Sun

The Sun is the 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 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 billionAw nummers in this aorticle are short scale. Ane billion is 109, or 1,000,000,000. 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.

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References

Category:G-teep main-sequence starns
Category:Licht soorces
Category:Plasma physics
Category:Space plasmas
Category:Starns wi proper names