It's time to see stars!

One of the most beautiful sights in nature is the night sky. Most of you must be familiar with the famous nursery rhyme 'Twinkle, twinkle little star...' As the rhyme states, the stars certainly do look like little diamonds, shining brightly in a velvety black sky.

The bright planets that wander among the stars and long-tailed comets that come and go, are indeed fascinating sights. How many of you have indulged in star-gazing or even visited the planetarium and looked up at the vast expanse of space, twinkling with stars and lit up by other celestial bodies?

There are millions of stars, but we cannot see all of them with our normal or naked eyes. We need the

 assistance of powerful telescopic lenses to see them. However, if you look closely at the night sky, you will notice that some stars sparkle more and are much brighter than the others. These bright stars make patterns that you can recognize every time you see them. These star patterns are known as constellations.

Whenever you look up into the night sky, you will notice that the constellations seem to be moving across the sky from east to west, just like the Sun does during the day. How or why do they move?

Ancient astronomers were of the view that the stars moved because they were fixed on the inside of the celestial sphere, which spun around Earth that was still. We know today that the opposite is true; it is the Earth and not the stars that are moving around. As the Earth spins round in space from west to east, it makes the stars appear to travel in the opposite direction.

Why the entire world can't see the same stars

As stars are up above us in space, you may be of the view that everybody around the world see the same stars. You are wrong. As our planet Earth rotates on its north-south axis, we can only see the stars in the sky above our hemisphere.

For example, people in the far north can always see the constellation of stars known as the Plough, but those in the far south can never see it, unless of course they travel to that part of the world.

In the same way, those living in the far south will always see the Southern Cross. However, those in the Equator can see almost all the stars visible to the naked eye, at some time of the year.

Major constellations and zodiac signs

There are 12 major constellations that have been identified. The six constellations in the Northern hemisphere are Pegasus, Perseus, Pole Star, Plough (or Little Bear), Great Bear and Leo (the Lion). The six constellations in the Southern hemisphere are; Aquarius (the Water-bearer), Orion (the Hunter), Scorpio (the Scorpion), Southern Cross, Hydra (Water Snake) and Libra (Scales).

Now, as you read these names, you will instantly connect some of them to the zodiac signs in astrology. These zodiac signs, also called star signs, are important in astrology because astrologers believe that human lives are affected by the stars.

What are stars and how hot are they?

Don't be fooled by the tiny, bright specks that twinkle in the night... They are not what they seem. Stars are huge balls of searing gas. They are in fact great globes of very hot gas with varying temperatures. Astronomers can tell the temperature of a star by the colour and brightness of the light it gives out.

Yellowish stars, like our very own Sun, have a temperature of about 5,500 degrees Celsius. This compares with about 3,000 degrees Celsius for a dim red star, to 30,000 degrees Celsius for a bright, blue-white star.

We cannot know the exact size of all the stars in our galaxy, but we can certainly measure our own star, the Sun. It is nearly 1,400,000 kilometres across. Astronomers do manage to work out the size of some stars.

They have discovered that there are stars which are smaller than the Sun, and also many stars which are much larger. It is due to the fact that astronomers have discovered red giant stars and super giant stars, tens of times bigger than the Sun, that they call our star, a dwarf. Some super giants are said to be about 400 million kilometres across!

Why stars twinkle

Why do you think stars twinkle? Is it because they change their brightness all the time or because we see them that way? Even though it seems as if stars do not give out a steady light and change brightness all the time, in reality they do shine steadily.

The reason we see them as twinkling stars is due to air currents. These air currents in the Earth's atmosphere make the light from the star bend in all directions. Some of this light gets into our eyes and

 some is bent away. So, to us on Earth, the stars seem to twinkle all the time. Isn't it fascinating?

Do stars live forever?

Most of you must have heard people say that the Sun will come to an end some day. Well, that means, stars too die out. Just like all living things, stars are born, they grow older and eventually die.

There are two different ways in which stars die. Now let's check out one method first. After shining steadily for some time, the stars start to swell up and turn into red giants.

Some of these red giants shrink into white dwarfs and finally end up as black dwarfs. This is what is going to happen to our own Sun one day. At the moment the Sun, which is believed to have been born about 5,000 million years ago, is giving us light and warmth.

But, in the future, it will swell up and become hotter, and the Earth's oceans will boil away; life will end.

As the Sun becomes a red hot giant, Earth will be scorched to a cinder.

The sun will gradually shrink again and become a white dwarf star, about the size of Earth. It will end up as a black dwarf, like any other star.

The other method stars die is by swelling up from a red giant to a supergiant. As super giants are unstable, they collapse and blast themselves to pieces in an explosion called a supernova. These are the biggest explosions in the Universe. Supernova explosions are extremely bright, as if a billion Suns have been put together.

A smaller star that explodes as a supernova ends its life as a tiny star which is called a pulsar. There's so much fascinating things you could learn not only about stars, but the entire universe. Don't fail to hitch a ride on Space station and learn about the mysteries out there.....