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Sun

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The Sun is the star at the center of our Solar System. It is a huge sphere made of hot plasma. This plasma is heated by nuclear fusion in the core. This process makes the Sun shine with light and heat. It is the main source of energy for life on Earth. Many cultures have honored the Sun for a very long time.

Highest resolution photo of Sun (NSF) as of January 20, 2020
Highest resolution photo of Sun (NSF) as of January 20, 2020

Inside the core, a special thing happens called nuclear fusion. This is when hydrogen atoms join together to become helium. Every second, the Sun fuses about 600 billion kilograms of hydrogen. This action turns 4 billion kilograms of matter into energy. This energy travels outward from the core to the surface. Most of it reaches us as visible light and infrared radiation.

Proton-proton reaction chain
Proton-proton reaction chain

The Sun formed about 4.6 billion years ago. It grew from a large cloud of matter that collapsed under gravity. Most of the matter gathered in the center to make the Sun. The rest of the matter flattened into a disk. This disk eventually became our Solar System. Scientists classify the Sun as a G-type main-sequence star. It is specifically known as a G2 star.

The life cycle of a Sun-like star (annotated)
The life cycle of a Sun-like star (annotated)

The Sun is much larger than anything else in our system. Its diameter is about 1,391,400 kilometers. This is 109 times wider than the Earth. The Sun holds about 99.86% of all the mass in the Solar System. Its mass is 330,000 times greater than Earth's mass. The surface, called the photosphere, is mostly hydrogen and helium. It also has small amounts of oxygen, carbon, neon, and iron.

Sun poster
Sun poster

In the far future, the Sun will change its shape. In about 4 to 7 billion years, it will run low on hydrogen. This will cause the outer layers to expand. The Sun will then become a red giant. Later, it might become a small, dense star called a white dwarf. It will eventually become a dark, cold object called a black dwarf.

Evolution of the Sun 2 EN
Evolution of the Sun 2 EN

We can measure the Sun's distance from Earth. It is about 149.6 million kilometers away. Light takes about 8 minutes to travel this path. This distance is used to define an astronomical unit. The Sun also orbits the center of our galaxy. It stays about 24,000 to 28,000 light-years away from that center.

Solar system
Solar system
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🖼️ Images & Media (37)
File:Sun poster.svg
Sun poster.svg
File:Oort cloud Sedna orbit.svg
Oort cloud Sedna orbit.svg
File:Proton-proton reaction chain.svg
Proton-proton reaction chain.svg
File:Evolution of the Sun 2 EN.svg
Evolution of the Sun 2 EN.svg
File:Sun red giant.svg
Sun red giant.svg
File:Heat Transfer in Stars.svg
Heat Transfer in Stars.svg
File:Stylised atom with three Bohr model orbits and stylised nucleus.svg
Stylised atom with three Bohr model...
File:Milky Way Arms ssc2008-10.svg
Milky Way Arms ssc2008-10.svg
File:Solar system barycenter.svg
Solar system barycenter.svg
File:The Local Interstellar Cloud and neighboring G-cloud complex.svg
The Local Interstellar Cloud and...
File:Sun symbol (bold).svg
Sun symbol (bold).svg
File:Highest resolution photo of Sun (NSF) as of January 20, 2020.jpg
Highest resolution photo of Sun (NSF) as...

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