On December 21, Jupiter and Saturn will line up to create what is known as the “Christmas Star” or “Star of Bethlehem.”
It is said that the event will coincide 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
The event occurs roughly every 19 to 20 years and is exceptionally rare because of how close the planets will appear to be to one another. Also, It’s around 800 years since they were so easily visible.
According to Forbes, It’s called a “great conjunction” because Jupiter and Saturn are the two largest planets in the Solar System, and to the naked eye they’ll look like a single bright star.
A star-sighting of this magnitude won’t occur next again until the year 2080. Stargazers must be ready with their telescopes about 45 minutes after sunset to see the planets align on December 21.
According to Indian Express, Jupiter and Saturn are bright planets and can be typically seen with the naked eye even from cities. But during a conjunction, they appear to be close to each other, which is what makes the event noteworthy.
NASA says that the planets will either look like an elongated star or that they will form a double planet.