What’s the Largest Planet in Our Solar System?

Written by Kyle Glatz
Updated: June 18, 2022
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Our solar system is packed with interesting celestial bodies. From planets and comets to asteroids and the star at the center of it all, humans have discovered plenty of interesting things in our local area. Most of the solar system’s mass is found in the sun, and much of the rest is found in the remaining planets, especially the larger ones. So, what’s the largest planet in our solar system?

Let’s take a look at what makes a planet, how many planets are in our solar system, and the largest one of them all.  

What Is a Planet?

A planet is a large celestial body that meets three specific criteria.

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Defining the term ‘planet’ is harder than it seems. After all, Pluto and Ceres were considered planets not all that long ago. However, neither is a planet today. In this case, we’ll defer to the experts of the International Astronomical Union and say that planets are defined by three factors.

A planet is defined as a celestial body that:

  • Orbits the Sun.
  • Has enough mass so that its self-gravity overcomes rigid body forces and takes on a hydrostatic equilibrium and a nearly round shape.
  • Clears the “neighborhood” near its orbit.

Neither Pluto nor Ceres meets these requirements despite previously being considered planets. So, they are no longer considered planets. As a result, the Solar system has 8 planets, five or more dwarf planets, lots of asteroids, and other celestial bodies.

What is the Largest Planet in Our Solar System?

jupiter
Jupiter is several times the diameter and mass of Earth.

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Jupiter is the largest planet in our solar system since it has the highest mass and the largest diameter. It has an equatorial radius of 44,423 miles, a mass of 4.1848×1027lbs, and a surface area of 2.3733×1010 sq mi. That is 11.2 times the equatorial radius of Earth, 317.8 times the mass of Earth, and 120.4 times the surface area of Earth.

These measurements should give you some idea of just how large Jupiter is compared to other planets. Jupiter is much larger than Saturn, the second-largest planet in the Solar system. Saturn has roughly 95 times Earth’s mass.

The rest of the planets in the Solar system are much smaller than those two. Jupiter is the fifth planet from the sun, and it’s a gas giant. That means the planet is mostly made of gases like helium and hydrogen.

That does not mean that the entire planet is made of gas, though. Scientists aren’t entirely sure what we will find at the center of Jupiter. Some theorize that there could be a rocky core that is several times larger than the Earth. Others believe that the core of the planet is made of metallic hydrogen that forms under extreme pressure.

Future explorations of the planet will yield new information about the composition of this gas giant. For now, though, we can only theorize what’s inside of Jupiter.

How Large Are the Rest of the Planets in Our Solar System?

mercury
Mercury is the smallest planet in the solar system.

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The two best ways to measure any planet are by diameter and mass. Jupiter is the largest planet according to both measures. However, we’re going to show you how large all the other planets using the scales of diameter in miles and mass in terms of 1021 tons.

Mass (1021 tons)Diameter (miles)
Mercury0.3643,032
Mars0.7074,220
Venus5.377,521
Earth6.587,926
Uranus95.731,765
Neptune11330,775
Saturn62674,897
Jupiter209288,846

As you can see, the planets vary a great deal in terms of their mass and overall size. Interestingly, Neptune has a higher mass than Uranus, but it also has a smaller diameter. Once again, Jupiter makes the rest of the planets seem small with its huge diameter and large mass.

What Are Dwarf Planets?

Pluto
Pluto was once considered a planet, but it is a dwarf planet.

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A dwarf planet is defined as any object in orbit around the Sun that has its gravity and pulls itself into a nearly round shape. These planets have not cleared their orbit, though, so they cannot be considered true planets.

The most famous dwarf planet is Pluto, a planet that does not clear its orbit. This planet famously lost its status as a planet in 2006.

Currently, the International Astronomical Union recognizes five dwarf planets in the Solar system. They include Ceres, Pluto, Eris, Makemake, and Haumea.

However, various scientists and other organizations claim that more dwarf planets can be found in our Solar system. Mostly, it depends on the definition of the term that they use. Some groups recognize six different dwarf planets while others believe many more exist.

According to NASA, thousands of dwarf planets may exist in the area beyond Neptune. However, humans have only discovered relatively few dwarf planets as we are still discovering much of what is in our Solar system.

Scientists will likely discover far more dwarf planets in the near future!

What Is the Largest Planet Ever Discovered?

The largest planet ever discovered is called ROXs 42Bb, a planet with 2.5 times the radius of Jupiter. This exoplanet was directly imaged and discovered in 2013. Unlike many of the other largest exoplanets, this one is believed to be a planet and not a brown dwarf, an object between a planet and a star.

If we are counting the largest exoplanet that includes brown dwarves, then it would be HD 100546 b. This exoplanet has a radius of 6.9 times that of Jupiter. However, this celestial body is going to shrink over time. Scientists estimate that this exoplanet will one day shrink down to the size of Jupiter.            

The title of the largest planet ever discovered depends on how one defines exoplanets, much like dwarf planets. Once again, the future will yield new and interesting discoveries that could change what we currently know about these planets.  

Planetary science is a complex topic. The definitions of planets, dwarf planets, and exoplanets are still being hashed out, and international groups don’t always agree. One thing is certain, though. Jupiter is the largest planet in the solar system. That fact is not going to change. However, our understanding of the planet is going to become more concise over time.

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Pacific Ocean
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About the Author

I'm a freelance writer with 8 years of experience. I've written in a variety of niches such as video games, animals, and managed service providers. I graduated from Rowan University in 2014 with degrees in English and Education. When I'm not working, I enjoy playing video games, reading, and writing for fun.

FAQs (Frequently Asked Questions) 

What's the largest star in the universe?

The largest star in the known universe is called Stephenson 2-18, a star that has a radius 2,150 times that of the sun.

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