-->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.

-->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.

-->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. They have their own heat and light, which they emit in large amounts. These celestial bodies are called stars. The sun is a star.

-->While watching the night sky, you may notice various patterns formed by different groups of stars. These are called constellations.

-->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 moon that we see in the sky is a satellite. It is a companion of our earth and moves round it.

-->The sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the solar system. We often call it a solar family, with the sun as its Head.

-->Interesting Fact
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 Sun
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 sun is about 150 million km away from the earth.

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 Neptune.

-->An easy way to memorise the name of the planets in order of their distance from the sun is: M Y V ERY E FFICIENT M OTHER J UST S ERVED U S N UTS .

-->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.

-->The Earth
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.

-->From the outer space, the earth appears blue because its two-thirds surface is covered by water. It is, therefore, called a blue planet.

-->Light travels at the speed of about 300,000 km per second. Yet, even with this speed, the light of the sun takes about eight minutes to reach the earth.

-->The Moon
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.

-->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.

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.

The small pieces of rocks which move around the sun are called meteoroids.

-->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.

Tick the correct answer.
(a)The planet known as the “Earth’s Twin” is
(i) Jupiter
(ii) Saturn
(iii) Venus

(b)Which is the third nearest planet to the sun ?
(i) Venus
(ii) Earth
(iii) Mercury

(c)All the planets move around the sun in a
(i) Circular path
(ii) Rectangular path
(iii) Elongated path

(d)The Pole Star indicates the direction to the
(i) South
(ii) North
(iii) East

(e)Asteroids are found between the orbits of
(i) Saturn and Jupiter
(ii) Mars and Jupiter
(iii) The Earth and Mars

Fill in the blanks.
(a) A group of ________ forming various patterns is called a ________.
(b) A huge system of stars is called________.
(c) ________is the closest celestial body to our earth.
(d) ________is the third nearest planet to the sun.
(e) Planets do not have their own________ and ___________________.