Saturn-Jupiter conjunction is the second closest after 1609; next such event will be after 80 yrs

Manasi Saraf Joshi

Pune, December 19, 2020: The second closest conjunction of Jupiter-Saturn after 1623 will be seen on Monday in the sky when the two huge planets will be seen close to each other. Both the planets will be just about 0.1 degrees or 06’06”(six minutes and six seconds) arc from each other. 

When two planets are seen close to each other in the sky the event is called conjunction (of planets). A conjunction of the two giant Jupiter and Saturn is called great conjunction.

“On 21st at 11:50 PM, IST the angle between the two planets will be just about 0.1 degrees or 06’06” (six minutes and six seconds) of arc from each other. For comparison, the angle between the two sides of the Moon is 0.5 degrees”, said director of Nehru Planetarium Arvind Paranjpye.

He further said, “This will be a very special event. The planets will be so close to each other that it will be extremely difficult, if not completely impossible to see them separately with the naked eyes. For reference, Alcor and Mizar of Ursa Major, the Great Bear ( known as Vasishtha and Arundhati of the Saptarshi tara mandala in Indian astronomy) are separated by 12 minutes of arc. Sighting of Alcor and Mizar as two separate stars has been considered as a test for good eyesight.

“This is the second closest conjunction of these two planets since the invention of the telescope in 1609. On 16 July 1623, the two planets were 5’10” from each other”, he informed.

“The ability of human eyes (without any optical aid) is that one can see objects as close as 0.025 degrees apart or just about 5% the size of the Moon. However, due to various physiological issues and age factor, this ability deteriorates”, Paranjpye explained.

Where to look for the planets:

From 20 to 23 December, both the planets will be so close together that it will not be easy to distinguish one from the other. The orbital period of Jupiter is 11.86 years and that of Saturn is 29.5 years. The combined effect of their travel around the Sun is that great conjunction takes place periodically in about 19 years and 7 months. However, the separation between the two varies from one conjunction to the other.

In the past, there were two other occasions when the planets were so close that one could not have seen them separately with the naked eye. The first was on 24 October 1682 (separation was 15’25”) and the second was on 9 February 1683 when the separation was 11’33”. This was because both Jupiter and Saturn were going through their retrograde motions.

The planets will again come this close, actually slightly closer, on 15 March 2080 when they will be separated by 06’01”.

There is no harm what so ever of this conjunction on humankind. The effect of this less than a person with 100 kg standing next to you. If at all it will give you a pleasure witnessing a phenomenon that no one will see for the next 60 years.

People’s participation in the Survey 

All one has to do is to look for the planets above the western horizon about 40 minutes after the sunset. If the sky is clear then it should be possible to see the planets well above the horizon. Now one must check if he or she can see the planets separately and convey the observations by clicking on the link below by filling the form

https://docs.google.com/forms/d/e/1FAIpQLSciN6yNkhpPcABfpJfjEObcpSlgC5hXJGQvJKcVr1PO1cOqA/viewform

Observations are to be made with the naked eye for the purpose of this exercise. One may start right from today and continue till 23 December.

One should fill the form every time he or she observes the planet.

Please do join this exercise and invite your friends and groups to participate in the once in a lifetime exercise.