As NASA noted earlier this month in anticipation of the event, the "Christmas Star" and/or the "Great Conjunction" is made possible by underrated planets Jupiter and Saturn.
"You can imagine the solar system to be a racetrack, with each of the planets as a runner in their own lane and the Earth toward the center of the stadium," Henry Throop, an astronomer in the Planetary Science Division at NASA Headquarters in Washington, explained last week. "From our vantage point, we'll be able to be to see Jupiter on the inside lane, approaching Saturn all month and finally overtaking it on December 21."
The timing of this visual gem, the first of its kind in hundreds of years, is a result of sheer happenstance. Per Throop, conjunctions of this type could actually happen on any given day of any given year, though the timing of this particular example is indeed considered a "rare coincidence" for a multitude of reasons. Chief among them, of course, is that its nighttime status made astronomical appreciation possible for so many on this increasingly damaged-by-us planet.
While the opportunity to view Jupiter and Saturn at the closest alignment has already passed, the days ahead will still include chances to peep the planets.
In the meantime, here's a grab bag of Great Conjunction porn:
Look up more often. There's much to see.