2020 has been a dumpster fire in most aspects, but there have been some bright spots for amateur astronomers and sky watchers. Another event is happening in the nighttime sky this month that skywatchers will want to pay attention to. In the nighttime sky, Jupiter and Saturn are meeting up, something they do every 20 years.
The big deal about the meet up this year is that the planets will appear closer to each other high up in the dome of the sky that at any point since the Middle Ages. On December 21, Jupiter and Saturn will be close enough together that they will show up as a single intensely bright “star.” This will be the first time in centuries this has happened.
When the two planets can be viewed as a single very bright point of light from the Earth, it’s referred to by many as the “Christmas Star” or “Start of Bethlehem.” While Jupiter and Saturn are neighbors in the solar system, they orbit at vastly different rates. Jupiter circles the sun every 12 years while it takes Saturn 30 years to complete an orbit.
Two planets appearing to meet in the nighttime sky is called a conjunction. This time the planets are close enough to each other that it is known as a great conjunction. While Saturn and Jupiter appear close from the Earth, they’re still 403 million miles apart. It’s our perspective from Earth that makes them appear to be so close together.
Jupiter and Saturn will combine in the sky, forming the optical equivalent of one-fifth of the full moon’s diameter. Anyone looking at the planets through a telescope will be able to view them at the same time. Researchers say that even with a modest telescope or binoculars, viewers should see Saturn and Jupiter in the same field of view and view the rings of Saturn and moons of Jupiter.