If no stars show obvious disks, then how do we measure their diameters? There are various methods. Of course, there is no problem at all with the Sun, which is a normal Main Sequence star of Type G; it is 865,000 miles across. We may not have discovered all its secrets, but we do know a great deal about it, and it gives us a guide to other stars – though the stars are amazingly diverse. Some are much larger than the Sun, others much smaller; some are far more luminous, others remarkably feeble.