Google’s latest Doodle celebrates both the Winter Solstice and the Great Conjunction of Jupiter and Saturn.
The animated graphic, made in collaboration with NASA, shows the two cartoon planets high-fiving as they closely align.
For the first time in 800 years, and on the same day as the Northern Hemisphere’s first day of winter, the two largest planets in our solar system will nearly overlap to form a “double planet”.
Here’s everything you need to know about the celestial event - and how you can view it for yourself.
What is the Great Conjunction?
Jupiter and Saturn are set to closely align in the night’s sky, in a once-in-a-lifetime phenomenon, to form a “Christmas Star”.
It’s a rare event, known as the Great Conjunction by astronomers, which sees the two planets crossing so closely that they appear to merge.
Experts have predicted that Jupiter and Saturn will be separated by less than the apparent diameter of the moon.
The last time the two planets appeared this close was way back in the 13th century, and NASA doesn’t predict another alignment this close for another 60 years.
Although they will look closely aligned from Earth, Jupiter and Saturn will actually be approximately 450 million miles apart.
Why is it called the ‘Christmas Star’?
The phenomenon has also been nicknamed the Christmas Star or Star of Bethlehem since it will happen during the festive period.
In the Bible, the Christmas Star was what the wise men used as a guide to help them find the birthplace of Jesus.
What the actual bright light was has been debated for many years - with one possible explanation being a rare alignment of multiple planets, just like this Great Conjunction.
When do the planets align - and how can I see it?
The Christmas Star will be visible from Earth, with the help of a clear night’s sky.
The two planets will line up to create a bright light on Monday 21 December - the same date as the winter solstice.
Stargazers can expect to see the phenomenon low in the western sky shortly after sunset, meaning people in the UK should be on the lookout from 3.54pm.
It is bright enough to be seen without the use of telescopes or binoculars, yet astronomers say several of the planets’ satellites will be visible with viewing aides.
What is the Winter Solstice?
The Winter Solstice marks the shortest day of the year - the day with the fewest sunlight hours - and it is widely regarded as the first day of winter in the Northern Hemisphere.
It always happens in December, though its timing varies slightly with every passing year.
The number of daylight hours on the shortest day amounts to 7 hours, 49 minutes and 42 seconds - some 8 hours, 48 minutes and 38 seconds shorter than the summer solstice, when daylight hours are at a maximum.
Solstice comes from the Latin word ‘solstitium’ which means ‘sun stands still’.
The winter solstice is an important time of the year for many cultures historically, with people still flocking to Stonehenge to celebrate the winter and summer solstices and get a glimpse of the sun’s rays beaming through the ancient stones.
When is the winter solstice in 2020?
This year’s winter solstice - the point where the sun is lowest in the sky - will take place on Monday 21 December, on the same day as the Great Conjunction.
According to the Royal Museum Greenwich website, the actual moment of the solstice will take place around 10.02am on 21 December across the UK.