Universe: The Physics of Universe

Universe is the limitless expanse of space around us consisting of solar system. star, galaxies etc.
Solar System

Solar system is a family of nine planets, satellites, asteroids, comets, meteors, meteroites and dust particles orbiting around the Sun.
(1) Planets : Nine planets revolving around the sun in elliptical orbits. In order of increasing distance from Sun, these are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
(i) The gravitational pull of the Sun on the planets control their motion.
(ii) There are other heavenly bodies (about 32) which revolve around the planets called satellites (or moons) of the planets.
(iii) A planet does not emit light of its own.
(iv) A planet do not twinkle at night.
(v) The planets are very small in size as compared to stars or Sun.
(vi) The relative positions of planets keep on changing day by day.
(vii) Most of the planets move around the sun from west to east.
(viii) The planets are made of rocks and metals.
(ix) The temperature of planet depends upon its distance from sun.
(2) Asteroids : The small pieces of planet revolving around the sun between orbits of Mars and Jupiter are called Asteroids.
(i) Astronomers have identified about 2000 asteroids ranging from the largest 770 km diameter to bodies 1.5 km in diameter.