Solar System - Sun

Sun

The Sun is the Solar System's star, and by far its chief component. Its large mass (332,900 Earth masses) produces temperatures and densities in its core high enough to sustain nuclear fusion, which releases enormous amounts of energy, mostly radiated into space as electromagnetic radiation, peaking in the 400–700 nm band of visible light.

The Sun is classified as a type G2 yellow dwarf, but this name is misleading as, compared to the majority of stars in our galaxy, the Sun is rather large and bright. Stars are classified by the Hertzsprung–Russell diagram, a graph that plots the brightness of stars with their surface temperatures. Generally, hotter stars are brighter. Stars following this pattern are said to be on the main sequence, and the Sun lies right in the middle of it. However, stars brighter and hotter than the Sun are rare, while substantially dimmer and cooler stars, known as red dwarfs, are common, making up 85 percent of the stars in the galaxy.

Evidence suggests that the Sun's position on the main sequence puts it in the "prime of life" for a star, in that it has not yet exhausted its store of hydrogen for nuclear fusion. The Sun is growing brighter; early in its history it was 70 percent as bright as it is today.

The Sun is a population I star; it was born in the later stages of the universe's evolution, and thus contains more elements heavier than hydrogen and helium ("metals" in astronomical parlance) than older population II stars. Elements heavier than hydrogen and helium were formed in the cores of ancient and exploding stars, so the first generation of stars had to die before the universe could be enriched with these atoms. The oldest stars contain few metals, while stars born later have more. This high metallicity is thought to have been crucial to the Sun's developing a planetary system, because planets form from accretion of "metals".

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Famous quotes containing the word sun:

    We are the party of all labor.
    The whole earth shall be ours to share
    And every race and craft our neighbor.
    No idle class shall linger there
    Like vultures on the wealth we render
    From field and factory, mill and mine.
    Tomorrow’s sun will rise in splendor
    And light us till the end of time.
    Eugène Pottier (1816–1887)

    The sceptics assert, though absurdly, that the origin of all religious worship was derived from the utility of inanimate objects, as the sun and moon, to the support and well-being of mankind.
    David Hume (1711–1776)

    Hath Britain all the sun that shines? day? night?
    Are they not but in Britain?
    William Shakespeare (1564–1616)