Today marks the winter solstice and the official first day of winter, which brings the longest night of the year. And in 2020, it brings a rare “Christmas Star,” a Great Conjunction in the night sky not seen for nearly 800 years.
The main culminating event of the Great Conjunction occurs on the evening of Monday, December 21, 2020. However, this conjunction will be visible to the unaided eye beginning on Monday and continuing for the two weeks that follow. Read below for tips on how to best view the great conjunction.
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Today brings the winter solstice and the great conjunction
The Winter Solstice occurs in the Northern Hemisphere beginning at 5:02 AM ET on Monday, December 21, 2020. Today officially marks the first day of winter, as well as brings the shortest day and longest night of the year. But this day is also special for another reason: a rare astronomical event occurs called the Great Conjunction of Jupiter and Saturn. This event is also popularly referred to as “the Christmas Star.” These two planets will appear so closely aligned from our viewpoint on Earth that they will look like a single star.
The last time this happened was 400 years ago, but the last time it occurred in the night sky was nearly 800 years ago, according to NASA, who says this conjunction will be easily visible in the night sky for the next two weeks.
Originally discovered by Galileo
In 1610, the famed Italian astronomer Galileo Galilei pointed his telescope to the night sky to take a look at Jupiter, a large planet easily visible in the night sky. But through the lens of the telescope, Galileo discovered the four moons of the gas giant – Io, Europa, Ganymede, and Callisto.Later, in that same year, Galileo aimed his telescope at Saturn. There, he discovered a strange oval surrounding the planet, which later observations determined to be its rings.
Thirteen years after that, in 1623, Jupiter and Saturn appeared to become one, in an astronomical event that became known as a “Great Conjunction.”
Jupiter and Saturn regularly appear to pass one another in the solar system. From our vantage point on Earth, the positions of Jupiter and Saturn align in the sky about once every twenty years. However, 2020’s alignment is rarer than others. The two planets have not passed this close to one another in 400 years, but it’s been nearly 800 years that this alignment occurred at night.
How to see the Great Conjunction
The Great Conjunction of 2020 will be easily viewable with the unaided eye. Each night, over the next two weeks, the two planets will appear closer low in the southwest in the hour after sunset. However, there are some ways to improve your viewing. NASA offers the following tips:
- Find a spot with an unobstructed view of the sky, such as a field or park. Jupiter and Saturn are bright, so they can be seen even from most cities.
- For the best viewing, wait until an hour after sunset, look to the southwestern sky. Jupiter will look like a bright star and be easily visible. Saturn will be slightly fainter and will appear slightly above and to the left of Jupiter until December 21, when Jupiter will overtake it and they will reverse positions in the sky.
- The planets can be seen with the naked eye, but if you have binoculars or a small telescope, you may be able to see Jupiter’s four large moons orbiting the gas giant planet.