Write short notes on the following:
(a) The sun
(b) The moon
(c) Galaxy. [V. Imp.]
(a) The sun is considered the "head"of the solar system. It is a star, although it is smaller and less bright than most other stars. It is a huge celestial body made up of extremely hot gases. It provides heat and light for the whole of the solar system. Life on earth depends on many factors, and sunlight is one of them. The sun is about 150 million kilometres away from earth.
(b) The moon is the only natural satellite of our planet earth. Its diameter is just about a quarter of the earth's diameter. It is comparatively closer (3,84,400 kilometres away) to earth than all other celestial bodies. It does not support life. It revolves around the earth and rotates about its own axis in about the same time, due to which only one side of the moon is visible to us.
(c) Galaxy is a term that refers to billions of stars, clouds of dust and gases, and other celestial bodies considered as a single unit. The only bigger unit is the universe, galaxies make up the universe. The galaxy we live in is called the Milky Way.
Why do we not feel the heat and light of the stars, even though they are so big and hot?
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 ……….
State whether these sentences are true (T) or false (F).
(i) The Sun appears bigger and brighter than the other stars because it is indeed so.
(ii) Saptarishi and Ursa Major are two different constellations.
(iii) The Pole Star is known to have a fixed position in the sky.
(iv) The earth is the only planet that has a natural satellite.
(v) Pluto was declared a "dwarf planet"in August 2006.
(vi) The earth is the third-largest planet in the solar system.
(vii) The geoid shape is not perfectly spherical.
(viii) The moon takes about the same time in rotating about its axis once as it does to complete a revolution around the earth.
Answer the following questions briefly.
(a) How does a planet differ from a star?
(b) What is meant by the ‘Solar System'?
(c) Name all the planets according to their distance from the sun.
(d) Why is the Earth called a unique planet?
(e) Why do we see only one side of the moon always?
(f) What is the Universe?
Fill in the blanks with appropriate words to complete each sentence:
(i) The Amavasya night occurs about ……….. days after the Poomima night.
(ii) Stars are celestial bodies that are ……….. and ………….
(iii) The planets do not possess their own ……….. and …………
(iv) The Small Bear constellation is better known as the ………….
(v) The Greek word which is the origin of the word "planets"means ………….
(vi) Three planets having rings around them are ………… , ………. and …………
(vii) …….. are elongated fixed paths in which a celestial body always remains.
(viii) Venus is similar to the earth in its ………. and ………….
(ix) The shadows on the moon's surface are due to ……….. , ……… and …………
(x) Meteoroids heat up and bum due to …………
Draw a diagram showing the eight planets of the solar system in their orbits around the’ sun. Also prepare a table mentioning the length of their days and years.