The sun is the center of our planetary system, its main element, without which there would be neither the Earth nor life on it. People have been observing the star since ancient times. Since then, our knowledge of the luminary has expanded significantly, enriched with numerous information about the movement, internal structure and nature of this cosmic 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 principles of "work".
Origination
The sun is an object that has existed, by human standards, for a very long time. Its formation began about 5 billion years ago. Then there was a vast molecular cloud in place of the solar system. Under the influence of gravitational forces, eddies began to appear in it, similar to terrestrial tornadoes. In the center of one of them, the matter (mostly hydrogen) began to condense, and 4.5 billion years ago a young star appeared here, which, after another long period of time, received the nameThe sun. Planets gradually began to form around it - 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 main sequence stars. The term of "service" released to such bodies is approximately 10 billion years. By the standards of space, this is quite a bit. Now our luminary, one might say, is in the prime of his life: not yet old, no longer young - there is still half a life ahead.
A yellow dwarf is a giant ball of gas whose light source is thermonuclear reactions occurring in the core. In the red-hot heart of the Sun, the process of transformation of hydrogen atoms into atoms of heavier chemical elements is continuously going on. While these reactions are taking place, the yellow dwarf radiates light and heat.
Death of a star
When all the hydrogen burns out, it will be replaced by another substance - helium. This will happen in about five billion years. The exhaustion of hydrogen marks the onset 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 all space up to the orbit of our planet. At the same time, its surface temperature will decrease. In about another billion years, all the helium in the core will turn into carbon, and the star will shed its shells. A white dwarf and a planetary nebula surrounding it will remain in place of the solar system. This is the life path of all stars like our sun.
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 core diameter is 350 thousand kilometers, the same figure for the entire star is estimated at 1.39 million km.
The temperature in the solar core reaches 15 million Kelvin. Here the highest density index, other inner regions of the Sun are much more rarefied. Under such conditions, thermonuclear fusion reactions take place, providing energy for the luminary itself and all its planets. The core is surrounded by a radiative transport zone, followed by a convection zone. In these structures, energy moves to the surface of the Sun through two different processes.
From the core to the photosphere
The core borders on the radiative transmission zone. In it, the energy propagates further through the absorption and emission of light quanta by the substance. This is a rather slow process. It takes thousands of years for light quanta to travel from the nucleus to the photosphere. As they advance, they move back and forth, and reach the next zone transformed.
From the zone of radiative transfer, energy enters the region of convection. Here the movement takes place according to somewhat different principles. The solar matter in this zone is mixed like a boiling liquid: the hotter layers rise to the surface, while the cooled ones sink deeper. Gamma quanta formed innucleus, as a result of a series of absorptions and radiations, 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 by means of radiant transfer. Hot streams reaching the photosphere from the underlying region create a characteristic granular structure, clearly visible in almost all images of the star.
Outer shells
Above the photosphere is the chromosphere and the corona. These layers are much less bright, so they are visible from Earth only during a total eclipse. Magnetic flares on the Sun occur precisely in these rarefied regions. They, like other manifestations of the activity of our luminary, are of great interest to scientists.
The cause of outbreaks is the generation of magnetic fields. The mechanism of such processes requires careful study, also because solar activity leads to perturbation of the interplanetary medium, and this has a direct impact on geomagnetic processes on Earth. The impact 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, and 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.
Observation from Earth
The sun affects all living beings on the planet. The change in the length of daylight hours, the increase and decrease in temperature directly depend on the position of the Earth relative to the star.
The movement of the Sun in the sky is subject to certain laws. The luminary 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 easy to notice if you watch it for a while. The point at which the sunrise occurs is moving. The same is true for sunset. When winter comes, the Sun is much lower at noon than in 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.
Changing Declension
On the celestial sphere is the so-called point of Aries. In it, the Sun changes its declination from south to north. The luminary reaches this point every year on the day of the spring equinox, March 21st. The sun rises much higher in summer than in winter. Associated with this is a change in temperature anddaylight hours. When winter comes, the Sun in its movement deviates from the celestial equator to the North Pole, and in summer - to the South.
Calendar
The luminary is located exactly on the line of the celestial equator twice a year: on the days of the autumn and spring equinoxes. In astronomy, the time it takes for the Sun to travel from and back to Aries is called the tropical year. It lasts approximately 365.24 days. It is the length of the tropical year that underlies the Gregorian calendar. It is used almost everywhere on Earth today.
The sun is the source of life on Earth. The processes taking place in its depths and on the surface have a tangible impact on our planet. The meaning of the luminary was already clear in the ancient world. Today we know quite a lot about the phenomena occurring on the Sun. The nature of individual processes has become clear thanks to advances in technology.
The Sun is the only star close enough to study directly. Data about the star help to understand the mechanisms of "work" of other similar space objects. However, the Sun still holds many secrets. They just have to be explored. Phenomena such as the rising of the Sun, its movement across the sky, and the heat it radiates were once also mysteries. The history of studying the central object of our piece of the Universe shows that over time, all the oddities and features of the star find their explanation.
