June 21, 2009
The most important feature of our solar system is the Sun. It is the largest object in it, and contains almost 98% of the total mass of the solar system. The visible outer layer of the Sun is known as the photosphere, and its temperature is 6,000 degrees Celsius. Inside the Sun’s core, the creation of solar energy takes place. The temperature is so high that nuclear reactions take place, which causes four protons or hydrogen nuclei to fuse together, thus forming one alpha particle, or helium nucleus.
The energy which is generated in the Sun’s core takes about a million years to reach the surface, and every minute, the Sun is getting lighter. The Sun has been active for a staggering 4.6 million billion years, and is expected to go on for another 5 billion years. Towards the end, it will fuse helium into heavier elements, this will make it swell up and grow so large that it will swallow up the Earth. It will then collapse into a white dwarf, and take a trillion years cooling down.
Right now, the Sun is a yellow dwarf, and stands at the centre of our solar system. Everything else – the planets, the asteroids, the meteoroids, etc. orbit the Sun. The distance between the Sun and the earth is almost 149,600,000 kilometres. The light from the Sun supports the process of photosynthesis, and is also responsible for our climate and weather. There is hydrogen on the Sun’s surface, which amounts to 74% of its mass, and 92% of its volume. There is also helium, which accounts for 24% mass, and 7% volume. Finally, there are traces of other elements, like silicon, sulfur, neon, calcium, chromium, magnesium, carbon, iron, nickel, and oxygen. The surface of the Sun often looks white, because of the process of atmospheric scattering, and appears to be yellow when seen from the earth’s surface.
The Sun is responsible for giving is sunlight, which is our primary source of energy. The amount of power per unit area deposited by the Sun, (areas which are directly exposed to sunlight) is called the solar constant. Plants undergo the process of photosynthesis, which takes the sunlight and converts it to oxygen and reduced carbon compounds. We, on the other hand, have developed solar cells, which capture the sunlight and convert it to electricity, or perhaps something else that comes in useful.
Sunlight has ultraviolet rays in it, which is sometimes used for the sanitization of tools and water, due to its antiseptic properties. However, it can also be responsible for sunburn, and has been known to produce Vitamin D. The Sun is actually a star that is magnetically active. A strong, dynamic magnetic field is supported by it, and this changes from year to year, and changes direction every eleven years, around the solar maximum. Though we have learnt a lot about the Sun over the years through constant research, many questions remain a mystery – like the origins of flares, the regular cycle of sunspot activity, etc.