The two largest planets will be separated by a tenth of a degree in what is being dubbed the ‘Great Conjunction’.
Jupiter and Saturn will merge in the night sky on Monday, looking closer to each other than since Galileo was alive in the 17th century.
Astronomers say the so-called conjunctions between the two largest planets in our solar system are not particularly rare – Jupiter spends its neighbor Saturn on its respective loops around the Sun every 20 years.
But the one that is arriving is especially close: Jupiter and Saturn will be separated by just a tenth of a degree from our perspective or about a fifth the width of a full moon.
They should be easily visible around the world shortly after sunset, weather permitting.
Combine the winter solstice in the northern hemisphere, the longest night of the year – and the summer solstice in the southern hemisphere – and the show promises to be one of the greatest of the great conjunctions.
To see it, be ready right after Monday’s sunset, looking southwest down the horizon.
Saturn will be the smallest and weakest bubble in the upper right corner of Jupiter. Binoculars will be needed to separate the two planets.
Despite appearances, Jupiter and Saturn will actually be more than 730 million kilometers (450 million miles) from each other.
The Earth, meanwhile, will be 890 million kilometers (550 million miles) from Jupiter.
“What is rarer is a close conjunction that occurs in our night sky,” said David Weintraub, professor of astronomy at Vanderbilt University.
“I think it is fair to say that this type of event can usually occur only once in anyone’s life, and I think ‘once in my life’ is a good test of whether something deserves to be labeled as rare or special.”
It will be the closest Jupiter-Saturn pair since July 1623, when the two planets appeared a little closer. This conjunction was almost impossible to see, however, because of its proximity to the sun.
Considerably closer and in sight was the conjunction of the two planets in March 1226, when Genghis Khan was conquering Asia.
Monday’s conjunction will be the closest pair visible since then.
Saturn and Jupiter have been approaching in the south-southwest sky for weeks. Jupiter – bigger and closer to Earth – is brighter.
Your next super close pair: March 15, 2080.