On Monday, Dec. 21, just after sunset, Jupiter and Saturn will align and appear as one bright, beautiful star that could, depending on whether you believe or not, be something more.
Physically, it’s actually a planetary “great conjunction,” where Earth is moving into a place where Jupiter and Saturn will appear to be aligned, said Keys astronomer Jay Elliott. Jupiter’s 12-year orbit and Saturn’s 29-year one will overlap and actually bring the planets closer together, from our vantage point on Earth.
Despite visually coming together in the night sky, the two giant planets will actually remain separated by a vast distance: five astronomical units (AU) ‒ 92 million miles, or the distance of Earth to the sun, Elliott explained.
The last time a great conjunction bright like this happened was in 1283, about 800 years ago, said NASA solar system ambassador Elizabeth Moore. There was also one in 2000, but it was so close to the sun that we couldn’t see it, she said.
“There’s another coming 80 years from now,” Moore told the Keys Weekly. “It’s not like it doesn’t happen, but it is a unique experience because it’s happening at the winter solstice, which gives us the longest night of the year, and because it’s close to Christmas.”
Moore said some speculate this same conjunction was the “Star of Bethlehem” of biblical fame, due to its brightness, the star that is said to have guided the three wise men across the deserts 20 centuries ago.
“That whole theory, being the possible cause of the ‘Christmas Star’ in the Bible, that’s unique,” Moore expanded. “It’s been a while since a conjunction happened near Christmas and it’s really cool.”
Several conjunctions of various planets occurred “within 10 years of the chronological point now taken as the beginning of the Christian era,” the Encyclopaedia Britannica says, adding historical fuel to the speculative fire that Monday’s event might indeed be special.
So, where should you go, when should you look up and what will you see?
The main event will occur on Dec. 21, but the views on Sunday, Monday and Tuesday nights will still be worthwhile, Moore said. Go anywhere without light pollution. Elliott suggested the state parks or any of the fishing bridges.
“If you get a good shot of the horizon, that’s a good thing,” Moore added. “If there are houses and trees in the way, you won’t be able to see it. Get away from people and light.”
Look low above the horizon (25 degrees) in the southwest about a half an hour after sunset and you should see a thin crescent moon and two bright objects next to it that flicker less than traditional stars. These would be Jupiter and Saturn. On the solstice, they should appear just one tenth of a degree apart – about the thickness of a dime held at arm’s length, NASA says.
You can view with the naked eye, binoculars or a telescope, if you have one.
The planets will only be visible for an hour or so, Moore estimated. “They will set just like the sun sets. We’re still rotating east, so they will set and we won’t be able to see them any more.”
Elliott and Moore and their Florida Keys Astronomy Club are hosting a special Zoom event focused on the great conjunction, where attendees can virtually connect to the club’s telescopes. Visit the club’s Facebook page on Sunday, Monday and Tuesday at 6 p.m. for the Zoom link and to get a chance to see the Christmas Star up close.