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Article Index
Universe and Solar System
Facts about Planets
Asteroids
All Pages

 

Universe and Solar system


  • Universe includes all the universal bodies and the complete solar family which comprises the sun, moon, planets, comets, planetoids etc.
  • The study of universe is known as Cosmology.
  • Origin of the universe is explained by the Big Bang Theory, formulated and proposed by Belgian astronomer and cosmologist Georges Lemaitre after his becoming acquainted with the findings of the American astronomers Edwin P. Hubble and Harlow Shapley on the expanding universe.
  • According to the Big Bang was an explosion occurred 15 billion years ago, leading to the formation of galaxies of stars and other heavenly bodies.
  • Since then, all the galaxies have been flying away from each other causing expansion of the universe
  • Light year is the unit of distance that is used in case of measuring distance in universe. It is equal to the distance travelled by light in one year.

Galaxy                    

  •  A galaxy is a vast system of billions of stars, which also contains a large number of gas clouds (mainly of hydrogen gas) and dust, isolated in space from similar systems.
  • There are about 100 billion galaxies (1011 galaxies) in the universe, and each galaxy has on an average 100 billion stars (1011 stars). So, the total number of stars in the universe in 1022 stars.
  • The Milky Way Galaxy is the home of the Earth and our Solar System. It is spiral in shape.

Star

  •  Clumps of dust and gas in a nebula come together due to their own gravity and form stars.
  • There are millions of stars.
  • Stars are made of hot burning gases.
  • They emit light of their own.
  • They 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

  • The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it
  • The earth is a member of a celestial group called Solar system
  • This group comprises of the sun, the eight planets and their satellites (or moons), and thousands of other smaller heavenly bodies such as asteroids, comets and meteors.
  • Initially Pluto was considered as the ninth planet.
  • The sun is at the centre of the solar system all these bodies revolves around sun
  • The planets and other heavenly bodies apart from Sun do not have light of their own.
  • The motion of all the members of the solar system is governed mainly by the gravitational force of the sun.
  • The planet nearest to the sun is Mercury and the planet farthest from the sun is Neptune.
  • Sun accounts for almost 99.9% of the matter in the whole solar system.
  • Sun is  the source of all the energy in the solar system, it is composed of 71% Hydrogen, 26.5% Helium and 2.5% other elements
  • The main source of energy in the sun is nuclear fusion of Hydrogen.
  • It has a surface temperature of about 60000 C and the temperature at the centre is around 15,000,0000 C.
  • The Sun is about 150 million kms away from the Earth.
  • The sequence of planets according to their distance from the Sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
  • The sequence of planets according to their size (in descending order i.e. from big to small) is Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury
  • The eight planets have been divided into two groups i.e. “Terrestrial” and “Jevian”
  • Mercury, Venus, Earth and Mars are called terrestrial planets, because their structure is similar to the earth
  • The four inner or terrestrial planets have dense, rocky compositions, few or no moons, and no ring systems.
  • The four smaller inner planets, Mercury, Venus, Earth and Mars, also called the terrestrial planets, are primarily composed of rock and metal.
  • The “Jevian” planets have ring around them and have large number of natural satellites
  • The two largest, Jupiter and Saturn, are composed mainly of hydrogen and helium; the two outermost planets, Uranus and Neptune, are composed largely of ices, such as water, ammonia and methane, and are often referred to separately as "ice giants".


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