Weather Blog: Great Conjunction of Jupiter & Saturn peaks tonight

Weather Blog

Mark Your Calendars for a Super Rare Event that Won't Happen Again Until 2080!

UPDATE: We’re going to have perfect viewing of the Great Conjunction on Monday, December 21st. The sky should be mostly clear with just a few passing high clouds rather low on the SW horizon, but this won’t block viewing of this once in a lifetime celestial event. Be on the lookout for Facebook Live broadcasts Monday evening to see both Jupiter and Saturn in the same field of view from a telescope.

Jupiter and Saturn in the Same Field of View in a Telescope. Pic Courtesy: Rick Ulrich


FAYETTEVILLE, Ark. (KNWA/KFTA) — A rare, spectacular sky event is about to unfold near the end of this year & it’s the greatest conjunction ever witnessed in our lifetime! On the exact day of the Winter Solstice, December 21, 2020, Jupiter and Saturn will be at their closest distance in nearly 400 years! When Jupiter and Saturn (the two biggest planets in our solar system) appear to meet, it’s named the “great conjunction.”


Jupiter/Saturn conjunctions are the rarest of bright-planet conjunctions due to their slow orbits around the sun. Saturn takes nearly 30 years to complete its circle around the sun whereas Jupiter takes nearly 12 years. So just about every 20 years, Jupiter catches up to Saturn as viewed from Earth causing a great conjunction.

Why every 20 years? Each year, Saturn completes about 12 degrees of its orbit around the sun, whereas Jupiter completes approximately 30 degrees. So in one year, Jupiter closes the gap to Saturn by about 18 degrees.

In a period of 20 years, Jupiter gains 360 degrees on Saturn (18 x 20 = 360 degrees), meaning lapping Saturn once every 20 years.

Here are the great conjunctions dates from 2000 to 2100 viewed from our planet Earth.

  • May 28, 2000
  • December 21, 2020
  • October 31, 2040
  • April 7, 2060
  • March 15, 2080
  • September 18, 2100

Not all great conjunctions are created equal! This year’s great conjunction will be very special due to the close proximity of the two planets. On December 21, 2020 Jupiter and Saturn will be only 0.1 degree apart, which is just 1/5 of a full moon diameter!

The last great conjunction this close occurred in the summer of 1623 (14 years after Galileo made his telescope), but these planets were just 4 degrees from the Sun making the conjunction not visible from Earth. We have to go all the back to March 4, 1226 back to medieval times to witness a great conjunction that compares to the one in 2020.

If you miss this year’s event, they won’t appear this close again until 2080.


So how can you view it?

  • First, we’ll need a cloud free sky low on the western horizon at sundown (we’ll provide cloud cover forecasts as we get closer to Dec 21st).
  • Next, you’ll want to look towards the southwestern sky just above the horizon shortly after sunset (5:06 p.m. CST) as the great conjunction will start to appear. The two planets will appear to the naked eye as a “double planet.” For those with normal vision, you should see them extremely close together, but as separate-looking “stars.”
Zoom Animation of the Close Proximity of the December 21, 2020 Great Conjunction.
Sky Chart for December 31, 2020
  • Best viewing is 30 minutes to an hour after sunset up until planets set at 7:23 p.m. CST.
  • Make sure you have a clear view of the southwestern horizon near sunset, since the planets will be pretty low in the sky.
  • If you can get access to a medium-power backyard telescope, you’ll truly be amazed, since the two largest planets in our solar system will be in the same field of view! That’s a stunning celestial sight no one alive has ever seen.
  • Powerful binoculars will easily reveal Jupiter’s four huge moons spread in a straight line.

Don’t wait until December 21 to view this spectacular conjunction taking place. You can actually see the planets getting closer each day ahead of this event. (see animation below)

Great conjunction animation from December 6-31, 2020 at 6 p.m. centered on Jupiter.
Notice how Saturn is getting closer each day up until December 21st.

On December 16, soon after sunset, look for the waxing crescent Moon in the southwest sky. Just above the Moon are the two bright planets Jupiter and Saturn. You can’t miss it.

Sky chart on December 16 with waxing crescent moon.

Unfortunately, having the planets appear this close will be a one-night affair. The day before and the day after, the planets will be noticeably farther apart and nowhere near as striking. So if the weather cooperates on the 21st, you’ll want to do all you can to witness the spectacle.

Are they in danger of colliding? The answer is no! This is not an occurrence that’s threatening in any way. They may seem close together, but Saturn is actually far behind Jupiter (twice as distant), so they are actually nowhere near each other. It’s just a matter of perception.


While you may have heard this event titled the “Christmas Star,” some Biblical scholars believe the “Star of Bethlehem” was a triple conjunction made up of the following:

  • Jupiter (known as the king planet)
  • Venus (the brightest planet in our solar system)
  • The star Regulus (known as the kingly star) in the constellation Leo.
Triple Conjunction Seen from Iraq Looking West

Regardless if Jupiter and Saturn is the “Christmas Star” or not, it will truly be a spectacular site very close to Christmas time, so make sure you get out and view this once in a lifetime experience.

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