JUPITER IS REALLY, REALLY BIG.
Thirteen hundred Earths could fit inside of Jupiter, like a big celestial gumball machine. It’s big, OK? And its powerful magnetosphere is even bigger—bigger, in fact, than the Sun, a fact made even more astounding when you consider that the Sun could hold a thousand Jupiters.
The amount of time it takes Jupiter to rotate on its axis is known as a Jovian day (Jove is another name for Jupiter in Roman mythology). It only takes about 9.9 hours, but a Jovian year is 4333 Earth days long.
Jupiter is about 5.2 astronomical units from the Sun, compared with Earth’s 1 AU. As such, it takes sunlight about 43 minutes to reach Jupiter. The planet has a lot of moons, too: 69 of them, and that number is still growing. (Two of those moons were discovered just this summer.) Those moons are good news for the future of the planet’s exploration, as they might provide a landing surface. Jupiter isn’t an option because it is a giant ball of gas with no surface that we know of—or at least, no surface that is accessible.
2. YES, IT’S A GAS GIANT. NO, YOU CAN’T JUST FLY YOUR SPACESHIP THROUGH IT.
Despite being a giant ball of gas, you can’t fly through it like a cloud. Its furious storms, ammonia atmosphere, and atmospheric pressure would all annihilate you. How great is the pressure at the center of Jupiter? Nobody knows, exactly, because its center is such a confounding mystery. But pressure at sea level here on Earth is about 14.7 pounds per square inch. That’s pretty comfortable. Pressure at the bottom of the Mariana Trench in the Pacific Ocean is much less pleasant at about 16,000 psi. Still, with the right equipment, it’s manageable, as submarines like the Deepsea Challenger have proven.
Jupiter’s pressure is not manageable. At something like 650,000,000 psi, the “bottom” of Jupiter would compress the Deepsea Challenger to… nobody knows! Because once you start reaching those pressures and heats, the very properties of matter itself become unknowable. (If, in fact, its center consists of liquid metallic hydrogen, you know right away that something weird is going on down there, because we’re describing hydrogen as liquid metal. Down is up, up is down—nothing matters at the center of Jupiter.)
3. JUPITER’S GORGEOUS AURORA? IT’S A SIGN THAT JUPITER IS TRYING TO SPIN UP SPACE ITSELF.
One of the things that most excites Mauk about Jupiter, he tells Mental Floss, is that it is a stepping stone from our solar system to the rest of the universe. “Jupiter is the place to go to if you want to understand how processes that operate within our solar system might apply to more distant astrophysical objects out in the universe,” he says. Jupiter, for example, can help scientists unlock some mysteries of stellar nurseries and regions like the Crab Nebula, where powerful magnetic fields play essential roles.
Consider Jupiter’s stunning auroras. “Earth’s aurora is powered by the solar wind blowing over the magnetic field of Earth. Jupiter’s aurora is powered by rotation. And Jupiter’s very bright aurora—it’s the most intense aurora in the solar system—is a signature of Jupiter’s attempt to spin up its space environment. Jupiter is trying to keep the space environment around it rotating at the same rate that Jupiter is.”
Why is this important? Because astrophysical objects use magnetic fields to shed angular momentum. “An example of that is solar system formation,” he says, where molecular clouds that would normally collapse to form stellar or solar systems spin so fast they can’t collapse. “Magnetic fields are thought to be one of the mechanisms by which angular momentum gets shed by a central object.” Auroras are evidence of this phenomenon.
4. ITS GIANT RED SPOT IS ACTUALLY A GIANT RED CATEGORY 12 HURRICANE.
The Great Red Spot is a massive storm that has been raging on Jupiter for centuries. Though its size varies, at its largest you could fit Earth, Venus, and Mars in there (and probably squeeze Mercury in there too if you really tried); at its smallest it could “only” hold the planet Earth. With wind speeds peaking at 400 miles per hour, it doesn’t even fit on the Saffir-Simpson Hurricane Scale used to measure such giant storms on Earth, though you could extrapolate its speed to being about a Category 12—more powerful, even, than “Humpty’s revenge.” (It would be an F7 tornado on the Fujita scale—an F7 tornado the size of the terrestrial planets of the solar system. The most powerful tornado ever recorded on Earth was an F5, in Oklahoma.)
Scientists recently discovered that the red storm is raging at 2400°F, heating the planet’s upper atmosphere. Still, the chemistry of the spot and its exact nature are still in question. Answers may come on July 11, 2017, when the Juno spacecraft makes a direct pass over the Great Red Spot, marking the most intensive exploration of it ever attempted.