Sun

The star at the centre of our solar system. In the sun, the basic fusion process converts hydrogen to helium liberating large amounts of energy. The sun converts about 2 million kg of mass to energy every second.

Equatorial radius6.96x108m
Mass1.9891x1030kg
Polar moment of inertia5.7x1046kgm2
Bolometric luminosity3.826x1026W
Effective surface temperature5770K
Solar constant
Bolometric flux at 1 astronomical unit
1.368x103Wm-2
Absolute magnitude
MV
Mbol
+4.83
+4.75
Apparent magnitude
mV
mbol
-26.74
-26.82

Faint Young Sun Paradox
Theories of stellar evolution indicate that as stars mature on the main sequence, they grow steadily hotter and brighter; calculations suggest that at about the time of the formation of Earth, the Sun was roughly two-thirds the brightness that it is now. However, there is no geological evidence on Earth (or on Mars) for the Sun being fainter in the past. At present there is no clear resolution for this paradox.

Historical Notes
300BC Aristarchus proposed that the earth revolves around the sun.
1611 Sunspots discovered by Galileo and Christoph Scheiner.
1919 Eddington recorded data on the sun's gravitational deflection of starlight during a solar eclipse, conirming Einstein's general theory of relativity.

See also: Active Sun, Chromosphere, Corona, Coronal Mass Ejection, Earth, Faculae, Halo, Heliocentric Model, Insolation, Irradiance, Jupiter, Lagrangian Points, Mars, Mercury, Moon, Neptune, Opposition, Perihelic Opposition, Perihelion, Photosphere, Pluto, Proton-Proton Chain, Protosun, Quiet Sun, Saturn, Solar Constant, Solar Cycle, Solar Energy, Solar Flare, Solar Resource, Solar Spectrum, Solar Storm, Solar System, Solar Wind, Star, Sunspot, True Sun, Uranus, Venus, Wolf Number, Yellow Dwarf.

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Subjects: Astronomy


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