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The truth about stars
Twinkle twinkle little star,
How I wonder what you are,
Up above the world so high,
Like a diamond in the sky.
Stars give great pleasure and have a cooling effect on our eyes. The glimmering night sky looks wonderful all due to the stars that shine on it. Stars are a great distance away from earth. Many questions rise in our mind when we look at them. Here we find answers to some of these questions.
Composition of the star
Every bright star is a sun, like our own sun. This means that stars are huge globes of glowing gas. In many of the stars, the gases are not very concentrated. This is because the particle, or atoms, of matter in the gas are far apart.
In cooler stars, the matter may be more dilute, somewhat like the boiling iron in a blast furnace. In some very old and cold stars, the matter may be so densely packed that a cubic inch of it would weight a ton such stars are called “dead” or “dark” stars.
Colour and temperature
The different colours of stars indicate the chemicals present in it. Different temperatures of stars also cause differences in the light they emit in their “spectrum” — which is a breakdown of the light shed.
In this way, the colour of stars range from blue to red. The blue stars are large and hot and brilliant. Their surface temperatures may be as high as 27,750 degrees or more. Red stars are rather cool and have surface temperatures of 1,650 degree or less.
Brightness
The brightness of the star is called its “magnitude”. So magnitude is a sort of scale for measuring brightness. Stars of the first magnitude are the brightest. A star fainter than sixth magnitude cannot be seen without a telescope.
Starlight
A star is a ball of very hot gas that shines by its own light. Planets, as you know, and our moon too, shines only by the light reflected from the sun. Planets shine with a steady light while stars appear to twinkle. This is because of substances in the medium between stars and our earth. The unsteady air bends the light from the star, and then it seem to twinkle.
Nearest to earth
To measure distance in the universe we use a special unit of measurement called the “light year”. A light year is simply the distance a ray of light will travel in a year. Since light travels about 186,000 miles per second, therefore in one year it will travel a distance of nearly six billion miles.
The closest star to us is 4-1/3 light years away i.e. at a distance of twenty six billion miles. The farthest star that we can see from our naked eye is about 8,000,000 light years away.
How many can we see?
When we look up at night and see the stars it may surprise us that about 6,000 stars can be seen with our naked eyes. Only one half stars are visible at one time as others are below the horizon. The star near the horizon cannot be seen because of thin atmospheric vapours.
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