Over the next three weeks, the gas giants' paths will appear closer and closer together before an event that astronomers call "the great conjunction," according to NASA.
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During the "great conjunction" on Dec. 21, the two will form a "double planet," appearing just a tenth of a degree apart -- or about the thickness of a dime at arm's length.
This phenomenon has been dubbed a "Christmas Star" in reference to the celestial light that guided the three wise men to Jesus in the Christian Bible's nativity story.
Some theories suggest that the Star of Bethlehem may have been a planetary conjunction, according to AccuWeather.
Skywatchers can differentiate Saturn and Jupiter from the stars because the planets will appear "brighter and more solid in the sky," NASA program officer and astronomer Henry Throop told "Good Morning America." He said the conjunction will be visible throughout the world, even in cities, on clear nights.
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In reality, the planets are still millions of miles apart, but every 20 years, the orbits of Earth, Jupiter, and Saturn periodically align, making these two outer planets appear close together. In 2020, however, astronomers are calling this phenomenon the "greatest" great conjunction, as the planets haven't been this close together and visible from earth since 1226, according to AccuWeather.
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Dec. 21 is also the winter solstice in the Northern Hemisphere, meaning it will be the shortest day of the year in terms of sunlight.
To spot Jupiter and Saturn's approach and ultimate conjunction, look for them low in the southwest in the hour after sunset, according to NASA. They will set before 8 p.m. local time.