Jupiter and Saturn will merge into the night sky on Monday, looking closer to each other since the time of Galileo in the 17th century.
Astronomers say the so-called coupling between the two largest planets in our solar system isn’t particularly rare. Jupiter passes its neighbor Saturn in its own orbits around the Sun every 20 years.
But what’s coming especially soon: Jupiter and Saturn will be about a tenth of a degree, or about a fifth of the width of the full moon, from our perspective. They should be easily visible around the world shortly after sunset, weather permitting.
Tossed at the northern hemisphere winter solstice, the longest night of the year – and the southern hemisphere summer solstice – this spectacle in time for Christmas is one of the greatest celebrations.
“The most rare thing is the close coupling that occurs in our night sky,” said David Weintraub of Vanderbilt University, a professor of astronomy.
“I think it’s fair to say that such an event may only happen once in a person’s life, and I think the phrase” once in my life “is a very good test of whether something deserves to be classified as rare or special.
The closest conjunction between Jupiter and Saturn will be since July 1623, when the two planets appeared slightly closer. This conjunction was nearly impossible to see, due to its proximity to the sun. The conjunction of the two planets in March 1226 was much closer and clear – when Genghis Khan was invading Asia.
Monday’s coupling will be the closest visual coupling since then.
Saturn and Jupiter have been approaching in the southwestern sky for weeks. Jupiter – bigger and closer to Earth – is brighter.
“I love watching them get closer and closer to each other and the fact that I can see them with my naked eyes from the back balcony!” Virginia Tech astronomer Nahum Araff said in an email.
To see it, be prepared shortly after sunset on Monday, with a view of the relatively low southwest on the horizon. Saturn will be the smallest and fainest point in Jupiter’s upper right. Binoculars will be needed to separate the two planets.
Despite appearances, Jupiter and Saturn will be more than 450 million miles (730 million km) away. Meanwhile, Earth will be 550 million miles (890 million km) from Jupiter.
The telescope will not only capture Jupiter and Saturn in the same field of view, but also some of their brightest moons.
The next super-pairing between them: March 15, 2080.