[[caption-width-right:200:No, it doesn't really look like the logo for Kellogg's Raisin Bran.]]

-->The Sun is a mass of incandescent gas \\
A gigantic nuclear furnace \\
Where hydrogen is built into helium \\
At temperatures of millions of degrees.
-->TheyMightBeGiants, "[[EarWorm Why Does The Sun Shine]]? ([[http://www.youtube.com/watch?v=uLpu2UP3rGI&feature=related The Sun Is A Mass Of Incandescent Gas]])"

Describe UsefulNotes/TheSun here.

Alright, I'll do it for you. The Sun is big, glowing, hot (approx. 5750 K. on the surface on average), basically a huge globe of plasma composed mostly of burning hydrogen and helium. Yeah, just like every [[UsefulNotes/{{Stars}} star]] you see. Altogether, it's nothing special, just a common G-class star, white (''not'' [[LiesToChildren yellow]], though atmospheric scattering of blue light may make it seem so) and rather small[[note]]To be precise, it's unimpressive compared to the stars visible in the sky which are mostly giants and supergiants. But most of the stars that actually exist are hard-to-see red dwarfs, and old Sol clearly outshines most of those.[[/note]], on the outer third of the Galaxy on the Orion arm or [[Franchise/TheHitchhikersGuideToTheGalaxy in the uncharted backwaters of the unfashionable end of the western spiral arm]]. It's just a little bit (on the cosmological time scale) older than Earth itself. It is currently around 5 billion years old, and it has enough fuel for another 5 billion. On the end of its life cycle, it will inflate to a red giant[[note]]Important nitpick: a red giant is not ''at all'' the same thing as a nova. A nova requires a white dwarf star siphoning material off another star it orbits, and only lasts for a few weeks or months; singular stars like the sun will not, and cannot, "go nova." Oh, and don't confuse either of these phenomena with a supernova, which is another beast entirely.[[/note]], consuming Mercury, Venus and probably Earth. [[UsefulNotes/{{Mars}} The Red Planet]] gets off with a sunburn, and [[UsefulNotes/TheMoonsOfSaturn Titan]] might thaw out and develop its own life... at least until the sun collapses into an Earth-sized white dwarf [[TimeAbyss and slowly cools to the ambient temperature of the universe over the next trillions of years]].

Still, for us [[HumansAreSpecial humans]] it holds a very huge significance and thus it's featured quite frequently in fiction as it is the closest star to us. In fact, the InsignificantLittleBluePlanet called Earth is orbiting around it. Yeah, we're orbiting in a roughly circular shape with a radius of 8.3 light minutes and the Sun in the center. And yes, you see it every (cloudless) day (unless you are living on a latitude greater than 66.7 North or South), so unless you are ''literally'' living under a rock and never leave, you must be kind of familiar with it.

As were people in the ancient times. The Sun has been revered as a deity, or as an object of divine origins by many religions. Helios (or Apollo/Apollon, as his better known name) was the [[Myth/ClassicalMythology Greek god]] of the Sun. The {{ancient Egypt}}ians saw it originally as the Pharaoh's soul; later it was associated with [[Myth/EgyptianMythology Ra and Horus]]. And this is only a very small part of [[http://en.wikipedia.org/wiki/Solar_deity the great number of solar deities]] found in cultures. In such cultures, the Sun is often contrasted with UsefulNotes/TheMoon. The very english word for "Sun" comes from Sunne, [[Myth/NorseMythology an anglo-saxon]] goddess, and and she also is ultimately the source for Sunday (Sunnedaeg).

Despite being made of ionized gas, the tremendous pressure in its interior squeezes the core into a very dense ball, bringing the sun's average density up above that of liquid water. As one astronomy professior said, if you put the sun in a bucket of water it'll sink. The core is less than a quarter of the sun's diameter, but it exists at over 100 ''billion'' times sea level pressure, up to 150 times the density of liquid water at its center [[note]]13.2 times the density of lead[[/note]], and a temperature of 15 million Kelvins (27 million degrees Fahrenheit). The only thing keeping the sun from collapsing in on itself still further is the nuclear fusion reaction going on in its core -- so much heat is produced that the radiation literally lifts up the outer layers against their own weight. Nevertheless, when compared to even the largest planets in the solar system, the sun is ''freakin' huge.'' It's over a hundred times bigger across than the Earth, and weighs over 300,000 times as much. In fact, all of the planets, asteroids, and comets in the solar system ''combined'' have only about one-tenth of 1% of the sun's mass. If the sun had a solid surface -- which it doesn't -- you'd experience 28 times Earth's surface gravity if you stood on it.

As said above, its core will run outta gas some 5 billion years from now. When this happens, the sun will inflate a lot[[note]]"But wait!" I hear you cry. "If the core is no longer providing any radiative pressure to support the sun's upper layers, why will it ''expand'' instead of shrinking under its own weight?" I'm glad you asked. When the core fizzles, the layer immediately above the core will collapse down upon it, and in the process this layer will get more and more compressed until it ignites in nuclear fusion itself, forming a hydrogen-burning shell.[[/note]] and consume at least some of the inner planets - likely including Earth, causing a [[ApocalypseHow Class 5 or Class X apocalypse]][[note]]Even if Earth survided, its fate would be to lose whatever water remains (see below) and atmosphere, becoming a [[DeathWorld planet covered by a magma ocean]] under the intense light of the huge red giant Sun[[/note]]. This inflation will take a time in astronomical terms and will be ''very'' gradual by human-lifetime standards: computer models of evolution of Sun-like stars suggest the sun will need around 1 billion years to grow from its end-of-main-sequence normal size to its full red-giant glory.[[note]][[UsefulNotes/LocalStars Delta Pavonis]], a star extremely similar and very close--about 20 ly--to the Sun is currently going through this phase. It started the process during the time that modern humans have existed--possibly even during recorded history--but only our descendants to the umpteenth generation will get to see the transformation in full. Astronomers have a mild interest in this star, since being the Sun's "near-identical older brother"--as we put it--its evolution will give hints about what's to come for old Sol.[[/note]] After a million or so years in this red giant phase, it will shrink again, then expand a second time as its core fuses helium into carbon, then finally shed its outer layers in a breathtaking display known as a "planetary nebula."[[note]]So named because such nebulas appear as an extensive disc in a telescope, and can be confused for a planet by an observer who doesn't know any better.[[/note]] What will remain afterward is the tiny, exposed core of the sun, now shrunk to a super-dense[[note]]one teaspoon of white dwarf matter would weigh several tons at the surface of the Earth[[/note]] white dwarf the size of the Earth, slowly cooling to a black dwarf over the next quadrillion years.

But we might not have that long to wait before things get ugly. According to current models of stellar evolution, in a paltry ''one'' billion years the sun will brighten enough that Earth's oceans will evaporate. We won't be around then, though -- either because ScienceMarchesOn and we will be on planets far away, or because [[HumansAreBastards we will kill ourselves]].

Note: some fictional extraterrestrial cultures will worship their central star as our ancient cultures worshiped the Sun. While it is definitely not the same star, for its significance for the given aliens it falls into this category.

Commonly referred to as Sol in SpeculativeFiction as in "Navigator, set a course for [[UsefulNotes/TheSolarSystem the Sol System]]."

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