Sun: Starn at the centre o the Solar Seestem

It is a geynear perfect sphere o het plasma, wi internal convective motion that generates a magnetic field via a dynamo process. It is bi faur the maist important soorce o energy for life on Yird. Its diameter is aboot 1.39 million kilometres, i.e. 109 times that o Yird, an its mass is aboot 330,000 times that o Yird, accoontin for aboot 99.86% o the tot mass o the Solar Seestem. Aboot three quarters o the Sun's mass conseests o hydrogen (~73%); the rest is maistly helium (~25%), wi muckle smawer quantities o hivier elements, includin oxygen, caurbon, neon, an airn.

The Sun

Sun wi sunspats an limm daurkenin as seen in veesible licht wi solar filter.
Observation data
Mean distance frae Yird	1 au ≈ 7011149600000000000♠1.496×108 km 8 min 19 s at licht speed
Visual brightness (V)	−26.74
Absolute magnitude	4.83
Spectral classification	G2V
Metallicity	Z = 0.0122
Angular size	31.6–32.7 meenits o arc
Adjectives	Solar
Orbital chairactereestics
Mean distance from Milky Way core	≈ 7020270000000000000♠2.7×1017 km 7004272000000000000♠27,200 light-years
Galactic period	(2.25–2.50)×108 yr
Velocity	≈ 7005220000000000000♠220 km/s (orbit aroond the centre o the Milky Way) ≈ 7004200000000000000♠20 km/s (relative tae average velocity o ither starns in stellar neeghbourheid) ≈ 7005370000000000000♠370 km/s (relative tae the cosmic microwave backgrund)
Physical chairactereestics
Equatorial radius	695,700 km, 696,392 km 7002109000000000000♠109 × Yird
Equatorial circumference	7009437900000000000♠4.379×106 km 109 × Yird
Flattenin	6994900000000000000♠9×10−6
Surface aurie	7018609000000000000♠6.09×1012 km2 7004120000000000000♠12,000 × Yird
Vollum	7027141000000000000♠1.41×1018 km3 7006130000000000000♠1,300,000 × Yird
Mass	7030198855000000000♠(1.98855±0.00025)×1030 kg 7005333000000000000♠333,000 × Yird
Average density	7003140800000000000♠1.408 g/cm3 6999255000000000000♠0.255 × Yird
Center density (modeled)	7005162200000000000♠162.2 g/cm3 7001124000000000000♠12.4 × Yird
Equatorial surface gravity	7002274000000000000♠274.0 m/s2 7001279400000000000♠27.94 g 7004275422900000000♠27,542.29 cgs 28 × Yird
Moment o inertia factor	6998700000000000000♠0.070 (estimate)
Escape velocity (from the surface)	7005617700000000000♠617.7 km/s 55 × Yird
Temperatur	Center (modeled): 7007157000000000000♠1.57×107 K Photosphere (effective): 7003577200000000000♠5,772 K Corona: ≈ 7006500000000000000♠5×106 K
Luminosity (Lsol)	7026382800000000000♠3.828×1026 W ≈ 7028375000000000000♠3.75×1028 lm ≈ 7001980000000000000♠98 lm/W efficacy
Mean radiance (Isol)	7007200900000000000♠2.009×107 W·m−2·sr−1
Age	≈ 4.6 billion years
Rotation chairactereestics
Obliquity	7.25° (to the ecliptic) 67.23° (tae the galactic plane)
Right ascension of North pole	286.13° 19 h 4 min 30 s
Declination o North pole	+63.87° 63° 52' North
Sidereal rotation period (at equator)	25.05 d
(at 16° latitude)	25.38 d 25 d 9 h 7 min 12 s
(at powls)	34.4 d
Rotation velocity (at equator)	7003199694444444444♠7.189×103 km/h
Photospheric composeetion (bi mass)
Hydrogen	73.46%
Helium	24.85%
Oxygen	0.77%
Caurbon	0.29%
Airn	0.16%
Neon	0.12%
Nitrogen	0.09%
Silicon	0.07%
Magnesium	0.05%
Sulfur	0.04%

The Sun is a G-teep main-sequence starn (G2V) based on its spectral cless. As sic, it is informally an nae completely accurately referred tae as a yellae dwarf (its licht is closer tae white nor yellae). It formed approximately 4.6 billion years ago frae the gravitational collapse o maiter within a region o a lairge molecular clood. Maist o this maiter gaithered in the centre, whauras the rest flattened intae an orbitin disk that becam the Solar Seestem. The central mass becam sae het an dense that it eventually ineetiatit nuclear fusion in its core. It is thocht that awmaist aw starms form bi this process.

The Sun is aboot middle-aged; it haes nae chynged dramatically for mir than fower billion years, an will remeen fairly stable for mair nor anither five billion year. It currently fuzes aboot 544 million tonnes o hydrogen intae helium ivery seicont, converting 3.6 million tonnes o maiter into energy ivery seicont as a result. This energy, that can take atween 10,000 an 170,000 year tae escape frae its core, is the soorce o the Sun's licht an heat. In aboot 5 billion year, whan hydrogen fusion in its core haes dimeenished tae the point at which the Sun is na langer in hydrostatic equilibrium, the core o the Sun will experience a merkit increase in density an temperatur while its ooter layers expand tae eventually acome a red giant. It is calculatit that the Sun will acome sufficiently lairge tae engulf the current orbits o Mercury an Venus, an render Yird uninhabitable. Efter this, it will shed its ooter layers an acome a dense teep o cuilin starn kent as a white dwarf, that na langer produces energy bi fusion, but still glowes an gies aff heat frae its previous fusion.

The enormous effect o the Sun on Yird haes been recognised syne prehistoric times, an the Sun haes been regairdit bi some culturs as a deity. The synodic rotation o Yird an its orbit aroond the Sun are the basis o solar calendars, ane o which is the predominant calendar in uise the day.