This December just a few days before Christmas, Jupiter and Saturn will be so close together they will look like a double planet. This is the closest the two planets have been since the Middle Ages. (1)

Jupiter and Saturn to Appear Like a Double Planet

After sunset starting on December 21, Jupiter and Saturn will appear closer together in the Earth’s sky than they have since the year 1226. The two planets have been getting closer and closer together since the summer. They will be separated by less than the diameter of a full moon from December 16 to 25, with their closest night being the 21. (1)

“On the evening of closest approach on Dec 21 they will look like a double planet, separated by only 1/5th the diameter of the full moon,” said Patrick Hartigan, a professor of physics and astronomy at Rice University. “For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening.” (1)

Jupiter and Saturn are aligned once every 20 some-odd years, however, being this close is extremely rare. (1)

How, When, and Where to View Them

Those who live near the equator will have the best view of the two planets, however, you will still be able to see them elsewhere in the world. The “double planet” will appear low in the western sky for about one hour after sunset each evening between the 16th and 25th of December. (1)

The further north you are, the less amount of time you will have to see Jupiter and Saturn together. If it happens to be a cloudy night, you might not be able to see them at all. (1)

The best time for American viewers might be around twilight because the planets will be shining very brightly. (1)

The next time they will be this close will be 2080, after that not again for another 400 years. (1)

What is A Real Double Planet?

In December Jupiter and Saturn will appear like a double planet, however, this is just what it will look like. An actual double planet refers to two planets that orbit each other around a common center of mass. This center of mass is not located inside either of these two planets. (2)

This term is an informal one because there is debate as to exactly when two planets are a double planet or a planet-moon system. (2)

Often, Pluto and its moon Charon are considered to be a double planet system, however, the International Astronomical Union has not decided on a formal definition of the term. This means that no planets or their moons can officially be one or the other. (2)

Up-Close and Personal

For avid stargazers and space fanatics, this planetary event is one that you will not want to miss. This might be your only chance to see Jupiter and Saturn so close together, so mark your calendars and hope for a clear night.

Keep Reading: Five Planets In The Solar System Will Be Visible This Month Without Binoculars

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