There’s a green, two-horned devil streaking across the night skies over Wyoming — and it’s restless, having several outbursts along its route.
12P/Pons-Brooks is the official name of the devil comet discovered in 1812 by French astronomer Jean-Louis Pons. The dirty celestial snowball making its first visit within eyeshot of Earth since 1954.
With its pristine night skies, Wyomingites always have an excellent chance to enjoy the otherworldly wonders of the universe, and the devil comet is already putting on quite a show, but none of the hellfire and destruction its name might insinuate.
Horned Head Or Forked Tail
12P/Pons-Brooks is a short-period comet, which means its orbit around the sun takes less than 200 years. It takes roughly 71 years for the comet to completely encircle the sun, slightly less than the 74.7-year orbit of Halley’s Comet.
This one’s known as the “devil comet” because it is often seen hurtling through space with two tails behind it, making it resemble a ball with horns. Max Gilbraith, planetarium coordinator for the University of Wyoming Physics and Astronomy Department, said the tails are attached to what’s basically an extraterrestrial snowman.
“A lot of comets are like a snowman,” he said. “They’re two snowballs stuck together in space. We’ve been exploring the Kuiper belt with the New Horizons probe, and it’s common to see these binary contact systems, two snowballs stuck together. When you get two lobes, you can sometimes develop a double tail that looks like these devil horns or something like that.”
A celestial snowman with two tails or a two-headed devil with horns. Pick your preference.
Devilish Outbursts
Since it’s an election year, the devil comet is sticking around for a while. Gilbraith said the two-tailed comet is visible now, although spotting it could be tricky.
“I'd say anytime now through its closest approach to Earth in June, and maybe a month or two after that,” would be the best viewing of it, he said. “It could be visible to the naked eye for some of that time or none of that time. But it seems like it's already had a nice, bright outburst.”
An outburst is an explosion of ice and other particles that briefly increases a comet’s brightness and visibility. Since its return to our solar system, the devil comet has had several outbursts.
Gilbraith said outbursts aren’t created as the comet is slowly torn apart as it travels through space. It’s not dangerous or an ill omen, just the nature of a dirty snowball.
“Comets get bright because they have ice and other volatiles that are very reflective, just like snow,” he said. “As it gets closer to the sun and heats up, that ice will sublimate. It turns directly from a solid to a gas and makes that ice tail, which reflects a lot of sunlight.”
Gilbraith said a comet's tail usually contains a lot of water ice, in addition to other volatiles like frozen oxygen and carbon dioxide. He compared the devil comet’s outbursts to a snow pile in a parking lot.
“If it gets a lot of dust on top of it, it's not very reflective,” he said. “But if you have a bright, fresh snowfall, it is visible from really far away.”
Behold The Devil
Comet 12P/Pons-Brooks is visible now, but it might not be the best time to see it. The dates to know are when the devil comet will reach its closest points to Earth and the sun.
The comet's next perihelion passage, its closest approach to the sun, is anticipated for April 21. It will be 0.78078 astronomical units (AU) away from our star, which means it’ll be a bit closer to the sun than we are on Earth (the distance between the sun and our planet is 1 AU).
Meanwhile, the comet will make its closest approach to Earth on June 2. That day, it will be 1.55 AU away from Earth, 144,158,116 miles, over 600 times more than the distance between Earth and the moon.
In terms of visibility, NASA anticipates 12P/Pons-Brooks will reach an apparent magnitude of 4.5 during its perihelion passage. That would make it dimmer than the North Star, Polaris, but brighter than Uranus, which are magnitude 2 and 6, respectively.
The exceptions are any outbursts, which could make the devil comet up to 40 times brighter. On Oct. 23, 2023, an outburst took the comet from magnitude 15 to magnitude 11.
Regardless, a maximum magnitude of 4.5 means 12P/Pons-Brooks will be visible but hard to spot with the naked eye. However, anyone tempted to use binoculars or a telescope might get a good glimpse of the devil.
12P/Pons-Brooks, aka the devil comet, leaves a trail with Andromeda behind it in this view. (Adobe Stock) 
Tailing The Eclipse
Closest to Earth is exciting, but most astronomers are excited about the perihelion of 12P/Pons-Brooks. According to NASA, "Comet 12P's April 21 perihelion passage will be only two weeks after the April 8 total solar eclipse, putting the comet in planet Earth's sky along with a totally eclipsed sun.”
Gilbraith explained that the timing of the perihelion could result in an unprecedented viewing experience. When the April 8 eclipse reaches totality, the comet could be visible.
“The comet’s only about 25 degrees away from the sun,” he said. “During totality, you might have a chance to look at the comet in the daytime sky. A total solar eclipse with a little comet tail just off to the side of it. If so, that'd be pretty cool.”
Unfortunately, Wyomingites won’t experience any part of the April 8 eclipse. If they want an audience with the devil comet, they’ll have to use their keen eyes or a telescope to find it before it ends its latest visit.
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
