Earth & Solar System PDF - Ojaank IAS Academy

OJAANK IAS ACADEMY Success is Yours LESSON -1 THE EARTH IN THE SOLAR SYSTEM  The sun, the moon and all those objects shining in the night sky are called celestialbodies.  Some celestial bodies are very big and hot. They are made up...

OJAANK IAS ACADEMY Success is Yours LESSON -1 THE EARTH IN THE SOLAR SYSTEM  The sun, the moon and all those objects shining in the night sky are called celestialbodies.  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.  Ursa Major or Big Bear is one such constellation. One of the most easily recognizable constellation is the Saptarishi (Sapta- seven stars).  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.  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.  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.  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.  The sun is in the centre of the solar system.  It is huge and made up of extremely hot gases.  The sun is the ultimate source of heat and light for the solar system.  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: MY VERY EFFICIENT MOTHER JUST SERVED US NUTS.  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 recently (August 2006), Pluto was also considered a planet. Mukherjee Nagar Office: Shop No. 5, G.F., GH-1B/B-19, Commercial Complex, Delhi-9 Nehru Vihar Office: C-346, Nehru Vihar, Mukherjee Nagar, Delhi-54 www.ojaankiasacademy.com (8285894079, 8750711144,8285894079, 8506845434)  OJAANK IAS ACADEMY Success is Yours  However, in a meeting of the International Astronomical Union, a decision was taken that Pluto like other celestial objects (Ceres, 2003 UB 313 ) discovered in recent past may be called ‘dwarf planets.”  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.  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 A Satellite is a celestial bodies. body that moves around  It is about 3,84,400 km away from us. the planets in the same way  The moon moves around the earth in about 27 days. as the planets move around  Look at the full moon and observe these shadows. the sun.  Apart from the stars, planets and satellites, there are numerous tiny bodies A Human-made Satellite which also move around the sun. These bodies are called ASTEROIDS. is an artificial body. It is designed by scientists to  They are found between the orbits of Mars and Jupiter gather information about  The small pieces of rocks which move around the sun are called meteoroids. the universe or for  Sometimes these meteoroids come near the earth and tend to drop upon it. communication. It is  During this process due to friction with the air they get heated up and burn. carried by a rocket and  Our solar system is a part of this galaxy. placed in the orbit around  A galaxy is a huge system of billions of stars, and clouds of dust and gases. the earth. Some of the Indian  There are millions of such galaxies that make the Universe. lli i Mukherjee Nagar Office: Shop No. 5, G.F., GH-1B/B-19, Commercial Complex, Delhi-9 Nehru Vihar Office: C-346, Nehru Vihar, Mukherjee Nagar, Delhi-54 www.ojaankiasacademy.com (8285894079, 8750711144,8285894079, 8506845434)