Jupiter Saturn Great Conjunction | 07 Dec 2020

Why in News

In a rare celestial event, Jupiter and Saturn will be seen very close to each other (conjunction) on 21st December 2020, appearing like one bright star.

Key Points

  • Conjunction: If two celestial bodies visually appear close to each other from Earth, it is called a conjunction.
  • Great Conjunction: Astronomers use the term great conjunction to describe meetings of the two biggest worlds in the solar system, Jupiter and Saturn.
    • It happens about every 20 years.
    • The conjunction is the result of the orbital paths of Jupiter and Saturn coming into line, as viewed from Earth.
      • Jupiter orbits the sun about every 12 years, and Saturn about every 29 years.
    • The conjunction will be on 21st December, 2020, also the date of the December solstice.
    • It will be the closest alignment of Saturn and Jupiter since 1623, in terms of distance. The next time the planets will be this close is 2080.
    • They will appear to be close together, however, they will be more than 400 million miles apart.
  • Jupiter:
    • Fifth in line from the Sun, Jupiter is, by far, the largest planet in the solar system – more than twice as massive as all the other planets combined.
      • Jupiter, Saturn, Uranus and Neptune are called Jovian or Gas Giant Planets. These have thick atmosphere, mostly of helium and hydrogen.
    • Jupiter’s iconic Great Red Spot is a giant storm bigger than Earth that has raged for hundreds of years.
    • Jupiter rotates once about every 10 hours (a Jovian day), but takes about 12 Earth years to complete one orbit of the Sun (a Jovian year).
    • Jupiter has more than 75 moons.
      • The planet Jupiter's four largest moons are called the Galilean satellites after Italian astronomer Galileo Galilei, who first observed them in 1610.
      • These large moons, named Io, Europa, Ganymede, and Callisto, are each distinctive worlds.
    • In 1979, the Voyager mission discovered Jupiter’s faint ring system.
    • Nine spacecraft have visited Jupiter. Seven flew by and two have orbited the gas giant. Juno, the most recent, arrived at Jupiter in 2016.
  • Saturn:
    • Saturn is the sixth planet from the Sun and the second largest planet in the solar system.
    • Saturn takes about 10.7 hours to rotate on its axis once - a Saturn “day” - and 29 Earth years to orbit the sun.
    • Saturn has 53 known moons with an additional 29 moons awaiting confirmation of their discovery - that is a total of 82 moons. It has the giant moon ‘Titan’.
    • Saturn has the most spectacular ring system, with seven rings and several gaps and divisions between them.
    • Few missions have visited Saturn: Pioneer 11 and Voyagers 1 and 2 flew by; But Cassini orbited Saturn 294 times from 2004 to 2017.