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"
Equinox Sunset
24/09/2009
Often inspiring, or offering a moment for contemplation, a sunset is probably the most commonly photographed celestial event. But this uncommonly beautiful sunset picture was taken on a special day, the Equinox on September 22. Marking the astronomical change of seasons, on that day Earth dwellers experienced nearly 12 hours of daylight and 12 hours of darkness (an equal night). Reflected in the calm waters of Lake Balaton with a motionless sailboat in silhouette, the Sun is setting due west and heading south across the celestial equator. In the background lies the Benedictine Archabbey of Tihany, Hungary.