For this first time since the Middle Ages people on Earth can see what resembles the Christmas star seen by shepherds on the night of Christ’s birth. The “bright point of light” is actually the result of the close proximity between the planets Jupiter and Saturn that will take place on the week of December 20.
The planets aren’t really as close as they look, according to the Forbes magazine report on the phenomenon:
In reality, of course, they won’t be close at all. Think about the distance from the Earth to the Sun. That’s what astronomers call an astronomical unit (au), and it’s how they measure distances in the vastness of the Solar System. Jupiter is 5 au from us. Saturn is 10 au.
These two planets aligned in the Solar System a few weeks ago, but on December 21 they’ll appear aligned to us on Earth. Our line of sight is different because we’re orbiting quickly around the Sun.
“Alignments between these two planets are rather rare, occurring once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets will appear to be to one another,” said Patrick Hartigan, astronomer at Rice University. “You’d have to go all the way back to just before dawn on March 4, 1226, to see a closer alignment between these objects visible in the night sky.”
The two planets actually align in this way every 19.6 years but they rarely appear so close from Earth as they will this month, and most brightly on December 21 when they will look like they are separated by less than the visual diameter of a full Moon.
“It’s thought by some—including legendary German astronomer Johannes Kepler—that the ‘star of Bethlehem’ in the story of the Magi or ‘three wise men’ could have been a rare triple conjunction of Jupiter, Saturn and Venus,” Forbes reported.
The magazine reported that the rare celestial event will be observable anywhere on Earth where skies are clear. The planets will be visible in the western sky for about an hour after sunset in in the northern hemisphere.
The planets will appear low in the western sky for about an hour after sunset as viewed from the northern hemisphere, and though they’ll be closest on December 21, 2020, you can look each evening that week.
A “great conjunction” like this won’t happen again until March 15, 2080, according to Forbes.
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