7 Astounding Facts About Jupiter

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 University Applied Physics Laboratory, which built JEDI. Here's what you need to know about Jupiter.


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.


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.)


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.


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.


Despite having been studied intently since 1609, when Galileo Galilei perfected his telescope, Jupiter remains a stormy mystery in space. The most pressing question is how the planet formed. Answering it will reveal to scientists the story of the early solar system and unlock the secrets of the formation of other worlds. As the most dominant object orbiting the Sun, and likely the oldest planet, in a very real way, the story of Jupiter is the story of the solar system itself.

Essential to the story of Jupiter's birth is whether or not it has a core. The best guess is that pressures at Jupiter's center have compressed hydrogen to a liquid metal state. (Hydrogen is by far the dominant constituent of Jupiter.)

One of the prime objectives of the Juno mission is to find out if a rocky core exists at the planet's center. The traditional theory is that Jupiter has a rocky core that's about 10 times the mass of Earth, and that core collects gases and other materials around it. Behold: the Jupiter you know and love. But recently, some scientists have proposed that Jupiter may have no core at all, and may have formed from the gas and dust particles that "lumped together" just after the formation of the Sun and compressed rapidly, allowing a planet to form without need of a rocky base.

Current data from the Juno mission suggests that perhaps neither model is accurate, and that Jupiter's core is "fuzzy"—without a clear line separating layers—and that it is much larger than anyone expected. Such unexpected results are consistent with Juno's tendency thus far to return textbook-shredding revelations. Already, data returned from the mission have invalidated vast swaths of conventional thinking concerning the Jovian interior.


The Juno spacecraft isn't our first attempt to get a grip on the cosmic behemoth that is Jupiter, and won't be our last. The spacecraft is currently zipping along just 3000 miles above Jupiter's cloud, at top speeds of 130,000 mph. It is rotating on a hugely oblong orbit that takes it close to the planet and then zinging off 5 million miles away. This orbit lasts 53 days. The mission has completed five orbits so far, four of which collected science data, and the mission is budgeted through 2018, at which time NASA officials will have to decide whether to extend its mission and learn more, or just shrug and say, "Ehn, we know enough. Destroy the spacecraft."

Once Juno ends, the next mission slated to launch to the Jovian system is the European Space Agency's JUICE mission in 2022. NASA's Europa Clipper will launch in that same timeframe, and upon its arrival in the system, will study the ocean moon Europa from Jupiter's orbit (where it is largely protected from the punishing radiation environment caused by the planet's magnetosphere).


With just about any telescope and a little bit of work, you can see Jupiter in surprising detail. Your view won't be as crisp as the one from Galileo (the spacecraft), but it'll be at least as good as it was for Galileo (the scientist). You can see its stripes from Earth, and with enough telescope power, even the Great Red Spot. Point a pair of binoculars at Jupiter, and you can see the four Galilean moons—Io, Europa, Callisto, and Ganymede—the same ones found by Galileo, who by spotting the moons ended the idea of a geocentric model of the solar system. Jupiter will next be at opposition (that is, as close to Earth and as bright as it'll get) on May 9, 2018.

A Rare ‘Full Cold Moon Kiss’ Is Coming This Week—Here’s How to See It

jamesvancouver/iStock via Getty Images
jamesvancouver/iStock via Getty Images

Every year ends with a cold moon—the name given to a full moon that appears in December. The full cold moon that's lighting up skies in 2019 will come with a bonus spectacle for sky-gazers. As Forbes reports, a planetary "kiss" between Saturn and Venus will coincide with the last full moon of the year. Here's what you need to know about the astronomical events.

What is a Full Cold Moon Kiss?

The full moon of each month has a unique nickname associated with the time of year it occurs. A cold moon happens as temperatures drop and winter settles in, hence the name. December's full moon has also been called the long nights moon by some Native American tribes and the moon Before Yule in Europe, according to Travel and Leisure.

This year's moon will be visible the night of December 11 through the morning of December 12. On this same night, the planets Venus and Saturn will appear closer than usual in the night sky. The celestial bodies will be less than 2° apart and share a celestial longitude, a phenomena known as a conjunction or a planetary "kiss."

How to See the Full Cold Moon Kiss

During twilight on Tuesday, December 10, the bright planet Venus and the dimmer planet Saturn will arrive at their closest conjunction, 1.8° apart, above the southwestern horizon. The following evening, they'll be just .01° further away. Stick around the night of Wednesday, December 11 to catch the full cold moon, which reaches peak illumination at 9:12 p.m. on the West Coast and at 12 minutes after midnight on the East Coast.

Not planning on staying up late to see the moon reach its fullest state? Moonrise on December 11 will be just as spectacular. When the moon surfaces around sunset, it will appear larger and more reddish in color in the sky. Meanwhile, Venus's and Saturn's kiss will be visible 180º away.

[h/t Forbes]

First-Ever Map of Titan Reveals That Saturn’s Moon Is a Lot Like Earth

NASA/JPL-Caltech/Univ. Arizona/Univ. Idaho
NASA/JPL-Caltech/Univ. Arizona/Univ. Idaho

If there's any life in this solar system outside Earth, we likely won't find it on Mars or even on another planet. Saturn's moon Titan is the place in our celestial neighborhood that's most similar to our own home, and it's where scientists think we have one of the best chances of discovering life. Now, as Nature reports, newly visualized data shows just how much Titan has in common with Earth.

Between 2004 and 2017, the NASA spacecraft Cassini performed more than 100 fly-bys of Saturn's moon. Titan is unique in that it's the only moon in the solar system with clouds and a dense, weather-forming atmosphere. This has made it hard to study from space, but by flying close to the surface, Cassini was able to capture the landscape in an unprecedented level of detail.

Map of Titan.
The first global geologic map of Titan.

NASA's new map of Titan, published in the journal Nature Astronomy, reveals a varied world of mountains, valleys, plains, and sandy dunes that starkly contrast with the desolate wastelands we've seen on neighboring planets. It's also home to seas and lakes, making it the only place in the solar system other than Earth with known bodies of liquid. But instead of water, the pools mottling the moon's surface consist of liquid methane.

Even with its Earth-like geology and atmosphere, chances of finding life on Titan are still slim: Temperatures on the surface average around -300°F. If life does exist there, it's likely limited to microbes in the moon's craters and icy volcanoes.

It will be a while before NASA is able to study Titan up close again: NASA's next drone mission to the body is set for 2034. Until then, scientists have plenty of data recorded by Cassini to teach them more about how the moon formed and continues to change.

[h/t Nature]