A cut-away view of the Sun showing the convection zone, the
photosphere, the chromosphere, many surface features and localized
atmospheric eruptions like sunspots, flares and prominences. Courtesy of
The Sun is a fairly average, middle-aged (some 4.5 billion years old) star which is currently composed of approximately 72% hydrogen, 26% helium and 2% of all other chemical elements (most notably those up to oxygen) in gaseous form. The source of the Sun's brightness (and that of other stars) is due to nuclear chemical reactions occurring in its innermost parts, where the temperature is 15,000,000 Kelvin (27,000,000F).
The Sun is 1,400,000 kilometers (900,000 miles) in diameter and liberates
about 3.86 watts of energy from its surface.
This energy, the solar luminosity, translates to about 1368 watts per
square meter at the orbit of the Earth.
Last revised: Wed May 17 11:28:21 MDT 2000