“Christmas Star”: Jupiter and Saturn combine for a rare Great Conjunction

ORLANDO, Fla. “It’s a heavenly event for hundreds of years.” Conjunctions are common, they occur when any object from our perspective approaches each other in space. The great conjunction is rare.

The Great Conjunction happens when Jupiter and Saturn are very close to each other from our perspective. However, not every great conjunction is created equal and that makes the one that appears at the winter solstice so rare and special.

Jupiter and Saturn will appear extremely close on December 21, 2020. Jupiter is the brightest of the two planets in the night sky.
Jupiter and Saturn will appear extremely close on December 21, 2020. Jupiter is the brightest of the two planets in the night sky.

“Each large conjunction has different angular separations, or the distances between the two planets may vary slightly depending on how everything is aligned,” said Seth Mayo, curator of astronomy at the Daytona Beach Museum of Arts and Sciences.

The last time the two planets were so close to each other, from the point of view of the Earth, came back in 1623. “The problem with this great conjunction is that it occurred very close to the setting sun, so the Sun’s brightness most likely hid it. the pair of planets, ”Mayo said. “The last observable date of these planets so close was 1226.”

Because the planets will be so close around Christmas, it is called by some “the Star of Christmas.”

On December 21, the two gas giants will be separated by only .1 degree. With the naked eye, it will probably appear as two separate separate points, rather than a “star”, but it depends on the view and the weather conditions.

If you have a telescope, the two planets will appear in the same field of view.

The great conjunction through a telescope.  The months of Jupiter Callisto, Io, Europa and Ganymede along with Saturn's largest moon, Titan, will be visible with a telescope.
The great conjunction through a telescope. The months of Jupiter Callisto, Io, Europa and Ganymede along with Saturn’s largest moon, Titan, will be visible with a telescope.

Also, in that visual field will live the largest months of the two bodies. A telescope or binoculars will be needed to see the months.

Beyond December 21, Jupiter and Saturn will begin to move away from each other. This trend will continue for the next ten years before the two giants begin to get closer together again in the 2030s. This will create the next Great Conjunction in 2040, although it will not be as bright as the year 2020.

Jupiter and Saturn over Lake Eola on December 17, 2020. (Image: Derek Demeter)
Jupiter and Saturn over Lake Eola on December 17, 2020. (Image: Derek Demeter) (Derek Demeter 2020)

The planets will not be so close until 2080. In an extremely rare way, Jupiter completely covers Saturn. This will not happen again until 7541.

Saturn takes about 30 years from Earth to travel around the sun.  It takes about 12 years on Earth to do the same.  In reality, Jupiter and Saturn are extremely distant, but they seem close from the point of view of the Earth.  Mars was intentionally left out of the diagram, but has an orbit between Earth and Jupiter.
Saturn takes about 30 years from Earth to travel around the sun. It takes about 12 years on Earth to do the same. In reality, Jupiter and Saturn are extremely distant, but they seem close from the point of view of the Earth. Mars was intentionally left out of the diagram, but has an orbit between Earth and Jupiter.

The Great Conjunction occurs because Jupiter has its inner path as it orbits the Sun in our solar system. Because Jupiter’s orbit is smaller than that of Saturn, Jupiter moves faster around the sun and reaches the ringed planet. Think of it as a NASCAR race, in which the terrain is the Sun. The car with the inner belt spins around the field faster than the outside car.

“In very rare cases, these great conjunctions between Jupiter and Saturn can occur several times a year, known as triple conjunctions, due to the Earth exceeding these planets with its much faster orbit,” Mayo said. “This will not happen until 2238-2239, so we have something to look forward to.”

The last time there was a triple conjunction was 1981.

The Seminole State College Planetarium Emil Buehler Perpetual Trust hosts a “Great Jupiter / Saturn Conjunction Virtual Star Party. It’s a free event for everyone.

There are events on December 19 and 21.

More information is available at seminolestate.edu/planet.

Details:

When: December 21, 2020

Where: Southwestern sky about 30 min. after sunset

Notes: The planets will gradually descend lower into the sky as the evening progresses, the sooner the better.

You don’t need a telescope or binoculars to see, but they will enhance your viewing experience.

You will notice these two bright spots, Jupiter and Saturn getting closer and closer every night until December 21st.

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