n.
Star around which the components of the solar system revolve.
It is about five billion years old and is the dominant body of the system, with more than 99% of its mass. It converts five million tons of matter into energy every second by nuclear fusion reactions in its core, producing neutrinos (see solar neutrino problem ) and solar radiation. The small amount of this energy that penetrates Earth's atmosphere provides the light and heat that support life. A sphere of luminous gas 864,950 mi (1,392,000 km) in diameter, the Sun has about 330,000 times the mass of Earth. Its core temperature is close to 27 million °F (15 million °C) and its surface temperature about 10,000 °F (6,000 °C). The Sun, a spectral type G (yellow) star, has fairly average properties for a main-sequence star (see Hertzsprung-Russell diagram ). It rotates at different rates at different latitudes; one rotation takes 36 days at the poles but only 25 days at the equator. The visible surface, or photosphere , is in constant motion, with the number and position of sunspot s changing in a regular solar cycle . External phenomena include magnetic activity extending into the chromosphere and corona , solar flare s, solar prominence s, and the solar wind . Effects on Earth include aurora s and disruption of radio communications and power-transmission lines. Despite its activity, the Sun appears to have remained relatively unchanged for billions of years. See also eclipse ; heliopause .