The ‘Great Conjunction’ of our solar system’s two largest planets, Jupiter and Saturn, will take place on Monday, December 21, and will be visible from 6:30pm to 7:30pm in India. Jupiter and Saturn regularly pass each other, as often as once every 20 years, but what makes this year’s conjunction special is that it is for the first time in nearly 400 years that the two planets will be this close to one another.
The National Aeronautics and Space Administration (Nasa) has said the closest alignment will appear just a tenth of a degree apart and last for a few days, and skywatchers on earth will be able to see the conjunction with the naked eye.
The event is also occurring, purely out of coincidence, on the day of the winter solstice and will be visible an hour after sunset in the south-western sky. The conjunction is popularly known as the ‘Christmas Star’, which, according to the Bible, was the star that guided the three wise men to baby Jesus.
The ‘Christmas Star’, or the ‘Star of Bethlehem’, is believed to be the conjunction of the two gas giants and it was first viewed in 1623. Astronomers have long debated the existence of such a star but it is theorized that in the year 7 BC, Jupiter and Saturn had three conjunctions in the same constellation, which could explain what the star actually was.
Apart from being the first time in nearly 400 years the planetary giants have been this close to one another, this is also the first time in 800 years that the alignment will occur at night.
“You can imagine the solar system to be a racetrack, with each of the planets as a runner in their own lane and the Earth toward the centre of the stadium,” Henry Throop, an astronomer with the Planetary Science Division at Nasa Headquarters in Washington, was quoted as saying by Nasa. “From our vantage point, we’ll be able to be to see Jupiter on the inside lane, approaching Saturn all month and finally overtaking it on December 21,” Throop said.
The timing of the conjunction, as per Nasa, is going to be such that nearly everyone in the world will be able to witness the stellar event.
“Conjunctions like this could happen on any day of the year, depending on where the planets are in their orbits,” said Throop. “The date of the conjunction is determined by the positions of Jupiter, Saturn, and the Earth in their paths around the Sun, while the date of the solstice is determined by the tilt of Earth’s axis. The solstice is the longest night of the year, so this rare coincidence will give people a great chance to go outside and see the solar system,” he added.
Apart from the great conjunction, 2020 has been witness to several celestial phenomena like the Geminids meteor shower, the total solar eclipse and the Ursoid meteor shower.