Jupiter and Saturn would seem to be merging into the night sky on Monday, becoming closer to each other than they have been since Galileo’s time in the 17th century.
Astronomers say that the so-called conjunctions between the two largest planets in our solar system are not especially uncommon.
Every 20 years, Jupiter passes its neighbour Saturn around the sun in their respective laps.
But the one coming up on Monday is extremely close: Jupiter and Saturn will be just one-tenth of a degree apart from our perspective, or around one-fifth of a full moon.
They should be visible around the world a little after sunset, weather permitting.
Toss in the winter solstice in the northern hemisphere, the longest night of the year-and the summer solstice in the southern hemisphere-and this just-in-time-for-Christmas display promises to be one of the best of the Great Conjunctions.
It is also known as the “Christmas Star.”
“What is most rare is a close conjunction that occurs in our night-time sky,” said Vanderbilt University’s David Weintraub, an astronomy professor.
‘I think it’s fair to say that such an event typically may occur just once in any one person’s lifetime.’
“I think it’s fair to say that such an event typically may occur just once in any one person’s lifetime, and I think ‘once in my lifetime’ is a pretty good test of whether something merits being labelled as rare or special.”
In Australia, the conjuncture is best visible after 8 p.m. WST or 11 p.m. AEDT on Monday, and there is only a small window in which to view it.
“To see the conjunction no matter where you are in the world, you will need to go out in the early evening and if you’re in the Southern Hemisphere, you will need to look low in the West and Jupiter will be on the left and Saturn will be on the right at about the 4 o’clock position from Jupiter,” the Perth Observatory states on its website.
“A few days before the conjunction, on the 17th of December, the crescent moon will scrape past the two planets providing us with another conjunction for astrophotographers and stargazers to see.”
Their next super-close pairing will take place on March 15, 2080.