Story at a glance
- Planets Jupiter and Saturn will orbit so close together that they will form a bright conjunction.
- This only happens every 20 years.
Just in time for the holidays, Dec. 21, the longest night of the year, is set to be particularly bright as two planets move closer together for the first time in hundreds of years.
NBC News notes that the cosmic occurrence, known as The Great Conjunction of 2020, will light up the darkest day of the year when Jupiter and Saturn appear close together on the winter solstice.
Astronomers have referred to the occurrence as the “Christmas Star,” a term that stems from the Christian Bible’s Star of Bethlehem. Some believe that the Star of Bethlehem could have been a planetary conjunction between Venus and Jupiter about 2,000 years ago.
While Jupiter-Saturn conjunctions occur every two decades, the last one happened close to the sun, making it difficult to see. The forthcoming 2020 conjunction will be the closest to Earth since 1623, and closest observable since 1226.
This conjunction won’t occur this visibly again until March 15, 2080.
Jupiter is brighter than any star in our solar system, and Saturn is about as bright as the brightest stars.
Their orbits are distinctly different; Jupiter takes nearly 12 years to rotate around the sun, and Saturn takes an even longer 29 years. The conjunction occurs when these two planets overlap.
To get the best spot to view the planetary event might be difficult for some locations. Astrophysicist Pat Hartigan noted that seeking out a good spot along the horizon will be a viewer’s best bet to see the conjunction.