A Christmas Conjunction: Jupiter and Saturn align in very close meeting Monday night

Dec 21, 2020

It will be a rare treat, weather permitting, for astronomy enthusiasts and casual stargazers alike. Shortly after sundown, near the southwest horizon, the planets Jupiter and Saturn will appear in the sky at just a fraction of one degree apart.

The conjunction is the closest observable meeting of the solar system's two largest planets in centuries.

The last time Jupiter and Saturn got this close, from Earth's vantage point, was in the year 1632. However, that conjunction generally couldn't be observed because the planets were positioned too close to the Sun. The last time most humans could observe such a close pairing was in the 13th Century.

Look to the southwest horizon shortly after 5 p.m. Monday to see the Jupiter-Saturn conjunction.
Credit NASA.gov

"The last time that they were this close, just to put this in historical perspective, was the year 1226. That is 11 years after the Magna Carta was signed," said Tim Collins, Observatory Astronomer at the Buffalo Museum of Science and Community Education Instructor at Williamsville North High School's Spacelab Planetarium.

The orbits of Earth, Jupiter and Saturn bring the latter two planets in close proximity, from Earth's point of view, about every 20 years.

Some are calling the conjunction the Christmas Star of 2020, and some social media posts have suggested the two planets, when paired, will form a more brilliant object. Collins was asked about what people should expect.

"Jupiter and Saturn are fairly bright objects on their own. And they're not passing directly in front of each other. The object that it's going to form is going to look a little bit larger, which will have a tendency to have somebody say 'oh, it's brighter' but they're looking at two objects at the same time," he told WBFO.

While they won't really form a "star," Jupiter and Saturn may have played roles in forming the legendary Star of Bethlehem, the object pursued by the Magi in the Christian story of the Nativity. Collins notes a planetary conjunction involving Jupiter, Saturn and Mars occurred around 6 BC.

The Buffalo Astronomical Association has been hosting online events on its Facebook page in the days leading up to the closest moment of the conjunction. Collins says if the weather doesn't cooperate, the Association will find a way to show it.

"If the weather is clouded out, they are planning to get a feed from somewhere else, so that people can see this," he said. "In addition, our panel is going to be discussing other things related to these conjunctions, and a little bit of a lesson on why and how."