Although it is not a real star, the two planets will definitely shine brightly 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 will look like a double planet. This narrow approach is called conjunction. The fact that this event takes place during the winter solstice is pure coincidence, according to NASA.
“Alignments between these two planets are quite rare, occurring once every 20 years, but this conjunction is exceptionally rare because of how close the planets will be to each other,” said astronomer Patrick Hartigan, a professor of physics and astronomy at Rice University in Houston in a statement.
“You should have returned by the morning of 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 have been approaching since summer. And they are currently visible in our night sky, leaning closer and closer to each other.
Between December 16 and 25, they will become even more comfortable. Look for the low Jupiter-Saturn conjunction in the western sky for about an hour after sunset every night during this time.
“You can imagine the solar system being a race track, with each of the planets as a runner on its own lane and the Earth toward the center of the stadium,” said Henry Throop, an astronomer in the Planetary Sciences Division at NASA’s Washington headquarters.
“From our point of view, we will be able to see Jupiter in the inner band, approaching Saturn all month and finally surpassing it on December 21.”
How to look
In the Bay Area, you will want to look at the southwest sky on the evening of December 21, just after sunset. It will only be visible for a short time, about an hour or so. Monday night’s forecast requires mostly clear skies, so the Christmas Star should be easy to spot.
“On the evening of the nearest approach on December 21 (ember) 21 will look like a double planet, separated by only 1/5 of the diameter of the full moon,” Hartigan said. “For most viewers, each planet and some of its largest moons will be visible in the same field of view that evening.”
While these two planets may seem close, they are still hundreds of millions of kilometers away, according to NASA.
Hope for clear skies, as the conjunction will be visible around the world, with the best prospect for those near the equator.
“The farther north a spectator is, the less time they will have to capture the conjunction before the planets sink below the horizon,” Hartigan said.
The planets will be bright enough to be seen at dusk, which may be the best time for many American spectators to observe the conjunction.
“By the time the sky is completely dark in Houston, for example, the conjunction will be just 9 degrees above the horizon,” Hartigan said. “Visualization would be easy to manage if the weather cooperates and you have an unobstructed view to the southwest.”
If you are in New York or London or along these latitudes, try to identify the conjunction immediately after sunset. Waiting an hour after sunset will only put the planets closer to the horizon, making them more difficult to observe.
The best conditions for seeing this astronomical event will include a clear southwestern horizon with no low clouds in the distance, Hartigan said. Binoculars or a telescope can help you distinguish the planets. A telescope would allow the view of Saturn’s rings and the brightest months of both planets, he said.
Jupiter will appear the brightest and will be easily visible. Saturn will be slightly weaker and will appear slightly above and to the left of Jupiter. On December 21, Jupiter will overtake Saturn and change places in our sky.
“On December 21, the sun will set around 4:30. After that, it’s a race – the sky must be dark enough to see Jupiter and Saturn before they can set, around 6:45.” said Walter Freeman, an assistant professor of physics at Syracuse University’s College of Arts and Sciences in New York State.
“Jupiter and Saturn will probably come out of the glow of twilight starting at 5:00 or 5:15. With binoculars, a telescope or a telephoto lens of 500 (millimeters) focal length or more, you may be able to see the four largest months of Jupiter. There is no better way to celebrate the longest night of the year than to look at the stars. So, if you are planning a night of stellar gazes at the solstice, start admiring the biggest planets before you start.
Live events around the conjunction
If you miss this conjunction and want to see the planets in the same proximity, even higher in the sky, it will not happen until March 15, 2080 – and then not again until after 2400.
Between 0 and 3,000 CE, or Common Era, only seven conjunctions were or will be closer than this – 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.
If the weather in your area is not pleasant to watch this heavenly event, more live streams will be available.
The Lowell Observatory in Flagstaff, Arizona, will host a program beginning at 7:00 p.m. ET, featuring live views through its telescopes. The feed will be on the observer’s YouTube page.
ABC7 News contributed to this report