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.

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.

5. THE MOST PRESSING QUESTION FOR SCIENTISTS: HOW DID JUPITER FORM?

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.

6. WE'RE KEEPING A CLOSE EYE ON IT.

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).

7. YOU DON'T NEED TO TAKE NASA'S WORD ON JUPITER. YOU CAN SEE IT YOURSELF.

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.

Tonight, the Lyrid Meteor Shower Peaks on Earth Day

iStock/dmoralesf
iStock/dmoralesf

Tonight, look up and you might see shooting stars streaking across the sky. On the night of Monday, April 22—Earth Day—and the morning of Tuesday, April 23, the Lyrid meteor shower will peak over the Northern Hemisphere. Make some time for the celestial show and you'll probably see meteors zooming across the heavens every few minutes. Here is everything you need to know about this meteor shower.

What is the Lyrid meteor shower?

Every 415.5 years, the comet Thatcher circles the Sun in a highly eccentric orbit shaped almost like a cat's eye. At its farthest from the Sun, it's billions of miles from Pluto; at its nearest, it swings between the Earth and Mars. (The last time it was near the Earth was in 1861, and it won't be that close again until 2280.) That's quite a journey, and more pressingly, quite a variation in temperature. The closer it gets to the Sun, the more debris it sheds. That debris is what you're seeing when you see a meteor shower: dust-sized particles slamming into the Earth's atmosphere at tens of thousands of miles per hour. In a competition between the two, the Earth is going to win, and "shooting stars" are the result of energy released as the particles are vaporized.

The comet was spotted on April 4, 1861 by A.E. Thatcher, an amateur skywatcher in New York City, earning him kudos from the noted astronomer Sir John Herschel. Clues to the comet's discovery are in its astronomical designation, C/1861 G1. The "C" means it's a long-period comet with an orbit of more than 200 years; "G" stands for the first half of April, and the "1" indicates it was the first comet discovered in that timeframe.

Sightings of the Lyrid meteor shower—named after Lyra, the constellation it appears to originate from—are much older; the first record dates to 7th-century BCE China.

How to See the Lyrid Meteor Shower

Monday night marks a waning gibbous Moon (just after the full Moon), which will reflect a significant amount of light. You're going to need to get away from local light pollution and find truly dark skies, and to completely avoid smartphones, flashlights, car headlights, or dome lights. The goal is to let your eyes adjust totally to the darkness: Find your viewing area, lay out your blanket, lay down, look up, and wait. In an hour, you'll be able to see the night sky with great—and if you've never done this before, surprising—clarity. Don't touch the smartphone or you'll undo all your hard ocular work.

Where is the nearest dark sky to where you live? You can find out on the Dark Site Finder map. And because the shower peaks on a Monday night—when you can expect to see 20 meteors per hour—your local astronomy club is very likely going to have an event to celebrate the Lyrid meteor shower. Looking for a local club? Sky & Telescope has you covered.

Other Visible Bodies During the Lyrid meteor shower

You don't need a telescope to see a meteor shower, but if you bring one, aim it south to find Jupiter. It's the bright, unblinking spot in the sky. With a telescope, you should be able to make out its stripes. Those five stars surrounding it are the constellation Libra. You'll notice also four tiny points of light nearby. Those are the Galilean moons: Io, Europa, Ganymede, and Callisto. When Galileo discovered those moons in 1610, he was able to prove the Copernican model of heliocentricity: that the Earth goes around the Sun.

What to Do if There's Bad Weather During the Lyrid Meteor Shower

First: Don't panic. The shower peaks on the early morning of April 23. But it doesn't end that day. You can try again on April 24 and 25, though the numbers of meteors will likely diminish. The Lyrid meteor shower will be back next year, and the year after, and so on. But if you are eager for another show, on May 5, the Eta Aquarids will be at their strongest. The night sky always delivers.

Does the Full Moon Really Make People Act Crazy?

iStock.com/voraorn
iStock.com/voraorn

Along with Mercury in retrograde, the full moon is a pretty popular scapegoat for bad luck and bizarre behavior. Encounter someone acting strangely? Blame it on the lunar phases! It's said that crime rates increase and emergency rooms are much busier during the full moon (though a 2004 study debunked this claim). Plus, there's that whole werewolf thing. Why would this be? The reasoning is that the Moon, which affects the ocean's tides, probably exerts a similar effect on us, because the human body is made mostly of water.

This belief that the Moon influences behavior is so widely held—reportedly, even 80 percent of nurses and 64 percent of doctors think it's true, according to a 1987 paper published in the Journal of Emergency Medicine [PDF]—that in 2012 a team of researchers at Université Laval's School of Psychology in Canada decided to find out if mental illness and the phases of the Moon are linked [PDF].

To test the theory, the researchers evaluated 771 patients who visited emergency rooms at two hospitals in Montreal between March 2005 and April 2008. The patients chosen complained of chest pains, which doctors could not determine a medical cause for the pains. Many of the patients suffered from panic attacks, anxiety and mood disorders, or suicidal thoughts.

When the researchers compared the time of the visits to the phases of the Moon, they found that there was no link between the incidence of psychological problems and the four lunar phases, with one exception—in the last lunar quarter, anxiety disorders were 32 percent less frequent. "This may be coincidental or due to factors we did not take into account," Dr. Geneviève Belleville, who directed the team of researchers, said. "But one thing is certain: we observed no full-moon or new-moon effect on psychological problems."

So rest easy (or maybe not): If people seem to act crazy during the full Moon, their behavior is likely pretty similar during the rest of the lunar cycle as well.

This story was updated in 2019.

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