First time in nearly 800 years: 'Christmas Star' to be visible in December; know about this celestial treat

The year is coming to an end and the solar system has decided to close the chapter on a beautiful cosmic phenomenon that will be witnessed the first time in nearly 800 years. 

A rare celestial treat awaits stargazers the world over as two of our solar system`s largest planets, Jupiter and Saturn, will look like double planet just after sunset on the evening of December 21, the beginning of the winter solstice. The two planets will line up to create what is known as the "Christmas Star" or "Star of Bethlehem".

This is the first time the two gas giants will appear this closer to each other in nearly 800 years. "Alignments between these two planets are rather rare, occurring once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets will appear to one another," Patrick Hartigan, Professor of Physics and Astronomy at Rice University in Houston, Texas, said in a statement.

"You`d have to go all the way back to just before dawn on March 4, 1226, to see a closer alignment between these objects visible in the night sky."

Although Jupiter and Saturn have been approaching one another in Earth`s sky since the summer, the two will be separated by less than the diameter of a full moon from December 16-25.

"On the evening of closest approach on December 21, they will look like a double planet, separated by only 1/5th the diameter of the full moon," said Hartigan.

"For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening." Though the best viewing conditions will be near the equator, the event will be observable anywhere on Earth, if the weather permits.

Those who prefer to wait and see Jupiter and Saturn this close together and higher in the night sky will need to stick around until March 15, 2080, Hartigan said.

After that, the two planets would not make such an appearance until sometime after the year 2400. As per Forbes, a star-sighting of this magnitude won't occur next again until the year 2080.

The event sometimes referred to as The Great Conjunction, occurs roughly every 19 to 20 years, however, for the uninformed, these two planets haven’t appeared this (relatively) close together from Earth's vantage point since the Middle Ages. 

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Stargazers in the northern hemisphere should turn their heads and telescopes to the southwest portion of the sky about 45 minutes after sunset to see the planets align on December 21. In reality, of course, the two planets won't be close at all. Jupiter is 5 au from Earth. Saturn is 10 au, but they will appear to be less than the diameter of a full moon apart.