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"
Europa: The Latest From Galileo
17/01/1997
Today, NASA revealed recent results from the Galileo Probe's December 19th flyby of Europa, Jupiter's ice-covered moon - including this close-up image of fractured and frozen terrrain. The highest resolution picture ever made of Europa, the snapshot shows a complex array of surface features in a 5.9 x 9.9 mile area near the moon's equatorial region. North is toward the top and the Sun illuminates the region from the right. The image was made from a distance of 2,060 miles. At the upper left are linear criss-crossing ridges and grooves probably caused by movements of the surface ice. Serpentine valleys and lumpy features of unknown origins are also visible. Only a few impact craters are apparent though, implying a geologically young surface. So far, Galileo's findings lend support to the exciting possibility that liquid water once existed and may still exist beneath Europa's surface.