Jupiter and Saturn – The ‘Great Conjunction’ of 2020

Weather Blog

Peoria, Ill. (WMBD) – As 2020 comes to an end, Jupiter and Saturn will be putting on a show in the evening sky. On December 21st, the winter solstice, the two planets will be separated by just 0.1° dazzling astronomers and avid stargazers alike. Until then, the two gas giants will appear to be on a collision course making for an awesome sight in the western sky.

The word conjunction describes the meeting of two planets and/or other objects in the sky. A great conjunction is a term reserved for the coming together of the two largest planets in our solar system, Jupiter and Saturn. While the two planets will appear to be colliding from our point of view, they will actually be about 407 million miles apart. After the conjunction on December 21st, the two planets will drift farther apart for the next decade before approaching each other again in the 2030s.

Here’s a rough simulation of how the conjunction will look to the naked eye in Central Illinois. View is looking to the southwest between December 10th through January 1st in six day increments.

Jupiter and Saturn cross paths in our night sky about once every 20 years, when Jupiter laps Saturn and passes between Saturn and Earth in it’s orbit around the Sun. The last great conjunction happened back in 2000 and the next one will happen on October 31st, 2040. Even though this event happens on a routine basis, this year’s event is the closest conjunction between Saturn and Jupiter since 1623 (just 14 years after Galileo built his first telescope.) However, that conjunction was closely following the sun at sunset making it unlikely that many noticed it. Prior to that, the last observable great conjunction of equal comparison to this month’s event occurred back in 1226, during the Middle Ages!

When and Where to Look

  • Southwestern sky after sunset throughout the month of December
  • The planets will get closer together through December 21st, then start to drift apart
  • On December 21st Saturn, Jupiter and many of their moons will be visible in the same field of view on a telescope

Here’s a simulated view of what the Great Conjunction
will look like through the lens of a telescope courtesy of Stellarium

Image courtesy of Stellarium.

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