Unknow facts about universe and its mysterious

 How old is the universe?

The night sky with twinkling stars is a fascinating sight. Although it looks very big with millions of stars what we can see is a very small part of the universe. According to scientists, there may be as many as

10, 000, 000, 000, 000, 000, 000, 000 stars in the universe!

It is difficult to find out how old the universe is, but scientists have found a way to calculate it, or at least to estimate how long it has been here in its present form.

Many scientists believe that the universe began with a big explosion that sent all matter flying out into space. This theory is called the big bang theory.

One of the reasons to believe in the Big Bang theory is that the universe seems to be expanding. All stars and galaxies are flying away from each other. Scientists can measure the speed of stars and by comparing the speed of the nearer and the distant stars they can figure out when the stars began to move through space. And they say that the universe is at least ten billion years old!

What are the misty shapes in space?

The misty shapes we see in the sky sometimes look like a familiar object – a ring – a crab – a veil. These are called nebulas and are in fact giant clouds of dust and gas. The word nebula means ‘mist’.

Most nebulas are the remains of stars that exploded long ago. When a star explodes, the explosion sometimes is tremendous, so great that it destroys the star. The explosion sends a gigantic cloud of glowing gas rushing out into space, and the once giant star suddenly becomes a little white dwarf star.

The Ring Nebula is a shell of gas that surrounds a star and looks like a ring from a distance. The veil nebula is dust particles spread rather thinly on a large space and looks like a thin veil.

Why are quasars mysterious?

Astronomers were excited to detect a very powerful source of energy in space in 1961. When they tried to ‘see’ the source of this great energy output was difficult to believe because it was giving off more energy than that given by a thousand galaxies, or ten trillion stars. And the source objects seem to be no bigger than a small portion of a galaxy.

Some scientists think that quasars are tremendous explosions taking place in the middle of distant galaxies. Others think that quasars are very distant objects that are moving at very high speeds away from us.

According to them, they are so far away that even the light takes very long to reach us from them. So long that when we look at them, we may be looking back in time almost to the beginning of the universe which could mean billions of years ago.

Do stars also live and die?

Yes, stars die in different ways. After a certain time, some stars get smaller and cooler until they simply stop burning while some stars explode and blow themselves apart and we call them supernovas.

It is difficult to say how long the average star lives because there really is no such thing as an average star. Some stars are so small that their diameter is only 1/70,000 the diameter of the sun, while others have a diameter thousand times larger than the sun’s.

What is a shooting star?

Shooting stars are not stars but are meteors entering the atmosphere of the Earth from outer space. Pieces of rock, some big and some small are floating everywhere in space. Some of these are attracted towards Earth and because of the gravity, approach Earth at a speed of up to 50 miles per second.

We can see them when they enter our atmosphere because they leave a trail of light behind them while coming down. Because of their tremendous speed, the friction with air heats them up until they glow like stars. They are a beautiful sight to look at, but you have to be quick to see them because they usually don’t last more than a second or two before they burn up completely and disappear.

Most of the meteors disintegrate like this but some of them, the larger ones, do land on earth, and when they do, we call them meteorites.

How many stars can we see at night?

There are billions of stars in the sky. Many stars are bigger than the sun, and some are even bigger than the entire solar system. Some are smaller. The very small ones called ‘white dwarfs’ may be less than half the size of the moon. Out of the billions of stars, only about 6,000 can be seen from the Earth without the help of a telescope. From the lands lying on the north of the equator, only about a quarter of these stars can be seen with the human eye.

Some of the stars we see look much brighter than others. The brightness of stars is expressed by scientists in terms of their ‘magnitude’. A star with a magnitude of one is twice as bright as a star with a magnitude of two. A star with a magnitude of two is twice as bright as a magnitude three-star, and so on. A magnitude-one star is more than a million times as bright as a magnitude-21 star.