EXPLORING SPACE :- STARS

          All stars are basically enormous balls of fire. They are made up of gases that give off both heat and light as they burn. Their power comes from nuclear energy, the same source that both powers atomic bombs and produces electricity in many parts of  the world.

          The life of a star span billions of years. A star is born from clouds of dust and the element hydrogen. This cloud mass forms a spinning ball and becomes extremely hot. It becomes so hot that the hydrogen gas begins to glow. The glowing gas ball is called a "Protostar" ('Proto' means 'beginning' or 'first').

          A protostar slowly becomes bigger until eventually it stops growing. It is then a star, and it can continue to glow for millions of years. But eventually it starts to cool off. It turns red and grows larger once more. It becomes a "Red Giant". Then the star begins to die. How long a star lives depends on how big it is. The bigger the star, the longer it lives.

          In large stars, the heat inside the star produces "IRON". This iron acts like a sponge and soaks up the star's energy. The energy eventually causes a big explosion called a "Supernova". In some cases, what is left may become a black hole. Black holes are like giant vacuum cleaners in space that suck up everything around them, including light.

          Our sun is still a young star, although it is already billions of years old. It will be many more billions of years before it begins to die. So there's still time to finish your homework !


          DID YOU KNOW ?

          After our own Sun, the nearest star to Earth is Alpha Proxima Centauri. It is 4.3 light years away, or almost 1.3 billion kilometres from Earth.

EXPLORING SPACE :- GALAXIES

          When we look at the sky at night, we can sometimes see thousands of stars shining brightly. They look as if they have been scattered around the sky. But actually, most stars are clustered together in huge groups. These groups are called "GALAXIES".

          Our Sun is part of a galaxy. It is the Milky Way Galaxy. On a very clear night, if you look carefully at the sky, you might see part of this whitish band of stars stretching from one side to other.

          The universe is so huge that the Milky Way Galaxy is only one of many galaxies. Astronomers think that there are billions of galaxies in the universe. Each of these galaxies may contain trillions of stars, many much bigger than our Sun! The Milky Way itself contains several billions stars.

          Some galaxies have no regular shape. Others, like the Milky Way, are shaped a bit like a giant merry-go-round. Each one has a centre around which stars move in circles.

          It is hard to see the other galaxies in the sky with naked eye. Even though they are incredibly large, they are also incredibly far away. Scientists must use powerful telescope to study other galaxies. For this reason it takes a long time to learn even a little bit about another galaxy. And there's still a great deal we haven't learned about our own galaxy.


          DID YOU KNOW ?

          Unlike galaxies, constellations are groups of stars. People used to imagine connecting the stars to make picture in the night sky. Most constellations are named after animals and mythological figures. They still help astronomers and navigators locate certain stars.

EXPLORING SPACE :- GRAVITY

          Raise your arm. Keep it in that position for as long as you can. What happens?

          After some time, your arm begins to hurt. Something seems to be pulling it down. Soon you will have to lower your arm.

          A force called "Gravity" causes you to lower your arm. Gravity acts a bit like magnet, tugging at your arm as if it were a piece of metal.

         We can't see gravity or touch it. we can only feel it. The Earth has gravity that pulls down on everything on or near it. It is this force that keeps us all on the Earth.

        The Moon and the Sun also have gravity. All bodies in the universe have gravity. In fact, gravity helps hold all of them together. Sir Isaac Newton first introduced the idea of gravity, and Albert Einstein added to Newton's ideas.

         Gravity works in a two-way system. This means that all bodies exert a pull on each other. For example, Earth's gravity forces the Moon to circle around it all the time. In return, the Moon's gravity attracts the waters of Earth's oceans to cause tides.

         The force of gravity becomes weaker and weaker as you move away from its source. That is partly why astronauts can float around in outer space. They are too far away for the Earth to have pull on them.

        What do you think would happen if there were no gravity on Earth ?

        DID YOU KNOW ?

        A 1961 Disney film, the Absent-Minded Professor, introduced a particularly far-fetched anti-gravity idea -  "F LUBBER", a super-bouncy "Flying -Rubber".

EXPLORING SPACE :- UNIVERSE

        The universe is a vast expanse of space that contains all matter and energy, from the smallest particle to the biggest galaxy. It contains all the Planets, the Sun, Stars, Asteroids, our Milky Way galaxy, and all the other galaxies too.

        No one know how big the universe is. Astronomers believe that it is still growing outwards in every direction.

        How did it all begin ? No one is really sure of that either.

        Most scientists believe that at first everything was one incredibly solid, heavy ball of matter. This ball exploded billions of years ago - and the universe was born. The moment of this explosion is called the "BIG BANG". It is from this moment that time begun.

        After the explosion, the early universe was small and extremely hot. As it cooled, it expanded and pieces spread out. Small pieces formed the basic elements hydrogen and helium. Other pieces began to join together, and objects began to form. Over billions of years, the objects became Galaxies, Stars, and planets.

        How the universe was formed is still only a theory (an idea). But different parts of it have proved to be true over the years. Astronomers continue to investigate the theory. One way they do this is by using a "spectroscope". A spectroscope measures the colour of light coming from an object. Changes in the colour indicate weather an object is moving away from or towards the Earth.

        Because of spectroscope readings, scientists believe that the universe is still growing outwards in every direction.


DID YOU KNOW ?

Scientists believe that much of the universe may be made of something called "DARK MATTER". This hidden mass may be a substance that people have never before encountered.

EXPLORING SPACE :- ASTRONOMY

Look at the sky. What do you see?

      If  it's day you'll see the Sun. If it's night you'll  see the Moon. And if the sky is clear you'll see Stars. In big cities you may see only few hundred stars. But out in the country or on the ocean you'll see many thousands. You may even see Planets and, if you're lucky, a COMET.

     There are people who look at the sky for hours and hours, night after night. They study stars, the planets, and other objects in the sky. These people are called "astronomers" . The word "astronomy" comes from Greek for "Star" and " arrangement".

    Astronomers study the universe in many different ways. Some watch faraway objects. Other work in laboratories where they look at samples of meteorites, rocks from Moon, and space debris from other planets. Some try to make models of the different objects people have studied.

    Not all astronomers get paid for the work they do. Some do it for a hobby. Such people are called "amateur astronomers".

    How do astronomers study objects that are millions, even billions, of  kilometres away ? They use powerful telescopes that make things look large enough to be seen in detail. Some telescopes are small enough to be held in the hand. Others are as big as a bus!


DID YOU KNOW ?

The planet Pluto is so far away from earth that the beam of a torch, travelling at the speed pf light, would take about five hours to get there.