If you love astronomy, then the most awaited day of the year has arrived. Two astronomical events will take place on December 21: the winter solstice and the great conjunction. While the winter solstice occurs every year when the Sun directly shines over the Tropic of Capricorn, the great conjunction is rare, taking place after every 20 years on average. Today, Google shared a doodle on the alignment of these two cosmic events. Here’s everything you need to know:

The Great Conjunction

Astronomers use the word conjunction to describe two celestial objects’ close approach as seen from the Earth. Great conjunction refers to Jupiter and Saturn’s close approach, two of the biggest worlds in our solar system. 

Great Conjunction
Jupiter and Saturn captured by astrophotographer Nikunj Rawal from Gujarat on December 20, 2020

What really happens in the solar system?

The rarity of great conjunctions is due to the slow-motion of Jupiter and Saturn across the sky. Among the planets visible to the naked eye, they are the two most distant from the Sun, taking 11.86 years and 29.5 years respectively to orbit it. As the two planets gradually move through the constellations at different speeds, they follow almost the same path across the sky, called the ecliptic. Annually, Jupiter completes 30 degrees of its orbit around the Sun. On the other hand, Saturn sweeps 12 degrees. Thus, Jupiter reduces Saturn’s gap and itself by (30-12) 18 degrees every year. So Jupiter laps the ringed beauty every 20 years on average.

Video: Top Astronomy Events In 2021

How to watch the great conjunction?

On 21 December at 13:30 UT, Jupiter will be 0.1° south of Saturn. The gas giant will appear together in a telescopic view. It’ll be the first Jupiter-Saturn conjunction since the year 2000 and the closest Jupiter-Saturn conjunction since March 1226. The next conjunction will take place in 2040. But this year’s conjunction won’t be matched until March 15, 2080.

Google Shares a Doodle On The Great Conjunction. Here's What You'll See In The Sky Tonight. 2
Saturn and Jupiter will almost ‘kiss’ each other on December 21 (Image: Dominic Ford, in-the-sky)

To spot Jupiter and Saturn, look in the south-west direction soon after sunset. The two beasts of the solar system will almost appear like a double star in the constellation of Capricornus. The brighter one is Jupiter. The planets will fit together in the field of a telescope, along with some of their moons. You can use these space apps to quickly locate the planets according to the place you live in.

The Winter Solstice

Also known as the first day of winter in the north, the Winter Solstice is when the Sun reaches its southernmost point in the sky. On this day, if you stand on the Tropic of Capricorn, you’ll see the Sunrise exactly in the East and sunset in the West. It’s the first time of the year when the Sun is over the Tropic of Capricorn.

Winter Solstice

On Winter Solstice, the northern hemisphere experiences the shortest day and the longest night of the year. In the south, it’s the opposite. From here on, the nights will start getting shorter in the north. The duration of a day and night will be equal on the spring equinox in March.

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