Solar System Planets PDF

The Sun is at the centre of our solar system The Sun is a star at the centre of our solar system. All stars are balls of very hot gas that give out heat and light. The Sun is the only star in our solar system. The other stars are all much further away and because they are so far away, we do not fee...

The Sun is at the centre of our solar system The Sun is a star at the centre of our solar system. All stars are balls of very hot gas that give out heat and light. The Sun is the only star in our solar system. The other stars are all much further away and because they are so far away, we do not feel their heat, or benefit from their light. The Sun is at the centre of our solar system. The planets and the asteroid belt Planets are different from stars because they are not made of hot gas and cannot give out their own heat and light. There are eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. All the planets travel around the Sun in a path called an orbit. Every planet has its own orbit around the Sun. The shape of each orbit is a bit like a slightly flattened circle. We call a shape like this an ellipse. Figure 1 The temperature at the surface of the Sun is about 6 000 ˚C Asteroids are chunks of rock that travel around the Sun. There are hundreds of thousands of asteroids. Most asteroids travel around the Sun between the orbits of Mars and Jupiter. This part of the solar system is known as the asteroid belt. You can see the asteroid belt in the diagram of the solar system. Figure 2 Asteroids differ in size and shape. The largest asteroid, Ceres, has a diameter of 1 000 km. Most are very much smaller. Source: NASA Each planet is different The planets are not all the same. Each planet has its own features. Planets are all different in size, move in different orbits and are different distances from the Sun. They also have different compositions: some are rocky like the Earth and others are gas planets. The four inner planets are solid rocky bodies; the four outer planets are gas giants -- huge balls of gas. They have different numbers of moons. A moon is a solid rocky object that travels around a planet. Some information about the planets Mercury Source: MichaelTaylor/Shutterstock Mercury is a rocky planet covered in a layer of fine soil. There are many huge circular holes called craters. It is the only planet that has no atmosphere. Its average temperature is 168 ˚C. There is evidence of ice near its north pole, but none of liquid water. It does not have a moon. Diameter: 4 878 km. Distance from the Sun: 60 million km. Venus Source: NASA Venus has a bare rocky surface, with many volcanoes. The thick atmosphere blocks the surface from observers on Earth. The atmosphere is made of carbon dioxide, which traps the Sun's heat, making the planet very hot. Its average temperature is 500 ˚C. It has white clouds made of carbon dioxide, not water. Venus has no water, and no moon. Diameter: 12 000 km. Distance from the Sun: 108 million km. Earth Source: NASA Earth is a rocky planet, but most of its surface is covered by soil and water. It also has an atmosphere. The atmosphere contains oxygen which animals breathe in, and carbon dioxide which plants take in. The water in the oceans and atmosphere make Earth appear blue from space -- so it is known as 'the blue planet'. It is the only planet in our solar system which can support life. Earth's average temperature is 15 ˚C, and it has one moon. Diameter: 12 750 km. Distance from the Sun: 150 million km. Mars Source: Peter Baxter/Shutterstock Mars is often called 'the red planet' because its rocky surface is covered in red dust. It has many volcanic mountains, including Olympus Mons which is 28 km high! There is frozen water in deep craters near its poles. Dry river beds suggest that there was once liquid water in other places. The atmosphere is thin. The average temperature is --55 ˚C. Mars has two moons. Diameter: 6 787 km. Distance from the Sun: 240 million km. Jupiter Source: MichaelTaylor/Shutterstock Jupiter is so large that all the other planets could fit inside it. It is a gas planet, made mainly of hydrogen and helium, like the Sun. Fast winds blowing from east to west around the planet give it a streaky appearance. It has a giant red spot which is a huge storm of swirling gases, with wind speeds of over 800 km per hour. Jupiter has three thin dark rings, made mainly of dust. Jupiter has 75 moons. The temperature at its surface is about --145 ˚C. Diameter: 142 800 km. Distance from the Sun: 800 million km. Saturn Source: NASA Saturn is a gas planet made up mainly of hydrogen and helium, like the Sun. Its gases make it so light that scientists think it could float in water! Its yellow bands are caused by winds blowing very fast through the gassy atmosphere. Its average temperature is --141 ˚C. Saturn has bright colourful rings around it, made of frozen water. Saturn has 62 moons. It is the furthest planet from the Earth that can be seen without a telescope or binoculars. Diameter: 120 660 km. Distance from the Sun: 1 400 million km. Uranus Source: Byron Moore/123RF Uranus is made mainly of frozen gas and is sometimes called an 'ice giant'. Its thick atmosphere is made mainly of hydrogen and helium, with some methane which gives it a green-blue appearance. Its axis is tilted so one pole always points to the Sun and it appears to lie on its side. It has 11 dark and 2 brightly coloured rings, and 27 known moons. Its average temperature is --216 ˚C Diameter: 51 118 km. Distance from the Sun: 3 000 million km. Neptune Source: NASA Neptune is an ice giant, like Uranus, and made of the same gases. Like Uranus, it has a blue-green colour because of methane in its atmosphere. It has extremely fast winds reaching up to 1 400 kilometres per hour. Neptune has 13 moons. It has several dark rings. Its average temperature is --218 ˚C. Diameter: 495 285 km. Distance from the Sun: 4 500 million km.