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1.5.1. Sun


The Sun is the star of our Solar System, to which it gives light and heat, allowing the existence of life on Earth. It is about 150 million kilometers from Earth. It is about 5 billion years old and will still be shining for another 4.5 billion years.

The Sun is a small or medium-sized yellow star (1400000 km in diameter) if we compare it with other stars, but it is huge if we compare it with the Earth (about 1,300,000 times the Earth's volume).

The Sun is about 40,000 light years from the core of the Milky Way. Its surface temperature is about 5500 ºC.

The Sun is formed by hydrogen (71%), helium (27%) and other elements (2%) as the oxygencarbon, neon and iron. The nuclear fusion  converts hydrogen into other elements, releasing energy that comes. When the hydrogen runs out, the solar core will only contain helium. Then the helium atoms will go on to form heavier elements (C, N and O). The Sun will expand and become a red giant star, increasing in size to the orbit of Mars, and will gradually shrink and fade. Later, it will emit gas transforming into a planetary nebula. The Sun will cool down until it becomes a white dwarf star.

The matter that constitutes the Sun is grouped in layers:

  • Inner layers. They contain the densest materials. Nuclear fusion reactions occur in the nucleus.
  • Outer layers. They contain the lightest materials. The outermost layer is the photosphere.

The Sun has a counterclockwise rotational motion (as opposed to clockwise motion) lasting about 28 days.