THE SUN
**The solar system is dominated by the sun, which accounts for almost 99.9% of the matter of the whole system.
**It is the source of light and heat to us.
**Scientists believe that the sun has been formed from a moving cloud of gases, which is called Nebula.
**The sun and the planets were born out of this cloud. The force of Gravity has created them.
**For millions of years, these balls of dust and gas are moving around the sun. The sun due to its mass and weight controls the movement of the planets. This force is called the force of gravity.
**Sun is at the center of the Solar system with eight planets (i.e. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune) and their satellites, dwarf planets, asteroids, meteors, and comets that move around the sun.
**It is believed that the sun was born about 5 billion years ago. Since that time, it is continuously emitting huge amounts of heat and light, and it is expected to glow in a similar manner for the next 5 billion years or so on.
**The sun is the nearest star to us.
**The sun is the source of almost all energy on the Earth. In fact, the sun is the main source of heat and light for all the planets.
**The Radius of the sun is almost 100 times the radius of the Earth and its mass is about a million times the mass of the Earth.
**The Sun is essentially a sphere of hot gases. The disc is also called the Photosphere.
**The layers of gas above the photosphere are extremely hot, but their densities are extremely low. These layers are very faint and are not visible in the presence of strong light from the disc of the Sun.
**At the time of the total solar eclipse, when the light of the sun's disc is completely cut off, the outermost layer becomes visible. It appears like a crown around the sun. This layer is called Corona.
**Solar flares are charged particles overcome by the sun's gravity and come into outer space. When these solar flares reach the Earth's atmosphere they collide with the gaseous particles and produce a colorful effect. In the south pole region, these effects are known as Aurora Australis, and in the North pole Aurora Borealis.
**The temperature of the bright disc is about 6000 k. At the center of the sun, the temperature is about 15 million K. The pressure is also extremely high. All these conditions are right for fusion reactions. In the sun, four protons (Nuclei of Hydrogen atoms) combine to form a Helium nucleus.
**The mass of the helium nucleus is slightly smaller than the combined mass of four protons. So, there is a loss of mass in the process. This loss of mass is the source of the sun's energy.
**The Sun is about 150 million km away from the Earth. Light travels at a speed of 300000km/s. So, the light of the sun takes about 8.3minutes to reach us.
**The light of the nearest star (proxima or Alpha centauri)to the sun reach Earth in about 4.3 light years.
PROCESS OF FUSION-
According to Einstein's equation, E=mc², E is the energy produced when a mass(m), is lost.
The quantity (c) is the velocity of light.
**Most stars produce their energy by the process of Fusion.