Sun
The Sun, sometimes called Sol, is the only star in our solar system. The planet Earth and all of her sister planets, both the other terrestrial planets and the gas giants, orbit the Sun in accordance with Newton's Laws of Gravity.
| Observation data | |
| Mean distance from Earth | 150,000,000 km |
|---|---|
| Visual brightness (V) | -26.8m |
| Absolute magnitude | 4.8m |
| Physical characteristics | |
| Diameter | 1,392,000 km |
| Relative diameter (dS/dE) | 109 |
| Surface area | 6.09 × 1012 km2 |
| Volume | 1.41 × 1027 m3 |
| Mass | 1.9891 × 1030 kg |
| Relative mass to Earth | 333,400 |
| Density | 1411 kg m-3 |
| Relative density to Earth | 0.26 |
| Relative density to water | 1.409 |
| Central density | 1.5 × 105 kg m-3 |
| Surface gravity | 274 m s-2 |
| Relative surface gravity to Earth | 27.9 |
| Surface temperature | 5780 K |
| Temperature of corona | 5 × 106 K |
| Luminosity (LS) | 3.827 × 1026 J s-1 |
| Orbital characteristics | |
| Period of rotation | |
| At equator: | 27d 6h 36m |
| At 30° latitude: | 28d 4h 48m |
| At 60° latitude: | 30d 19h 12m |
| At 75° latitude: | 31d 19h 12m |
| Velocity of rotation at equator | |
| Photospheric composition | |
| Hydrogen | 73.46 % |
| Helium | 24.85 % |
| Oxygen | 0.77 % |
| Carbon | 0.29 % |
| Iron | 0.16 % |
| Neon | 0.12 % |
| Nitrogen | 0.09 % |
| Silicon | 0.07 % |
| Magnesium | 0.05 % |
| Sulphur | 0.04 % |
The Sun is the nearest star to Earth and the brightest object in the sky.
Other bodies that orbit the Sun include asteroids, meteoroids, comets, Trans-Neptunian objects, and, of course, dust.
Physical and other characteristics
The Sun is a main sequence star, with spectral class G2, meaning that it is somewhat bigger and hotter than the average star but far smaller than the largest red giant star. A G2 star has a main sequence lifetime of about 10 billion years, and the Sun is probably about 5 billion years old, as determined by nucleocosmochronology. One outstanding question about the Sun is the difference between the number of neutrinos observed from the Sun, and the number predicted by theory, the solar neutrino problem.
All matter in the Sun is in the form of plasma due to its extreme temperature. This makes it possible for the sun to rotate faster at its equator than it does at higher latitudes, since the Sun is not a solid body. The differential rotation of the Sun's latitudes causes its magnetic field lines to become twisted together over time, causing magnetic field loops to erupt from the sun's surface and trigger the formation of the Sun's dramatic sunspots and solar prominences.
Observation of the Sun can reveal such phenomena as:
(Caution: looking directly at the sun can cause blindness.)
Other terms related to the Sun :
See also: Sun mythology
Sun - Mercury - Venus - Earth - Mars - Asteroids - Jupiter - Saturn - Uranus - Neptune - Pluto - Comets
Several newspapers are called The Sun.