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Chapter 1 - Solar System And Earth- A Brief Insight

“Father of Geography” Eratosthenese  (Ist to measure earth circumfrence)
“Systematic Geography”Alexander Von Humbolt
“Regional Geography”Karl Ritter

Origin & Evolution of Earth

Ist ArgumentImmanuel Kant (Germany)
“Nebular Hypothesis” & “Binary Theories”Laplace (1796)

Modern Theory

“Father of Big Bang Theory” - Georges Lemaitre (Belgium), Propounded by Edwin Hubble (1920)
“Steady State Theory” - Hoyle 

The solar system consists of the Sun and 8 planets revolving around it in different orbits. The statistics of the sun and the planets are given below:

•Age : About 5 Billion years
•Distance : 149.8 Million Kms
•Diameter : 1,38,400 Kms.
•Photosphere temperature : 5,770 K
•Core temperature : 150,000,000 K
•Absolute visual magnitude : 4.75
•Rotation (as seen from the earth at the equator) : 25.38 days
•Rotation (near the poles) : 33 days
•The sun consists of 71% of Hydrogen, 26.5% Helium and 2.5% of other elements.
•The rays of the Sun take about 8 minutes to reach the earth.

Types of planets

Inner Planets (Terrestrial Planets) – are four in number i.e. Mercury, Venus, Earth, Mars
They all have solid surface                                                                                             
They are made up of mostly heavy metals such as iron & Nickel
They have either no moons or some moons
They all have high density

Asteroid Belt – region between Mars & Jupiter having numerous asteroids

Outer Planets (Jovian Planets) – are also four in number i.e. Jupiter, Saturn, Uranus, Neptune
They are bigger in size
They all have rings present around them
They have large number of moons
They all have low density 


•It is the planet nearest to the earth.
•No Natural Satellite & no atmosphere
•Two Spacecrafts visited one is Mariner 10 (1970) & MESSENGER (2004)
•Average distance to the Sun : 57.6 Million Kms.
•Diameter : 4,849.6 Kms.
•Period of revolution : 88 days
•Period of rotation : 58 days 15 hrs 30 mts. 34 sec.

•It is also known as ‘Earth’s Twin’ & 'Morning Star or the Evening Star'
Hottest (Green house effect due to CO2) & Brightest
•Rotates East to West (Clockwise)
•Diameter : 12,032 Kms.
•Period of revolution : 224.7 days
•Period of rotation : 257 days (slowest)

•Equatorial diameter : 12,756 Kms.
•Polar diameter : 12,714 Kms.
•Distance from the Sun : 149,597,900 Kms.
•Period of revolution : 365 days 5 hrs, 48 mts, 45.51 sec.
•Period of rotation : 23 hrs 56 mts. 4.09 sec.
•Known as ‘Blue Planet’

 (4) MARS
•Distance from the Sun : 225.6 Million Kms.
•Period of revolution : 687 days
•Period of rotation : 24 hrs 37 mts. 22.663 sec.
•Known as ‘Red Planet’
•Thin atmosphere comprising of Nitrogen & Argon
•Highest mountain ‘Nix Olympia’
•Two satellites ‘Phobos’ & ‘Deimos’

•Diameter : 141,968 Kms.
•Distance from the Sun : 772.8 Million Kms.
•Period of revolution : 11.9 years
•Period of rotation : 9.8 Hrs (Fastest)
•This is the largest planet in the solar system
•Known as ‘Lord of Heavens’
•Has largest satellite of solar system ‘Gannymede’

•It was discovered by Galileo.
•Diameter : 119,296 Kms.
•Distance from the Sun : 1,417.6 Million Kms.
•Period of revolution : 29.5 years
•Period of rotation : 10.3 Hrs
•Least Density
•Spacecraft ‘Cassini’ visited
•Prominent satellite is ‘Titan’
•3 rings are present

•Diameter : 52,096 Kms.
•Distance from the Sun : 2,852.8 Million Kms.
•Period of revolution : 84 years
•Period of rotation : 16 hrs 10 mts.
•Discovered by ‘William Hershel’ (1781)
•Axial tilt is 98 degree, that is why seems flat
•Rotates East to West (Clockwise)
•Spacecraft visited was Voyager 2 (1986)

•Diameter : 49,000 Kms.
•Distance from the Sun : 4,497 Million Kms.
•Period of revolution : 165 years
•Period of rotation : 18 hrs 26 mts.
•Known as ‘Greenish Star’
•Discovered by JG Galle in 1846
Spacecraft visited was Voyager 2 (1989)

Moon is earth's satellite. Its period of rotation and Period of Revolution are the same. i.e.29 ½ days.


Earth Movement
•The Earth also called Blue Planet. It is the densest of all planets.
•Surface Area : 510,100,500 Sq.Kms.
•Land Surface : 148,950,800 Sq.Kms. (29.08%)
•Water Surface : 361,149,700 Sq.Kms.(70.92%)
•Equatorial circumference : 40,075 Kms.
•Polar circumference : 40,008 Kms
•Equatorial radius : 6,377 Kms.
•Equatorial Diameter : 1,22,756 Kms.
•Polar radius : 6,357 Kms.
•Polar Diameter : 12,714 Kms.
•Mean distance from the Sun : 14,95,97,900 Kms.
•Period of revolution : 365 days 5 hours 48 mts. 45.51 Sec.
•Period of rotation : 23 hrs. 56 mts. 4.091 Sec.
•Escape Velocity from the earth : 11 Km per Sec. (minimum)

Important Key to remember
•Earth Circumference : 40,232 Kilometers.
•Earth Perihelion : Nearest position of earth to sun. The earth reaches its perihelion on January 3 every year at a distance of about 147 million-Kilometers.
•The life of a star is spread over billions of years. It begins to form by compression of galactic gas and dust. Compression generates heat which in turn causes hydrogen to be converted into helium in nuclear fusion, thereby emitting large amount of heat and light.
•If the star is of sun’s size, it becomes a White Dwarf. Their central density can reach up to 10grams per cubic cm.
•If die star is bigger than the sun but not more than twice as big, it will turn into a Neutron Star or Pulsar. Their
•central density is 1014 grams per cubic cm. They are formed due to Novae or Super novae explosion.
•Stars having mass greater than three times that of the sun, because of their great gravitational power, have contracteso much that they have developed super density of 1016 grams per cubic cm. It is so dense that nothing, not even light, can escape from its gravity and hence called ‘Black Hole’.
•Brightest star outside our Solar System is Sirius, also called Dog Star.
•Closest star of Solar System is Proxima Centauri (4.2 light years away). Then come Alpha Centauri (4.3 light years away) and Barnard’s Star (5.9 light years away).
•Light Year : It is the distance covered by light in one year in vacuum at a speed of 3 105 km/s.
•Astronomical Unit (A.U) : It is the mean distance between the earth and the sun. One light year is equal to 60,000 A.U.
•Parsec : It represents the distance at which the mean radius of earth’s orbit subtends an angle of one second of an arc. It is equal to 3.26 light years.
•Stars are self – luminous bodies that account for 98 per cent of the material in the galaxy. The rest 2 per cent consists of interstellar or galactic gas and dust in an attenuated form.
•A star’s colour indicates the temperature of its surface. Blue colour denotes maximum temperature. Then comes yellow, then red, etc.


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