This month, if you should incline your head slightly upwards at night, you will receive a treat in the form of six of the eight planets visible in the skyline.
Mercury, the closest planet to the Sun (and all the other planets), will not make the show in its current position behind the Sun, while you won’t see the eighth planet because you’re standing on it. If you would like to see seven planets in the sky, you can simply wait until mid-February, when Mercury will pop its hot head out from behind the Sun.
But will all eight planets (sorry Pluto) ever align all together in the sky? Well, that depends on your perspective.
First off, it’s actually pretty rare for planets to align perfectly, with their orbital inclinations making a full alignment virtually impossible. If you were waiting for the planets to align so that they are within 1 degree of each other (and assuming the Sun and the planets cheated their demise) you would have to wait around 13.4 trillion years for such an event, and unless you’re Bryan Johnson you probably aren’t planning on living that long.
“The planets’ orbits don’t all exist perfectly in the same plane. They’re all tilted a little, so that planets don’t all fall exactly along a line in the sky,” Philip C. Plait explains in the book Bad Astronomy. “Sometimes a planet is a little above the plane, and sometimes a little below… For this reason, surprisingly, it’s actually rather rare for more than two planets to be near each other in the sky at the same time.”
When people refer to alignment, they are generally referring to the planets being in the same region of the sky, rather than perfectly lined up from our perspective, also known as a “planetary parade“.
It’s pretty uncommon to see all the planets on the same side of the Sun, too, with that taking place roughly once every thousand years, with the last occurrence taking place in 949 CE. The closest we will get to all the planets being aligned, at least within an imaginable timeframe, will be on May 6, 2492. On this date, at around 5:00 am EST, you would be able to see seven planets in a planetary parade, making an arc just above the horizon. Looking down, of course, you would see the eighth beneath you.
Though you will not get to witness this (with apologies to Bryan Johnson), you can see the position the planets will appear in the sky using free software Stellarium, setting the date and time, and your position to just off the coast of New York. But look up at the sky early this year, and you will also get the gist of it.
Source Link: Have All The Planets Ever Aligned? The Closest We'll Get Is May 6, 2492
