The sun is the center of our planetary system, its main element, without which there would be neither Earth, nor life on it. People have been observing the star since ancient times. Since then, our knowledge of the luminary has greatly expanded, enriched with numerous information about the movement, internal structure and nature of this space object. Moreover, the study of the Sun makes a huge contribution to understanding the structure of the Universe as a whole, especially those of its elements that are similar in essence and the principles of "work".
Origin
The sun is an object that exists, by human standards, for a very long time. Its formation began about 5 billion years ago. Then in place of the solar system was an extensive molecular cloud. Under the influence of gravitational forces, turbulences like earth tornadoes began to appear in it. In the center of one of them, the substance (mainly hydrogen) began to condense, and a young star appeared here 4.5 billion years ago, which after a long period of time was named the Sun. Around him, planets gradually began to form - our corner of the universe began to take on the form familiar to modern man.
Yellow dwarf
The sun is not a unique object. It belongs to the class of yellow dwarfs, relatively small stars of the main sequence. The life span allocated to such bodies is approximately 10 billion years. By the standards of space, this is quite a bit. Now our luminary, one might say, in the prime of life: not yet old, not young - half a life is still ahead.
The yellow dwarf is a giant ball of gas, in which the thermonuclear reactions occurring in the nucleus are the light source. In the red-hot heart of the Sun, the process of conversion of hydrogen atoms into atoms of heavier chemical elements is continuously going on. While these reactions take place, the yellow dwarf emits light and heat.
Star death
When all hydrogen burns out, it will be replaced by another substance - helium. It will happen in about five billion years. The exhaustion of hydrogen marks the beginning of a new stage in the life of a star. She will turn into a red giant. The sun will begin to expand and occupy the entire space up to the orbit of our planet. In this case, its surface temperature will decrease. In about a billion years, all the helium in the core will turn into carbon, and the star will drop its shells. A white dwarf and the surrounding planetary nebula will remain in place of the solar system . This is the life path of all stars like our star.
Internal structure
The mass of the sun is huge. It accounts for approximately 99% of the mass of the entire planetary system.
About forty percent of this number is concentrated in the core. It occupies less than a third of the solar volume. The diameter of the core is 350 thousand kilometers, the same indicator for the entire luminary is estimated at 1.39 million km.
The temperature in the solar core reaches 15 million Kelvin. Here is the highest density indicator, other internal areas of the sun are much more sparse. Under such conditions, thermonuclear fusion reactions occur that provide energy to the luminary itself and all its planets. The core is surrounded by a radiative transfer zone, then the convection zone is located. In these structures, energy, through two different processes, moves to the surface of the Sun.
From the core to the photosphere
The nucleus borders on the radiant transmission zone. In it, energy propagates further through the absorption and emission of light quanta by matter. This is a fairly slow process. Light quanta fall from the nucleus into the photosphere over thousands of years. As they move, they move forward and backward, and reach the next zone transformed.
From the radiative transfer zone, energy enters the convection region. Here the movement takes place according to slightly different principles. Solar matter in this zone mixes like boiling liquid: the hotter layers rise to the surface, while the cooled layers descend into the interior. Gamma quanta formed in the nucleus, as a result of a series of absorption and radiation, become quanta of visible and infrared light.
Behind the convection zone is the photosphere, or the visible surface of the Sun. Here again, the energy moves through radiant transfer. The hot streams reaching the photosphere from the underlying area create a characteristic granular structure that is clearly visible in almost all photos of the star.
Outer shells
Above the photosphere is the chromosphere and corona. These layers are much less bright, therefore, from the Earth they are available for observation only during a total eclipse. Magnetic flares on the Sun arise precisely in these rarefied areas. They, like other manifestations of the activity of our luminary, cause great interest among scientists.
The cause of outbreaks is the generation of magnetic fields. The mechanism of such processes requires careful study, including because solar activity leads to disturbance of the interplanetary medium, and this has a direct effect on geomagnetic processes on Earth. The influence of the luminary is manifested in a change in the number of animals, almost all systems of the human body react to it. The activity of the Sun affects the quality of radio communications, the level of ground and surface waters of the planet, climate change. Therefore, the study of the processes leading to its increase or decrease is one of the most important tasks of astrophysics. To date, not all questions related to solar activity have been answered.
Earth observation
The sun affects all living things on the planet. Changing the duration of daylight hours, raising and lowering the temperature directly depends on the position of the Earth relative to the luminary.
The movement of the sun in the sky is subject to certain laws. The star moves along the ecliptic. This is the name of the annual path that the sun travels. The ecliptic is the projection of the plane of the earth's orbit onto the celestial sphere.
The movement of the luminary is not difficult to notice if you observe it for some time. The point at which the sun rises is moving. The same is true for sunset. When winter comes, the sun at noon is much lower than in the summer.
The ecliptic passes through the zodiac constellations. Observation of their displacement shows that at night it is impossible to see those celestial drawings in which the luminary is currently located. It turns out to admire only those constellations where the Sun stayed about six months ago. The ecliptic is inclined to the plane of the celestial equator. The angle between them is 23.5º.
Declination change
On the celestial sphere is the so-called Aries point. In it, the Sun changes its declination from south to north. The luminary reaches this point every year on the day of the vernal equinox, March 21. The sun rises much higher in summer than in winter. A related change in temperature and daylight hours. When winter comes, the Sun in its movement deviates from the celestial equator to the North Pole, and in summer to the South.
The calendar
The star is located exactly on the line of the celestial equator twice a year: on the days of the autumn and spring equinox. In astronomy, the time it takes for the Sun to move from Aries and return to it is called the tropical year. It lasts approximately 365.24 days. It is the duration of the tropical year that underlies the Gregorian calendar. It is used today almost everywhere on Earth.
The sun is the source of life on Earth. The processes taking place in its bowels and on the surface have a tangible effect on our planet. The meaning of the luminary was clear already in the ancient world. Today we know quite a lot about the phenomena occurring on the Sun. The nature of individual processes, thanks to technological advances, has become clear.
The sun is the only star located close enough for direct study. Data on the luminary helps to understand the mechanisms of "work" of other similar space objects. However, the Sun still holds many secrets. They only have to scout. Phenomena such as the rising of the Sun, its movement through the sky, the heat emitted by it, once also represented puzzles. The history of the study of the central object of our piece of the Universe shows that over time all the oddities and features of the luminary find their explanation.