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An unusual horned comet notable for a series of explosions, dubbed the “Devil’s Comet,” will come closest to Earth on Sunday around 3 a.m. ET.
Although the comet has not been visible to residents of the Northern Hemisphere since the first week of May, skywatchers in the Southern Hemisphere have a better chance of spotting the blurry object using binoculars or a telescope.
Exactly why the dynamic comet takes on a shape that has drawn comparisons to the Millennium Falcon spacecraft from the “Star Wars” films when it is explosively active remains a conundrum for scientists. But the celestial object only orbits the sun about every 71 years, like Halley’s Comet, making the chances of observing it for in-depth study a unique opportunity.
Since the comet won’t pass by Earth again for decades, astronomers’ collective observations could provide key insights into its true nature and behavior.
Officially known as Comet 12P/Pons-Brooks, the celestial object made its closest pass to the sun on April 21, coming within 74.4 million miles (119.7 million kilometers) of our star.
The comet will pass closest to Earth on Sunday, but it will be more than 230 million kilometers from our planet and will not present any risk. For reference, the Sun is 93 million miles (149 million kilometers) from Earth.
Gianluca Masi/Virtual Telescope Project
The virtual telescope project captured a view of the comet above Manciano, in the Italian region of Tuscany, under the darkest sky on the peninsula.
The comet’s brightness peaked in late April and has been fading steadily for three to four weeks, said Dr. Dave Schleicher, an astronomer at Lowell Observatory in Arizona.
“For people living below the equator, the coming weeks and months could be the first good opportunity to see this thing since the 1950s,” said astronomer Dr. Teddy Kareta, a postdoctoral associate at Lowell.
Two prolific discoverers, Jean-Louis Pons and William Robert Brooks, independently observed the Devil’s Comet: Pons in 1812 and Brooks in 1883. But the comet probably made numerous trips around the sun for thousands of years, long before that astronomers consider comets to be comets. anything other than “something weird in the atmosphere,” Schleicher said.
Astronomers estimate that the massive comet has a diameter of between 10 and 20 kilometers, Kareta said.
The rare visitor has a green appearance typical of most comets, because they contain diatomic carbon molecules that absorb sunlight and emit a color that appears green from our perspective, Schleicher said.
Pons-Brooks recently attracted the attention of astronomers after showing intriguing behavior that gave the comet a horny appearance and its flyby through our solar system.
The comet has experienced several explosions over the past eight months, causing ejections of gas and dust. Although such releases are not uncommon on comets and a crescent or Pac-Man shape has been observed on other comets, it is difficult to say what is normal for Pons-Brooks.
“I would say the number of explosions is somewhat unusual,” Schleicher said. “On the other hand, it’s not like you have any good records from the past to really let you know what’s typical. And I suspect that given the fairly large number of explosions that have occurred over the past eight months, this is clearly a regular occurrence for Pons-Brooks.
Comets are bits of dust, rock and ice, essentially frozen remains from the formation of the solar system. They also contain frozen elements such as carbon dioxide and carbon monoxide.
Comets heat up and brighten as they approach the sun, and some of the frozen gases stored in comets don’t need to warm up much before they start turning into vapor, Schleicher said.
Theodore Kareta/Lowell Observatory
The bright expanding blob (center) is an explosion from Comet 12P/Pons-Brooks that occurred a day before the Lowell Discovery Telescope in Arizona captured this October 2023 image.
“We think the ultimate factor, of course, is heating from the sun,” he said. “The comet is coming; it has been sitting in a freezer for years. The heat will travel from the surface to where the carbon dioxide or carbon monoxide ice is.
Astronomers suspect that Pons-Brooks explosions occurred in repeated events when heat vaporizes material inside the comet, causing pressure to build up and rupture across the surface. Even though a gas explosion wouldn’t be visible in telescopes, the dust it would kick up would create the kind of events seen from Pons-Brooks, Schleicher said.
Scientists traced the jets of material observed releasing from the comet during its explosion to two source regions on its surface. Astronomers wonder why “the entire surface isn’t collapsing like crazy,” Schleicher said.
The observations imply that the ice either crusted over the majority of the surface, or that the ice was vaporized, leaving only dirt behind, but astronomers “are not sure which of these mechanisms drives the show,” he said.
The comet’s explosions appear to have stopped, however, and it has not shown any explosive activity since February, Kareta said.
Astronomers are observing Pons-Brooks in hopes of discovering more details about its spin rate, or the speed at which comets spin as they move through space. Pons-Brooks has a rotation period of 57 hours, which is longer than expected, and astronomers want to know whether the jets of material released by the comet are speeding it up or slowing it down.
A series of overlapping events likely contributed to Pons-Brooks’ distinctive appearance, but it could also be due to our perspective of the comet, Kareta said.
“They are three-dimensional objects,” Kareta said. “When we take images of the night sky, we take them in a limited range of colors, all flattened into two dimensions. This will make things that might make perfect sense to you, if you are able to go up and walk around and see things from different angles, they will seem much more complicated than they really are.