Jupiter was appropriately named after the king of the gods. It’s massive, has a powerful magnetic field, and more moons that any planet in the Solar System. Though it has been known to astronomers since ancient times, the invention of the telescope and the advent of modern astronomy has taught us so much about this gas giant.

In short, there are countless interesting facts about this gas giant that many people just don’t know about. And we here at Universe Today have taken the liberty of compiling a list of ten particularly interesting ones that we think will fascinate and surprise you. Think you know everything about Jupiter? Think again!

1. Jupiter Is Massive:

It’s no secret that Jupiter is the largest planet in the Solar System. But this description really doesn’t do it justice. For one, the mass of Jupiter is 318 times as massive as the Earth. In fact, Jupiter is 2.5 times more massive than all of the other planets in the Solar System combined. But here’s the really interesting thing…

If Jupiter got any more massive, it would actually get smaller. Additional mass would actually make the planet more dense, which would cause it to start pulling it in on itself. Astronomers estimate that Jupiter could end up with 4 times its current mass, and still remain about the same size.

2. Jupiter Cannot Become A Star:

Astronomers call Jupiter a failed star, but that’s not really an appropriate description. While it is true that, like a star, Jupiter is rich in hydrogen and helium, Jupiter does not have nearly enough mass to trigger a fusion reaction in its core. This is how stars generate energy, by fusing hydrogen atoms together under extreme heat and pressure to create helium, releasing light and heat in the process.

This is made possible by their enormous gravity. For Jupiter to ignite a nuclear fusion process and become a star, it would need more than 70 times its current mass. If you could crash dozens of Jupiters together, you might have a chance to make a new star. But in the meantime, Jupiter shall remain a large gas giant with no hopes of becoming a star. Sorry, Jupiter!

3. Jupiter Is The Fastest Spinning Planet In The Solar System:

For all its size and mass, Jupiter sure moves quickly. In fact, with an rotational velocity of 12.6 km/s (~7.45 m/s) or 45,300 km/h (28,148 mph), the planet only takes about 10 hours to complete a full rotation on its axis. And because it’s spinning so rapidly, the planet has flattened out at the poles a little and is bulging at its equator.

In fact, points on Jupiter’s equator are more than 4,600 km further from the center than the poles. Or to put it another way, the planet’s polar radius measures to 66,854 ± 10 km (or 10.517 that of Earth’s), while its diameter at the equator is 71,492 ± 4 km (or 11.209 that of Earth’s). This rapid rotation also helps generate Jupiter’s powerful magnetic fields, and contribute to the dangerous radiation surrounding it.

4. The Clouds On Jupiter Are Only 50 km Thick:

That’s right, all those beautiful whirling clouds and storms you see on Jupiter are only about 50 km thick. They’re made of ammonia crystals broken up into two different cloud decks. The darker material is thought to be compounds brought up from deeper inside Jupiter, and then change color when they reacted with sunlight. But below those clouds, it’s just hydrogen and helium, all the way down.

5. The Great Red Spot Has Been Around For A Long Time:

The Great Red Spot on Jupiter is one of its most familiar features. This persistent anticyclonic storm, which is located south of its equator, measures between 24,000 km in diameter and 12–14,000 km in height. As such, it is large enough to contain two or three planets the size of Earth’s diameter. And the spot has been around for at least 350 years, since it was spotted as far back as the 17th century.

The Great Red Spot was first identified in 1665 by Italian astronomer Giovanni Cassini. By the 20th century, astronomers began to theorize that it was a storm, one which was created by Jupiter’s turbulent and fast-moving atmosphere. These theories were confirmed by the Voyager 1 mission, which observed the Giant Red Spot up close in March of 1979 during its flyby of the planet.

However, it appears to have been shrinking since that time. Based on Cassini’s observations, the size was estimated to be 40,000 km in the 17th century, which was almost twice as large as it is now. Astronomers do not know if or when it will ever disappear entirely, but they are relatively sure that another one will emerge somewhere else on the planet.

6. Jupiter Has Rings:

When people think of ring systems, Saturn naturally comes to mind. But in truth, both Uranus and Jupiter have ring systems of their own. Jupiter’s were the third set to be discovered (after the other two), due to the fact that they are particularly faint. Jupiter’s rings consist of three main segments – an inner torus of particles known as the halo, a relatively bright main ring, and an outer gossamer ring.

These rings are widely believed to have come from material ejected by its moons when they’re struck by meteorite impacts. In particular, the main ring is thought to be composed of material from the moons of Adrastea and Metis, while the moons of Thebe and Amalthea are believed to produce the two distinct components of the dusty gossamer ring.

This material fell into orbit around Jupiter (instead of falling back to their respective moons) because if Jupiter’s strong gravitational influence. The ring is also depleted and replenished regularly as some material veers towards Jupiter while new material is added by additional impacts.

7. Jupiter’s Magnetic Field Is 14 Times Stronger Than Earth’s:

Compasses would really work on Jupiter. That’s because it has the strongest magnetic field in the Solar System. Astronomers think the magnetic field is generated by the eddy currents – i.e. swirling movements of conducting materials – within the liquid metallic hydrogen core. This magnetic field traps particles of sulfur dioxide from Io’s volcanic eruptions, which producing sulfur and oxygen ions. Together with hydrogen ions originating from the atmosphere of Jupiter, these form a plasma sheet in Jupiter’s equatorial plane.

Farther out, the interaction of the magnetosphere with the solar wind generates a bow shock, a dangerous belt of radiation that can cause damage tos spacecraft. Jupiter’s four largest moons all orbit within the magnetosphere, which protects them from the solar wind, but also make the likelihood of establishing outposts on their surface problematic. The magnetosphere of Jupiter is also responsible for intense episodes of radio emission from the planet’s polar regions.

8. Jupiter Has 67 Moons:

As of the penning of this article, Jupiter has a 67 confirmed and named satellites. However, it is estimated that the planet has over 200 natural satellites orbiting it. Almost all of them are less than 10 kilometers in diameter, and were only discovered after 1975, when the first spacecraft (Pioneer 10) arrived at Jupiter.

However, it also has four major moons, which are collectively known as the Galilean Moons (after their discovered Galileo Galilei). These are, in order of distance from Jupiter, Io, Europa, Ganymede, and Callisto. These moons are some of the largest in the Solar System, with Ganymede being the largest, measuring 5262 km in diameter.

9. Jupiter Has Been Visited 7 Times By Spacecraft:

Jupiter was first visited by NASA’s Pioneer 10 spacecraft in December 1973, and then Pioneer 11 in December 1974. Then came the Voyager 1 and 2 flybys, both of which happened in 1979. This was followed by a long break until Ulysses arrived in February 1992, followed by the Galileo space probe in 1995. Then Cassini made a flyby in 2000, on its way to Saturn. And finally, NASA’s New Horizons spacecraft made its flyby in 2007. This was the last mission to fly past Jupiter, but it surely won’t be the last.

10. You Can See Jupiter With Your Own Eyes:

Jupiter is the third brightest object in the Solar System, after Venus and the Moon. Chances are, you saw Jupiter in the sky, and had no idea that’s what you were seeing. And here at Universe Today, we are in the habit of letting readers know when the best opportunities for spotting Jupiter in the night sky are.

Chances are, if you see a really bright star high in the sky, then you’re looking at Jupiter. Get your hands on a pair of binoculars, and if you know someone with a telescope, that’s even better. Using even modest magnification, you might even spot small specks of light orbiting it, which are its Galilean Moons. Just think, you’ll be seeing precisely what Galileo did when he gazed at the planet in 1610.

We have written many interesting articles about Jupiter here at Universe Today. Here’s The Gas Giant Jupiter, How Strong Is Jupiter’s Gravity?, Does Jupiter Have A Solid Core?, and Jupiter Compared To Earth.

And here are 10 Interesting Facts About Planet Earth, and 1o Interesting Facts About Mars.

For more information, check out the Hubblesite’s News Releases about Jupiter, and NASA’s Solar System Exploration.

We’ve also recorded an entire show just on Jupiter for Astronomy Cast. Listen to it here, Episode 56: Jupiter, and Episode 57: Jupiter’s Moons.