Jupiter and Saturn will appear closer to each other in the night sky tonight than they have in 800 years — forming a celestial beacon akin to the ‘Star of Bethlehem’.
The gas giants — the largest planets in the solar system — have been slowly getting closer in the sky since the summer, and will now appear like a double planet system.
This conjunction can be viewed by eye from anywhere on Earth. Weather permitting, those in the UK will best see it in the hour after sunset, between around 3.45 and 4.45pm, when it will drop below the horizon.
The planets will look around a fifth of a full moon’s width apart tonight — appearing low above the horizon for UK viewers — and for the rest of the week until Christmas Day.
The German astronomer Johannes Kepler wrote in 1614 that he believed the ‘star of Bethlehem’ in the Nativity story may have been a conjunction of Jupiter and Saturn.
Others researchers have suggested instead that the ‘three wise men’ may have followed a triple conjunction of Jupiter, Saturn and Venus.
While Venus won’t be part of the this week’s conjunction, it will still be an impressive astronomical site — one best viewed on the equator, but visible worldwide.
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Jupiter and Saturn will appear closer to each other in the sky tonight than they have in the last 800 years — forming a celestial beacon akin to the ‘Star of Bethlehem’. Pictured, how the night sky in the south west will appear this evening, on the winter solstice
The planets will look less than a full moon’s width apart tonight — appearing low above the horizon for UK viewers — and for the rest of the week until Christmas Day. Pictured, Saturn (top) and Jupiter (below) seen between the twin steeples of the St Joseph Catholic Church in Topeka, Kansas on December 19, 2020
Saturn and Jupiter will appear low on the horizon just after sunset in the south west tonight — less than a full Moon width apart — appearing almost as one object
Onlookers with a telescope viewing the conjunction tonight will see not only Jupiter and Saturn, but also some of their largest moons in the same field of view, astronomers have said
The German astronomer Johannes Kepler wrote in 1614 that he believed the ‘star of Bethlehem’ in the Nativity story may have been a conjunction of Jupiter and Saturn
HOW TO CATCH IT
Tonight’s conjunction of Jupiter and Saturn, weather permitting, will be visible by eye across the globe tonight.
The best views will be had from locations along Earth’s equator
From the UK, the planets will appear to almost overlap low above the horizon in the south west for an hour after sunset tonight — from 3.48 onwards.
The phenomenon will be visible for the rest of the week up until Christmas.
Those with a telescope may also be able to see some of Jupiter and Saturn’s largest moons in the same field of view, experts have said.
Astrophysicist Megan Argo of the University of Central Lancashire told BBC Radio 4 Today that the event was highly unusual.
‘The best way to look is to go outside after sunset, by the time the sky has gone a bit dark and Jupiter should be the first thing you see in the night sky after the moon,’ she explained.
The view will be best, Dr Argo added, from places with a good western horizon — clear of trees and buildings.
Those in London and New York will see the planets close to the horizon — at around 5.3° and 7.5°, respectively — around an hour after the sun sets tonight.
‘Alignments between these two planets are rather rare, occurring once every 20 years or so,’ said astronomer Patrick Hartigan of Rice University of Houston, Texas.
‘But this conjunction is exceptionally rare because of how close the planets will appear to one another,’ he explained.
‘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.’
A similar conjunction also occurred in 1623 — but at this time, the planets would have only been visible during the day, making them very difficult to see.
The next such conjunction of the two bodies after that will not be until sometime after the year 2400.
‘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,’ Professor Hartigan added.
‘For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening.’
This conjunction can be viewed by eye from anywhere on Earth. Pictured, Saturn and Jupiter close to each other in the night sky above Jersey City, New Jersey, on December 18, 2020
‘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,’ said astronomer Patrick Hartigan of Rice University of Houston, Texas. Pictured (left) Saturn and Jupiter approach each other in the night sky above Las Vegas, Nevada on Dec. 20 and (right) a close-up of the two planets seen today from central Seoul, in South Korea
The next time that Jupiter and Saturn will seem as close in the sky will not be until March 15, 2080 — at which time they will be higher in the sky and visible for longer
Twitter users have been sharing images of the night sky showing Jupiter and Saturn (seen in the centre between the trees) as they get have grown closer together in recent weeks
While Kepler thought a conjunction of Jupiter and Saturn was behind the ‘star of Bethlehem’ story in the bible, others believed that it may have been another astronomical event — such as a large comet in the sky.
Professor Hartigan said that the planetary duo will appear low in the western sky around sunset — and should be bright enough to be viewed in the twilight sky.
In reality the two planets will still be millions of miles apart — Jupiter is about 5AU from the Earth (one AU is the distance of the Earth from the Sun) and Saturn is 10AU away from the Earth — but they appear together due to differences in their orbit.
When Jupiter and Saturn (pictured as bright lights here) come together, they will be visible at twilight in the south western sky
Having been ‘nearing’ each other since the summer, the giant planets will come to appear less than a full moon’s width apart just after sunset on the winter solstice tonight, pictured
The two planets have been gradually appearing closer and closer throughout November and December, to appear as a single object tonight — before moving apart after Christmas
‘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,’ Professor Hartigan explained.
‘By the time skies are fully dark in Houston, for example, the conjunction will be just 9 degrees above the horizon,’ he added.
‘Viewing that would be manageable if the weather cooperates and you have an unobstructed view to the southwest.’
Onlookers with a telescope viewing the conjunction tonight will see not only Jupiter and Saturn, but also some of their largest moons in the same field of view, astronomers have said.
Users have been sharing images of Jupiter and Saturn — that appear as bright stars — as they come closer together on the run up to their conjunction tonight, on December 21
THE STAR OF BETHLEHEM: INSPIRED THE THREE WISE MEN TO BABY JESUS IN BIBLE STORIES
The Star of Bethlehem, or the Christmas Star, is said to have inspired the three wise men from the East to visit the baby Jesus in bible stories.
It appears in the nativity story of the Gospel of Matthew, where they are said to have asked King Herod of Judea ‘where is he who has been born King of the Jews’ For we have seen His star in the East and have come to worship Him.’
It is said the star led them to Jesus’ home town where they worship him and give him gifts of gold frankincense and myrrh.
The gospel describes the visitors as ‘Magi’ which is usually translated as ‘wide men’ but can also be used to mean astronomer/astrologer.
Astronomers have made several attempts to calculate what this star may have been – whether it was a celestial event or pious fiction.
The famed German astronomer Johannes Kepler wrote in 1614 that he believed the ‘star of Bethlehem’ in the biblical story of the three wise men could have been a rare triple conduction of Jupiter, Saturn and Venus.
This would create a very bright point of light in the sky that would only appear for a few days. A similar conjunction is due to happen Christmas 2020.
Other theories are a supernova explosion reasonably close – that could appear like a very very bright sky for a relatively short period, or even a comet.
Chinese and Korean stargazers have written about a bright object that may have been a comet or supernova around 5 BC seen for more than 70 days.
Ancient astronomers have written of comets ‘hanging over’ specific cities — just as the Star of Bethlehem is said to have ‘stood over’ the place where Jesus was born — the town of Bethlehem.