At night the whole sky is filled with tiny shining objects some are bright, others dim. They all appear to be twinkling. A full moon occurs once in about a month’s time called Full moon night or Poornima. A fortnight later, you cannot see the moon at all which is called New moon night or Amavasya.
Celestial bodies – The sun, the moon and all those objects shining in the night sky are called celestial bodies. Some celestial bodies are very big and hot. They are made up of gases.
Stars – Stars are celestial bodies which have their own heat and light, which they emit in large amounts. The sun is a star.
Constellations: In the night sky, various patterns are formed by different groups of stars called constellations. Ursa Major or Big Bear is one such constellation.
One of the most easily recognisable constellations is the Saptarishi (Saptaseven, rishi-sages). It is a group of seven stars that forms a part of Ursa Major Constellation.
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.
Planets – Planets are celestial bodies that do not have their own heat and light. They are lit by the light of the stars. 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. The moon that we see in the sky is a satellite. It is a companion of our earth and moves around it. Like our earth, there are seven other planets that get heat and light from the sun. Some of them have their moons too.
Ring Around The Planet
- Jupiter, Saturn and Uranus have rings around them.
- These are belts of small debris.
- These rings may be seen from the earth with the help of powerful telescopes.
THE SOLAR SYSTEM
- The sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the solar system.
- We call it a solar family, with the sun as its Head.
Meaning Of Solar
- Sol’ in Roman mythology is the ‘Sungod’.
- ‘Solar’ means ‘related to the sun’.
- The family of the sun is, therefore, called the solar system.
- The sun is in the centre of the solar system.
- It is huge and made up of extremely hot gases.
- It provides the pulling force that binds the solar system.
- The sun is the ultimate source of heat and light for the solar system.
- The tremendous heat is not felt so much by us because despite being our nearest star, it is far away from us.
- The sun is about 150 million km away from the earth.
- Stars are hot and very big in size.
- They appearsmall to us as they are very far away from us.
- The Sun is astar.
- Stars have their own heat and light.
- Various patterns are formed by different groups of stars.
- These patterns are called constellations.
- Some known constellation are the Ursa Major (Big Bear) and the Saptarishi (Little Bear).
- Saptarishi is a group of seven stars which can be recognized easily and is part of the Big Bear.
- The North Star,also known as the Pole Star,indicates the north direction.
- In the ancient times, people tried to find out the location of places with the help of the Pole Star
- Humans have always been fascinated 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.
- Astronomers all over the world are busy exploring the universe. constellation
- There are eight planets in our solar system.
- In order of their distance from the sun, they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and
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- All the eight planets of the solar system move around the sun in fixed paths.
- These paths are elongated.
- They are called orbits.
- Mercury is nearest to the sun.
- It takes only about 88 days to complete one round along its orbit.
- Venus is considered as ‘Earth’s-twin’ because its size and shape are very much similar to that of the earth.
- Till August 2006 Pluto was also considered a planet.
- International Astronomical Union, a decision was taken that Pluto like other celestial objects (Ceres, 2003
UB313) discovered in recent past may be called ‘dwarf planets.”
|Stars have their own light||Planets do not have they light their own. They shine by reflecting the sun light.|
|There are billions of stars in the sky||There are only eight planets|
|Stars twinkle||Planets do not twinkle|
|Stars have high temperature||Planets have low temprature|
- The earth is the third nearest planet to the sun.
- In size, it is the fifth largest planet.
- It is slightly flattened at the poles.
- That is why, its shape is described as a Geoid.
- Geoid means an earth-like shape.
- Conditions favourable to support life are probably found only on the earth.
- The earth is neither too hot nor too cold.
- It has water and air, which are very essential for our survival.
- The air has life-supporting gases like oxygen.
- The earth is a unique planet in the solar system.
- From the outer space, the earth appears blue because its two-thirds surface is covered by water.
- It is called a blue planet.
- Light travels at the speed of about 300,000 km per second.
- With this speed, the light of the sun takes about eight minutes to reach the earth.
- Our earth has only one satellite, that is, the moon.
- Its diametre is only one-quarter that of the earth.
- It appears so big because it is nearer to our planet than other celestial bodies.
- It is about 3,84,400 km away from us.
- The moon moves around the earth in about 27 days.
- It takes exactly the same time to complete one spin.
- As a result, only one side of the moon is visible to us on the earth.
- The moon does not have conditions favourable for life.
- It has mountains, plains and depressions on its surface.
- These cast shadows on the moon’s surface.
- Neil Armstrong was the first man to step on the surface of the moon on 21 July 1969.
- A Satellite is a celestial body that moves around the planets in the same way as the planets move around the sun.
A Human-made Satellite
- A Human-made Satellite is an artificial body.
- It is designed by scientists to gather information about the universe or for communication.
- It is carried by a rocket and placed in the orbit around the earth.
- Some of the Indian satellites in space are INSAT, IRS, EDUSAT, etc.
- Apart from the stars, planets and satellites, there are numerous tiny bodies which also move around the sun.
- These bodies are called asteroids.
- They are found between the orbits of Mars and Jupiter.
- Scientists are of the view that asteroids are parts of a planet which exploded many years back.
- The small pieces of rocks which move around the sun are called meteoroids.
- Sometimes these meteoroids come near the earth and tend to drop upon it.
- During this process due to friction with the air they get heated up and burn.
- It causes a flash of light.
- Meteor without being completely burnt, falls on the earth and creates a hollow.
Whitish Broad Band
- It is a cluster of millions of stars.
- This band is the Milky Way galaxy
- Our solar system is a part of this galaxy.
- In ancient India, it was imagined to be a river of light flowing in the sky.
- Thus, it was named Akash Ganga.
- A galaxy is a huge system of billions of stars, and clouds of dust and gases.
- There are millions of such galaxies that make the Universe.
- It is difficult to imagine how big the universe is.
- Scientists are still trying to find out more and more about it.