Great Conjunction of Jupiter and Saturn to occur Monday evening

Wednesday, 23 Dec, 2020

Skies are expected to be mostly clear in areas across the state, making it possible to see the so-called "Christmas Star," which happens when Jupiter and Saturn align.

When two astronomical bodies appear close in the sky, as seen from Earth, it is called a conjunction.

Photo by Richard Heathcote/Getty ImagesWhat is the Great Conjunction? It happens every 20 years to some degree, but on December 21 they were supposed to be visibly closer than any time in the last 800 years. However, the occurrence is exceptionally rare as Saturn will be much closer to the biggest planet in the solar system.

It was discovered in 1623, that the solar system's two gas giants, Jupiter and Saturn traveled together across space. And because of our perspective from the earth, this great conjunction will make it appear as if the two planets are actually touching. But, back then, the positioning was nearly impossible to see because of its closeness to the sun.

On Monday night the two planets had been roughly one-fifth the width of a full moon apart.

Viewers would not require any special equipment to witness the event, as the planets would be visible with naked eye as Jupiter and Saturn are bright. Given their different orbits round the sun, the one on Monday will appear to be the closest the planets have come in about 400 years. But for the other planets, they're a little bit slower.

Hendricks said the closest places to Pittsburgh that will afford a clear view of the two planets meeting up is likely to be in western OH and eastern Indiana.

If you missed this conjunction and want to see the planets with the same proximity, just higher in the sky, it won't happen until March 15, 2080 - and then not again until after 2400.

A crescent moon (L) is seen with Saturn (upper right) and Jupiter (lower right) ahead of their closest visible conjunction on December 17, 2020 in Antalya, Turkey.

Look toward an unobstructed part of the southwestern sky about 45 minutes to an hour after sunset.

The "star" will be bright enough that most city dwellers should be able to spot it despite light pollution, according to NASA, but for ideal viewing, go somewhere open with few physical obstructions.