Stars

                                                                                                              Stars

The stars are great globes of hot, glowing gas just like our sun. They contain a great deal of hydrogen and helium gases. They shine by changing hydrogen into helium in the vast nuclear furnaces of their central core.

Astronomers have discovered that the stars contain most of the other elements found on the earth. They have identified more than sixty of the elements like air, water, fire etc. found on the earth. The elements are not in the same proportion as they are on the earth. They vary from star to star. The stars contain lighter elements like hydrogen, helium, iron and calcium in a large proportion.

Astronomers use an instrument called spectroscope to split the starlight into a broad band of colours. Sometimes there are a number of dark lines in the band. The position, the number and the size of the lines, give a lot of information about a star’s atmosphere including its gaseous chemical content, its density and temperature.

The movement of a star towards or away from us is called its radial motion. Astronomers can detect and measure this motion using that invaluable tool, spectroscope. The spectrum of light from a star shows dark lines characteristic of the chemical elements it contains. The interesting thing is that when a star is moving towards or away from us the lines show a shift in position from where they would have been if the star were at rest. When the motion is towards us the lines shift towards the blue end of the spectrum. When the motion is away from us the lines shift towards the red end. The extent of the shift is a measure of the speed at which the star is traveling towards or away from us.

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