What are the gas planets?

The four planets that are furthest from the Sun are known as the gas planets.

They are named this because they are all made from gas.

The four gas planets are Jupiter, Saturn, Uranus and Neptune.

You could not stand on their surface as they are not solid. They are giant balls of hydrogen, helium and other gases.

The four gas planets are much larger than the rocky planets, and each one has many moons that orbit it.

• Jupiter has the shortest day in our Solar System, only lasting ten hours.

• Jupiter is twice as massive as all of the other planets in our Solar System combined.

• Saturn is nine times wider than Earth.

• NASA scientist's think that Saturn's rings were once chunks of comets, asteroids, or shattered moons that broke up around the planet.

• Uranus was first discovered by astronomer William Herschel in 1781.

• Uranus has two sets of rings. The inner system has nine dark grey rings and the outer system is made up of 2 rings; 1 which is reddish coloured and the other which is blue.

• The only spacecraft to have visited Neptune was NASA's Voyager 2.

• Neptune is about four times wider than Earth.

Jupiter

Jupiter is the fifth planet from the Sun and is the largest planet in our Solar System.

It has a diameter that measures a whopping 89,000 miles!

It is so big that it is sometimes called a gas giant.

Jupiter has big storms across the planet. The most famous is called 'the red spot' which has been swirling around on Jupiter for at least 300 years.

Jupiter rotates quickly on its axis and one day goes by in just 10 Earth hours. However, because it is further away from the Sun, a year on Jupiter is over 11 Earth years.

There are currently 95 recognised moons orbiting Jupiter, and thousands of other small objects in its orbit.

Saturn

Saturn is the sixth planet from the Sun and is most famous for its rings. There are seven rings surrounding Saturn. These rings are made of chunks of ice and rock.

Saturn is another gas giant measuring 75,000 miles in diameter.

Like Jupiter, Saturn rotates on its axis quickly and one day on Saturn goes by in just over 10 Earth hours. However, because of its distance from the Sun, one year on Saturn is the same as 29 Earth years.

Saturn currently has 146 recognised moons.

Uranus

Uranus is the seventh planet from the Sun. It has a rocky centre and the surface is made up of a dense fluid of "icy" materials, mainly water, methane and ammonia. Because of this, Uranus is referred to as an ice giant.

It is blue in colour because of the methane gas in its atmosphere.

It has a diameter of 32,000 miles.

Uranus is surrounded by 11 rings.

Uranus is the only planet that rotates on its side. This is thought to be because it was hit by a large object a long time ago.

Like the other gas planets, Uranus rotates quickly on its axis and a day on Uranus lasts just over 17 Earth hours. As it is so far away from the Sun, it takes 84 Earth years to complete one full rotation.

It has 28 known moons.

Neptune

Neptune is the furthest planet from the Sun. It is very similar in size to Uranus and has a diameter of 31,000 miles.

Like Uranus, it is an ice giant with a thick cloud of water, ammonia and methane surrounding a solid centre. It is cold, dark and extremely windy.

The methane in the atmosphere gives it the same blue colour as Uranus.

There are five rings around Neptune but they are difficult to see through a telescope.

Neptune spins on its axis quickly and one day on this planet is 16 Earth hours. However, as Neptune has such a distance to orbit around the Sun, it takes 165 Earth years to travel around it once.

Currently scientists believe that Neptune has 16 moons.

Did you know?

Jupiter doesn’t have a surface, as it's made up of a mix of gases and liquids.

This means that we couldn't land humans or a rover on Jupiter, but even flying through it's atmosphere would be dangerous as the extreme pressures and temperatures deep inside the planet would crush and burn anything going through it.

Atmosphere – The gases that surround a planet or celestial body.

Axis – An imaginary line that marks the centre of a spinning object, like a planet.

Gas – A state of matter where the particles not in a fixed state. Nitrogen, oxygen, helium and methane are all types of gas.

Gas planets – Planets made up of gas like hydrogen and helium. Jupiter, Saturn, Uranus and Neptune are all gas planets.

Moon – A moon is a large ball of rock that orbits a planet.

Orbit – The curved path of a celestial object that moves around something which has gravity, like the Moon and the Earth.

Rocky planets – Planets made up of rock and metals, like Mercury, Venus, Earth and Mars.

Solar System – The Solar System is where Earth lies. It is a gravitational system of planets, dwarf planets, moons and asteroids that all circle our Sun.

Research one of the gas planets and its moons.
Create a fact-file or poster about your chosen planet.

Can you make any comparisons with Earth?

Question: Could humans live on a gas planet and survive?

Try to write down five different reasons and explain why.