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’.
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, which is at 3.48 pm.
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.
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
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.’
The next time that Jupiter and Saturn will seem as close in the sky will not be until March 15, 2080 — when they will be higher in the sky and visible for longer.
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
