Jupiter and Saturn will line up in the night sky on Monday. It will be the closest they have appeared in 800 years.
The two planets move in alignment or conjunction every 20 years. But this year they will be so close that they will look like a “double planet”.
The last time Saturn and Jupiter were so close and visible was in 1226.
Here are the best ways to see, photograph or watch a live stream of the conjunction.
Go to the Business Insider homepage for more stories.
Jupiter and Saturn are about to line up in the night sky, becoming so close to the moon that they will seem to touch each other.
The last time they looked so closely at the Earth’s point of view was almost 800 years ago, on March 4, 1226.
An astronomical event in which celestial bodies align is called a conjunction. Because this conjunction involves the two largest gas giants in our solar system, it is known as the great conjunction. It happens to some extent every two decades.
“But it’s fair to say that this conjunction is truly exceptional in that the planets are very close to each other,” Patrick Hartigan, a professor of physics and astronomy at Rice University, explained on his website.
He added: “In fact, they will be so close that it could be a challenge to separate them with the naked eye for many people.”
Here’s how you can see this rare conjunction Monday night.
How to view a “double planet”
A photograph of Jupiter captured by NASA’s Hubble Space Telescope on August 25, 2020.
NASA, ESA, STScI, A. Simon (Goddard Space Flight Center) and MH Wong (University of California, Berkeley) and the OPAL team
Jupiter and Saturn are actually more than four times the distance between Earth and the sun.
But on Monday, the night of the winter solstice, they will be separated in the sky by a distance of about one-fifth the diameter of the full moon, according to Hartigan. It is so close that the two points of light will look as if they were forming a double planet. According to NASA, a pink finger at arm’s length should easily cover both Jupiter and Saturn in the sky.
This “Christmas star,” as the conjunction was nicknamed, should look brighter than almost every star in the sky, according to NASA.
Viewed through a small telescope, Jupiter and Saturn should appear in the same field of view along with some of their moons.
How Jupiter and Saturn will appear in a telescope installed in Houston, Texas, on December 21, 2020.
Patrick Hartigan / Rice University / Adapted from Stellarium graphics
For viewers in the United States, Canada and Europe, it could be a challenge to see this conjunction because of how low it will be on the horizon in the northern hemisphere, Hartigan said.
“The viewing conditions are closest to the equator, although no matter where you are, there is an hour or so to observe this conjunction before the planets sink into the fog,” he added.
To take a look, go out around dusk – the hour after sunset – and point the telescope at the southwest sky. (Websites like Stellarium can help you orient your telescope.)
“You will need to have a clear southwestern horizon and no low clouds in the distance,” Hartigan said.
He recommends setting up your telescope before dark and bringing binoculars, which can help you observe the four months of Jupiter.
A graph showing what the conjunction of Jupiter and Saturn with the naked eye will look like immediately after sunset in the northern hemisphere, on December 21, 2020.
GODMOTHER
If it ends up being cloudy where you live on Monday, don’t worry, Hartigan said. The conjunction is an ongoing event that lasts until December 25 – Monday is exactly when the two planets will be closest to the sky.
“You can imagine that the solar system is a racetrack, with each of the planets as a runner on its own lane and the Earth toward the center of the stadium,” NASA astronomer Henry Throop said in a news release. “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.”
You can photograph the combination with your phone
A man with a telescope looks at the night sky above the San Gabriel Mountains National Monument in Los Angeles, July 19, 2020.
David McNew / Getty
The conjunction of Jupiter and Saturn “can be easily photographed on DSLR cameras and many mobile phone cameras,” NASA said.
The agency suggests using the “night mode” feature on an iPhone, Pixel or Galaxy to get a stable photo with long exposure.
“Try to frame the planets with something – the silhouette of a tree, an outdoor landscape, the arch of a building or even a neon sign,” NASA said.
If you use a DSLR camera, a tripod is recommended to get good photos with long exposure. In the absence of a tripod, set the camera to a shutter speed of less than a quarter of a second. Also, make sure you open the camera’s aperture to the widest setting and use manual focus mode, NASA said.
For those who can’t get out at the event, the Lowell Observatory in Flagstaff, Arizona, will host a live stream of views from YouTube through its telescopes, starting at 19:00 ET on Monday. In Rome, the Virtual Telescope Project also intends to share live views of the conjunction.
Another conjunction like this will come in 2080
In the last 2,000 years, only twice have Jupiter and Saturn come closer to the sky than they will get this year. One was in 1623, but the brightness of the sun made it impossible to see. The other was in 1226.
But if you miss the conjunction on December 21, another will come in 60 years.
A photo of Saturn and two of its moons, taken by Voyager 1 in 1980.
SSPL / Getty
On March 15, 2080, Jupiter and Saturn will look as close as this month. This event will be easier to see because it will appear higher above the horizon, Hartigan said.
“The major challenge there,” he added, “is that you will have to stay alive for another 60 years to see it!”
