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
24/11/2010
Have you ever seen an aurora? Auroras are occurring again with increasing frequency. With the Sun being unusually dormant over the past three years, the amount of Sun-induced auroras has also been unusually low. More recently, however, our Sun has become increasingly active and exhibiting a greater abundance of sunspots, flares, and coronal mass ejections. Solar activity like this typically expels charged particles into the Solar System, some of which may trigger Earthly auroras. As this year unfolded, the above timelapse displays of picturesque auroras were captured above Troms�, Norway. Curtains of auroral light, usually green, flow, shimmer and dance as energetic particles fall toward the Earth and ionize air molecules high up in the Earth's atmosphere. With solar maximum still in the future, there may be opportunities to see spectacular aurora personally over the next three years.