WHAT ARE CELESTIAL BODIES

WHAT ARE CELESTIAL BODIES

How wonderful it is to watch the sky after sunset! One would first notice one or two bright dots shining in the sky. Soon you would see the number increasing. You cannot count them anymore. The whole sky is filled with tiny shining objects – some are bright, others dim. It seems as if the sky is studded with diamonds. They all appear to be twinkling. But if you look at them carefully you will notice that some of them do not twinkle as others do. They simply glow without any flicker just as the moon shines.

Along with these bright objects, you may also see the moon on most of the days. It may, however, appear at different times, in different shapes, and at different positions. You can see the full moon only once in about a month’s time. It is Full moon night or Poornima. A fortnight later, you cannot see it at all. It is a New moon night or Amavasya. On this day, you can watch the night sky best, provided it is a clear night.

Do you wonder why can’t we see the moon and all those bright tiny objects during day time? It is because the very bright light of the sun does not allow us to see all these bright objects of the night sky.

The sun, the moon, and all those objects shining in the night sky are called celestial bodies.

Do you know?

Humans have always been fascinated by gazing at the night sky. Those who study the celestial bodies and their movements are called astronomers. Aryabhatta was a famous astronomer of ancient India. He said that the moon and the planets shine due to reflected sunlight. Today, astronomers all over the world are busy exploring the universe.

STARS AND CONSTELLATIONS

STARS AND CONSTELLATIONS

Stars

Some celestial bodies are very big and hot. They are made up of gases. They have their own heat and light, which they emit in large amounts. These celestial bodies are called stars. The sun is a star.

Countless twinkling stars in the night sky are similar to the sun. But we do not feel their heat or light, and they look so tiny because they are very very far from us.

In ancient times, people used to determine directions during the night with the help of stars. The North star indicates the north direction. It is also called the Pole Star. It always remains in the same position in the sky. We can locate the position of the Pole Star with the help of the Saptarishi. Look at Figure 1.1. You will notice that, if an imaginary line is drawn joining the pointer stars and extended further, it will point to the Pole Star.

Activity:

Let’s Do

You’ll need 1 torch,1 sheet of plain paper, a pencil, and a needle.

Steps:

       1. Place the torch in the centre of the paper with its glass front touching the paper.

      2. Now draw a circle around the torch.

      3. Perforate the paper with the needle within the circled area.

      4. Now place the perforated circle part of the paper on the glass front and wrap the paper around the torch with a rubber band.

      5. Take care that the switch of the torch is not covered.

      6. In a dark room, stand at some distance facing a plain wall. Switch off all other lights. Now flash the torchlight on the wall. You will see numerous dots of light on the wall like stars shine in the night.

      7. Switch on all the lights in the room. All dots of light will be almost invisible.

      8. You may now compare the situation with what happens to the bright objects of the night sky after the sun rises in the morning.

Constellations      

           You must have noticed that all objects look smaller when seen from a distance. How small an aeroplane looks when it is flying at a great height!

While watching the night sky, you may notice various patterns formed by different groups of stars. These are called constellations. Ursa Major or Big Bear is one such constellation. One of the most easily recognisable constellation is the Saptarishi (Sapta- seven, rishi-sages). It is a group of seven stars (Figure 1.1) that forms a part of Ursa Major Constellation. Ask someone elder in your family or neighbourhood to show you more stars, planets, and constellations in the sky.

PLANETS

PLANETS

Some celestial bodies do not have their own heat and light. They are lit by the light of the stars. Such bodies are called planets. The word ‘planet’ comes from the Greek word “Planetai” which means ‘wanderers’. The earth on which we live is a planet. It gets all its heat and light from the sun, which is our nearest star. If we look at the earth from a great distance, say the moon, it will appear to be shining just as the moon.

The moon that we see in the sky is a satellite. It is a companion of our earth and moves round it. Like our earth, there are seven other planets that get heat and light from the sun. Some of them have their moons too.