The Backyard Astronomer: For the first time in 40 centuries, a Christmas Star conjunction in the night sky

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      The year 2020 will never be forgotten. For the past 11 months, the entire world has suffered a high level of stress and anxiety from the coronavirus pandemic. Normal routines of going to work, school, restaurants, concerts, sporting events, and movies came to a halt.

      Other than reading, playing games, or binge-watching TV, people began looking skyward, some for the first time. And why not? Astronomy is the oldest of the allied sciences, and the night sky has been a place of deep relaxation for thousands of years. We also have the means of learning science as it plays out in the cosmos.

      And now, for the first time in almost four thousand years, the night sky will deliver an end-of-year spectacle that might instill hope for the new year in the minds of those so inclined.

      This year, we desperately needed a distraction, and then came Comet Neowise. It put on a fantastic show throughout July, as it was seen with the naked eye even in the moonlight. This allowed millions of people around the world to observe and photograph this interstellar visitor. Neowise is now on its way back to the icy depths of space, not to be seen again until its return—about 6,800 years from now.

      Then the first week of October saw Mars at its closest approach to Earth since 2003. Our two worlds swing close to each other every 26 months, but every seventh return is deemed the closest. Mars is still seen for most of the night, appearing high overhead as a bright orange object. Over the weeks and months, Mars dims ever so slowly as our distance increases

      To close the year, we have two more celestial events that will entice people to look up once again: a grand meteor shower and a "great conjunction" of two planets. (A conjunction, in astronomy terms, is when two objects in space—such as planets, stars, moons, etcetera—appear to be unusually close to each other in the night sky as seen from our planet. The term great conjunction refers specifically to such an alignment involving the planets Jupiter and Saturn.)

      Like ping-pong balls on a table, the planets lie on the plane of the solar system with the sun at the center. Over months and years, the planets revolve around the sun at different speeds. On occasion, two planets will, optically, come close to each other in the sky. This is called a planetary conjunction. Brilliant Jupiter (887 million kilometres away) and Saturn (1.6 billion kilometres away, to the upper left) are now visible low in the southwestern sky and will appear extremely close to each other on the night of December 21 (which also happens to be the winter solstice).

      A previous conjunction of Saturn and Jupiter.
      Gary Boyle

      A typical Jupiter-Saturn conjunction occurs every 20 years or so, but this year they will appear as a double planet with a separation equal to one-fifth the width of the full moon. This will give telescope owners a rare treat of seeing these gas giants and their moons in the same field of view. This extremely close approach plays out every 397 years.

      Many are associating this with the Star of the Magi (or the Christmas Star) in the Christian nativity story, which was actually the close conjunction of our solar system's two brightest planets: namely, Venus and Jupiter. On the night of June 17, 2 BC, they appeared to touch each other, which was deemed a miraculous sign. (This is the closest astronomical event of the time; Halley’s Comet was seen 10 years prior, in 12 BC, as recorded by the Chinese.)

      Woodcut of the nativity story by Julius Schnorr von Carolsfeld for the book Die Bibel in Bildern (1860), with the light of the Star of the Magi shining down.
      Wikimedia Commons

      A week before the December 21 great conjunction, the Geminid meteor shower will peak on the night of December 13 to 14, producing 120 slow-moving meteors per hour. There will be a few fireballs that can actually light up the ground. This is one of the best showers of the year, and moonlight will not interfere.

      Till next time, clear skies.

      Known as “The Backyard Astronomer”, Gary Boyle is an astronomy educator, guest speaker and monthly columnist for the Royal Astronomical Society of Canada. He has been interviewed on more than 50 Canadian radio stations and local Ottawa TV. In recognition of his public outreach in astronomy, the International Astronomical Union has honoured him with the naming of Asteroid (22406) Garyboyle. Follow him on Twitter: @astroeducator or his website: