Jupiter and Saturn will appear closer together in the sky than they have at any point for 800 years next month.
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 in late December.
When and how can I see it?
The planets will be visible around 30 to 45 minutes after sunset on 21 December.
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 21 December 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.
And if you miss it, you’ll have something of a wait before it happens again, as the next one is not 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.”