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Rare “Christmas Star” planetary conjunction event lights up Alaska’s sky

Published: Dec. 21, 2020 at 4:05 PM AKST
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FAIRBANKS, Alaska (KTVF) - On Monday night, the two largest planets in the solar system will appear as one bright object in the night sky, coming closer together than they have in hundreds of years.

The “Christmas Star” is a planetary conjunction that becomes visible in the evening for over two weeks as the planets Jupiter and Saturn come together, coincidentally culminating on the night of the winter solstice.

“This is a case where essentially Jupiter and Saturn come into an alignment, so that as we look at them from Earth they get very close together,” said Peter Delamere, Professor of Space Physics at the Univsersity of Alaska Fairbanks.

Only from our vantage point on Earth will the huge gas giants appear very close together. In space, they actually remain hundreds of millions of miles apart from one and other.

“I always think of it in terms of astronomical units. 1 AU is the distance from the sun to the earth. Jupiter is at 5 AU roughly, sun to Saturn is almost 10 AU. So Saturn is almost twice as far away as us a Jupiter roughly speaking,” said Delamere.

The last Jupiter-Saturn conjunction was in 2000, but according to Delamere not all conjunctions are equal. It’s been almost 400 years since the planets passed this close to each other in the sky.

“This conjunction, they’ll only be .1 degrees apart. Being so close together, that’s why they may look like an elongated star, vs. a double planet. Historically speaking this will be the closest that they’ve been together since 1623, and the closest observable since 1226 - and this conjunction won’t be matched until 2080,” said Delamere.

The Christmas Star appears visible for about an hour after sunset. Look to where the sun has dipped below the horizon, and the light of Jupiter should be visible. For best viewing results avoid towns and cities to minimize light pollution.

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