By Michael Wing
The saga of the planetary parade now rolls into spring. As we cross the threshold from winter into bloom season 2023, five planets—Jupiter, Mercury, Venus, Uranus, and Mars—plus the quarter moon are set to align on March 28, forming an imperfect arc from low on the western horizon, heavenward toward the southwest.
Hopeful planet hunters will have a good chance to spot at least part of it with their naked eyes, though a clear horizon and optical aids, such as pair of good binoculars or a telescope, will up one’s chances of catching the whole thing.
In just days, looking due west shortly after sundown, the avid sky watcher will find Mercury (with brightness magnitude -1.3) and Jupiter (magnitude -2.1) near the horizon in the constellation Pisces, marking one end of a cosmic convoy spanning a 50-degree section of sky. The two bright objects will hold a convergence here, one degree apart—about the same distance as two full moons. They may be challenging to spot; luckily Venus will beacon brightly almost directly overhead, which one can trace to the setting sun to find them.
As both planets are so close to the horizon, observers will need a nearly flat western horizon, free of obstruction and a clear sky to see them.
Next in the lineup, Venus will sparkle brilliantly in the constellation Aries with a magnitude of 0.4 and easily be seen with the naked eye. Nearby, two degrees from Venus, the planet Uranus will appear very faint with a magnitude of 5.8, requiring a strong pair of binoculars or telescope to distinguish it from the surrounding stars.
Lastly, high in the southwestern sky, Mars will join the alignment, glowing rust-red with a magnitude of 0.9, accompanied by the first quarter moon slightly higher, located in the constellation Gemini.
What Is a Planetary Alignment?
One might notice that the lineup is anything but exactly lined up; it’s a buckled procession at best—with a rather lackadaisical parade marshal, it would seem. But by definition, planetary alignments call for approximation rather than rigid, mathematical precision. Currently, there are two common definitions of planetary alignment in use:
- A number of planets all gathered on one side of the sun at the same time, from a vantage point above the solar system; or
- A visual phenomenon where a number of planets appear in close proximity to each other in a small sky sector, from the perspective of the Earth.
In other words, planets do not have to line up exactly to constitute an alignment but merely be close, or appear close, to each other.
Why might that be, you ask?
In truth, both the laws of physics and common sense prevent our planets from forming a perfectly straight line in the 3-dimensional space we inhabit. How might they? For one, the appearance of an alignment depends on the position of the viewer, which isn’t fixed; so there is the problem of defining such an alignment.
Secondly, each planet has its own elliptic plane (or orbital plane around the sun), none of which is exactly the same as the others, though they’re roughly similar to each other and do generally follow Earth’s elliptic (the path the sun appears to follow in our skies). Thus, it’s physically impossible that they will ever align perfectly. Yet it’s because they almost line up that planetary alignments, as we know them, are so common.
Meanwhile, “planetary parade” is a synonymous, looser, and more playful astrological term, meaning multiple planets located in the same zodiac constellation, according to starwalk.space.
So, as frigid temps thaw and warmer weather prevails, come twilight on March 28, cast a gaze westward from your patio or swimming pool lounger. Venus should shimmer brightly over the horizon, with Mars and dimmer Uranus heavenward and to the south. Given a clear horizon, you may trace the parade to the set sun to find the glowing objects Mercury and Jupiter lingering in the twilight.
Next on the Planetary Parade Itinerary
The next planetary alignment will occur in April 2023, which features four planets gathering within 35-40-degree sky sectors. June features a three-planet alignment all within 70 degrees in the morning. Ushering in summer, watch out on June 17 as five planets align across 95 degrees of sky, according to starwalk.space.
Further down the pike: Come March 2080, six planets will line up in the morning sky within an 82-degree sector. In May 2161, all solar system planets, including Earth, will gather within 171 degrees from the Earth’s standpoint. In May 2492, all solar system planets, plus earth, will align on one side of the sun within a 162-degree sky sector. It should be glorious. Don’t hold your breath, of course.