He Sol it’s a huge gas and fire ball which was formed millions of years ago when a large cloud of gases gathered at one point due to the effect of gravity. The temperature then increased rapidly due to the large amount of matter in a very small space.
If we look at the solar chemical composition, there are two basic elements: hydrogen y helio. The first represents 75% of mass and helium the remaining twenty-five percent. In terms of volume, hydrogen accounts for more than 91% of the total, while helium represents only 8.7%.
In the hottest core
Let’s go now with its structure. The Sun, despite the fact that from Earth we only see the outer layer (photosphere), has three perfectly defined parts: the innermost is the nucleus, covered by the radioactive zone, and the outermost, called the convection zone.
In the solar core there is a pressure ten times greater than that existing in the center of the Earth and it is at a temperature of fifteen million degrees Celsius. There the heat is produced thanks to a thermonuclear or fusion reaction, caused by the conversion of hydrogen into helium.
The energy produced during this process escapes to the outside and passes through the radioactive zone. During this process the temperature drops to two million degrees Celsius.
In the outermost layer –convective area- the temperature is reduced to about 6,000 ºC and the heat is transmitted by convection, not by thermal radiation. Finally, the heat is diffused in the form of photons through space, reaching the Earth.
Given that our planet travels an elliptical orbit around the Sun, one might think a priori that temperatures would be higher the closer we are to the Sun and lower the further we are, but this is not the case.
The key is in the inclination
The eccentricity of the orbit that our planet draws in its journey around the Sun is small, quite close to a circle. In this way, the distance that separates us from our star goes from about 152 million kilometers, at the furthest point (aphelion), to around 146 million, at the closest (perihelion).
Perihelion occurs around January 4 and aphelion around July 4, in other words, when the Earth is closest to the sun it is winter in the northern hemisphere.
To understand why this happens, we must keep in mind that, in addition to the translational movement, the Earth behaves like a gyroscope, that is, it moves on its own axis every 24 hours, with an inclination of 23.5 degrees with respect to the Earth. to the plane of its orbit.
This aspect is essential to know why it is hotter in summer, since if the Earth’s axis were not tilted, the seasons would not exist and we would receive the same amount of radiation every day; On the contrary, if the axis were completely horizontal, we would have six months of darkness and six months of light.
When the Earth’s axis is tilted towards the Sun, we receive more solar radiation, since the rays hit more perpendicularly. This is what happens in the northern hemisphere during the summer months, curiously when the Earth is further away from the Sun. In the southern hemisphere, obviously, the reverse is true.
Now, what happens at the equator? Direct and constant sunlight is received there, with very little variability in relation to day length and temperature throughout the year.