December 21st should always be around the calendar, as it marks Winter Solitis – the smallest day of the year.

From tomorrow the days start to get longer, which means more time in daylight and less time in darkness.

However, this year’s date is even more special because we are treated to a celestial event that has not been seen in 800 years.

It’s called the Great Conjugation, and it’s accepted today as a Google Doodle.

Here’s everything you need to know about it.

What is the great combination?

This month the two largest planets in the Solar System, Jupiter and Saturn, will appear very close together, as if they were merging into a light in the Earth’s sky.

The event is called the Great Conjunction, but also the Christmas Star, because it appears throughout the year.

Jupiter and Saturn have not been deployed in the sky like this since 1226, so this is a very rare occurrence.

They appear to be 0.1 degrees away or one-fifth the width of the moon. However, in reality, they are still 450 million miles apart.

When?

The event will be visible for a month.

However, the Christmas star will be easier to see on December 21st, just after sunset.

How can I see it?

If you look inside the clear sky you can see the planets without any special equipment.

However, you can get a closer look with a telescope, perhaps even on some of Jupiter’s moons or Saturn’s rings.

In addition to being in the sky above us, we can also watch space events on YouTube.

The Lowell Observatory will hold a live stream of the Great Connection Here on its YouTube channel.

Close-up views of the combination with a powerful telescope will show the stream and discuss what is happening.

How can I tell the planets separately?

Although they dissolve almost in one light, one way to distinguish between Jupiter and Saturn is to make Jupiter appear brighter.

This is because it is larger than Saturn and closer to Earth – about twice as far away as Saturn.