The Sun
The Sun is a yellow dwarf star (G2V), about 4.6 billion years old, and the dominant gravitational force in the Solar System. It has a diameter of roughly 1.4 million kilometers and contains around 99.8% of the Solar System’s mass. Nuclear fusion in its core converts hydrogen into helium, producing energy that warms the planets. Above the core lie the radiative and convective zones, followed by the visible photosphere (~5,500 °C), the chromosphere, and the much hotter corona (~2 million °C).
Source: science.nasa.gov
APODs including "The Sun"
Sharp Silhouette
21/09/2006
Though it's 93 million miles away, the Sun still hurts your eyes when you look at it. But bright sunlight (along with accurate planning and proper equipment!) resulted in this sharp silhouette of spaceship and space station. The amazing telescopic view, recorded on September 17, captures shuttle orbiter Atlantis and the International Space Station in orbit over planet Earth. At a range of 550 kilometers from the observing site near Mamers, Normandy, France, Atlantis (left) has just undocked and moved about 200 meters away from the space station. Tomorrow, yet another satellite of planet Earth can be seen in silhouette - the Moon will eclipse the Sun. This last eclipse of 2006 will be seen as an annular solar eclipse along a track that crosses northern South America and the south Atlantic.