PORTLAND, Maine — This doesn’t happen often.
In fact, this uncommon celestial event hasn’t been seen in the night sky over the Pine Tree State for more than a decade. So, you don’t want to miss it.
On Wednesday night, a brilliant, almost full moon will slip in front of our radiant red neighbor Mars, obscuring it from view. Then, almost a half hour later, the scarlet planet will reappear from behind the far side of the moon as our heavenly, gray satellite moves along its nighttime orbit.
The phenomenon is known as an “occultation.” It comes from the verb “occult,” meaning to cut something off from view via an interposing object.
It’s totally scientific and has nothing to do with witches, warlocks, Harry Potter or anything supernatural.
The moon gets between earthling eyes and our solar system’s planets several times every year. But occultations are only ever viewable on tiny swaths of earthly acreage each time.
That’s because the moon is so much closer to us than everything else up there. Its visible position in the sky above us varies greatly depending on where we’re standing on Earth at any given moment.
“So it’s not super common for any particular spot on Earth to see [occultations] frequently,” said Preston Dyches of NASA’s Jet Propulsion Laboratory in California.
But this time around, Mainers are among the lucky few who get to watch.
Maine skywatchers haven’t had the opportunity to see a Mars occultation in over a decade and the next chance won’t be until Jan. 14, 2025.
Of course, any heavenly event can be thwarted by simple cloud cover. That makes uncommon opportunities like this even more exciting, or disappointing, depending on the outcome.
No special equipment is needed to watch, though a simple pair of binoculars or small telescope will enhance the experience. Exactly when it begins and ends depends on your geographic location.
For Portland observers, the show starts at 10:57 p.m. in the southeastern sky and ends at 11:24 p.m. The further north you go, the earlier it starts, though not by much. Houlton observers will watch Mars disappear a minute earlier at 10:56 p.m.
A couple of other factors will make this Mars occultation spectacular.
First, the moon will be dazzling. Technically, it will not be full until the next night but it will be close enough to be indistinguishable from the real thing.
Second, Mars also will be particularly bright.
The night after the occultation, Mars will reach full opposition. That means the red planet will be directly opposite the sun from our vantage point, reflecting as much of the star’s light back at our eyes as possible.
Around the same time Mars gets to opposition, it also will be making its closest approach to Earth. That’s known as its perigee.
Being near us, and directly opposite the sun, our crimson neighbor will be quite spectacular in the sky, holding its own against the very bright moon. Mars won’t shine this bright again for 11 years.
Dyches said planetary occultations are more visually stunning than their stellar counterparts.
“The Moon passes in front of stars all the time. If you’re watching through binoculars, they just blink right out,” Dyches said. “But planets are not just points of light like stars — they appear as circular little disks, so planets actually take several seconds to disappear and later reemerge.”
If clouds and weather ruin the Martian occultation on Wednesday, the heavens have a little holiday gift in store for us later this month, as well.
On Christmas Eve, about a half hour after sunset, bundle up and take the family outside. Then, look southwest, a little higher than the horizon. Bring binoculars and hot cocoa if you can.
If it’s clear, you’ll see a skinny, thumbnail crescent moon rising with Venus and Mercury forming a triangle.
If it’s cloudy, at least you have each other’s company and something sweet and hot to drink.