Over the last few weeks you may have noticed two bright lights just above the horizon in the early evening sky when looking in a south-westerly direction.
These are not stars but planets – Jupiter and Saturn. There is nothing new about the presence of these two planets, however what is exciting is that they are moving closer and closer together until they will ‘meet’ in what is known as a Great Conjunction on December 21st, the summer solstice (for the southern hemisphere).
Jupiter and Saturn conjunctions occur every 20 years due to the difference in how long it takes each planet to orbit the sun. Jupiter takes nearly 12 years to orbit the sun whereas Saturn takes nearly 30 years. This means that for every year that these planets orbit, Jupiter catches up to Saturn bit by bit until the giant ball of gas overtakes the ringed gem. The result? An elongated double star, presumably extremely bright.
You may be thinking, “Well this happens every 20 years so it’s not that special.”
Well, a conjunction does happen every 20 years, however the timing is not always so perfect. For example the last conjunction took place near the sun making the phenomena difficult to view. In fact this year’s Great Conjunction will be the closest observable one since 1226 and it will not be matched until 2080!
A lot of the time these astronomical spectacles are hyped up only to reveal something a bit disappointing unless you’re sitting behind Hubble’s space telescopes. But even if the Great Conjunction of Jupiter and Saturn is not as visually mesmerising as we imagine it to be, there is something quite profound and alluring about watching the two biggest planets in our solar system dancing toward one another and embracing on the shortest night (southern hemisphere) or longest night (northern hemisphere) in the calendar year. So do yourself a favour, whip out your binoculars on the 21st and watch the Great Conjunction of Jupiter and Saturn.