Sun

The Sun, sometimes called
Sol, is the star in our                      larger image
solar system. The planet                  Observation data
Earth and all of her      Mean distance from Earth  150,000,000 km
sister planets, both the
other terrestrial planets Visual brightness (V)     -26.8m

and the gas giants, orbit Absolute magnitude        4.8m
the Sun. Other bodies
that orbit the Sun                    Physical characteristics
include asteroids,        Diameter                  1,392,000 km
meteoroids, comets,
Trans-Neptunian objects,  Relative diameter (dS/dE) 109

and, of course, dust.     Surface area              6.09 × 1012 km2

                          Volume                    1.41 × 1027 m3

Physical and other        Mass                      1.9891 × 1030 kg
characteristics           Relative mass to Earth    333,400
The Sun is a main         Density                   1411 kg m-3
sequence star, with a     Relative density to Earth 0.26
spectral class of G2,
meaning that it is        Relative density to water 1.409
somewhat bigger and       Surface gravity           274 m s-2
hotter than the average
star but far smaller than Relative surface gravity  27.9 g
a red giant star. A G2    Surface temperature       5780 K
star has a main sequence  Temperature of corona     5 × 106 K
lifetime of about 10
billion years, and the    Luminosity (LS)           3.827 × 1026 J s-1
Sun is probably about 5
billion years old, as                  Orbital characteristics
determined by             Period of rotation         
nucleocosmochronology.                  At equator: 27d 6h 36m
At the center of the Sun,          At 30¡ latitude: 28d 4h 48m
where its density is 1.5           At 60¡ latitude: 30d 19h 12m
× 105 kg m-3,                At 75¡ latitude: 31d 19h 12m
thermonuclear reactions
(nuclear fusion) convert     Period of orbit around 2.2 × 108 years
hydrogen into helium. 3.9           galactic centre
× 1045 atoms                    Photospheric composition
undergo nuclear reactions Hydrogen                  73.46 %
there every second. This  Helium                    24.85 %
releases energy which
escapes from the surface  Oxygen                    0.77 %
of the Sun as light.      Carbon                    0.29 %
Physicists are able to
replicate thermonuclear   Iron                      0.16 %
reactions with hydrogen   Neon                      0.12 %
bombs. Sustained nuclear  Nitrogen                  0.09 %
fusion on earth for
electricity generation    Silicon                   0.07 %
may be possible in the    Magnesium                 0.05 %
future, with nuclear      Sulphur                   0.04 %
fusion reactors.

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.

The corona has 1011 atoms/m3, and the photosphere has 1023 atoms/m3.

For some time it was thought that the number of neutrinos produced by the
nuclear reaction in the Sun was only one third of the number predicted by
theory, a result that was termed the solar neutrino problem. When it was
recently found that neutrinos had mass, and could therefore transform into
harder-to-detect varieties of neutrinos while en route from the Sun to
Earth, measurement and theory were reconciled.

Observation of the Sun can reveal such phenomena as:

   * Sunspots
   * Faculae
   * Solar flares
   * Solar prominences
        o quiescent prominences
        o eruptive prominences

Caution: looking directly at the sun can damage the retina and one's
eyesight.

There are several newspapers called The Sun.

Sun is a shortened name for Sun Microsystems.

The Solar System

Sun - Mercury - Venus - Earth - Mars - Asteroids - Jupiter - Saturn - Uranus
- Neptune - Pluto - Comets - Kuiper belt - Oort cloud

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