PhysicsCelestial bodies


Once Shyam and Sita visited their village and went on the roof in the moonless night. They are looking up in the sky and saying that there are several twinkling stars there and they are looking very beautiful. Suddenly Sita asked Shyam from which the stars are made up of and why they are shining? Then Shyam replied that the stars are made up of gasses like Hydrogen, Helium etc. and they are shining because these gasses are doing a reaction called Nuclear fusion from which they are producing light and heat.

Again they start looking in the sky and again get stuck when they see a certain pattern that their stars are making as shown in the figure 1. Suddenly Sita asked Shyam, “Did you notice these patterns that stars are making?” Shyam smiles and appreciates Sita for her observation, he said that these patterns of stars are observed by our ancient people from years and they named them Constellations. He says that the Constellation is the group of stars that forms recognisable patterns.

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Figure 1: Constellation

In ancient times people named the constellation according to the shape of some object or animal whatever they resemble. They build several stories on the basis of constellations in ancient times which are somehow famous in today's generation too. One of the mythology of Greeks is based on the group of stars named Andromeda, Perseus, Cassiopeia, Cetus and Pegasu. Even in Indian Mythology, Meena is the name of a constellation which means fish and similarly in the Greeks it is called Pisces (which means fish). After this they went to sleep.

Again, after 4-5 days they come on the roof at night. Sita gets surprised that some of the constellations move to the west as compared to the last time. Then Shyam replied that since our earth is rotating from west to east, that is why the constellation seems to move from east to west like our Sun. Again Sita asked, “Can all the people on the earth can see all the constellations which are visible to us right now?” Shyam replied that no, since our earth is of geoid shape (almost spherical) so the person who lives near the north pole is not able to see the constellations of that person living near the south pole of the earth because line of sight is different for them. But yes, the person living near the equator will be able to see all the constellations. Now Shyam wants to share his knowledge about constellation to Sita,

Few Famous Constellations

Ursa major/Big Dipper/The Great Bear/The Saptarshi

This constellation is usually visible during summer in India and specially in the early part of night. In this constellation, there are seven stars arranged in the pattern of a big ladle or question mark shape as shown in the figure - 2. Also out of that 7 stars, 4 stars are there in the bowl of the ladle and 3 in the handle of the ladle. In Indian mythology, these seven stars are named on the seven Indian sages or rishis and due to this the pattern is known as ‘Saptarshi’.

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Figure 2: Saptarshi

Also, in the early part of the night, we can locate the position of the pole star with the help of Ursa major. We have to just draw a straight line from the two stars at the end of the Ursa major, then at a distance equal to the 5 times the distance between the two stars toward the north direction, we will find the Pole star (shown in the figure-3). It will be less shiny.

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Figure 3: Ursa major


It is one of the most commonly seen constellations from the earth. This constellation can be seen during winter in the early night or late evening. This constellation also consists of seven or eight stars. This pattern of stars looks like a hunter. Out of those seven or eight stars, three stars in the middle of the constellation are aligned such that it looks like the belt of the hunter. The remaining four stars are arranged in the form of a quadrilateral. Also the brightest star of the sky, Sirius can be easily located with the help of Orion. For that we can draw a straight line (shown in the figure 4) from the belt of hunter in the east direction, that straight line will lead to Sirius.

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Figure 4: Sirius


This is also one of the very famous constellations in the northern sky. The shape of the pattern will look like a distorted M or W. It is visible in the early night of winter. It looks.

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Figure 5: Cassiopeia

Zodiac Constellations

Shyam again asked Sitathat she must have heard about the zodiac sign, especially from our papa (Father) and mumma (Mother). She replied, yes. Shyam again asked but do you know the theory behind that? Yes, the theory of that zodiac sign is based on the constellations. As you must have heard, there are 12 zodiac signs and all these are based on 12 major constellations.

All these are -

  • Aries - Mesha
  • Taurus - Vrushabha
  • Gemini - Mithuna
  • Cancer - Karka
  • Leo - Simha
  • Virgo - Kanya
  • Libra - Tula
  • Scorpion - Vruschika
  • Saggitarius - Dhanusha
  • Capricorn - Makara
  • Aquarius - Kumbha
  • Pisces - Meena

In ancient times, these constellations are used to track the time because these constellations lined up in the Sun’s path.

Then Shyam and Sita went to sleep and all the concepts of constellations were clear to Sita.


Q1. Why are stars shining?

Answer - Stars are shining because of Nuclear fusion of the gases like hydrogen which is present inside the star or from which stars are made up of.

Q2. How many stars are there in Ursa major?

Answer - Ursa major contains seven stars. It is in the form of a ladle, in which 3 stars are on the handle of ladle and 4 on the bowl of the ladle

Q3. Which star can be located with the help of Ursa major?

Answer - Pole star can be located with the help of Ursa major. It can be located with the help of two stars at the end of Ursa major.

Q4. What does the shape of Orion look like?

Answer - The meaning of Orion is hunter and Orion looks like a hunter.

Q5. What do you mean by Constellation?

Answer - Constellation is the group of stars having a fixed pattern and that pattern is recognisable. Examples of constellations are - Ursa major, Orion, Cassiopeia etc.

Updated on 13-Oct-2022 11:19:47
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