P1- OCR 21ST Century

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Planets orbit the sun in Ellipses.

8 Planets

Closest to the sun-Mercury, Venus, Earth , Mars

Then the asteroid belt

Then the outer planet- Jupiter, Saturn, Uranus, Neptune

There are also other things. Such as Dwarf planets, comets, dust (all orbit the Sun)

Stars/Planets are different:

Stars are huge, very hot, and very far away.

They give off a huge amount of light, so you can see them from a long distance.

Planets are smaller and only reflect light

Planets in the solar system are much closer than any star

Solar system is 5 Thousand Million years old:

It is believed that the solar system was formed from a big clouds of dust/gas

One cloud started to get squeezed slightly

Once the particles were closer gravity took over

The whole cloud collapsed on itself

At the centre of the collapse, particles came together to form a protostar

A high temperature caused a process called fusion.This occurs in our sun.

Hydrogen nuclei join together to form Helium.

Fusion gives out masses of heat a and light energy

Chemical elements with heavier atoms were formed in stars due to the fusion of different nuclei.

Around the sun material form the cloud containing H,He and other heavier elements started to clump together and became planets.

Asteroids:

Left over material from when the solar system was formed

Rocks between Mars and Jupiter didn't form planets and stayed as they were

Smallish bits of rubble and rock. These are called asteroids.

Comets:

Are small balls of dust,ice and rock, which orbit in elongated ellipses.

Often in different planes from planets

As the comet approaches the sun, the ice melts leaving a bright tail behind, which can be millions of kilometers long and can be seen from Earth.

Known as shooting stars

The solar system and its contents

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