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.

How to See the Full Sturgeon Moon on Thursday

Brook Mitchell, Stringer/Getty Images
Brook Mitchell, Stringer/Getty Images

The full moon of every month has a special nickname. Some—like September's harvest moon, December's cold moon, and May's flower moon—have obvious connections to their seasons, while other names are harder to decode. August's sturgeon moon is an example of the latter. It may not be the prettiest lunar title in The Old Farmer's Almanac, but that doesn't mean the event itself on August 15, 2019 won't be a spectacular sight to behold.

What is a Full Sturgeon Moon?

The first (and normally the only) full moon that occurs in August is called a sturgeon moon. The name may have originated with Native American tribes living around the Great Lakes in the Midwest and Lake Champlain in New England. These bodies of water contain lake sturgeon, a species of freshwater fish that grows up to 6.5 feet in length and can live 55 years or longer. August's full moon was dubbed the sturgeon moon to reflect its harvesting season. This full moon is sometimes called the green corn moon, the grain moon, and the blackberry moon for similar reasons.

When to See the Full Sturgeon Moon

On Thursday, August 15, the full sturgeon moon will be highly visible around sunrise and sunset. The satellite will be 99.9 percent illuminated by the sun when it sets Thursday morning at 5:57 a.m EDT—just nine minutes before dawn. On the West Coast, the setting moon will coincide perfectly with the rising sun at 6:15 a.m. PDT.

If you aren't interested in getting out of bed early to catch the sturgeon moon, wait until Thursday evening to look to the horizon. Twenty-seven minutes after sunset, the full moon will rise on the East Coast at 8:21 p.m. EDT. On the West Coast it rises at 8:10 p.m. PDT, 30 minutes after the sun sets.

The moon generally looks bigger and brighter when it's near the horizon, so twilight and dawn are ideal times to catch the spectacle. But it's worth taking another peek at the sky closer to midnight Thursday night; the Perseid meteor shower is currently active, and though the light of the moon may wash them out, you're most likely to spot a shooting star in the late night and early morning hours.

A Full Harvest Moon Is Coming in September

suerob/iStock via Getty Images
suerob/iStock via Getty Images

The Old Farmer's Almanac lists a special name for every month's full moon, from January's wolf moon to December's cold moon. Even if you're just a casual astronomy fan, you've likely heard the name of September's full moon. The harvest moon is the full moon that falls closest to the fall equinox, and it's associated with festivals celebrating the arrival of autumn. Here's what you need to know before catching the event this year.

What is a harvest moon?

You may have heard that the harvest moon is special because it appears larger and darker in the night sky. This may be true depending on what time of night you look at it, but these features are not unique to the harvest moon.

Throughout the year, the moon rises on average 50 minutes later each night than it did the night before. This window shrinks in the days surrounding the fall equinox. In mid-latitudes, the moon will rise over the horizon only 25 minutes to 30 minutes later night after night. This means the moonrise will occur around sunset several evenings in a row.

So what does this mean for the harvest moon? If you're already watching the sunset and you catch the moonrise at the same time, it will appear bigger than usual thanks to something called the moon illusion. It may also take on an orange-y hue because you're gazing at it through the thick filter of the Earth's atmosphere, which absorbs blue light and projects red light. So if you've only seen the full harvest moon around sunset, you may think it always looks especially big and orange, while in reality, any full moon will look that way when it's just above the horizon.

When to See the Harvest Moon

This year, the harvest moon will be visible the night of Saturday, September 14—about a week before the fall equinox on September 23. The moon will reach its fullest state at 12:33 a.m. ET—but if you're still convinced it's not a true harvest moon without that pumpkin-orange color, you can look for it at moonrise at 7:33 p.m. on September 13.

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