The enormous significance of the Sun to our lives has been felt ever since ominous eclipses and mysterious sunspots were observed many thousands of years ago. Scientists and astronomers from many different fields have contributed over the centuries to the rich knowledge we have of the Sun and its relationship with the Earth. What is the Sun made of? What is the solar wind? What could magnetism have to do with the Sun? How have scientists madethese discoveries, and what does it all mean for us here on Earth? And what of the deep scientific mysteries that remain unresolved? Understanding our closest star has never been more important. Delve into the secrets of the Sun in this guide from Brendan Owens, Astronomer Emeritus for Royal Observatory Greenwich and Open Science Coordinator at Science Gallery at Trinity College Dublin.