Noticed some bright starts just above the moon?

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Those are actually planets. Jupiter and Saturn’s great conjunction is December 21st.

Astronomers use the word conjunction to describe meetings of planets and other objects on our sky’s dome. They use the term great conjunction to describe meetings of the two biggest worlds in our solar system, Jupiter and Saturn. The December 21, 2020, great conjunction of Jupiter and Saturn is already underway! It’s highly conspicuous in the west after sunset each evening now. On December 21, the pair will be only 0.1 degree apart. Some say the pair will look like an elongated star on that date. Will they? Or will they look like a double planet? What if you’re clouded out? How can you watch online?

Though the two planets will appear spectacularly close together on the sky’s dome, Jupiter and Saturn are actually 456 million miles apart. They are lined up from our point of view, but Saturn is in fact nearly twice as far away as Jupiter.

Jupiter-Saturn conjunctions happen every 20 years; the last one was in the year 2000. But these conjunctions aren’t all created equal. The 2020 great conjunction of Jupiter and Saturn will be the closest since 1623 and the closest observable since 1226! 2020’s extra-close Jupiter-Saturn conjunction won’t be matched again until the Jupiter-Saturn conjunction of March 15, 2080.

While you’re looking at them, you might notice that – unlike the twinkling stars – Jupiter and Saturn both shine steadily.

In November – during the period when the moon swept past Jupiter and Saturn (about November 16 to November 21) – the two gas giant planets were some 3 degrees apart.

Over the time between November 21 and the day of the conjunction itself, December 21, Jupiter will travel about 6 degrees and Saturn 3 degrees on the sky’s dome. That movement will mean that Jupiter bridges the 3-degree gap between itself and Saturn.

No matter how you see them, or which evening between now and December 21, Jupiter and Saturn will surely be an appealing and mind-expanding sight. Just don’t miss them!