In an astronomical event last night referred to as a conjunction, Saturn and Jupiter appeared closer in the night sky then they ever have since 1623.
Although the distance between the two is 734 million kilometers in reality, the planets appeared only 0.1 degrees apart overhead on Monday from Earth. Jupiter that is more massive than the other two planets was about 885 million kilometers from Earth and Saturn was about 1.6 billion kilometers away.
In a clear sky, the duo could be seen shining brightly in the southwestern sky soon after sunset while glowing in the southern hemisphere’s western sky.
“Jupiter comes around every 20 years or so and catches up with and passes Saturn. That’s when we have one of these conjunctions,” says Jeffrey Cuzzi, a research scientist at NASA’s Ames Research Center in Mountain View, Calif.
Such conjunctions recur every two decades owing to their orbital periods. Cuzzi says that “even after December 21st, you can watch the planets start to move away, which is kind of fun, because normally you don’t notice the motion of the planets in the sky.”
The last time this event had happened, it wasn’t visible as it happened during daylight hours. Astronomer Galileo Galilei had discovered Jupiter’s satellites 13 years before that time and people today can pay homage to him by observing this phenomenon with a pair of binoculars there are “probably about as good” as the telescope Galileo used to discover Jupiter’s moons, Cuzzi says.
The previous one that was actually visible happened way back in 1226; and to put it into perspective, infamous warlod of the Mongols, Genghis Khan was still leading his army on wars throughout Asia.
It was also believed to have happened around the time of the “Christmas star,” also known as “the star of Bethlehem,” in Christian mythology, leading debates of these phenomenons being the conjunction itself.
“There was a conjunction in 7 BC, kind of like this one, and there was another one with Jupiter and Venus in 2 or 3 BC,” Cuzzi notes. “These things were happening then, and it’s possible that they could have inspired a lot of these stories.”
This event will not occur again until 2080.