Outer Planets


Mighty Jupiter is the biggest planet in our Solar System. It’s so large, in fact, that it has 2.5 times the mass of all the rest of the planets in the Solar System combined. Jupiter orbits from the Sun at an average distance of 779 million km. Its diameter at the equator is 142,984 km across; you could fit 11 Earths side by side and still have a little room. Jupiter is almost entirely made up of hydrogen and helium, with trace amounts of other elements.


Saturn is the 6th planet from the Sun, and the 2nd largest planet in the Solar System. It orbits the Sun at an average distance of 1.4 billion km. Saturn measures 120,000 km across; only a little less than Jupiter. But Saturn has much less mass, and do it has a low density. In fact, if you had a pool large enough, Saturn would float!
Of course, the most amazing feature of Saturn is its rings. These are made of particles of ice ranging in size from a grains of sand to the size of a car. Some scientists think the rings are only a few hundred million years old, while others think they could be as old as the Solar System itself.


Next comes Uranus, the 7th planet from the Sun. It orbits the Sun at an average distance of 2.9 billion km. Uranus measures 51,000 km across, and is the 3rd largest planet in the Solar System. While all of the planets are tilted on their axes, Uranus is tilted over almost on its side. It has an axial tilt of 98°. Uranus was the first planet to be discovered with a telescope; it was first recognized as a planet in 1781 by William Herschel.


Neptune is the 8th and final planet in the Solar System, orbiting at an average distance of 4.5 billion km from the Sun. It’s the 4th largest planet, measuring about 49,000 km across. It might not be as big as Jupiter, but it’s still 3.8 times larger than Earth – you could fit 57 Earths inside Neptune. Neptune is the second planet discovered in modern times. It was discovered at the same time by both Urbain Le Verrier and John Couch Adams.

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