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"
Contemplating the Sun
28/05/2012
Have you contemplated your home star recently? Pictured above, a Sun partially eclipsed on the top left by the Moon is also seen eclipsed by earthlings contemplating the eclipse below. The above menagerie of silhouettes was taken from the Glen Canyon National Recreation Area near Page, Arizona, USA, where park rangers and astronomers expounded on the unusual event to interested gatherers. Also faintly visible on the Sun's disk, just to the lower right of the dark Moon's disk, is a group of sunspots. Although exciting, some consider this event a warm-up act for next week's chance to comtemplate the Sun -- a much more rare partial eclipse by the planet Venus. Astronomy Seminar of the Week: The 2012 Transit of Venus