Rare ‘Christmas Star’ brightens Canadian sky on winter solstice
First time in 800 years that Saturn, Jupiter have been this close together
It’s a cosmic coincidence said to have not been seen since medieval times.
On Dec. 21, which is also the date of the winter solstice, the gas giants Jupiter and Saturn will appear to align in the night sky, occurring as a single ultrabright light in a rare event known as the “Christmas Star.” This of course depends on a forecast of clear skies.
It’s known as a great conjunction, and while it technically occurs every 19.6 years, scientists say the last time the two planets were this close to each other would have been in 1623.
But that great conjunction would have happened so close to the sun that it’s unlikely people would have been able to see it, said Rachel Ward-Maxwell, a researcher-programmer in astronomy and space sciences at the Ontario Science Centre. The last time the event would have been visible to the naked eye would have been in 1226, or nearly 800 years ago, WardMaxwell added.
“It really is a once-in-a-lifetime — once-in-multiple-generations really — event,” WardMaxwell said.
The two planets will look like a single bright star, and it will be the brightest object in the sky, she added.
The great conjunction is named so because it involves the two largest planets in the Milky Way. The timing of this event has brought it the name “Christmas Star.” Some have pointed to it as an astronomical explanation for the biblical “Star of Bethlehem,” which is said to have been connected to the birth of Jesus, and now serves as a symbol of the season.
While there’s no way to know if the biblical story was in fact linked to a great conjunction, it is certainly one possible explanation, Ward-Maxwell said.
The two planets are already moving closer in alignment, but Dec. 21 is when the conjunction will be brightest and most visible from Earth. Stargazers will be able to see the planets moving closer together in the nights preceding Dec. 21.
“Even if that moment is not clear at that particular time, you still sort of get that anticipation and part of that experience,” Ward-Maxwell said.
While this close encounter will make the planets look as if they are overlapping, they will actually be separated by about 0.1of a degree, or one-fifth of the apparent diameter of the full moon in our sky, Ward-Maxwell said.
If you’re looking to get a glimpse, Ward-Maxwell suggests heading out about 45 minutes after sunset and looking toward the southwest. Depending on conditions, the conjunction should be visible in Canada without binoculars or a telescope.
“Shortly after sunset is when you’re going to want to take a look,” Ward-Maxwell said. “If you wait too long until the sky gets much darker, it will be far too low to see.”
People should also be mindful of light pollution, tall trees, buildings or other obstructions.
The next time the two planets will appear so close together will be in 2080.
“Shortly after sunset is when you’re going to want to take a look.” RACHEL WARD-MAXWELL ONTARIO SCIENCE CENTRE