Zirin, Harold Formerly, Department of Physics, California Institute of Technology, Pasadena, California.
Pasachoff, Jay M. Hopkins Observatory, Williams College, Williamstown, Massachusetts.
Last reviewed:June 2019
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- Formation of the Sun
- Location of the Sun
- Solar structure, behavior, and properties
- Energy production
- Solar atmosphere
- Solar composition
- Solar activity
- Solar-terrestrial effects
- Solar eclipses
- Related Primary Literature
- Additional Reading
The star around which the Earth revolves and the source of our planet's light and heat. Containing 99.8% of the solar system's mass, the Sun holds all the system's planets and objects under its gravitational sway. The Sun measures 1.4 million km (865,000 mi) in diameter and with a mass 333,000 times that of the Earth. The surface temperature of the Sun is about 6000 K (5700°C or 10,000°F); since solids and liquids do not exist at these temperatures, the Sun is entirely gaseous. Almost all the gas is in atomic form as plasma, a hot, ionized state of matter. Appearing as an extremely bright disk in the sky, the Sun is too bright to look at except during sunrise or sunset, when the light must travel through substantially more of Earth's atmosphere to reach an observer (Fig. 1). See also: Earth; Earth rotation and orbital motion; Gravitation; Matter (physics); Planet; Plasma (physics); Solar system; Star
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