What is Great Conjunction?

Great Conjunction happens when two planets seem to be closest in the sky. The word Conjunction is used to explain meetings of planets and the rest of the objects on our sky’s dome. Astronomers use the term, Great Conjunction to explain the meetings of Jupiter and Saturn, which are the 2 biggest planets in our solar system. However, these two planets will look hugely close together on the sky’s dome now, but they are 456 million miles (734 million km) away from each other.

In 1610, while pointing the telescope towards the sky, Italian astronomer Galileo Galilei discovered the four moons of Jupiter – lo, Europa, Ganymede and Callisto. In the same year, he also discovered an unusual oval surrounding Saturn, which later came out to be its rings. These discoveries transformed how people understood the far reaches of our Solar System.

Later in 1623, the solar system’s two biggest planets, Jupiter and Saturn, travelled together with each other in the sky. Jupiter bucked up and passed Saturn, in an astronomical affair known as a “Great Conjunction”. These planets regularly seem to pass each other in the solar system, with the positions of Jupiter and Saturn being on the same line in the sky, about once every twenty years.

We can visualize the solar system to be a racetrack, where all the planets are runners in their lane and the Earth sits in the centre of the stadium. Jupiter and Saturn conjunctions take place every Twenty years; Jupiter passes Saturn in its orbit. The last conjunction was in the year 2020 and before that it took place in 2000. These conjunctions are not always equal. The 2020 great conjunction of Jupiter and Saturn was the closest since 1623 and was the closest observation since 1226. 2020’s too close Jupiter-Saturn conjunction cannot be compared again until the next conjunction on March 15, 2080.

Jupiter-Saturn conjunctions can take place on any day of the year, depending on where the planets are in their orbit. The date of the conjunction can be determined by the location of Jupiter, Saturn and the Earth in their way around the Sun, however, the date of the solstice can be determined by the tilt of Earth’s axis. The solstice is the longest night of the year, so this exceptional coincidence will give people a tremendous chance to see our amazing Solar System.

For those who are willing to see this phenomenon for themselves, here is what you should do:

1.    Look for a spot with a clear view of the sky, such as a park or a field. Jupiter and Saturn are bright, so they can be viewed even from most cities.

2.    An hour after sunset, look towards the southwest sky. Jupiter will look like a bright shiny star and can be easily detectable. Saturn will be a little bit dimmer and will look a little above and to the left of Jupiter when Jupiter will overtake it and they will exchange positions in the sky.

3.    The planets can be seen with naked eyes, but if you have binoculars or a telescope, you will be able to see Jupiter’s four leg large moons orbiting the big planet.