The Sun may be our closest and most familiar star, but we are learning more about it every day. We believe it is about 4.5 billion years old and may live to an age of about 10 billion years. Astronomers are space detectives who must take the evidence they have to understand the story of our Sun. Also, the more evidence they uncover, the more knowledge they can apply to other, more distant stars that cannot be studied in such detail.
Many questions still remain unanswered. Has the Sun always been active? Why is the corona hotter than the photosphere? Could sunspots ever completely cover the Sun or completely disappear?