Image of The Sun
|Mean distance from Earth:||1.496×108 km
8 min 19 s at Lightspeed
The Sun is a yellow (actually white but classified as a yellow dwarf) star made of hydrogen, Helium and small amounts of other elements. The planets and planetoids of the Solar System revolve around the sun.
The sun produces massive amounts of energy through the process of nuclear fusion, in which hydrogen is changed into helium due to the pressure generated at the center of a such a massive object. The Sun's energy is what warms the Earth and its atmosphere sufficiently to support life, and provides energy to support life. Almost all life on earth depends on solar energy.  Plants convert sunlight into sugars that provide food not only for the plants, but for animals that eat those plants.
Occasionally magnetic storms occur on the Sun's surface which bombard of the Solar System with massive amounts of electromagnetic radiation. This can result in damage to satellites orbiting the Earth, as well as disruption of radio and television signals. In a few Billion years the Sun will evolve into a "red giant", becoming so large that it will actually engulf Mercury, Venus, and Earth.
We know for certain that stars like the sun can sustain life. Stars somewhat brighter than the sun may be able to sustain life as well. Red dwarf stars may also be able to sustain life.
When the Moon comes between the Earth and the Sun, there is a solar eclipse. A total solar eclipse results in such total darkness. Even the stars come out in the sky for a brief period during the daytime.
During eclipses primitive people fear that the sun has gone and will never come back. Quite a few Myths and legends involve the sun going away and coming back later. In these legends typically the sun stayed away far longer than the few minutes that a total eclipse lasts. As the frightening event was retold over the generations it got exaggerated.
- Some small ecosystems depend on geothermal energy.