Jupiter and Saturn are about to line up in a way not seen since the Middle Ages

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Jupiter and Saturn are about to line up in a way not seen since the Middle Ages

Next month, Jupiter and Saturn will appear closer in the night sky than at any point since the Middle Ages.

The two gas giants will be just 0.06º apart, forming an incredible ‘double planet’ that will give stargazers the rarest of treats. Known as the Great Conjunction, the celestial event will take place on the night of December 21, 2020.

The last time these two planets were this close together was back in 1623 – but at 13º east of the sun, nobody would have seen it.

If you’re looking for a Great Conjunction that was visible, you’d have to go even further back to March 4, 1226. (800 years ago.)

"Alignments between these two planets are rather rare, occurring once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets will appear to one another," said Rice University astronomer Patrick Hartigan in a statement.

The approach of the two planets has been going on since the summer. As it reaches its peak, between 16 December and Christmas Day, they will be separated by less than the width of a full Moon.

"On the evening of closest approach on Dec 21 they will look like a double planet, separated by only 1/5th the diameter of the full moon," said Professor Hartigan.

The two planets should be visible to anyone on Earth, as long as the weather allows an unrestricted view. But the best visibility will come about an hour after sunset – when the planets will appear low in the western sky – and will look better nearer the equator.

If you do miss it, you’ll have another chance to catch Jupiter and Saturn forming a ‘double planet’ later this century. Set a reminder in your diary for March 15, 2089.