Sun

Sun . It is the most important element in the Solar System , being the largest star. It contains approximately 98% of the total mass of the solar system. One hundred and nine Earths would be required to complete the solar disk, and the interior could contain more than 1.3 million Earths. The visible outer layer of the king star is called the Photosphere and has a temperature of 6,000 ° C, 11,000 ° F. This layer has a blotchy appearance due to turbulent eruptions of energy on the surface.

Summary

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• 1 Features
• 2 Gravitational contraction
• 3 Radioactivity
• 4 The solar hydrogen cycle
• 5 Structure
• 6 Layers of the Sun
• 7 The solar constant
• 8 Importance of solar energy
• 9 Dangers of Excessive Sunlight Exposure
• 10 See in the Solar System
• 11 Sources
• 12 See also

Characteristics

The Sun is a common star of the G2 type, one of the 100,000 million stars in the Galaxy . It has a surface temperature of 5,800 K, 15,600,000 K core, diameter 1,390,000 km, and a mass of 1.989e30 kg. It is by far the largest object in the solar system. He has been personified in many mythologies: The Greeks called him Helios and the Romans called him Sol.

It is made up of around 75% Hydrogen and 25% Helium by mass 92.1% hydrogen and 7.8% helium by number of atoms; the rest of metals only reaches 0.1%. These ratios slowly change as the sun converts hydrogen to helium at its core.

The most superficial layers of the sun show differential rotation: at the equator the surface rotates once every 25.4 days; near the Poles takes 36 days. This strange behavior is due to the fact that he is not a solid body like the earth. Similar effects can be seen on gaseous planets. The differential rotation extends considerably into the sun, but the solar core rotates as a solid body.

Conditions at the core of the sun are extreme. The temperature reaches 15.6 million degrees Kelvin and the pressure is 250,000 million atmospheres. The core gases are compressed to a density 150 times that of water.

The radiant energy of the sun 3.86e33 ergs / sec or 386 trillion megawatts is produced by nuclear fusion reactions. Every second about 700,000,000 tons of hydrogen are converted into 695,000,000 tons of helium and 5,000,000 tons equal to 3.86e33 ergs of energy in the form of gamma rays.

As it travels towards the surface, the energy is continuously absorbed and re-emitted at lower and lower temperatures so that when it reaches the surface it is mainly converted into visible light. During the last 20% of the way to the surface, energy is transported by convection rather than radiation. A small region known as the Chromosphere extends over the photosphere.

The highly rarefied region above the chromosphere is called the Corona and spans millions of km. in space but is only visible during total eclipses. The temperature in the corona exceeds 1,000,000 K. The solar magnetic field is very strong compared to the Earth’s and very complex. Its magnetosphere, also known as the heliosphere, extends beyond Pluto.

In addition to light and heat, the sun emits a low-density jet of charged particles, mainly electrons and protons, called the solar wind, which propagates through the solar system at about 450 km / sec. The solar wind and the much more energetic particles ejected by solar flares can have dramatic effects on Earth, ranging from surges in power grids to radio interference to the beautiful Northern Lights .

Recent data collected by the Ulysses Sonde shows that the solar wind emanating from the polar regions flows at twice the speed, 750 km / sec, than that of lower latitudes. It also appears that the composition of the solar wind is different in the polar regions.

The solar magnetic field appears to be surprisingly uniform. The solar wind has a great effect on the tails of comets and even measurably affects the trajectories of space probes. Spectacular loops and prominences are often visible on the solar rim.

The emission of the sun is not totally constant. Neither is the number of sunspots. There was a very low spotting period during the second half of the 17th century called the Maunder Minimum. It coincided with an unusually cold period in northern Europe that is sometimes called the Little Ice Age. Since the formation of the solar system, solar emission has increased by 40%.

The sun is about 4.5 billion years old. Since its birth it has consumed half of the hydrogen in its nucleus. It will continue to radiate quietly for another 5 billion years or so, although its luminosity will double in that period.

But at some point your supply of hydrogen will run out. Then radical changes will take place that, as usual for a star, will cause the total destruction of  Planet_Earth and, probably, the creation of a planetary nebula.

Gravitational contraction

By means of the conservation of energy, which had proven to be a useful tool, other possible causes of the origin of the Sun’s light and heat were analyzed . It was then assumed that the Sun’s energy source was itself in contraction. gravitational that suffered from the weight of its components and as a residue of its origin from a large cloud of gases that floated in space.

With the contraction theory the Sun must have been the size of the Earth’s orbit about eighteen million years ago and therefore the Earth should be younger than that age, but geologists and biologists had found that age of the Earth and by the processes that occurred on it, it was much larger.

Radioactivity

After Physics and Chemistry had managed to know what the Sun and the stars were composed of by studying their

Active sun

luminous spectrum, it was determined that in the Sun there were many chemical elements, the main one was hydrogen followed by helium.

With the discovery of radioactivity it was found that in the Sun there could be another explanation for the mysterious source of this seemingly inexhaustible energy. But when trying to search the Sun for radioactive elements like uranium and plutonium, they found nothing but hydrogen and helium which were not radioactive materials.

However, the most accurate explanation seemed to be related to some type of nuclear reaction in which the mass was transformed into energy, but not in the radioactive decay of heavy nuclei.

On the other hand, the radioactivity served to determine what the age of the Earth should be, and that turned out to be more than 4,500,000,000 years. So the Sun had to be greater than or approximately equal.

The solar hydrogen cycle

Energy production turned out to be made up of the so-called proton-proton cycle in which three collisions occur in a row, in this process four hydrogen nuclei are fused into a helium nucleus and release a quantity of energy.

This type of nuclear reaction in which the nuclei unite and give off energy was called fusion, but the temperature necessary to produce fusion in the Sun is not reached at the surface, which only reaches 6,000 ° C, but at its interior where the reactions take place in combination with the gravitational force that compresses the gases towards the core of the Sun. Thus, the expansion that had to occur due to the great temperature was compensated by the gravitational attraction.

Structure

The Sun can be visualized as a huge atomic furnace that, thanks to the extremely high temperatures and pressures present in its core, is capable of fusing hydrogen to generate helium. Put simply, this process involves 4 hydrogen nuclei fusing with one proton each to form a helium nucleus made up of 2 protons and 2 neutrons.

However, the resulting helium nucleus has only 99.3% of the weight of the 4 hydrogen nuclei, which means that in the process 0.7% of the mass is converted into energy. It is estimated that every second the sun transforms about 600 million tons of hydrogen into 596 million tons of helium: the 4 million tons of missing mass have been converted into energy.

It is a difficult amount to imagine, especially if we consider that each gram of mass converted into energy is equivalent to burning more than 3,000 liters of gasoline. Thus, the sun provides around 6,200 watts, which is equivalent to the light generated by 62 100-watt bulbs, for each square centimeter of its surface. Only a small part of that energy reaches the earth, while the rest is dispersed in outer space.

Due to the average distance between the sun and the earth, approximately 150 million kilometers, it takes 8.5 minutes for solar radiation to reach Earth. This period is insignificant if we take into account that the energy generated in the center of the sun takes about a million years to reach the solar surface.

As a whole, the sun is a gigantic sphere of hot gases composed mainly of 70% hydrogen and 28% helium. It also contains carbon, nitrogen, oxygen, and other elements that make up the remaining 2%. Its internal structure is characterized by a succession of spherical layers.

It is difficult to establish with precision the limits between each of these layers, as well as the differences in their chemical composition, although it is possible to differentiate them by the physical phenomena that occur in them. The most accepted model establishes six layers in the structure of the sun: nucleus, radiant zone, convective zone, photosphere, chromosphere and corona.

Layers of the Sun

Nucleus: In the nucleus of the Sun the nuclear reactions that produce all the energy of the star take place, in it a

Layers of the sun

At a temperature of 14,000,000 ° C, everything is under great pressure and in it matter is transformed into energy at a rate of 14,500,000 tons every second and is emitted in the form of gamma radiation.

Photosphere: It is the one that emits light and heat, its temperature is 600 degrees Celsius, in it are sun spots, grains of rice and protrusions, they are tongues of fire that rise to more than a million km high and they are observable in the total eclipses of the sun on its crown. It is literally a sphere of light, the visible surface of the Sun.

It should be specified that when it is said surface, it is not referring, in this case, to a solid surface, since the photosphere is formed by a layer of gas.

Almost all the light that is received from the Sun comes from the photosphere, even though the energy source is much lower down, in the solar core. The photosphere is approximately 300 km thick. and average temperatures of 6,000 degrees.

Chromosphere: It is where prominences and solar flans take place. It is relatively thin with a thickness between 9,000 and 16,000 km. Despite being very tenuous and considered to be almost empty, it exhibits a very well defined structure and spicules emerge from it like threads that form complex patterns.

Corona: It is the outer part of the Sun. It is one hundred thousand times more opaque than the photosphere. It is not actually spherical, since it oscillates, undulates and has changes in its shape due to the interaction of the plasma that forms it with the Sun’s magnetic field. The corona is only visible with the use of the coronagraph or during eclipses. The gases that escape from the corona give rise to the Solar Wind.

Radiant zone: It is an area where highly compressed gases receive the energy of the gamma radiation that is produced in the core of the Sun. This radiation is not completely absorbed by the atoms that make up the gases but rather bounces off them, is partially absorbed and it disperses with which there is a decrease in its wavelength and are transformed into X and ultraviolet radiation

Convective zone: In this zone the gases from the Sun have a sufficient thermal gradient for convective movement to occur. As the gases are colder, they are capable of absorbing the photons from the radiant area and through convection they transmit the energy to the photosphere from where it is emitted to the outside, with this there is a cooling of the gases that descend again until the energy of the radiant area is absorbed again.

The solar constant

The solar constant is the amount of energy received by the Earth at the average distance that separates us from the Sun, and its approximate value is about two calories per square centimeter per minute, that is, every minute, at an Astronomical Unit, in a square of two centimeters on a side will receive two calories.

The study and measurement of this constant is of extreme interest because survival depends on the ability to be prepared and prevent a hypothetical significant variation in the solar constant. A change of 1% in the solar constant would produce an alteration of the temperature on Earth of 1 or 2 ° C. Taking into account that during the last ice age, the average temperature on the planet was 5 ° C colder than the Today, you can get an idea of ​​how important it is to know the Sun well.

There are historical references that could indicate a decrease in the solar constant. From 1430 to 1850 the Little Ice Age took place, with unusually cold weather in Europe and America. Within this period is the one known as the Maunder minimum.

In 1893 , Edward Maunder , trying to graph solar activity from Galileo Galilei’s first telescopic observations , found that between 1640 and 1715 there was virtually no record of spots.

Later it has been verified by other methods that, indeed, the solar activity was exceptionally low in those years. Ironically, the Maunder minimum coincides with the reign of Louis XIV of France , the Sun King, The State is me.

Importance of solar energy

Solar energy, as its name implies, is produced by the sun, and represents one of the most widely used renewable energies on the entire planet. You can take advantage of

Sun

basically to heat something, for example food or water, through water heaters or solar stoves. This type of use is called solar thermal energy.

But its main use is mainly based on the production of electricity, which is called photovoltaic solar energy. In the case of electricity, it is possible to make it by using solar cells or panels. Likewise, there are tanks, better known as solar collectors, that when exposed to the sun, heat the water they contain, which can be used for showering, heating at home or even for swimming pools.

On the other hand, the energy from the sun allows us to make water drinkable, as well as it is important in drying, evaporation, distillation and refrigeration. The implementation of this type of energy contributes to the fight against global warming.

However, for the moment, access to its use is very expensive for people, which prevents its use from being available to everyone. Its value will decrease when the mass consumption of those devices that work with such fuel is achieved. But outside of the conventional uses that have been named, man has managed to use such renewable energy to create something truly innovative: the solar car .

Dangers of excessive exposure to sunlight

Eye damage Around the world there are about 15 million people who have lost their sight due to cataracts, the leading cause of blindness. Cataracts form when proteins in the lens of the eye break down and accumulate pigments that cloud the lens. This disease is one of the long-term effects of exposure to UV ( ultraviolet ) radiation . In fact, it is estimated that up to 20% of cases are caused or aggravated by chronic sun exposure over the years. Sadly, the area called the cataract belt , near the equator , includes developing countries where the majority of the population is poor. So millions of people from Africa, Asia , Central and South America are blind because they cannot afford the operation that would cure their cataracts.

Skin damage One third of all diagnosed cancers in the world affect the skin. Each year there are 130,000 new cases of melanoma , the most dangerous type of skin cancer , and two to three million other skin cancers, such as basal and squamous cell carcinomas . An estimated 60,000 people die each year from cancer. How does sunlight affect the skin? The most common and well-known acute effect of excessive sun exposure is erythema, or redness from a burn. Its immediate consequences, including blisters and shedding of the skin, can last for several days. When a sunburn occurs, UV radiation destroys most of the cells in the outer skin layer and damages the deeper layers. Any change in skin color caused by sun exposure indicates injury. Cancer appears as a consequence of damage to the DNA of the genes that control the growth and division of skin cells. Sunlight also alters the skin’s texture and weakens its elasticity, causing premature wrinkles and sagging. It also contributes to easy bruising.

Damage to the immune system Some research shows that absorbing too much UV radiation through the skin negatively affects the function of certain parts of the immune system and can reduce the body’s ability to defend itself against certain diseases. Even moderate sun exposure is known to increase the risk of infections from bacteria , fungi , parasites, or viruses . Many people have noticed that exposure to the sun causes repeated breakouts of cold sores or simplex. A report from the World Health Organization (WHO) explainsthat a category of ultraviolet light called UVB “appears to decrease the effectiveness of the immune system: in the case of cold sores, it can no longer keep the herpes simplex virus under control, causing it to reactivate the infection.” When it comes to cancer, sunlight can cause serious disorders in two ways. First, by causing direct DNA damage, and second, by reducing the natural ability of the immune system to counteract such damage. So the wise thing is that we take precautions in order not to expose ourselves too much to the sun. Our health and indeed our own life may be at stake.

Protection measures

• Reduce exposure to the sun during the central hours of the day – ten in the morning to four in the afternoon – when UV radiation is particularly intense.
• Try to stay in the shade.
• Cover your arms and legs with loose, tightly woven clothing.
• Wear a wide-brimmed hat to protect your eyes, ears, face, and the back of your neck.
• Wear good quality sunglasses. They must be enveloping, that is, have a side coverage and provide between 99 and 100% protection against UVA and UVB radiation (ultraviolet light categories), as this will greatly reduce the risk of eye damage.
• Use a broad spectrum sunscreen with an SPF 15 or higher, and apply it generously every two hours.
• Since UV lamps, tanning beds and tanning salons use UV radiation – which can damage the skin – the WHO recommends avoiding them.
• Be sure to protect babies and young children, whose skin is particularly delicate.
• Never fall asleep in the sun.
• If you get a mole, freckle, or spot that worries you, see your doctor.