Christmas Star - the Great Conjunction of Jupiter and Saturn

An amazing astronomical event will happen next week that hasn’t been seen by human eyes for eight centuries.

Thursday, 17th December 2020, 2:49 pm

Weather permitting, in a year like no other, the forthcoming winter solstice will itself be like no other as we gaze at The Great Conjunction of Jupiter and Saturn - the two biggest planets in the solar system. The resulting spectacle has been labelled ‘the Christmas Star’.

When Irish eyes last gazed upon such an otherwordly sight, Henry III was on the English throne and Richard Mor deBurgh was just embarking on the Norman conquest of Connacht, a bloody campaign that lasted for nine years. William Shakespeare, arguably the greatest playwright ever, wouldn’t be born for over 300 years when two mighty planets last put on such a wonderful show as we hope to see on December 21.

Jupiter and Saturn (pictured) will appear closer together in the sky than they have at any point since 1226.

In an astronomical event known as the Great Conjunction of Jupiter and Saturn, the two distant planets will appear to almost touch in the night sky.

When and how can I see it?

The planets will be visible around 30 to 45 minutes after sunset on December 21.

Observers should look 10 degrees above the south-southwest horizon to catch a glimpse of the spectacle.

It will be visible to the naked eye, but will look better through telescopes – even binoculars will make some difference.

The time of sunset on December 21 will differ slightly depending on your location in the UK, but is expected to be at 15:39 in Edinburgh, 15:53 in London, 15:59 in Belfast and 16:06 in Cardiff.

While they will seem closest on this date, the two gas giants have been appearing progressively closer together since summer, and you can track their progress until the night of the great conjunction.

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

“For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening.

“The further north a viewer is, the less time they’ll have to catch a glimpse of the conjunction before the planets sink below the horizon.”

Next conjunction not until 2080

The chance to see the two planets in conjunction is a rare one, with this opportunity coming around after 800 years.

If you miss it, you won’t have just as long to wait before it happens again - but the next one is due to happen until March 2080!

Patrick Hartigan, an astronomer at Rice University, explained:

“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.

“You’d have to go all the way back to just before dawn on March 4, 1226, to see a closer alignment between these objects visible in the night sky.”