Length of a Day on Each Planet | 04 Nov 2019

Why in News

  • Recently, the research was undertaken to calculate the accurate length of a day on Venus and Saturn which has been changing since 1963.
    • Venus:
      • The recent observation of the Magellan spacecraft’s observations (1991) concluded that the rotation period for Venus has an uncertainty of about 9 seconds.
    • Saturn:
      • The recent, the Cassini spacecraft showed that there is an uncertainty of 6 minutes with a rotation period of Saturn.

The Solar System

  • The Solar System consists of the Sun and eight planets.
    • It also consists of bodies such as comets, asteroids, and meteors.

Planets vs Dwarf Planets

  • The definition of a planet was adopted by the International Astronomical Union in 2006. A planet must:
    • Orbit a star (in our system, it is the Sun).
    • Be big enough to have enough gravity to force it into a spherical shape.
    • Be big enough that its gravity cleared away any other objects of a similar size near its orbit around the Sun.
  • On the other hand, dwarf planet is a celestial body orbiting a star that is massive enough to be rounded by its own gravity but has no clear orbit (Gravitationally not dominant in its orbit).

Planets Facts
Mercury
  • It is the nearest to the Sun and also the smallest planet in our solar system.
  • It has no satellite of its own.
  • It takes 1408 hours to complete a rotation.
Venus
  • It is called morning or an evening star, although it is not a star.
  • Sometimes it is called as Earth’s twin.
  • Venus has no moon or satellite of its own.
  • It rotates from east to west while the Earth rotates from west to east.
  • It takes 5,832 hours to complete a rotation.
Earth
  • The Earth is the only planet in the solar system on which life is known to exist.
  • The axis of rotation of the Earth is 23.5 degrees relative to the orbital plane – the plane of Earth’s orbit around the sun. The tilt is responsible for the change of seasons on the Earth.
  • The Earth has only one moon.
  • The Earth takes 24 hours to complete a rotation.
Mars
  • It appears slightly reddish and, therefore, it is also called the red planet.
  • Mars has two small natural satellites.
  • It takes 25 hours to complete a rotation.
Jupiter
  • Jupiter is the largest planet of the solar system.
  • Jupiter has 53 named satellites and another 26 awaiting official names.
  • It also has faint rings around it.
  • It takes only 10 hours to complete a rotation.
Saturn
  • The Saturn is yellowish in colour.
  • It has an icy ring around it.
  • It has more than 60 known moons.
  • It takes 11 hours to complete a rotation (second-shortest day in the solar system).
Uranus
  • Uranus also rotates from east to west (like Venus).
  • It has a highly tilted rotational axis.
  • It takes 17 hours to complete a rotation.
Neptune
  • It is the eighth and most distant planet in our solar system.
  • The Neptune is dark, cold and has a presence of supersonic winds.
  • It takes 16 hours to complete a rotation.

    Source: IE