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Sun
The Sun is the star at the center of our Solar system. Earth orbits the Sun, as do many other bodies, including other planets, asteroids, meteoroids, comets and dust. Its heat and light support almost all life on Earth. It is sometimes referred to by its Latin name, Sol.
The Sun is a ball of plasma with a mass of about 2×1030 kg, which is somewhat higher than that of an average star. About 74% of its mass is hydrogen, with 25% helium and the rest made up of trace quantities of heavier elements. It is thought that the Sun is about 5 billion years old, and is about halfway through its main sequence evolution, during which nuclear fusion reactions in its core fuse hydrogen into helium. In about 5 billion years time the Sun will evolve into a red giant and then a white dwarf.
Although it is the nearest
star to Earth and has been intensively studied by scientists, many questions
about the Sun remain unanswered, such as why its outer atmosphere has a temperature
of over 106 K when its visible surface (the photosphere) has a temperature of
just 6,000 K.
Looking directly at the Sun can damage the retina and one's eyesight.
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