Jupiter and Saturn are likely to be approaching the night sky on the winter solstice this Monday, in a rare alignment that has only happened twice since the Middle Ages.
Weather permitting, the connection between the two largest planets in the solar system at Christmas will be clear enough to see after dark with a pair of binoculars. It is not the star of Bethlehem, astronomers say, but a quirk of orbital mechanics last recorded decorating the skies with such enthusiasm in 1226, when artisans were still building a City- Notre Dame church in Paris and Genghis Khan take over Asia.
“Jupiter and Saturn will have a very close approach,” said astronaut Larry Wasserman at the Lowell Observatory in Flagstaff, Ariz.
Crossing Christmas
Co-occurrences occur when two celestial objects appear to pass close to each other as seen from Earth. They are not physically close, they just look like that because of their orbital alignment.
The connection between Jupiter and Saturn under a dark sky did not occur for about 800 years.
The two planets are visible looking outwards on the western horizon in the hour or so after sunset across most of the world and appear to be separated by an orbit. on one-fifth the diameter of the moon.
The two worlds appear so close to December 21 that they resemble a double planet, separated by a distance equal to just one-fifth of the diameter of the full moon – about a dime thick – as can be seen. from Earth, astronomers say. They will be visible just above the western horizon in the hour after sunset almost all over the world in the days before and after their approach to sunrise.
This month’s planetary connection is part of the solar system’s cloud clock operation. Jupiter orbits the sun every 11.86 years. Saturn circles every 29.46 years. They regularly appear in the sky about once every 20 years or so but are rarely so interconnected.
“It’s almost like watching two runners go around a very big track, one faster than the other,” said Rice University astronaut Patrick Hartigan in Houston, who is on the coalitions. that of Jupiter and Saturn recorded going back 2,000 years and aligned the futures of a pair for the next 1,000 years. “Every once in a while, they show up. ”
Astronomers often use these apparent alignments to help measure orbits more accurately, to estimate distant earth’s magnitudes and to study planetary systems orbiting other stars.
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The two planets had an even newer connection, Dr. Hartigan said, in 1623, just 14 years after Galileo made his first telescope. But it didn’t seem to attract any attention at the time, happening so close to the setting sun that no one could see it. “As far as I know, there are no records of anyone seeing that one,” said Dr Hartigan.
Among some observers of the skies, the pair of planets at Christmas has inspired a comparison with the star of Bethlehem mentioned in the New Testament. No one knows what happened in astronomy, if any, that inspired that biblical tune, Dr. Wasserman said.
Jupiter and Saturn have aligned about 100 times in the last 2,000 years. In the year 7 BC, they made a liner, as seen from Earth, in May, September and early December in a rare triplet, astronomers say. At those levels, however, the planets were relatively far apart and would have appeared significantly lower than expected this month.
There are many other celestial events that could be a Christmas star, astronomers say. In a much clearer and easier-to-see event, for example, Jupiter aligned with Venus in 2 BC
For many, the upcoming winter solstice consortium offers a moment to appreciate the beauty of the night sky.
“It is a truly friendly connection between generations going into the past and the future, to celebrate times and pass time,” said Dr Hartigan. “Whatever our problems or difficulties as human beings, this great celestial clock just keeps going and moving forward.”
Write to Robert Lee Hotz at [email protected]
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