Celestial Show Set to Climax on Winter Solstice

In this final month of 2020, Jupiter and Saturn, the two largest and brightest planets in our solar system, have been putting on a celestial show. Through the entirety of December, skywatchers can look up each evening to watch these two gas giants approach one another. Their apparent merging will occur on December 21, in what astronomers are calling the Great Conjunction of 2020. During this close encounter, Jupiter and Saturn will form a rare "Christmas Star" on winter solstice when the conjunction reaches its climax.

Tonight, December 16, Earth's moon will sit just five degrees away from the planetary duo, offering a visual comparison. Jupiter currently appears brighter than any star in the sky. Although Saturn sits east of Jupiter and is slightly dimmer, it is still just as bright as the brightest stars, with a recognizable glow. Because they will be visible anywhere on Earth without the aid of binoculars or a telescope, skygazers can observe both planets in the southwestern sky just after sunset, weather and cloud conditions permitting. Located approximately 20 degrees above the horizon, the planetary pair will appear low in the western sky for about an hour until they slip below the horizon.

Composed mostly of hydrogen and helium gas, which surround a relatively dense core of ice and rock, the two planets will appear so close together that they'll almost look like one object. The last time Jupiter and Saturn passed this closely to one another was approximately 800 years ago. According to information from NASA, the two planets won't actually be physically close because they will remain hundreds of millions of miles apart; they will simply look that way from Earth because of their orbital alignment.

In late November, Rice University's Office of Public Affairs released a news brief about the planets' alignment. In that statement, Patrick Hartigan, a professor of physics and astronomy at Rice, said: "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. 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. On December 21, the evening of closest approach, they will look like a double planet."

For most telescope viewers, each planet and several of its larger moons will be visible in the same field of view that evening. Those with observing equipment will be able to zoom in to view Jupiter's four moons--Europa, Io, Callisto, and Ganymede-as well as Saturn's massive rings.

Those without telescopes can watch a livestream of the Great Conjunction of 2020 online, courtesy of Lowell Observatory. Beginning at 7 P.M. EST on December 21, Lowell astronomers and educators will share live views of Jupiter and Saturn through observatory telescopes while discussing the nature of conjunctions.

Despite all of the fanfare this conjunction is receiving, conjunctions themselves are actually quite common. They happen whenever two celestial objects appear to pass close to one another as seen from Earth. For example, throughout the year, the moon regularly appears alongside a number of planets and bright stars. And two or more planets come together fairly frequently. The last conjunction of Jupiter and Saturn occurred in May 2000. However, that close approach occurred relatively near the Sun, making it difficult to observe. Partially hidden in solar glare, it wasn't eye-catching. Furthermore, the planets never came anywhere as close together as they will this month.

We won't have to wait another 800 years to see the solar system's two largest planets repeat this month's performance. Another Great Conjunction will occur in 2080. Of course, many of us alive today won't be around then, so we best try to catch a glimpse of this display.

Experienced skygazers remind those who wish to enjoy the Great Conjunction of 2020 to keep in mind that Jupiter appears brighter because it's bigger and closer to Earth than Saturn. Jupiter sits just over half a billion miles away, while Saturn is roughly double that distance from Earth.

Harlem resident and Librarian at Aaniiih Nakoda College, Eva English has long been fascinated by the night sky. In 2017, English took that fascination to the next level when she applied and was accepted to become a volunteer for the Solar System Ambassadors (SSA) program through the NASA Jet Propulsion Laboratory.

As defined on their website, NASA's SSA program is "a public engagement effort that works with motivated volunteers across the nation to communicate the science and excitement of NASA's space exploration missions and discoveries with the people in their communities."

About her work as an Ambassador, English said: "Honestly, the moon is what fascinates me most about the night sky. I suppose that fascination dates back to childhood and the Apollo moon landings. I remember my mom and dad-who were both grade school teachers-bringing some of their students to our house to watch the landings on television.

"As an adult when I had the opportunity to go to Kennedy Space Center in Florida for the first time in 1997, that was nearly a religious experience for me. You know, there's a library there! But really, I'd be happy working in the gift shop just to be around all that history!

"While I've always looked to the night sky, my participation in this group is what has increased my interest in more 'sky' things. And in my role as an SSA, I use my Facebook page to try to promote any solar system news. This has truly been an interesting and exciting time for both astronomy and space exploration, with things like the NEOWISE comet, Starlink (and generally, the force that is Elon Musk), meteor showers, and NASA's partnership with SpaceX to return Americans to space on American vessels.

"And now we have the 'Christmas Star.' I hope people won't look too late in the evening and end up missing it because the planets will have already gone below the horizon. I believe that with COVID, people are looking for anything positive, leading to more interest in exactly this type of thing," English explained.

As we gaze out at the two planets to observe this holiday magic in the skies, we're reminded of our place in the solar system. Perhaps the experience will make us all feel a bit closer and more connected to our own planet, even if the pandemic currently has us feeling rather distant and disconnected.