Jupiter/Saturn Conjunction
Monday – 12/21/2020 between 4:50 pm and 6:30 pm EST.
The conjunction of Jupiter and Saturn will take place on Monday, December 21st. The last conjunction that was this close was about 400 years ago.
The Great Conjunction of 2020
Background:
This Summer, majestic planets Jupiter and Saturn sat high in the southern sky, and since that time have traveled as a pair down towards the southwest with each successive night. Soon they will set below the horizon and after a short winter break, reemerge next Spring low in the southeast.
You have undoubtedly noticed that the two planets have also been getting closer and closer to one another as the months’ pass. Because Jupiter’s orbital speed is greater than Saturn’s, it moves faster along the ecliptic (the plane of the solar system) and will soon overtake the ringed planet.
On December 21st, the two will have a brief, but significant meeting in the night sky.
Since the Sun, Moon, and planets all move along the ecliptic upon the celestial sphere, we get to witness a number of “close encounters” between various objects in the night sky throughout the year. Of course, this is just a matter of perspective, as they are all still quite distant from one another once “depth” is added into the equation. Astronomers call these apparent get-togethers between the Moon and planets, multiple planets, and even planets and bright stars, “conjunctions.”
The Great Conjunction of 2020:
While there have been a number of wonderful conjunctions this year, all pale in comparison to what will be taking place in the early evening hours of December 21st. In fact, a meeting of this significance is called a “Great Conjunction.” And great it is! Jupiter and Saturn, the two largest planets in our solar system, will have an angular distance from one another of just 1/10th of a degree! To put that into perspective, that’s the relative *thickness* of a dime held at arm’s length. In fact, the two planets will be so close to one another, they will initially appear “as one” to the unaided eye. Upon inspection, those with good visual acuity should be able to separate the two even with the glaring brightness of Jupiter. All the same, you may wish to have a pair of binoculars or a telescope on hand. Whatever you do, don’t miss this amazing conjunction, as it is the closest the two have been in 397 years! We are fortunate to have another like Great Conjunction this century, but in the year 2080, it might be a bit too long to wait for many of us.
Where and When:
Jupiter and Saturn, once high in the late evening sky, are now setting earlier and earlier. By Monday the 21st, they will already be low in the Southwest sky during the hours of Civil and Astronomical Dusk, between 4:50 pm and 6:30 pm EST (5:30 and 6:30 pm CST). The pair will set at 7:20 pm CST but will probably be lost from view well before that time.
On Monday the 21st, go outside around 4:50 pm EST, preferably in a location with a clear view of the southwest horizon, and look about 15° above the sky-line. It may take a few moments to find them this early, but should come into view as they will be the first and brightest “star” in the area. Depending on your location, you will have just about one hour to enjoy this amazing astronomical event. It should be noted, that the day before and the day after, Jupiter and Saturn are nearly the same distance, so you really have three days to experience the Great Conjunction should the weather be an issue.
Telescopic Views:
If you are fortunate enough to have a telescope on hand, a magnification of 75x to 275x will be able to present both planets within the same field of view. Note, however, the *quality* of view will not only depend on your equipment but the state of the atmosphere as well. Unfortunately, with the two planets being so close to the horizon, atmospheric refraction will be an issue.
The Christmas Star:
We would be remiss not to observe the proximity to the Christmas holiday and the biblical “Star of Bethlehem.” In the time period depicted for the appearance of the Christmas Star, purveyors of the celestial sphere used their term for “star” to describe any number of objects in the night sky. Planetary conjunctions would not only fit this description but would also be of great interest to Priests of Zoroastrianism (aka the Wise Men). Currently, conjunctions between Jupiter and Saturn, Jupiter and the Moon, Jupiter and Venus, and Jupiter, Venus, and the star Regulus (between 7 and 2BC) are among the more popular hypotheses for a literal Christmas Star. Although our Great Conjunction is taking place days before Christmas, it *is* taking place the day of the Winter Solstice, the conclusion of Saturnalia, an ancient Roman festival which has influenced many Christmas traditions.
Michael Sibbernsen
NASA/JPL Solar System Ambassador
