Although Earth is large, it is not the biggest planet in our Solar System. That honor goes to Jupiter, a gas giant and the fifth planet from the Sun. All of the four outer planets are larger than the four inner ones, but Jupiter is especially large. You could fit over 1300 Earths inside of Jupiter.
Its mass is much smaller than its volume though. Made mostly of gases, Jupiter’s mass is only 318 times that of Earth’s. In other words, its mass is two and a half times greater than the volume of the other seven planets combined. The circumference of Jupiter around its equator is 449,197 km, which is 11 times the circumference of Earth. Jupiter’s diameter is one-tenth the diameter of the Sun.
Jupiter was named after the Roman king of the gods due to its size. So far, 63 moons have been discovered around Jupiter, most of which have been found in the past decade. It has the most moons of any planet in the Solar System. Galileo discovered four of the moons when he built his telescope. Ganymede is the biggest moon of Jupiter and Jupiter also has a set of planetary rings, which is not very noticeable. As a gas giant, the planet has no solid surface. Additionally, the atmosphere is filled with huge storms and fast winds. The largest storm on the planet has been raging for hundreds of years and is known as the Great Red Spot; the storm is at least three times the size of Earth. Because of the planet’s size, something on Jupiter weighs approximately 2.5 times it would weigh on Earth.
Although Jupiter is the largest planet in our Solar System, scientists have discovered a larger one in another Solar System in the constellation of Hercules. Discovered in 2006, the planet is known as TrES-4. Its diameter is 1.7 times that of Jupiter’s. Even though it is 70% larger than Jupiter is, the planet’s mass is only 75% of Jupiter’s mass. TrES-4 is about as dense as cork. Scientists are amazed at the size of this planet and think it may be linked to the extreme temperature of the planet. It is much closer to the Sun than Jupiter is and reaches temperatures of about 1260° C. Although TrES-4 is far larger than any other planet scientists expected to find, they may still find even larger planets as technology continues to advance.
Astronomy Cast has an episode on Jupiter.