The Sun

Introduction

For astronomers, the Sun is fascinating because it is our nearest star. By studying the Sun, they can gain an insight into the workings of the other millions of stars that are visible in the night sky. Learning that the Sun is a star can be a little surprising. After all, the Sun is a brightly glowing, yellow object – so bright that it is dangerous to look at it directly, and so hot that we can feel its radiation warming the whole Earth. Stars, on the other hand, are mere silvery pinpoints of light that are visible only against the darkness of the night sky and with no discernible heating effect on Earth. How can they possibly be the same sort of object? The key to the answer lies in their distances.

In astronomical terms, the Sun is relatively close, being only about 150 million kilometres (93 million miles) from Earth. The stars that are visible at night are much further away: the nearest is about 40 million million kilometres from Earth, and most are much more distant than that. Imagine looking at a glowing light bulb first from very close up and then from a much greater distance. Close up, you would see the shape of the bulb but, from far away, it would be just a point of light.

This unit is from our archive and is an adapted extract from Introducing astronomy (S194) which is no longer taught by The Open University. If you want to study formally with us, you may wish to explore other courses we offer in this subject area [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] .