Sun

The Sun is in fact a star in the galaxy which forms the centre of our solar system. It is an ordinary middle-aged star. As far we know, it has been estimated that the Sun is 4.5 billion years old. It is a globe consisting of a mass of vapour at white heat, and of such enormous size that it is 500 times larger than all the planets of the system put together, or of a bulk one million and a half times greater than the earth, from which it is ninety-two and a half million miles distant.

It has its own light. The bright surface of it is called the photosphere, and this brightness is diversified with brighter spots called faculæ, and dark ones called sun-spots, and by watching which latter as they move over the sun's disk we find it takes 25 days to revolve on its axis, and by means of Spectrum Analysis we find that it is composed of hydrogen and a number of vaporised metals.

This gaseous burning star might have a temperature of 27 million degrees celsius at its core. It has 11 year cycle. During this cycle, when it approaches a solar maximum, we see frequent sunspots and flares. Amazing sky streamers appear which are popularly known as Northern Lights.

Its diameter is 1,384,000 kms (865,000 miles). It has nine satelites. These satelites are also known as planets.