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"
The Analemma and the Temple of Olympian Zeus
23/12/2006
An analemma is that figure-8 curve you get when you mark the position of the Sun at the same time each day throughout planet Earth's year. Above, 47 separate exposures (plus one foreground exposure) were recorded on a single piece of film to illustrate this annual cycle of solar motion from March 30, 2003 to March 30, 2004. In the remarkable foreground are standing Corinthian columns of the ancient Temple of Olympian Zeus in Athens, Greece. Solstices, like the one that occurred at 0022 UT on December 22, correspond to the bottom of the figure-8 or the southernmost excursion of the Sun in the sky. The tilt of planet Earth's axis and the variation in speed as it moves around its orbit combine to produce the graceful analemma curve.