How to see the historical great coincidence of Jupiter and Saturn of 2020

Great combinations do not come along every night, and such incidents occur once in a lifetime.

Jupiter and Saturn are set to align in the night sky next week, with what astronomers call a great combination – what some are calling a “Christmas star” this year – an event like this in almost 400 years.

Two planets can appear as a bright point of light when viewed with the naked eye, a sight some stargazers describe as a long star or double planet. The telescope should be sufficient to show separation between the two, while a telescope will reveal the rings of Saturn, the belt of Jupiter and the moons of both planets, all in the same view.

The astronomical event will take place on Monday, December 21, the first day of winter. Jim Todd, director of astronomy education at OMSI, said people in the Portland area want to go out after sunset at 4:30 in the afternoon, when Jupiter and Saturn will be low in the sky.

Planets will quickly set below the horizon, Todd said, so a good view of the southwest horizon is required, and people will need to look up at the sky over time to capture it.

As with all astronomical events in the fall and winter, cloud cover will determine whether those of us in the Pacific Northwest will actually get a view. The National Weather Service is currently forecasting clouds in the Portland area and the possibility of rain on Monday.

The winter solstice is a spiritually important time for great assemblage, as is its proximity to Christmas. Some are referring to the planet alignment as a “Christmas star” in reference to the star of Bethlehem from the biblical story of the birth of Jesus. Although the two planets may appear as one point of light, they will actually remain separate.

While the great conjugations of Jupiter and Saturn occur approximately once every 20 years, it is extremely rare to obtain this view. The Great Concentration of this year will be the closest since 1623, and the closest observable coincidence since 1226. The next closest great conjugation is expected in 2080.

Most planetary alignments are simply called conjugations, but astronomers refer to the alignment of Jupiter and Saturn – the two largest planets in our solar system – as a “great conjugation”. While the two planets would only be .1 degrees apart in our sky, they would actually be 455,762,323 miles apart, Todd said.

The Great Junction of Jupiter and Saturn will be the closest since 1623.

– Jamie Hale; [email protected]; 503–294–4077; @HaleJamesB

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