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.[49]
The Sun is a type G2 main-sequence star. Compared to the majority of stars in the Milky Way, the Sun is rather large and bright.[50] 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. Stars brighter and hotter than the Sun are rare, whereas substantially dimmer and cooler stars, known as red dwarfs, are common, making up 85% 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, not yet having exhausted its store of hydrogen for nuclear fusion. The Sun is growing brighter; early in its history its brightness was 70% that of what 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 the older population II stars.[53] 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, whereas stars born later have more. This high metallicity is thought to have been crucial to the Sun's development of a planetary system because the planets form from the accretion of "metals".
The Sun is a type G2 main-sequence star. Compared to the majority of stars in the Milky Way, the Sun is rather large and bright.[50] 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. Stars brighter and hotter than the Sun are rare, whereas substantially dimmer and cooler stars, known as red dwarfs, are common, making up 85% 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, not yet having exhausted its store of hydrogen for nuclear fusion. The Sun is growing brighter; early in its history its brightness was 70% that of what 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 the older population II stars.[53] 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, whereas stars born later have more. This high metallicity is thought to have been crucial to the Sun's development of a planetary system because the planets form from the accretion of "metals".
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