The Sun is our star. Here’s a nice introduction from Dr. Plait. It’s a rather typical star , actually. When compared to the Earth , we see that a star is an entirely different type of object from a planet. It is a huge sphere of hydrogen and helium gas almost one and one half million km in diameter. It is a fairly typical star, about average in all respects. Its spectral type is G2V; that puts it right in the middle of the H-R diagram. The visible surface of the Sun shows indications of massive storms which release energy into space and toward the Earth. We have a spacecraft called SOHO that regularly monitors the Sun's weather . With a properly filtered telescope , we can see a variety of features on its surface. This NASA video shows the Sun in an entirely different light, quite literally. Since we believe the Sun to be a rather typical star, we can make some assumptions of the physical details of most other stars. For instance, we are certain that other stars have ‘ starspots ’. We see other features on the surface of our star which must be similar to those seen on other stars.