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"
Eclipse Shadow Cone Over Patagonia
04/08/2010
Sometimes, during a total eclipse of the Sun, a strange shadow of darkness can be seen stretching off into the distance. Called shadow cones, they are visible because the Earth's atmosphere is not completely transparent, scattering sunlight and hence appearing blue during the day. Shadow cones are particularly dramatic for eclipses near the horizon, as geometry creates a long corridor of sun-blocked air. Visible above is a shadow cone caught during a sunset total solar eclipse visible last month from Patagonia, Argentina. The eclipsed Sun itself still appears bright around the edges of the Moon because of light from the surrounding corona. A few minutes later, the Moon began to move away from the Sun as both set behind distant Andes mountains.