Sun (Anteria)

Sun

Pictured in visible light with solar filter in 2013 with sunspots and limb darkening.
False color image taken in 2010 as seen in ultraviolet light (wavelength of 30.4 nm)
Name	Sun
Adjectives	Solar
Observation data
Mean distance from Anteria	1 AU ≈ 1.496×108 km 8 min 19 s at speed of light
Apparent magnitude (V)	−26.74
Absolute magnitude	4.83
Spectral classification	G2V
Metallicity	Z = 0.0122
Angular size	31.6–32.7 minutes of arc ≈ 0.5 degrees
Orbit al characteristics
Mean distance from galactic core	≈ 2.7×1017 km ≈ 29,000 light-years
Galactic year	(225–250) million years
Velocity	≈ 220 km/s (orbit around the center of the galaxy) ≈ 20 km/s (relative to average velocity of other stars in stellar neighborhood) ≈ 370 km/s (relative to the Cosmic microwave background radiation
Physical characteristics
Equatorial radius	695,700
Equatorial circumference	4.379×106 km
Flattening	9×10−6
Surface area	6.09×1012 km2
Volume	1.41×1018 km3
Mass	1.9885×1030 kg
Average density	1.408 g/cm3
Center density (modeled)	162.2 g/cm3
Equatorial surface gravity	274 m/s2
Moment of inertia factor	0.070<
Escape velocity	617.7 km/s
Temperature	Center (modeled): 1.57×107 K
Luminosity	3.828×1026 W ≈ 3.75×1028 lm ≈ 98 lm/W Luminous efficacy
Color (B-V)	0.63
Mean radiance	2.009×107 W·m−2·sr−1
Age	≈ 4.6 billion years
Rotation characteristics
Obliquity	7.25° (to the ecliptic) 67.23° (to the galactic plane)
Right ascension of North pole	286.13° 19 h 4 min 30 s
Declination of North pole	+63.87° 63° 52' North
Sidereal rotation period (at equator)	25.05 d
(at 16° latitude)	25.38 d
(at poles)	34.4 d
Rotation velocity (at equator)	7.189×103 km/h
Photospheric composition (by mass)
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 star at the center of the Tendor System. It is a nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy mainly as visible light and infrared radiation. It is by far the most important source of energy for life on Anteria. Its diameter is about 1.39 million kilometres (864,000 miles), or about 109 times that of Anteria. Its mass is about 330,000 times that of Anteria; it accounts for about 99.86% of the total mass of the Tendor System. Roughly three quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon and iron.

The Sun is a G-type main-sequence star (G2V) based on its spectral class. As such, it is informally and not completely accurately referred to as a yellow dwarf (its light is closer to white than yellow). It formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Tendor System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core. It is thought that almost all stars form by this process.

The Sun's core fuses about 600 million tons of hydrogen into helium every second, converting 4 million tons of matter into energy every second as a result. This energy, which can take between 10,000 and 170,000 years to escape the core, is the source of the Sun's light and heat. When hydrogen fusion in its core has diminished to the point at which the Sun is no longer in hydrostatic equilibrium, its core will undergo a marked increase in density and temperature while its outer layers expand, eventually transforming the Sun into a red giant. It is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury and Venus, and render Anteria uninhabitable – but not for about five billion years. After this, it will shed its outer layers and become a dense type of cooling star known as a white dwarf, and no longer produce energy by fusion, but still glow and give off heat from its previous fusion.

The enormous effect of the Sun on Anteria has been recognized since prehistoric times. The Sun was thought of by some cultures as a deity. The synodic rotation of Anteria and its orbit around the Sun are the basis of solar calendars, one of which is the international calendar, the predominant calendar in use today.