Jupiter and Saturn will align tonight (21 December) for the closest Great Conjunction in 800 years - which will create a phenomena some have dubbed a 'Christmas Star'
Great Conjunctions appear every 20 years, but today the two planets will appear the closest in the night sky since 1623.
It will be the first conjunction to be visible to the naked eye since 1226.
You'll have to wait until 2080 for the next one - so it's best not to miss it.
The event is sometimes called the 'Christmas Star' or 'Star of Bethlehem' as some believe the star that guided the 'three wise men' to Jesus could have been an extremely rare triple conjunction of Jupiter, Saturn and Venus.
When the planets align, they create a bright light, which gives them the appearance of a huge star.
According to astronomy journalist Dr Stuart Clark, the 'star' should be visible looking south-west at around 5pm (GMT), and will be joined by a bright crescent moon.
Patrick Hartigan, astronomer at Rice University, said it was a special event.
He said: "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 be 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.
"On the evening of closest approach on Dec 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."
But if one preacher had been correct, the event may have meant for something much more ominous than a rather delightful spectacle.
Earlier this year, Pastor Paul Begley announced that the end of the world was set to occur next Monday, a 'theory' he had concocted from a combination of the Mayan calendar and the Great Conjunction.
However, he recently backtracked on this idea, you will all be pleased to know.
In a video posted to his YouTube channel, the preacher admits he cannot be certain as to a date for the end of days, because no one knows that but the big man upstairs. Which seems fair.
He says: "The end is near, I'm just gonna tell you right now, the end is near. Now, well, people wanna know what day, what hour, what year?
"The Bible says no man knows the day nor the hour, no. Not the angels in Heaven, not the son of God, but the Father only. We know this in Matthew 24."
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