Geography Notes – Important Definitions – Static Science GK Material for Competitive exams

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Geography Notes

  • The study of universe is known as cosmology.
  • A galaxy is vast system of billions of stars.There are about 100 billion galaxies in the universe, and each galaxy has, on an average, 100 billion stars.
  • The Milky Way Galaxy is the home of the Earth and our Solar System. It is spiral in shape.
  • Latest known galaxy is known as Dwarf Galaxy.
  • Clumps of gas and dust in a nebula come together due to gravity and form stars. Stars are made up of hot burning gases. They emit light of their own and are very large and very hot.
  • Light takes about 4.3 years to reach us from the next nearest star Proxima Centauri.
  • The solar system consists of the Sun,the eight planets and their satellites(or moons), and thousands of other smaller heavenly bodies such as asteroids, comets and meteors.
  • The gravitational pull of the Sun keeps all the planets and other objects revolving round it. Thus the motion of all the members of the solar system is governed mainly by the gravitational force of the sun.
  • Planets revolve around the sun in elliptical orbits. Mercury, Venus, Earth, Mars are called terrestrial planets and Jupiter, Saturn, Uranus and Neptune are called gaseous planets.
  • Hydrogen and Helium are the main gases present in the Sun. Within the Sun, hydrogen is converted to helium due to nuclear fusion releasing a tremendous amount of heat and light. 
  • The outer layer of Sun’s atmosphere made up of thin hot gases, is called Corona. Corona is visible only during a total eclipse of the sun.
  • Light takes about 8.5 minutes to reach the Earth from the Sun.
  • The sequence of planets in descending order is Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury.
  • Jupiter is the biggest planet and mercury is the smallest planet of our solar system.
  • Venus is the second planet in distance from the Sun. This planet is nearest to the Earth and is also the brightest planet. Venus is known as the Evening Star’ as well as the ‘Morning Star’.
  • Venus is like the Earth in size and mass, and hence also known as the ‘Earth’s twin’. It also rotates clockwise like Uranus. It is the hottest planet of our solar system, due to veil of cloud.
  • The temperature of moon during daytime is about 100 degree Celsius and during night it drops down to about -180 degree Celsius. The light from the moon takes 1.3 seconds to reach the earth.
  • Gravitational pull of moon is one sixth of that of the earth.
  • Iron rich red soil and pink sky of mars give it the name, ‘Red Planet’.
  • Jupiter is the largest planet of the solar system. It is also known as the winter planet as its average temperature is very low. Gannymeda, satellite of Jupiter is the largest satellite in the solar system.
  • Saturn is the second largest planet in the solar system. It has bright concentric rings which are made up of ice and ice covered dust particles which revolve around it. Titan is the largest satellite of Saturn.
  • Uranus is about four times the size of the Earth.This planet appears greenish in colour because of methane gas present in its atmosphere. It rotates from east to west on its axis, which is opposite to other planets except Venus.
  • Neptune is the eighth planet of the solar system. It is surrounded by methane rings of sub zero temperature.
  • Asteroids are also known as minor planets. They are the objects that revolves around the Sun. They are mostly found between the orbits of Mars and Jupiter.

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