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 Rotating Jets of Comet Hyakutake
14/04/1996
Comet Hyakutake will reach its closest point to the Sun on May 1, passing well inside the orbit of Mercury. At this time, the comet's dust and ion tail will be at their greatest physical length. As the comet nears the Sun, gas and dust are driven off the surface, sometimes being shot off in jets. Although much of this material ends up in the tail, some interesting features can be seen close to the comet's three kilometer nucleus. Because the comet's nucleus rotates, the jets can be seen to form arcs around the comet's center resembling a pinwheel. The above photograph, taken April 8, shows two expanding arcs of cometary material and two source jets. The outermost arc is at a projected distance of 12,000 kilometers from the nucleus. The inner is about 8,000 kilometers from the nucleus. They are expanding from the nucleus at 870 km per hour. The inner arc ends at the brightest of the Comet Hyakutake's many jets. Information: The Scale of the Universe Debate in April 1996