What’s the Biggest Planet in Our Solar System?

Jupiter is the biggest planet in our solar system by a long way. Add up the mass of all the other planets. Multiply by two, and that’s how big Jupiter is!

Imagine a grape and a basketball side-by-side. The grape represents Earth’s size, while the basketball shows the giant world of Jupiter. We’d call that a considerable size difference. It’s hard to grasp just how large the gas giant is, so let’s jump right in to discover the biggest planet in our solar system. Then, we’ll look at some of the biggest planets in the universe, too.

In the color-enhanced version of Jupiter below, a citizen scientist evokes a marbled world through image processing. The JunoCam initially took the image on September 12, 2019. It came during the spacecraft’s 22nd close pass by the giant world. Prateek Sarpal calls his view of Jupiter “A mind of limits, a camera of thoughts.”

How Are Planets Measured?

Scientists consider a planet’s mass and width when determining its overall size. The width equals twice the planet’s radius. While the width and mass are related, they aren’t always directly correlated. For example, planets vary in their densities. Some gas giants puff up to enormous sizes with lower mass than other heavier terrestrial worlds.

The most common way astronomers measure planets is by learning how long it takes nearby objects to orbit them. Then, scientists determine how far away the objects are from the planet. So, the time it takes a natural satellite to orbit a world depends on how far away it is and how much mass the planet holds.

Heavier planets have stronger gravitational pulls on nearby spacecraft or moons. Also, the closer the object is to the world, the stronger gravity’s tug becomes. 

Determining how heavy a planet is by weight gets tricky. And that’s because weight changes depending on gravity. So, that’s why scientists use mass to establish a planet’s size. Mass doesn’t change with gravity; instead, it stays the same. Here’s a simplified illustration of mass versus weight. 

Law of Universal Gravitation

Planets like Venus that don’t have moons need other measurement tools. Scientists take radar observations of spacecraft orbiting the world to help determine its mass and size. In addition, Isaac Newton developed the Law of Universal Gravitation. 

It says two objects have a force of attraction proportional to the product of both masses divided by the distance between both their centers of mass squared. Now, that’s a lot to wrap your head around.

But since scientists know Earth’s radius, they used it to determine the planet’s mass (with the radius as the distance.) And the Law of Universal Gravitation then reveals the Sun’s size and mass. From there, scientists can determine which is the biggest planet in the solar system.

Jupiter’s Gigantic Size

Jupiter has an enormous diameter of about 86,881 miles (139,822 kilometers), making it more than 11 times wider than Earth. Its immense size sets it apart from all the other planets in our solar system.

The planet is so massive that NASA scientists say it could have become a star rather than a planet. However, it would have had to gather about 80 times more mass to do so. The giant world gathered more gasses than any other planet after the Sun’s formation. That implies that Jupiter was likely the first planet to form, pulling in the Sun’s leftover gas.

Jupiter creates its own mini-planetary system within the solar system. It has four huge moons and many other small satellites. Some it stole, some formed naturally.

The Biggest Planet is Also the Heaviest Planet 

Jupiter is also the heaviest planet in the solar system, containing more than twice the mass of all the other planets, moons, comets, and asteroids combined.

Temperature and pressure increase deep within Jupiter’s atmosphere. The extreme pressure compresses hydrogen gas to a liquid metallic hydrogen form. Scientists think it conducts electricity and drives the planet’s intense magnetic field.

Further in, near the gas giant’s center, the temperature becomes hotter than the Sun’s surface. And the pressure continues increasing to tens of millions of times Earth’s air pressure. Finally, scientists believe a central dense core that’s larger than Earth sits at the planet’s center. They think it is full of heavy elements.

The Biggest Planet’s Rapid Rotation

Jupiter is a fast spinner, completing one rotation on its axis in just short of 10 hours. A Jovian day is the shortest one in the solar system. This rapid rotation results in strong equatorial bulging, causing the planet to flatten slightly at the poles.

Scientists think Jupiter formed by accreting (accumulating) helium and hydrogen gases from the dusty disk around the Sun. These leftover gases account for more than 95% of Jupiter’s total mass. The planet spun more quickly as it consumed the angular momentum from the gas.

The protoplanetary disk began collapsing and spun in a counterclockwise direction. So, as Jupiter formed, it also rotated in the same direction.

Additionally, Jupiter orbits the Sun in about 4,333 Earth days. That equals nearly twelve years on our home planet. The biggest planet in our solar system has an almost upright spin. With only a three-degree tilt, the planet doesn’t experience extreme seasonal weather patterns like other planets.

The Gas Giant’s Intense Magnetic Field

Jupiter boasts the strongest magnetic field of any planet in our solar system. Its magnetic field is about 20,000 times more powerful than Earth’s, creating a massive magnetosphere that extends millions of miles into space.

The biggest planet’s magnetosphere rotates with Jupiter and traps charged particles, both ions and electrons, in a radiation belt near the gas giant. That belt creates a unique hazard for spacecraft flybys and visits. Since the trapped particles get accelerated to high energies, they make damaging radiation. It becomes incredibly hazardous for nearby moons and spacecraft.

In addition, the magnetosphere is tadpole-shaped. It bellows outward up to 2 million miles (3 million kilometers) to the Sun. But the tail end stretches and tapers for more than 600 million miles (about 1 billion kilometers) toward Saturn’s orbit.

The biggest planet in our solar system has such a gigantic magnetic field that it ranges from 16 to 54 times as potent as Earth’s field. It creates some of the most incredible polar aurorae in the whole solar system.

The Hubble Space Telescope’s ultraviolet capabilities allow it to capture aurora images like the one below. Auroras occur when high-energy particles enter a planet’s atmosphere near the magnetic poles. Once there, they collide with gas atoms, forming a dazzling light show.

Does the Biggest Planet Have the Fastest Winds?

Jupiter experiences incredibly high-speed winds in its atmosphere. The most potent jet streams can reach speeds of up to 267 miles per hour (430 kilometers per hour.) And in its storms, like the Great Red Spot, winds reach 384 miles per hour (618 kilometers per hour.)

But those aren’t the fastest winds on the biggest planet. Researchers say polar winds could reach speeds as high as 900 miles per hour (1,448 kilometers per hour.) And that is about three times Earth’s most substantial hurricane speeds.

However, Neptune has the fastest winds in the solar system. In its highest altitudes, the eighth planet from the Sun gets winds exceeding 1,100 miles per hour (1,770 kilometers per hour.) That is about one and a half times faster than the speed of sound. So, while the biggest planet’s winds greatly exceed the most robust rates on Earth, they are not the fastest in the solar system.

The Biggest Planet Has the Biggest Storms

Not only does the biggest planet host stunning aurora displays at its poles, but it also sports gigantic storms that are larger than other solar system planets. You might be wondering how squalls bigger than entire worlds are even possible. And that gives you an indication of just how gigantic Jupiter really is.

For example, Jupiter is home to the Great Red Spot (seen in the right 2023 Hubble image below.) It’s a massive and violent storm that has been raging for at least 350 years. The whole Earth could fit into this enormous anticyclonic storm. It’s big enough to swallow our home planet up, even though it has shrunk to the smallest diameter noted over the past 150 years.

But that’s not the only storm on the gas giant. In addition, check out the left Hubble image below to see “Vortex Street.” That’s the informal name some planetary astronomers call the prominent row of alternating storms.

Notice the wave pattern of cyclones and anticyclones that lock together like cogs or gears in a machine. If the storms grew closer to one another, they could merge to form a Great Red Spot rival. But the chances are unlikely since the storms’ staggered clockwise and counterclockwise pattern keeps them apart.

This row of cyclones and anticyclones has sprung up over the past decade since Hubble saw none of them in observations during the 1990s. This image from November 12, 2022, shows thunderstorms of immense sizes.

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Jupiter’s Many Moons

Jupiter has an impressive moon system, with over 92 known moons, plus thousands of small celestial objects in the planet’s orbit. The four largest Galilean moons (Io, Europa, Ganymede, and Callisto), were discovered by Galileo Galilei in 1610 and are some of the largest moons in the solar system.

So, the biggest planet has many natural satellites, partly because more sizeable planets have stronger gravitational pulls. Jupiter captured some of its larger moons when they were passing asteroids. However, the smaller moons likely are collision fragments.

In 2022, astronomer Scott S. Sheppard discovered three new moons in Jupiter’s orbit. He’s found the most Jovian moons of any modern astronomer. Scientists are now so good at discovering moons that the tiniest ones no longer get names.

Does the Biggest Planet Have Rings?

While Jupiter does have rings, they are very faint compared to Saturn’s prominent ring system. Jupiter’s rings are primarily composed of dust and are challenging to observe from Earth. The rings aren’t visible with most telescopes, but the James Webb Telescope has recently captured some images of them.

The cut-away view of Jupiter’s rings below also shows the small inner moons. Those natural satellites provide the dust that forms the rings. Asteroid impacts send dust particles flying into space, where the moons’ orbits mold them into faint rings.

Does the Biggest Planet Have the Potential for Life?

Jupiter is inhospitable to life as we know it due to its lack of a solid surface and extreme radiation. The planetary extremes in temperature and air pressures are too volatile for organism adaption.

However, its moon, Europa, is a potential candidate for the search for extraterrestrial life due to its subsurface oceans. The moon’s surface gets radiation from Jupiter, so life could not exist above ground. However, that same radiation has the potential to create fuel for ocean life below the moon’s surface.

Here’s how it works:

• The radiation splits water molecules in the moon’s atmosphere.
• Hydrogen floats away.
• Oxygen stays and can bind to other elements.
• If that oxygen gets into the ocean, it could react with other chemicals to provide energy for microbial life forms.

Additionally, scientists think the subterranean ocean has a warm rock seabed. Then, as the moon orbits Jupiter, its interior flexes. The flexing forces energy that creates heat. So, the warm rock interactions could provide hydrogen to the ocean.

Unlike Earth, where our energy comes mainly from the Sun, Europa’s energy may stem from surface chemistry and seafloor water-rock interactions. Time will tell if those energy inputs can support life forms.

What’s the Biggest Planet in the Universe?

Jupiter is the most giant planet in our solar system. However, there are exoplanets in other star systems and distant galaxies that are bigger. Exoplanet researchers proved the existence of gas giants similar to Jupiter, known as “super” or “hot Jupiters.” These worlds are up to ten times Jupiter’s mass and twice its size.

Science can only speak definitively about the biggest planet in our solar system, Jupiter. Determining the largest world throughout the universe would require knowledge of all worlds across the vast expanse of the cosmos. That is currently beyond our technological and observational capabilities, but scientists learn more daily.

Let’s look at a few contenders for the largest world in the cosmos.

HIP 67522 b

Hot Jupiters are Jupiter-sized exoplanets that orbit close to their stars. One way planet candidates get identified is by NASA’s Transiting Exoplanet Survey Satellite (TESS.) Scientists see a dip in a star’s brightness, which could indicate an orbiting planet passed between the star and the observer. TESS helps detect planets through this transit method.

Astronomers found HIP 67522 b with TESS and confirmed the world with data from the Spitzer Space Telescope (retired.) This exoplanet is the youngest hot Jupiter found so far. Its star is well-studied and about 17 million years old. That means the exoplanet is probably a few million years younger, which is significantly less than most hot Jupiters at a billion years old.

Studying this young exoplanet helps scientists better understand how gas giants form. HIP 67522 b lies about 490 light-years away from our home planet. And like our own Jupiter, it is about ten times Earth’s diameter. The giant size indicates the likelihood of this being a gas-dominated planet.

Astronomers know HIP 67522 b orbits its Sun-like star in about seven days. Scientists don’t yet know why it orbits so closely to its star and need more data to explain the phenomenon.

51 Peg b

Dimidium, or 51 Peg b, was the first confirmed exoplanet. Swiss astronomers Michel Mayor and Didier Queloz made history for their 1995 discovery.  The pair even shared a 2019 Nobel Prize in Physics for finding the gas giant.

51 Peg b lies about 51 light-years away and orbits its Sun-like star every four days. Temperatures on the exoplanet range between 1,000 and 1,800 degrees F (538-982 degrees C). It is about half of Jupiter’s mass, even though the exoplanet is almost 50% larger than our solar system’s biggest planet. This discovery took astronomical research into a brand new field: exoplanet search.

A 1992 discovery found a planet orbiting a pulsar star, but astronomers at the time were skeptical that the volatile stars could host planetary systems. The confirmation of Dimidium changed everything.

Kappa Andromedae b

This super Jupiter exoplanet orbits a B-type star about 163 light-years from Earth. The star is visible with the naked eye but is easier to see with a telescope. The gas giant has a mass of 13.616 Jupiters, which makes it super giant.

Kappa Andromedae b is further from its star than the hot Jupiters mentioned above. It is 55.0 astronomical units (AU) from its star and takes about 253.1 years to make a complete orbit. That’s nearly twice the distance from the Sun to Neptune.

Check out this artist’s rendition of how the exoplanet likely appears. Astronomers discovered Kappa Andromedae b in 2012 through direct imaging.

TOI-4127 b

NASA’s TESS finds a lot of hot Jupiters, but it recently discovered this “warm Jupiter” exoplanet.  In March 2023, scientists confirmed a TESS Object of Interest, TOI- 4127 b. It’s more than twice as massive as Jupiter.

As TESS continues its mission to find exoplanets by surveying over 200,000 stars, it has identified about 6000 candidates. TOI-4127 b is one of the over 3100 confirmations. According to the news release, this new warm Jupiter orbits its star at a close distance of 0.31 AU in a highly eccentric orbit. The exoplanet circles its host once every 56.4 Earth days.

Scientists say it is a “warm Jupiter” since its equilibrium temperatures are only around 630 degrees Fahrenheit (332 Celsius.) If another celestial object were to contact the exoplanet and force it into a closer orbit to its star, temperatures could rise. That potential increase could turn the planet into a hot Jupiter.

Wasp-12b

One of the most interesting hot Jupiters is Wasp-12b. It’s a doomed exoplanet that orbits so close to its star that it is slowly ripping apart. This world orbits its host in only 1.1 days, and the star’s heat is consuming the exoplanet’s atmosphere. Scientists estimate the star will ultimately destroy the alien world within another ten million years.

Wasp-12b is a scorching 4,000 degrees Fahrenheit (2,210 degrees Celsius.) It’s about twice the size of Jupiter, but its shape differs significantly from the solar system’s biggest planet. Wasp-12b stretches into an egg shape because of the enormous tidal forces gravity subjects it to.

Emily: Get the code to embed a 3D version of Wasp-12b here.

Wrap-Up: The Biggest Planet in Our Solar System

While Jupiter is the most giant planet within our solar system, it is by no means the biggest planet in the universe. Missions like NASA’s TESS seek to find and confirm exoplanets, and some of these discoveries make Jupiter look downright puny.

Jupiter is a massive gas-dominated giant with so many natural satellites that it is, in many ways, its own planetary system. The four large moons of the biggest planet hold great interest for astronomers who believe there is a possibility for potential microbial life forms. 

As scientists continue exploring these cold worlds far from Earth, they hope to determine whether or not life could exist in the solar system’s outer reaches. The biggest planet, Jupiter, still holds many mysteries that astronomers and scientists wish to continue unraveling.