While not a true star, the two planets are sure to make a bright splash in the night sky.
On the night of December 21, the winter solstice, Jupiter and Saturn will appear so closely aligned in our sky that they look like a double planet. This close approximation is called a conjunction. The fact that this event occurs during the winter solstice is pure coincidence, according to NASA.
“Alignments between these two planets are quite rare, they occur once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets will appear to each other,” said astronomer Patrick Hartigan, a professor of physics and astronomy at Rice. University in Houston, in a statement.
“You would have to go all the way back to just before sunrise on March 4, 1226, to see a closer alignment between these objects visible in the night sky.”
If you’re a stargazer, you’ve probably noticed that Jupiter and Saturn are getting closer to each other since the summer. And they are currently visible in our night sky, closer and closer together.
Between December 16 and 25 they get even more fun. During this time, look for the Jupiter-Saturn conjunction low in the western sky for about an hour after sunset each evening.
“You can imagine the solar system as a racetrack, with each of the planets like a runner in its own orbit and the Earth toward the center of the stadium,” said Henry Throop, astronomer with the Planetary Science Division at NASA headquarters. in Washington. .
“From our vantage point, we can see Jupiter on the inner orbit, approach Saturn for the entire month, and finally catch up on December 21.”
How to watch
In Chicago, on the evening of December 21, right after sunset, you’ll want to gaze at the lower southwest sky. It will only be visible for a short time, about an hour or so. Monday night’s forecast calls for mostly clear skies, so the poinsettia should be easy to spot.
“On the night of the closest approach on December 21 (December), they will look like a double planet, separated by only 1/5 the diameter of the full moon,” Hartigan said. “For most telescopes, every planet and several of their largest moons will be visible that evening in the same field of view.”
While these two planets may seem close, they are still hundreds of millions of miles apart, according to NASA.
Hope for clear skies as the conjunction will be visible all over the world, with the best perspective for those near the equator.
“The farther north a viewer is, the less time they have to get a glimpse of the conjunction before the planets sink below the horizon,” Hartigan said.
The planets will be bright enough to be viewed at dusk, which may be the best time for many American viewers to observe the conjunction.
“For example, by the time the sky is completely dark in Houston, the conjunction will be only 9 degrees above the horizon,” said Hartigan. ‘It would be manageable if the weather cooperated and you had an unobstructed view of the southwest.’
If you’re in New York or London, or along those latitudes, try to spot the conjunction right after sunset. Waiting an hour after the sun sets will only move the planets closer to the horizon, making them harder to see.
The best conditions for seeing this astronomical event include a bright southwestern horizon and no low clouds in the distance, Hartigan said. Binoculars or a telescope can help you distinguish the planets. A telescope would allow viewing of Saturn’s rings and the brightest moons of both planets, he said.
Jupiter will appear brightest and be easily visible. Saturn will be slightly fainter and will appear slightly above and to the left of Jupiter. On December 21, Jupiter will overtake Saturn and they will switch places in our sky.
“On December 21, the sun will set around 3:30. Then it’s a race – the sky needs to get dark enough to see Jupiter and Saturn before they also set, around 6:45 AM,” said Walter Freeman. the physics department at Syracuse University’s College of Arts and Sciences in New York State.
Jupiter and Saturn are likely to be noticed between dusk and dawn from about 5:00 or 5:15 a.m. With binoculars, a telescope, or a telephoto lens with a focal length of 500 (millimeters) or more, you may also be able to see the four largest moons of “Jupiter. There is no better way to celebrate the longest night of the year than to gaze at the stars. So if you plan a night of stargazing at the solstice, start by admiring the greatest planets before they set.”
Live events around the conjunction
If you miss this conjunction and want to see the planets with the same proximity, only higher in the sky, it won’t happen until March 15, 2080 – and then again after 2400.
Between 0 and 3000 CE, or Common Era, only seven conjunctions were or will be closer than this one – and two of them were too close to the sun to be seen without a telescope, according to Hartigan. So yes, this is an incredibly rare event.
In case the weather conditions in your area are not pleasant to witness this celestial event, there will be several live streams available.
The Lowell Observatory in Flagstaff, Arizona, is hosting a program that starts at 7 p.m. ET, featuring live images through its telescopes. The stream is on the observatory’s YouTube page.
The Virtual Telescope Project in Rome will also share live images on its website.
And if you want to learn more about the “Great Conjunction” itself, NASA Science LIVE will be sharing an episode about the event on December 17 at 3:00 pm ET on NASA TV and its website.
WLS-TV contributed to this report