|
 The Sun is the star in our solar system. The planet Earth and all other
planets, asteroids, meteoroids, comets, Trans-Neptunian objects, and, of
course, dust, orbit the Sun. The Sun is a main sequence star, with a spectral class of G2, meaning
that it is somewhat bigger and hotter than the average star but far smaller than a red giant star. 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.
At the center of the Sun, where its density is 1.5 × 105 kg m-3,
thermonuclear reactions (nuclear fusion) convert hydrogen into helium. 3.9 × 1045 atoms undergo nuclear reactions there every second. This
releases energy which escapes from the surface
of the Sun as light. Physicists are able to replicate thermonuclear
reactions with hydrogen bombs. Sustained nuclear
fusion on earth for
electricity generation may be possible in the future, with nuclear 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.
To obtain an uninterrupted view of the Sun, the European Space Agency and
NASA cooperatively launched the Solar and Heliospheric Observatory (SOHO) on
December 2, 1995.
Observation of the Sun can reveal such phenomena as:
Sun facts
Physical characteristics
Type of star: G2V
Surface area: 6.09 × 1012 km2
Equatorial diameter: 1,385,645 km
Volume: 1.41 × 1027 m3
Mass: 1.9891 × 1030 kg
or 332,946 times earth's
Density: 1411 kg m-3
Relative density to Earth 0.26
Relative density to water: 1.409
A Surface gravity: 274 m s-2
Relative surface gravity: 27.9 g
Surface temperature: 5780
K
Temperature of corona: 5 × 106 K
Luminosity: 3.827 × 1026 J s-1
Visual brightness: -26.8m
Absolute magnitude: 4.8m
Interior temperaure: 14 million
degrees C
Surface temperature: 6093.3
degrees C
Orbital characteristics
Mean distance from Earth: 150,000,000 km
Age: 4.5 billion years old
Rotational period: 27 earth days
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
Home Galaxy: the Milky Way
Distance from galaxy center: 24,000 light years
Period of orbit: around the
galactic centre: 2.2 × 108 years
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 %
|
