Sun

We explain everything about the Sun, the parts that make it up, its temperature and other characteristics. Also, the Solar System.

What is the Sun?

The Sun It is the closest star to planet Earth located 149.6 million kilometers away. All the planets in the Solar System orbit around it at different distances, attracted by its gigantic gravity, as well as the comets and asteroids that we know. The Sun is commonly known as Astro King.

It is a fairly common star in our Milky Way galaxy: it is neither very big nor very small compared to its millions of sisters. Scientifically, the Sun It is classified as a yellow dwarf star, type G2.

It is currently in its main life sequence. It is located in an outer region of the galaxy, in one of its spiral arms, 26,000 light years from the galactic center.

However, the size of the Sun is such that represents 99% of the entire mass of the Solar System equivalent to about 743 times the total mass of each and every one of its planets combined, and about 330,000 times the mass of our planet.

Its diameter is 1.4 million kilometers making it the largest and brightest object in the Earth's sky. That is why its presence makes the difference between day and night.

Furthermore, the Sun It's a huge plasma ball almost round. It is composed mostly of hydrogen (74.9%) and helium (23.8%), as well as a small portion (2%) of heavier elements such as oxygen, carbon, neon and iron.

Hydrogen is the main fuel of the Sun. However, due to combustion it is converted into helium, leaving behind a layer of helium “ashes” as the star advances in its main life cycle.

See also: Nebula

Structure and parts of the Sun

The Sun It is a spherical star, with a slight flattening at its poles the result of its rotation movement. Despite being a gigantic and continuous atomic bomb of fusion of hydrogen atoms, the enormous force of gravity that its mass gives it compensates the thrust of the internal explosion, thus reaching a balance that allows the continuity of its existence.

The Sun is structured in layers, more or less like an onion. These layers are:

• The core The innermost region of the Sun, which occupies one fifth of the star's total: about 139,000 kilometers of its total radius. It is there where the gigantic atomic explosion of hydrogen fusion takes place; But the gravity in the solar core is such that it takes around a million years for the energy produced in this way to emerge towards the surface.
• The radiant zone It is composed of plasma, that is, gases such as helium and/or ionized hydrogen, and it is the region that allows the easiest radiation of energy to the outer layers, which considerably reduces the temperature recorded in this place.
• The convective zone This is a region where the gases are no longer ionized, making it more difficult for energy (in the form of photons) to escape from the Sun. This means that the energy can only escape through caloric convection, much more slowly. Thus, the solar fluid is heated unevenly, causing expansion, loss of density and ascending or descending currents, like an internal tide.
• The photosphere The region of the Sun where visible light is emitted, perceived as bright granules on a darker surface, although it is a transparent layer about 100 to 200 km deep. It is considered the surface of the star, and it is where sunspots appear.
• The chromosphere This is the name given to the outer layer of the photosphere itself, which is even more translucent and difficult to appreciate, as it is obscured by the brightness of the previous layer. It has a size of around 10,000 km and seen during an eclipse, it has a reddish exterior tone.
• The solar corona This is known as the most tenuous layers of the Sun's external atmosphere, in which the temperature increases considerably compared to the interior layers. This is a mystery of solar nature. However, there are low densities of matter together with intense magnetic fields, crossed by energy and matter at very high speeds, as well as by numerous X-rays.

Sun Temperature

As we have seen, The temperature of the Sun varies depending on the region of the star although by our standards it is, in all of them, incredibly high.

Temperatures close to 1.36 x 10 can be recorded in the solar core.⁶ degrees Kelvin (that is, about 15 million degrees Celsius), while on the surface the temperature drops to “just” 5,778 K (around 5,505 °C), and rises again in the solar corona to 2 x 10⁵ degrees Kelvin.

Importance of the Sun for life

Due to its continuous emission of electromagnetic radiation, including the light perceptible by our eyes, The Sun provides heat and lighting to our planet, making life possible as we know it. For this reason, the Sun is irreplaceable.

Its light allows photosynthesis without which the atmosphere would not contain the oxygen levels we need, nor the plant life to sustain the different food chains. On the other hand, its heat keeps the climate stable allows the existence of liquid water and gives energy to the different climate cycles.

Finally, Solar gravity keeps planets orbiting around it including the Earth. Without it there would be no day and night, no seasons, and Earth would surely be a cold, dead planet, as many of the outer planets are.

This is reflected in human culture: the Sun usually occupies a central place in the religious imagination, as a fertilizing father god, throughout almost all known mythologies. All the great gods, kings or messiahs have been in one way or another associated with its brilliance, while death, nothingness and evil or secret arts are associated with the night and the nocturnal.

Solar system

We call this the planetary “neighborhood” where the Earth is located, that is, the circuit of eight planets that constantly orbit the Sun. This neighborhood is part of the Local Interstellar Cloud, part of the Local Bubble of the Orion arm. It is estimated that emerged 4,568 million years ago as a consequence of the collapse of a molecular cloud.

It is made up of the following objects:

• The Sun the only star located in its center.
• The inner planets smaller and warmer: Mercury, Venus, Earth and Mars. Next to them, their respective moons or satellites.
• The outer planets gigantic balls of frozen gas: Saturn, Jupiter, Neptune and Uranus. Next to them, their respective moons or satellites.
• The dwarf planets like Pluto, Ceres or Pallas.
• The asteroid belt that separates the inner planets from the outer ones.
• The Kuiper Belt and the Oort Cloud two sets of trans-Neptunian objects from which comets come.

References

• “Sun” in Wikipedia.
• “The Sun” in National Geographic.
• “The Nature of the Sun” at NASA.
• “The Temperature of the Sun” on Nature.com.
• “Sun (Astronomy)” in The Encyclopaedia Britannica.