Chemical Composition
    The Sun is composed primarily of the chemical elements hydrogen (74.9%) and helium
    All heavier elements, called metals in astronomy, account for less than 2% of the mass.
    The most abundant metals are oxygen (roughly 1% of the Sun"s mass), carbon (0.3%), neon
     (0.2%), and iron (0.2%).
    Planet word comes from Greek (astēr planets), which means wandering star.
    Planets are heavenly bodies, which revolve around the Sun in elliptical orbits.
    There are 8 planets in the solar system.
    The 8 planets in order of increasing distance from the Sun are Mercury, Venus, Earth,
     Mars, Jupiter, Saturn, Uranus, and Neptune.
    The arrangement of the planets according to their sizes in increasing order is Jupiter,
     Saturn, Uranus, Neptune, Earth, Venus, Mars and Mercury.
Classification of Planets
    The 8 planets are classified into 2 main groups. These are inner planets and outer
    Between Inner & Outer Planets, there is a ring of small bodies, which are made of rock &
     metal, these are called Asteroids. They also keep moving around the Sun .This ring is also
     called Asteroids Belt.
                INNER PLANETS                                     OUTER PLANETS
They are also called as Terrestrial planets.     They are also called as Gas giants or Jovian.
Mercury, Venus, Earth and Mars                   Jupiter, Saturn, Uranus, and Neptune
They are nearer to the Sun.                      They are far away from the Sun.
They have greater density.                       They have smaller density.
They spin slowly.                                They spin quickly.
They orbit the Sun quickly.                      They orbit the Sun slowly.
They have few moons.                             They have lots of moons.
These planets are quite solid and are made up of These planets are not really solid and are made up
rock and metals.                                 of gases.
Biggest planet                   Jupiter
Smallest planet                  Mercury
Hottest planet                   Venus
Coldest planet                   Neptune
Fastest rotating planet          Jupiter
Slowest rotating planet          Venus
Heaviest planet                  Jupiter
Lightest planet                  Mercury
Closest planet to Sun            Mercury
Farthest planet from Sun         Neptune
High dense planet                Earth
Low dense planet                 Mars
Red Planet                       Mars
Green Planet                     Uranus