Solar System: Geography UPSC

Universe and Solar system Planets information

Solar System: The Solar System is the gravitationally bound system of the Sun and the objects that orbit it, either directly or indirectly.


  • Cosmic energy engines which produce heat, light, ultraviolet rays, x-rays, and other forms of radiation.
  • Composed largely of gas and plasma, a superheated state of matter composed of subatomic particles
  • Luminosity: Brightness-a factor of how much energy they put out
  • The primary building block of stars: Hydrogen


  • The Earth’s only natural satellite
  • was formed 4.6 billion years ago around some 30–50 million years after the formation of the solar system
  • It is in synchronous rotation with Earth meaning the same side is always facing the Earth
  • The rise and fall of the tides on Earth are caused by the Moon: There are two bulges in the Earth due to the gravitational pull that the Moon exerts; one on the side facing the Moon, and the other on the opposite side that faces away from the Moon, The bulges move around the oceans as the Earth rotates, causing high and low tides around the globe.
  • A person would weigh much less on the Moon: The Moon has much weaker gravity than Earth, due to its smaller mass, so you would weigh about one-sixth of your weight on Earth.
  • The Moon has quakes: These are caused by the gravitational pull of the Earth. Lunar astronauts used
    seismographs on their visits to the Moon and found that small moonquakes occurred several kilometers beneath the surface, causing ruptures and cracks. Scientists think the Moon has a molten core, just like Earth.


  • A group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure
  • Pole Star/North Star: Indicates the north direction (Locate the position of the Pole Star with the help of the Saptarishi)


Planets do not have their own heat and light and are lit by the light of the stars. A planet is a celestial body that:

  • is in orbit around the Sun
  • has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and has cleared the neighborhood around its orbit.

Planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

  • Pluto now falls into the dwarf planet category on account of its size and the fact that it resides within a zone of other similarly sized objects known as the transneptunian region.
  • Planets with rings: Jupiter, Saturn, and Uranus have rings around them – belts of small debris
  • Smallest planet: Mercury
  • Largest planet: Jupiter
  • Inner planets: Mercury, Venus, Earth, and Mars
  • Outer planets: Jupiter, Saturn, Uranus and Neptune
  • Planet Orbit: An orbit is a path an object takes in space as it revolves around another object. While a planet travels in one direction, it is also affected by the Sun’s gravity causing it to take a curved route that eventually brings it back to its starting point. This complete revolution equates to a single orbit.

Milky Way Galaxy

  • Our solar system is a part of this galaxy
  • Ancient India: Was imagined to be a river of light flowing in the sky and thus, named Akash Ganga.


  • The center of the solar system and is made up of extremely hot gases; is the ultimate source of heat and light for the solar system
  • Provides the pulling force that binds the solar system
  • Contains more than 99.8% of the total mass of the Solar System (Jupiter contains most of the rest)
  • The Sun is, at present, about 70% hydrogen and 28% helium by mass everything else (“metals”) amounts to
    less than 2%. This changes slowly over time as the Sun converts hydrogen to helium in its core.
  • Light travels at the speed of about 300,000 km per second—the light of the sun takes about eight minutes to reach the earth.


  • The third nearest planet to the Sun
  • Fifth largest planet
  • Geoid shaped: It is slightly flattened at the poles and that is why its shape is described as a Geoid (an earth-like shape)
  • Blue Planet: its two-thirds surface is covered by water.


  • Natural Satellite: A celestial body that moves around the planets in the same way as the planets move around the sun.
  • Human-made Satellite: An artificial body designed by scientists to gather information about the universe or for communication. It is carried by rocket and placed in the orbit around the earth.


  • Numerous tiny bodies moving around the sun
  • Found between the orbits of Mars and Jupiter
  • Largest asteroid: Ceres


  • Small pieces of rocks moving around the sun
  • Some meteors while entering the Earth’s surface with a flash of light signifying the air getting heated up due to friction
  • Sometimes these meteors without being completely burnt to fall on the earth and creates a hollow.

Get detailed Article on Solar System planets information: Click Here

References: NCERT Geography, Certificate Physical And Human Geography: G C Leong


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