GREAT CONJUNCTION

Subject : Geography

Context : On 21 December 2020, almost all the viewers across the world seen the two gas giants very close to each other, while they will still be hundreds of millions of miles apart in space.

Concept :

• After nearly 400 years, Saturn and Jupiter – the two largest planets in our solar system were brought closest in the night sky by an astronomical event called the “great conjunction” and popularly referred to as the “Christmas Star”.
• The event coincided with the winter solstice (shortest day of the year in terms of hours of sunlight received) in the Northern Hemisphere and summer solstice in the Southern Hemisphere.

Great Conjunction

• A conjunction is not unique to Saturn and Jupiter however, it is the name given to any event where planets or asteroids appear to be very close together in the sky when viewed from the Earth.
• In June 2005 for instance, as a result of the “spectacular” conjunction, Mercury, Venus and Saturn appeared so close together in the sky that the patch of sky where the three planets were could be covered by a thumb.
• Astronomers use the word “great” for the conjunction of Jupiter and Saturn because of the planets’ sizes.
• The “Great Conjunction” happens once in about 20 years because of the time each of the planets take to orbit around the Sun. Jupiter takes roughly 12 years to complete one lap around the Sun and Saturn takes 30 years (Saturn has a larger orbit and moves more slowly because it is not as strongly influenced by the Sun’s gravitational force as planets that are closer to the Sun).
• As the two planets move along their orbits, every two decades, Jupiter catches up with Saturn resulting in what astronomers call the great conjunction.
• Every two decades Jupiter–which can be thought of as a fast runner on the inside track of a racecourse–will overtake Saturn.
• This overtaking is what viewers on Earth witnessed on the night of 21 December 2020, when the planets appeared aligned in the sky, while they will still be millions of miles apart in space.