Galaxy, Stars, Asteroids, Planets, Satellites:

v   Galaxy (Greek = galaxies means milky): It is massive, gravitationally bound system that comprises of stars, stellar, remnants and interstellar material.

Galaxies as per of two sizes:

ð  Dwarfs: about ten millions stars.

ð  Giant: hundred trillion stars.

  There are about 170 billion galaxies in the universe.

v   Stars: Star is a massive, luminous, ball of plasma that is held together by gravity.

v   Asteroids: Class or combination of various objects present in the solar system but lying in the orbits to various planets.

v   Planets: Celestial objects that are present around sun (they revolves round sun) and they capable of generating their own gravitational field.

v   Satellites: Satellites are the objects placed into orbits around planets.

Satellites are of two kinds:

                                       => Natural satellite.       E.g.: Moon.

=> Artificial satellite.    E.g.: Sputnik in   1957(Russia)

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