The two largest planets in our solar system are coming closer together than they have been since the Middle Ages, and it’s happening just in time for Christmas – hence the nickname of the “Christmas Star.”
So, there are some things to look forward to in the final month of 2020.
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 close approach is called a conjunction. The fact that this event is happening during the winter solstice is pure coincidence, according to NASA.
“Alignments between these two planets are rather rare, occurring once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets will appear to one another,” said Rice University astronomer and professor of physics and astronomy Patrick Hartigan in a statement.
“You’d have to go all the way back to just before dawn on March 4, 1226, to see a closer alignment between these objects visible in the night sky.”
If you’re a stargazer, you’ve likely noticed Jupiter and Saturn have been getting closer together since the summer. And they’re currently visible in our night sky, inching ever closer to one another.
Through December 25, they will become even cozier. Look for the Jupiter-Saturn conjunction low in the western sky for about an hour after sunset each evening during this time.
“On the evening of closest approach on Dec(ember) 21 they will look like a double planet, separated by only 1/5th the diameter of the full moon,” Hartigan said. “For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening.”
While these two planets may appear close, they are still hundreds of millions of miles apart, according to NASA.
Hope for clear skies because the conjunction will be visible around the world, with the best perspective for those near the equator.
“The further north a viewer is, the less time they’ll have to catch a glimpse of the conjunction before the planets sink below the horizon,” Hartigan said.
![These six infrared images of Saturn's moon Titan represent some of the clearest, most seamless-looking global views of the icy moon's surface produced so far. The views were created using 13 years of data acquired by the Visual and Infrared Mapping Spectrometer (VIMS) instrument on board NASA's Cassini spacecraft. The images are the result of a focused effort to smoothly combine data from the multitude of different observations VIMS made under a wide variety of lighting and viewing conditions over the course of Cassini's mission.
Any full color image is comprised of three color channels: red, green and blue. Each of the three color channels combined to create these views was produced using a ratio between the brightness of Titan's surface at two different wavelengths (1.59/1.27 microns [red], 2.03/1.27 microns [green] and 1.27/1.08 microns [blue]). This technique (called a "band-ratio" technique) reduces the prominence of seams, as well as emphasizing subtle spectral variations in the materials on Titan's surface. For example, the moon's equatorial dune fields appear a consistent brown color here. There are also bluish and purplish areas that may have different compositions from the other bright areas, and may be enriched in water ice. (NASA/JPL-Caltech/University of Nantes/University of Arizona_](https://media.cnn.com/api/v1/images/stellar/prod/201028112246-01-titan-atmosphere-molecule.jpg?q=x_3,y_0,h_1684,w_2993,c_crop/h_144,w_256)
The planets will be bright enough to be viewed in twilight, which may be the best time for many US viewers to observe the conjunction.
“By the time skies are fully dark in Houston, for example, the conjunction will be just 9 degrees above the horizon,” Hartigan said. “Viewing that would be manageable if the weather cooperates and you have an unobstructed view to 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 put the planets closer to the horizon, making them more difficult to spot.
The best conditions to see this astronomical event will include a clear southwestern horizon and no low clouds in the distance, Hartigan said. Binoculars or a telescope may help you distinguish the planets. A telescope would enable a view of Saturn’s rings and the brightest moons of both planets, he said.
If you miss this conjunction and want to see the planets with the same proximity, just higher in the sky, it won’t happen until March 15, 2080 – and then not again until after 2400.
Between 0 and 3000 CE, or Common Era, only seven conjunction were or will be closer than this one – and two of those were too close to the sun to be seen without a telescope, according to Hartigan. So, yes, this is an incredibly rare event.