Article by ITV Wales journalist Kelsey Redmore
Monday evening will see the peak of the conjunction of the planets Jupiter and Saturn in the night sky, where the planets will appear as one object, also known as the 'Christmas Star'.
This rare event, also known as 'The Greatest Conjunction' of the planets will coincide with the Winter Solstice - the shortest day of the year.
Dark Sky Wales says the last time this phenomena was observed was 400 years ago during the day. The last night time observation took place in 1623 - 800 years ago - just 13 years after the Italian astronomer Galileo turned his telescope to the sky.
If the weather conditions are right, you can even photograph the conjunction, where the planets will appear close together.
Will I be able to see the 'Christmas Star' in Wales?
The 'Christmas Star' will peak on Monday evening, but clear conditions are needed to get a good view of the conjunction of Jupiter and Saturn in the night sky.
The Met Office has currently forecast cloud and rainfall this evening for most of Wales, meaning that many may not be able to see the planets together.
For your best chance of spotting the 'Christmas Star', Dark Sky Wales recommends doing the following:
Find a spot with an unobstructed view of the south western horizon;
Just after sunset, begin to look for a bright object beginning to appear (this will improve as the sky darkens, about 45 minutes after sunset);
A telescope or binoculars will then show the Jupiter as a point of light with its largest moons visible and Saturn as an elongated cigar-shaped object.
Telescopes will improve the view and show the bands of Jupiter and the rings of Saturn.
Royal Observatory Greenwich Astronomer, Hannah Baynard said: "Tonight, Jupiter and Saturn will appear so close together in the sky they will almost look like one object.
"The two gas giants will be only 0.1 degrees apart, the closest since 1623. The great conjunction will be visible nationwide, look towards the Southwest after sunset quite low on the horizon to see the pair.
"A great conjunction occurs every 20 years however they are not always observable and the two planets are not usually this close together. This is the closest they have been since 1623, when it was difficult to see them as they were close to the sun. A great conjunction this close together has not been easily seen in almost 800 years."