The outer solar system is the name of the planets beyond the asteroid belt. These planets are called gas giants because they are made up of gas and ice.
The first stop of our tour is the fifth planet, Jupiter. Jupiter is bigger than three hundred Earths! It is made up of hydrogen and helium and a few other gases. There are violent wind storms that circle around Jupiter. The most famous storm is called the Great Red Spot. It has been churning for more than four hundred years already. At last count, Jupiter has sixty-three known moons and a faint ring around it too.
Next in our space neighbourhood comes Saturn. It is well-known for the series of beautiful rings that circle it. They are made up of tiny bits of frozen dirt and ice. Like Jupiter, Saturn is made up of mostly hydrogen and helium. It is smaller though, at only ninety-five times the size of Earth. Saturn has sixty-two moons.
The seventh planet, Uranus and its twenty-seven moons orbit very far from the sun. In addition to helium and hydrogen, Uranus atmosphere also contains ammonia ice and methane ice. It is a very cold planet, with no internal heat source. One of the strangest things about Uranus is that it is tipped over and orbits the sun on its side at a ninety-degree angle. The twenty-seven moons it has orbit from top to bottom, instead of left to right like our moon.
The eighth planet is Neptune. Like Uranus, it is made up of hydrogen, helium, ammonia ice and methane ice. But unlike Uranus, Neptune does have an inner heat source, just like Earth. It radiates twice as much heat as it receives from the sun. Neptune's most distinctive quality is its blue colour. Most of the information we know about it came from the Voyager 2 spacecraft passing close by it in 1989.
Pluto is the last and was considered a planet after its discovery in 1930. In 2006, Pluto was demoted and reclassified as a dwarf planet. Pluto exists in the Kuiper belt. That's just a fancy name for the band of rocks, dust and ice that lies beyond the gas giants. Scientists have found objects bigger than Pluto in this belt. Thus, the outer solar system has many secrets to explore.
