The Sun is a star. It is at the centre of the Solar System, and all eight planets orbit around it.

The Sun is very large; in fact it is so big that over 1 million Earths could fit inside it! The Sun also has a very large mass; over 99.8% of the Solar System’s total mass is just from the Sun.

The Sun is very important to us, as its light provides Earth with the energy needed to sustain life.

The Sun was formed around 4.5 billion years ago — along with the rest of the Solar System — in a big cloud of gas and cosmic dust called a nebula.

In about 5 billion years time, the Sun will start to grow in size into a red giant. It will become so big that it will engulf the Earth!

The closest planet to Sun is Mercury. Mercury is the first of the Solar System's four rocky ‘inner planets’.

Mercury is the smallest planet in the solar system, and is only about 40% wider than the Moon. Like the Moon, Mercury is heavily cratered in appearance.

Because of its proximity to the Sun, Mercury is very hot (in the daytime, temperatures can get to 430°C!) Surprisingly, Mercury isn’t even the hottest planet in the solar system. The award for that goes to the planet coming next…

The 2^nd planet from Sun is called Venus.

The rocky surface of Venus is completely obscured by clouds of sulphuric acid. These clouds cause acid rain to pour down onto the surface, which would very badly burn your skin.

Venus’s clouds also trap heat from escaping the planet’s surface (this is known as the greenhouse effect). As a result, Venus is the hottest planet in the Solar System! (with a surface temperature of about 475°C)

Venus has two things going for it that no other planet has:

1) Venus spins backwards compared to all the other planets
2)A day on Venus is longer than a year!

The 3^rd planet from Sun is called Earth.

The Earth is the only known planet to contain life. It is also the only known planet to have liquid water on its surface (and there’s a lot of it: about 70% of the Earth’s surface is water!).

The Earth is closest planet to the Sun that has a moon. The Earth’s moon was likely the result of a collision of Earth with another planet (called Theia) billions of years ago.

The 4^th planet from Sun is called Mars.

Mars is also known as ”the Red Planet”, as the rust (iron oxide) on its surface gives it a red-orange colour.

Mars used to have water on its surface. Around 3 billion years ago, this water evaporated. However, there is still ice on the poles of Mars.

Mars is home to Olympus Mons, the largest mountain (and volcano) in the Solar System. Olympus Mons is two and a half times the height of Mount Everest!

Mars has two moons, Deimos and Phobos. They look a bit like potatoes.

Beyond Mars, there is a huge doughnut-shaped region containing millions of asteroids. It is known as the asteroid belt.

Asteroids are made of rock and metals. They are too small and irregularly-shaped to be considered planets.

It is thought that the asteroid belt might be the shattered remains of an early planet, which couldn’t fully form because of the influence of Jupiter’s strong gravity.

Despite there being so many asteroids in it, the asteroid belt is mostly empty. This is simply because the asteroids are spread over so much space!

The asteroid belt has quite a small mass: the total mass of all asteroids is only about 4% that of the moon. And half of this mass comes from only 4 asteroids!

The 5^th planet from Sun is called Jupiter.

Jupiter is the largest planet in the Solar System. Over 1000 Earths could fit inside it!

Jupiter is the first of the Solar System's four ‘giant planets’. Unlike the rocky inner planets, the giant planets have a very thick atmosphere (containing mostly hydrogen and helium gas.)

Jupiter contains the Great Red Spot, a massive storm that has been going for at least 300 years. This storm is even wider than Earth!

Jupiter bulges slightly around the equator because Jupiter spins quickly for a planet. (it spins over twice as fast as Earth)

Jupiter has at least 80 moons, although by far the biggest are the four Galilean moons: Ganymede, Callisto, Io and Europa. In fact, Ganymede is so large that it’s bigger than Mercury!
All of Jupiter’s other moons are probably asteroids that Jupiter captured in its gravitational pull.

It is thought that Europa might contain a massive ocean of water under its icy surface. This is of interest to scientists, as it could be home to extra-terrestrial life.

The 6^th planet from Sun is called Saturn.

Saturn is famous for its rings. Saturn’s rings are made up of rock, dust and ice particles that are orbiting the planet. These rings may have come from a shattered moon of Saturn.

Saturn is less dense than water. This means if you were to put Saturn in a big bath, it would float!

Like Jupiter, Saturn has many moons (at least 83!) However, the vast majority of the mass of Saturn’s moons is from just one moon: Titan. Titan is a humongous moon, and is even larger than the planet Mercury (although it not quite as big as Jupiter’s moon Ganymede).

The 7^th planet from Sun is called Uranus.

Despite not quite being the furthest planet from the Sun, Uranus is the coldest planet in the Solar System. Temperatures get as chilly as −224°C!

Strangely, Uranus rotates sideways compared to all the other planets. This can be seen in this photo of Uranus with its rings:

Unlike Jupiter and Saturn, Uranus contains methane gas in its atmosphere (as well as hydrogen and helium). This methane is what gives Uranus its blue colour.

Uranus was the first planet to be discovered since ancient times. It was found by British astronomer William Herschel in 1781. William named it George’s Planet (after the current king, George III). Luckily the name didn’t catch on, and we got the hilarious name Uranus instead.

The 8^th (and furthest) planet from Sun is called Neptune.

Neptune is a very long distance from the Sun: about 30 times as far as Earth. Because of this, it takes Neptune 165 years to orbit the Sun!

Neptune is named after the Roman god of the Sea, which reflects its ocean-blue colour. However it is not water on the surface of Neptune! Much like Uranus, methane gas in the atmosphere gives Neptune its blue colour.