Discuss the salient aspects of the structure of Sun and the various activities going on in it.

Discuss the salient aspects of the structure of Sun and the various activities going on in it. 

Answer:

Sun is the only visible star to us during the daytime because it is the star closest to earth. Sun is the head of our solar system consisting of nine planets, including earth, satellites, asteroids, and comets. All the planets and asteroids and some comets revolve around the Sun in elliptical orbits. Sun’s gravitational attraction keeps them revolving in their orbits. If the Sun vanished suddenly, all the planets would fly off in straight lines at a tangent to their orbits.

Sun is the only planet near to the earth and enough to be studied in considerable detail. The Sun is largely made up of Hydrogen and helium. Nuclear fusion is the source of the Sun’s energy, that is, the hydrogen nuclei fuse together to form helium nuclei giving off energy. The mass of the Sun is approximately 2x10³³ grams and it contains almost 99.87% of the entire Solar System. The diameter of the Sun is almost 110 times that of Earth. The average density, i.e. its mass per unit volume, is about 1.4 g/cm³.

The Sun rotates about its axis once every 25 days. From time to time dark patches called sunspots appear on the surface of the Sun, usually in pairs or groups. Sunspot is a region on the surface of the Sun that consists of gases almost 1000⁰C cooler than those surrounding the area. The movement of the sunspots is an indication of the Sun’s movement.

The Sun’s body is made up of several layers. The layer that forms the visible surface of the Sun is called the photosphere. The temperature of the photosphere is 6000⁰C. The innermost layer of the Sun is its core where its energy is produced through nuclear reactions. The outermost layer of the Sun’s atmosphere is called corona, it is seen during a total solar eclipse.

The most dynamic activity associated with the Sun’s surface and atmosphere are solar wind and solar flare. Streams of electrons and protons continuously flow out from the Sun’s atmosphere and travel across the Solar system. This rapidly moving stream of charged particles is called the solar wind. In the form of solar wind about one-million-ton material is removed every second from the Sun.  Solar flare represents a tremendous release of energy in a very short time. Usually, it occurs in the neighbourhood of a sunspot. There is sudden lightning accompanied by a violent flow of energy in the form of light, radio waves, X-rays and solar materials like electrons and protons.

So, these are some salient features of the Sun’s structure and its activity.