tribal sun

tribal sun

sun

{{otheruses}}
{| border="1" cellpadding="2" cellspacing="0" align="right" style="margin: 0 0 1em 1em; border-color:#ccc"
|+
|+ Sun
|-
| colspan="2" align="center" | Sun_SOHO_image.jpg
|-
! bgcolor="#ffffc0" colspan="2" align="center" | Observation data
|-
! align="left" | Mean distance from
Earth
| 149.6×10⁶ km
(92.95×10⁶ mi)
|-
! align="left" | Visual brightness (V)
| −26.8^m
|-
! align="left" | Absolute magnitude
| 4.8^m
|-
! bgcolor="#ffffc0" colspan="2" align="center" | Orbital characteristics
|-
! align="left" | Mean distance from
Milky Way centre
| ~2.5×10¹⁷ km
(26,000 light-years)
|-
! align="left" | Galactic period
| ~2.26×10⁸ a
|-
! align="left" | Velocity
| ~217 km/s
|-
! bgcolor="#ffffc0" colspan="2" align="center" | Physical characteristics
|-
! align="left" | Diameter
| 1.392×10⁶ km
(109 Earths)
|-
! align="left" | Oblateness
| ~9×10^-6
|-
! align="left" | Surface area
| 6.09 × 10¹² km²
(11,900 Earths)
|-
! align="left" | Volume
| 1.41 × 10¹⁸ km³
(1,300,000 Earths)
|-
! align="left" | Mass
| 1.9891 × 10³⁰ kg

(332,950 Earths)
|-
! align="left" | Density
| 1.408 g/cm³
|-
! align="left" | Surface gravity
| 273.95 m s^-2

(27.9 g)
|-
! align="left" | Escape velocity
from the surface
| 617.54 km/s
|-
! align="left" | Surface temperature
| 5780 K
|-
! align="left" | Temperature of corona
| 5 MK
|-
! align="left" | Approximate
core temperature
| 13.6×10⁶ K
|-
! align="left" | Luminosity (L_S)
| 3.827×10²⁶ J s^-1
|-
! align="left" | Mean Intensity (I_S)
| 2.009×10⁷ W m^-2 sr^-1
|-
! bgcolor="#ffffc0" colspan="2" align="center" | Rotation characteristics
|-
! align="left" | Obliquity
| 7.25[[degree (angle)|º]]
(to the ecliptic)
67.23º
(to the galactic plane)
|-
! align="left" | Right ascension
of North pole ¹
| 286.13º
(19 h 4 min 31.2 s)
|-
! align="left" | Declination
of North pole
| 63.87º
|-
! align="left" | Rotation period
at equator
| 25.3800 days (25 d 9 h 7 min 12±8 s) ¹
|-
! align="left" | Rotation velocity
at equator
| 7174.21 km/h
|-
! bgcolor="#ffffc0" colspan="2" align="center" | Photospheric composition
|-
! align="left" | Hydrogen
| 73.46 %
|-
! align="left" | Helium
| 24.85 %
|-
! align="left" | Oxygen
| 0.77 %
|-
! align="left" | Carbon
| 0.29 %
|-
! align="left" | Iron
| 0.16 %
|-
! align="left" | Neon
| 0.12 %
|-
! align="left" | Nitrogen
| 0.09 %
|-
! align="left" | Silicon
| 0.07 %
|-
! align="left" | Magnesium
| 0.05 %
|-
! align="left" | Sulfur
| 0.04 %
|}
The Sun (also called Sol) is the star to which our solar system belongs. Planet Earth orbits the Sun, as do other bodies including other planets, asteroids, meteoroids, comets and dust.

In common usage, the primary stellar body around which an object orbits is called its "sun", and stars in a multiple star system are referred to as the "suns" of bodies in that system.

Physical and other characteristics

The Sun is a main sequence star, with a spectral class of G2, meaning that it is somewhat more massive and hotter than the average star but far smaller than a blue giant star. A G2 star is on the main sequence, and has a lifetime of about 10 billion years (10 G a), and the Sun formed about 5 Ga (5 billion years) ago, as determined by nucleocosmochronology. The Sun orbits the Milky Way galaxy at a distance of about 25,000 to 28,000 light-years from the galactic centre, completing one revolution in about 226 Ma (226 million years). The orbital speed is 217 km/s, i.e. 1 light-year in ca. 1400 years, and 1 AU in 8 days.

The Sun is a near-perfect sphere, with an oblateness estimated at about 9 millionths (mostly due to the gravitation of Jupiter), which means the polar diameter differs from the equatorial by 10 km at most. This is partly because the centrifugal effect of the Sun's rather sedate rotation is 18 million times weaker than its surface gravity (at the equator).

Perhaps counterintuitively, the Sun does not have definite boundaries as rocky planets do. Instead, the density of gases comprising the Sun drops off following an exponential relationship with distance from the centre of the Sun. The Sun's radius is measured from centre to the edges of the photosphere.

High_Resolution_Solar_Spectrum.jpg plasma and as the energy in the Sun's magnetic field). A fusion reactor, which some physicists believe may one day provide power for human use, would use a similar process to extract atomic energy.

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 (about 25 days) than it does at higher latitudes (28 days near its poles). 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 solar activity cycle includes old magnetic fields being stripped off the Sun's surface starting from one pole and ending at the other.

The corona has a particle density of 10¹¹/m³, and the photosphere a particle density of 10²³/m³.

For some time it was thought that the number of neutrinos produced by the nuclear reactions in the Sun was only one third of the number predicted by theory, a result that was termed the solar neutrino problem. Several neutrino observatories were created including the Sudbury Neutrino Observatory to try and measure the amount of neutrinos given off by the Sun. From these observatories and experiments it was recently found that neutrinos had rest mass, and could therefore transform into harder-to-detect varieties of neutrinos while en route from the Sun to Earth; thus 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:

- Sunspots
- Faculae
- Granules
- Solar flares
- Solar prominences
-- Quiescent prominences
-- Eruptive prominences
-- Spicules
- Coronal mass ejection
- Limb darkening

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

The astronomical symbol for the Sun is a circle with a point at its centre.

The composition of the Sun is not known with any great precision. A solar wind sample return mission, Genesis, returned to Earth in 2004 and is undergoing analysis, but it was damaged by crash-landing when its parachute failed to deploy on reentry to Earth's atmosphere.

The Death of Sol

Our Sun does not have the mass to Nova or Supernova. However in 4-5 billion years it will enter its red giant phase, expanding as the hydrogen fuel in the core is consumed and it starts to burn heavier elements that are present. While it is likely that this expansion will reach the current position of Earth's orbit, recent research suggests that mass loss from the Sun earlier in its red giant phase will cause the Earth's orbit to move further out, preventing it from being swallowed. Following the red giant phase, the Sun will become a white dwarf, slowly cooling for a further 5 billion years or so.

tribal sun

sun

Physical and other characteristics

The Death of Sol

See also

External links

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