The Sun It is the star that constitutes the center of the Solar System and the one closest to the Earth, to which it provides energy in the form of light and heat, giving rise to the seasons, the climate and the ocean currents of the planet. In short, offering the primary conditions necessary for life.
The Sun is the most important celestial object for living beings. It is believed that it had its origin about 5 billion years ago, from an immense cloud of stellar matter: gas and dust. These materials began to clump together thanks to the force of gravity.
Most likely, the remains of some supernovae were counted there, stars destroyed by a colossal cataclysm, which gave rise to a structure called proto-star..
The force of gravity caused more and more matter to accumulate, and with it the protostar's temperature also increased to a critical point, around 1 million degrees Celsius. It was precisely there that the nuclear reactor that gave rise to a new stable star was ignited: the Sun.
In very general terms, the Sun can be considered a fairly typical star, albeit with mass, radius, and some other properties outside of what might be considered the "average" among stars. Later we will see in which category the Sun is among the stars that we know.
Humanity has always been fascinated by the Sun and has created many ways to study it. Basically the observation is done through telescopes, which for a long time were on Earth and are now also on satellites.
Through light, many properties of the Sun are known, for example spectroscopy allows us to know its composition, thanks to the fact that each element leaves a distinctive trace. Meteorites are another great source of information, because they maintain the original composition of the protostellar cloud..
Here are some of the main characteristics of the Sun that have been observed from Earth:
-The Sun is considered a yellow dwarf star. In this category are stars that have a mass between 0.8-1.2 times the mass of the Sun..
-Its shape is practically spherical, it barely flattens slightly at the poles due to its rotation, and from Earth it is seen as a disk, hence it is sometimes called as solar disk.
-The most abundant elements are hydrogen and helium.
-Measured from Earth, the angular size of the Sun is about ½ degree.
-The radius of the Sun is approximately 700,000 km and is estimated from its angular size. The diameter therefore is about 1,400,000 km, approximately 109 times that of the Earth.
-The average distance between the Sun and the Earth is the Astronomical Unit of distance.
-As for its mass, it is obtained from the acceleration that the Earth acquires when it moves around the Sun and the solar radius: about 330,000 times greater than the Earth or 2 x 1030 kg approximately.
-It experiences cycles or periods of great activity, related to solar magnetism. Then, sunspots, flares or flares and eruptions of coronal mass appear.
-The density of the Sun is much lower than that of the Earth, as it is a gaseous entity.
-Regarding its luminosity, which is defined as the amount of energy radiated per unit of time -power-, it is equivalent to 4 x10 33 ergs / s or more than 10 2. 3 kilowatts. For comparison, an incandescent light bulb radiates less than 0.1 kilowatt.
-The effective temperature of the Sun is 6000 ºC. It is an average temperature, later we will see that the core and the corona are regions much hotter than that..
To facilitate its study, the structure of the Sun is divided into 6 layers, distributed in well-differentiated regions, starting from the inside:
-The solar core
-Radiative zone
-Convective zone
-Photosphere
-Chromosphere
Its size is about 1/5 of the solar radius. There the Sun produces the energy it radiates, thanks to the high temperatures (15 million degrees Celsius) and prevailing pressures, which make it a fusion reactor.
The force of gravity acts as a stabilizer in this reactor, where reactions take place in which various chemical elements are produced. In the most elementary, hydrogen nuclei (protons) become helium nuclei (alpha particles), which are stable under the conditions that prevail inside the nucleus..
Then heavier elements are produced, such as carbon and oxygen. All these reactions release energy that travels through the interior of the Sun to spread throughout the Solar System, including the Earth. It is estimated that every second, the Sun transforms 5 million tons of mass into pure energy.
The energy from the core moves outwards through a radiation mechanism, such as the fire of a bonfire heats the surroundings.
In this area, matter is in a plasma state, at a temperature not as high as in the nucleus, but which reaches about 5 million kelvin. The energy in the form of photons - the packets or "quanta" of light - are transmitted and reabsorbed many times by the particles that make up the plasma..
The process is slow, although on average it takes about a month for the photons from the nucleus to reach the surface, sometimes it can take up to a million years to continue traveling to the outer areas so that we can see it in the form of light..
Since the arrival of photons from the radiative zone is delayed, the temperature in this layer drops rapidly to 2 million kelvins. The transport of energy happens to be by convection, since the matter here is not so ionized.
The transport of energy by convection is produced by the movement of eddies of gases at different temperatures. Thus, the heated atoms rise towards the outermost layers of the Sun, carrying this energy with them, but in a non-homogeneous way..
This "sphere of light" is the apparent surface of our star, the one that we see from it (you should always use special filters to see the Sun directly). It is apparent because the Sun is not solid, but is made of plasma (a very hot, highly ionized gas), therefore it lacks a real surface..
The photosphere can be viewed through a telescope fitted with a filter. It looks like shiny granules on a slightly darker background, with the brightness diminishing slightly towards the edges. The granules are due to the convection currents we mentioned earlier.
The photosphere is transparent to some extent, but then the material becomes so dense that it is not possible to see through.
It is the outermost layer of the photosphere, equivalent to the atmosphere and with a reddish luminosity, with a thickness varying between 8,000 and 13,000 and a temperature between 5,000 and 15,000 ºC. It becomes visible during a solar eclipse and it produces gigantic incandescent gas storms whose height reaches thousands of kilometers.
It is an irregularly shaped layer that extends over several solar radii and is visible to the naked eye. The density of this layer is lower than that of the rest, but it can reach temperatures of up to 2 million kelvin.
It is not yet clear why the temperature of this layer is so high, but in some way it is related to the intense magnetic fields produced by the Sun.
Outside the corona there is a large amount of dust concentrated in the equatorial plane of the sun, which diffuses the light from the photosphere, generating the so-called zodiacal light, a faint band of light that can be seen with the naked eye after sunset, near the point on the horizon from which the ecliptic emerges.
There are also loops that go from the photosphere to the corona, formed of gas much colder than the rest: they are the solar bulges, visible during eclipses.
A diffuse layer that extends beyond Pluto, in which the solar wind is produced and the magnetic field of the Sun is manifested.
Almost all the elements that we know from the Periodic Table are found in the Sun. Helium and hydrogen are the most abundant elements.
From the analysis of the solar spectrum, it is known that the chromosphere is composed of hydrogen, helium and calcium, while iron, nickel, calcium and argon have been found in the ionized state..
Of course, the Sun has changed its composition over time and will continue to do so as it uses up its supply of hydrogen and helium..
From our point of view, the Sun seems quite calm. But in reality it is a place full of activity, in which phenomena occur on an unimaginable scale. All the disturbances that occur continuously in the Sun are called solar activity.
Magnetism plays a very important role in this activity. Among the main phenomena that happen on the Sun are:
The prominences, protrusions or filaments are formed in the crown and consist of structures of gas at high temperature, which reach a great height.
They are seen on the edge of the solar disk in the form of elongated structures that intertwine, being continuously modified by the Sun's magnetic field..
As its name indicates, a large amount of matter is ejected at high speed by the Sun, at a rate of about 1000 km / s. It is because the magnetic field lines intertwine with each other and around a solar prominence, causing the material to escape..
They usually last for hours, until the magnetic field lines break apart. Coronal mass ejections create a large flow of particles that reaches the Earth after a few days.
This flow of particles interacts with the Earth's magnetic field and manifests itself, among other things, as northern lights and southern lights..
They are regions of the photosphere where the magnetic field is very intense. They look like dark spots on the solar disk and are at a lower temperature than the rest. They generally appear in highly variable groups, whose periodicity is 11 years: the famous Solar Cycle.
The groups of spots are very dynamic, following the rotation of the Sun, with a larger spot that goes in front and another that closes the group. Scientists have tried to predict the number of spots in each cycle, with relative success.
They occur when the Sun expels material from the chromosphere and the corona. They are seen as a flash of light that makes some regions of the Sun look brighter.
As long as its nuclear fuel lasts, the Sun will continue to exist. Our star hardly meets the conditions to die in a great supernova-type catastrophe, because for that a star needs a much greater mass.
So most likely, as reserves are depleted, the Sun will swell and turn into a red giant, evaporating the Earth's oceans..
The layers of the Sun will spread around it, engulfing the planet and forming a nebula consisting of very bright gas, a sight that humanity could appreciate, if by then it has settled on a distant planet..
The remnant of the ancient Sun that will remain inside the nebula will be a White dwarf, very small, about the size of Earth, but much denser. It will cool down very, very slowly, and may pass at this stage about 1 billion more years, until it becomes a black dwarf.
But at the moment there is no reason to worry. It is estimated that the Sun at this time has lived less than half its life and it will be between 5000 and 7000 million years before the red giant stage begins..
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