An "incredibly rare" celestial event involving Saturn and Jupiter is taking place over the next couple of nights. Photo / 123RF
An "incredibly rare" celestial event is taking place over the next couple of nights to the delight of Kiwi stargazers across the country.
However, weather forecasts have put a damper on the "once in a lifetime" experience, with Metservice saying forecasts of thick cloud could make spotting the event difficult.
"Most of New Zealand is looking pretty cloudy," Metservice meteorologist Tuporo Marsters said.
Marsters said there may be some breaks in the cloud to reveal the conjunction, but "I wouldn't put my money on it."
The incredibly rare event - also known as the Great Conjunction - has happened for hundreds of years and won't happen again until 2080, Otago Museum director and astronomer Dr Ian Griffin told RNZ's Morning Report.
"They are going to be so close together, you won't be able to separate them with your eyes... you'll need binoculars and a telescope to split them."
"Jupiter and Saturn come together roughly every 20 years, that's nothing particularly special, but to get this close together in the sky is incredibly rare".
Some astronomers' calculations have suggested that the last time the two planets were this close together was 1226, he said.
It's also called the Star of Bethlehem because "in 7BC there was a conjunction between Jupiter and Saturn, and back then the 'wise men' were astrologers and this would have had some significance to them," he told RNZ.
It was mentioned in the Bible as well.
Stardome astronomer Dr Grant Christie said although the planets would be at their closest points in our sky since the invention of the telescope, they weren't close in space.
"On December 21, Jupiter will be 763 million km from Earth while Saturn will be a further 856 million km beyond it."
When & where
Griffin said the best seat in the house for viewing the conjunction is anywhere with clear skies tonight or tomorrow night - however, they may be hard to come by.
The best chance of spotting is from sunset onwards for about an hour and half later, he said.
"They disappear by 11.15pm, so you need to be out just after sunset.
"Jupiter and Saturn are relatively low in the southwestern sky. So, go out tonight, find the moon, and then look down to the left and you should see a bright star and that is Jupiter and Saturn," he told Morning Report.
"Then if you point your telescope or even a pair of binoculars at that bright star you'll see there are two planets - Jupiter and Saturn with its wonderful rings.
"And you if look really carefully you'll see some of the moons, four of Jupiter's moons and one of Saturn's. It will be seven planetary bodies all in that one field of view.