The Moon (left), Saturn, and Jupiter (lower right; Saturn is above and to the left of Jupiter) were seen in the sky above the Washington Memorial on Dec. 17, 2020. At the time, Saturn and Jupiter were nearing each other in the sky, culminating in a “great conjunction” on Dec. 21, where they appeared a tenth of a degree apart.
Great conjunctions between Jupiter and Saturn happen every 20 years, making the planets appear to be close to one another. This closeness occurs because Jupiter orbits the Sun every 12 years, while Saturn’s orbit takes 30 years, causing Jupiter to catch up to Saturn every couple of decades as viewed from Earth.
The last great conjunction was even more special: Jupiter and Saturn had not appeared that close in the sky to each other since 1623.
For skywatching tips, visit What’s Up.
Image Credit: NASA/Bill Ingalls