I
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 kF (15 million kC) and its surface temperature about 10,000 kF (6,000 kC). 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 .
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[c mediumvioletred] (as used in expressions)
Sun tzu
Baltimore Sun
the Sun King
Moon Sun Myung
sun bear
sun dance
sun worship
{{link=Sun Yat sen">Sun Yat sen
Sun Yixian
Yi Sun shin