Which Is the Largest Planet?

Jupiter is the largest planet in the Solar System and holds many fascinating secrets. This enormous gas giant is so big that 1,000 planet Earths could fit inside it. Reddish and white bands of cosmic dust cover Jupiter’s surface, blown around by dozens of prevailing winds blowing hundreds of miles per hour. Cyclones dot its atmosphere with a centuries-old storm that is larger than Earth.

Jupiter: King of the Planets

Jupiter is the King of Planets. The ancients knew the largest planet since they could see it with the unaided eye. It probably held many names over the eons, but the Romans named the gas giant after their king of all gods, Jupiter. He was the god of thunder and the skies, so giving the largest object in the sky the same name was only fitting.

The Largest Planet’s Size: Jupiter in Detail

Planet Type	Gas Giant
Year Length	4,3333 Earth Days
Equatorial Radius	43,440.7 miles
Equatorial Circumference	272,945.9 miles
Distance from the Sun	740,714,309 miles (460,258,384 km)
Mass	318x Earth’s mass, 1/1000 Sun’s mass

Moons of the Largest Planet, Jupiter

Jupiter has 80 moons, making it a mini-solar system. Galileo Galilei observed the largest planet’s four biggest moons in 1610 with an early telescope. Today’s scientists call these moons the Galilean satellites.

• Io – Solar System’s most volcanically active object.
• Europa – Might have the potential for life in the liquid-water ocean under its frozen crust.
• Ganymede – Largest solar system moon is bigger than Mercury.
• Callisto –  May have a salty ocean beneath its icy crater-pocked surface, which might also have the potential for life.

10 Fun Jupiter Facts

Jupiter is the largest planet in our Solar System and a fascinating gas giant. Here are some fun facts about our solar system’s “big shot.”

1. The King of All Planets

The largest planet is so enormous that it is twice as massive as every other planet combined. Jupiter is basketball size compared to our home planet, while Earth looks like a tiny grape. You could line eleven Earths across the equator of Jupiter. Now that’s a King!

2. A World With Rings

The 1979 NASA Voyager I mission discovered Jupiter’s four rings. Their small, dark cosmic dust particles make the rings faint, unlike fellow gas-giant Saturn, whose fabulous rings are full of sparkling ice boulders. 

The largest planet’s rings likely form as interplanetary meteoroids crash into the gas giant’s smaller moons. The reddish and white cloud bands show up best when the Sun’s light shines through and reflects off them.

3. Spacecraft Explorations to Jupiter

Jupiter is one of the most explored planets. Some spacecraft traveled explicitly to the largest planet, while others, like Cassini and New Horizons, snapped images on their trips to other destinations. Juno arrived in the neighborhood in July 2016 and has flown by 49 times.

• Pioneer 10 and 11 – fly by
• Voyager 1 and 2 – fly by
• Galileo – orbited and dropped a probe into Jupiter’s atmosphere.
• Cassini – fly by with detailed photos on the way to Saturn
• New Horizons – fly by with clear images on the way to Pluto and Kuiper Belt.
• Juno – orbiting and studying the largest planet since 2016.

4. The Fifth Planet From the Sun

Jupiter is the fifth planet from our star. The first four planets are terrestrial because of their rocky surfaces. The largest planet lies beyond Mars and is the first of the four outer worlds. Jupiter and Saturn are gas giants, and then Uranus and Neptune are the ice giants.

Jupiter orbits the Sun at 484 million miles (778 million kilometers). The distance is measured in Astronomical Units (AU). For instance, Earth orbits at one AU, while Jupiter is at 5.2 AU.

5. The Largest Planet Is Very Light

Like the Sun, Jupiter’s structure is mostly helium and hydrogen. As the Solar System formed billions of years ago, gravity pulled leftover gases and cosmic dust from the Sun into the gas giant Jupiter. 

Jupiter’s ingredients are the same as a star’s, but even though it gobbled up twice the material of all the other planetary objects combined, the largest planet still didn’t have enough mass to ignite.

This gas giant doesn’t have a rocky surface like Earth. Its structure comes mostly from gasses and liquids.

6. Jupiter Has Short Days but Long Years

The largest planet rotates on its axis once every 10 hours, creating a Jovian day. Then it takes about 4800 Earth days (12 Earth years) to make a complete circuit around the Sun. So Jupiter has short days but long years.

7. The Largest Planet Is a Movie Star

Hollywood loves featuring space objects in movies, and Jupiter certainly plays to the crowd. Not only has the largest planet been in film, but it has also been featured in video games, comic books, and TV shows. Here are a few of the movies Jupiter and its moons starred in over the years.

• A Trip to Jupiter (1909)
• 2001: A Space Odyssey (1964)
• Europa Report (2013)
• Jupiter Ascending (2015)
• The Wandering Earth (2019)

8. The Great Red Spot

The Great Red Spot is not another movie featuring Jupiter. Instead, an enormous centuries-old storm rages on the largest planet’s surface. This tornado-like mammoth is twice Earth’s width. Because of data from Juno, scientists believe the storm reaches depths of 300 miles, making it even larger than previously thought.

Even the ancients could see Jupiter’s Great Red Spot and noted its presence. The storm stays trapped between two jet streams. High atmospheric pressure at its center makes it an anticyclone, which rotates opposite Earth’s hurricanes.

9. Polar Cyclones

Besides the Great Red Spot, Jupiter has plenty of other storms brewing. The enormous tornado storms at both of the largest planet’s poles arrange themselves in polygonal structures. The north pole has eight storms shaping an octagon. The south pole has a pentagon pattern of five cyclones. 

Juno scientists discovered that the storms stay in the exact locations. The storms “want” to move towards the poles, behaving in the same manner as Earth’s hurricanes. However, different storms at both poles’ centers push them back and hold them in the polygonal arrangements.

The individual storms are enormous! They cover the North American distance from Canada’s southern border down to Texas’ southern reaches. Each cyclone measures 1,500 miles (2,400 kilometers) to 1,740 miles (2,800 kilometers) across.

Below is one of JPL’s composite images from Juno’s pole fly-by data. It compiles the largest planet’s north pole central cyclone surrounded by eight circumpolar storms.

10. Three Cloud Layers on Its Surface

Scientists think the largest planet in the Solar System has three cloud layers spanning about 44 miles (71 kilometers.) The top layer is ammonia ice, the middle is ammonium hydrosulfide crystals, and the layer closest to the planet likely holds water, ice, and vapor.

Final Thoughts on Which Is the Largest Planet

Jupiter is a fascinating gas giant and the largest planet in the Solar System. It is the king of all planets, with a storm bigger than Earth and a moon vaster than Mercury. Scientists continue learning about Jupiter’s world with ongoing Juno exploration. So expect more Jovian news in the months and years ahead.