My 5-year-old is fascinated by the night sky and loves to look at the moon and stars. She wants to buy a telescope so that she can see all the stars in space! But she wonders why are all the stars white?
Well, they’re not but you can’t see their colours by looking at them with just your eyes. They are so very far away from Earth that you need to use a telescope to study them in more detail.
Stars are bright, shining balls of gas that are mostly made up of two chemical elements: hydrogen and helium. You can find out more about these gases by clicking on their symbols (H and He) in this interactive periodic table.
Most stars are ‘main sequence stars’, which live for about 5 billion years. They turn hydrogen into helium in a type of chemical reaction called ‘fusion’. This reaction gives off lots and lots of heat and light.
Different types of stars are grouped together into seven classes: O, B, A, F, G, K and M
O stars are the brightest and hottest; M stars are the dimmest and coolest. They range in colour from blue to white to yellow to orange to red.
The Sun turns hydrogen into helium but it also contains small amounts of some other chemical elements (like carbon, oxygen, iron and neon). It looks yellow to us on Earth because it is close enough for us to be able to see its colour. But you should NEVER look directly at the Sun because it shines so brightly that it can damage your eyes very badly!
This video tutorial gives a nice introduction to the different types of stars and a handy mnemonic to remember them by.