The Sun is the only star of the solar system, around which turn other objects of this system: the planets and their satellites, dwarf planets and their moons, asteroids, meteoroids, comets and space dust. Sun's mass is 99.866% of the total mass of the entire solar system. Rotation of the Sun around its axis is in the same direction as the rotation of the Earth. Solar radiation sustains life on Earth (photons are needed for the initial stages of the process of photosynthesis), defines climate. The Sun consists of hydrogen (~ 73% of the mass and ~ 92% by volume), helium (~ 25% by weight and 7% by volume), and other elements with lower concentrations: iron, nickel, oxygen, nitrogen, silicon, sulfur, magnesium, carbon, neon, calcium and chromium. Astronomy is studying this star from the ancient times. Now to study the sun people have built special oso. Many different studies carried out in these stations. The sun is located about 26,000 light years from the center of the Milky Way and revolves around it, making a turnover of more than 200 million years. Solar radiation is the main source of energy on Earth. Its capacity is characterized by the solar constant - the amount of energy passing through the area of unit area perpendicular to the sun. Ultraviolet radiation from the sun has antiseptic properties that allow using it to disinfect water and miscellaneous items. It also causes sunburn and has other biological effects - for example, stimulates production of vitamin D. Since the solar plasma has a sufficiently high electrical conductivity, it may have electrical currents and, consequently, the magnetic field. Complex phenomena caused by the generation of strong magnetic fields on the sun, called solar activity. These fields are manifested in space as sun spots and cause phenomena such as solar flares, generating flows of accelerated particles, the changes in the levels of electromagnetic radiation from the sun in different bands, coronal mass ejections, solar wind disturbances, variations of galactic cosmic rays, etc. Since solar activity is also linked variations in geomagnetic activity (including magnetic storms), which are a consequence of reaching the Earth's interplanetary disturbances caused, in turn, active phenomena on the Sun.