The Christmas Star - Historic Conjunction Of Jupiter and Saturn

Great Conjunction Christmas star
Raysastrophotograhy, CC BY-SA 4.0, via Wikimedia Commons

Stargazers are in for an end of the year treat as Jupiter and Saturn come together in vibrant planetary conjunction, which will be visible in the night sky on the 21st of December. 

In 1610, two years after the telescope was invented, Galileo Galilei, the inventor, discovered the four moons of Jupiter, and also Saturn’s rings. Thirteen years later, in 1623 for the first time ever recorded, Galileo with his telescope saw an astronomical marvel. Jupiter caught up to and passed by Saturn, in an event now known as “The Great Conjunction”.  This celestial event will only occur next in 2080. 

According to Nasa, the timing of the conjunction will be such that everyone will be able to view it. If viewed through a telescope, one might even be able to see four of Jupiter’s moons. In India, the conjunction will likely be visible to the naked eye between 6:30-7:30 pm, that is after the sunsets. 

As to why this phenomenon is known as the ‘Christmas Star’, legend says that though these planets will be far apart, they will appear as one large star, like that of the Christmas Star or the Star of Bethlehem in the sky the night Jesus Christ was born. This conjunction will also coincide with the December solstice, the shortest day of the year in the northern hemisphere and longest in the southern. 

What makes this event extraordinary? NASA (National Aeronautics and Space Administration) says, "It's been nearly 400 years since the planets passed this close to each other in the sky, and nearly 800 years since the alignment of Saturn and Jupiter occurred at night, as it will for 2020, allowing nearly everyone around the world to witness this 'Great conjunction'".  

Jupiter and Saturn will be separated by just "0.1 degrees or about one-fifth the apparent width of the Moon".