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An unusual horned comet notable for a series of outbursts dubbed the “Devil’s Comet” will make its closest approach to Earth on Sunday around 3 a.m. ET.
Although the comet has not been visible to those in the Northern Hemisphere since the first week of May, sky watchers in the Southern Hemisphere have a better chance of catching a glimpse of the fuzzy object through binoculars or a telescope.
Exactly why the dynamic comet takes on a shape that draws comparisons to the Millennium Falcon spacecraft from the Star Wars movies when it is explosively active is still an enigma to scientists. But the celestial object completes only one revolution around the sun every 71 years, like Halley’s Comet, making the chances of observing it for close study a once-in-a-lifetime opportunity.
Given that the comet won’t pass by Earth again for decades, astronomers’ collective observations could provide key insight into its true nature and behavior.
Officially known as Comet 12P/Ponce-Brooks, the celestial object made its closest pass by 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 will be more than 143 million miles (230 million kilometers) from our planet and pose no 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 over Manciano, in Italy’s Tuscany region, under the peninsula’s darkest sky.
The comet peaked in brightness in late April and steadily faded for three to four weeks, said Dr. Dave Schleicher, an astronomer at the Lowell Observatory in Arizona.
“For people below the equator, the coming weeks and months may be their first good chance to see this thing since the 1950s,” said astronomer Dr. Teddy Carretta, a postdoctoral fellow 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 many trips around the sun over thousands of years, long before astronomers to consider comets as something other than “something weird in the atmosphere,” Schleicher said.
Astronomers estimate the massive comet to be between 6.2 and 12.4 miles (10 to 20 kilometers) in diameter, Carretta said.
The rare visitor has the 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 caught the attention of astronomers after it showed intriguing behavior that caused the comet to take on a hornlike appearance and soar through our solar system.
The comet has undergone a series of outbursts over the past eight months, causing it to eject gas and dust. Although such discharges are not unusual in comets, and a crescent or Pac-Man shape has been observed in others, it is difficult to say what is normal for Ponce-Brooks.
“I would say it’s a little unusual in the number of outbreaks that there are,” Schleicher said. “On the other hand, it’s not like you have good records from the past to really let you know what’s typical. And I suspect, given the fairly large number of outbreaks that have occurred in the past eight months, that this is quite common for Ponce-Brooks.
Comets are chunks of dust, rock and ice, essentially frozen remnants of 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 have to warm much before they start to vaporize, Schleicher said.
Theodore Carretta/Lowell Observatory
The expanding bright spot (center) is an outburst from Comet 12P/Pons-Brooks that occurred the day before the Lowell Discovery Telescope in Arizona captured this image in October 2023.
“We think the main driver, of course, is heating from the sun,” he said. “The comet enters; it’s been sitting in a deep freeze for years. Heat will make its way from the surface down to where the carbon dioxide or carbon monoxide ice is.
Astronomers suspect that Pons-Brooks bursts occur over the course of repeated events as heat vaporizes material inside the comet, causing pressure to build up and break through the surface. While a gas explosion would not be visible to telescopes, the dust it kicks up would create the kind of events observed by Pons-Brooks, Schleicher said.
Scientists have traced the plumes of material seen ejected from the comet during its explosion to two sources on its surface. Astronomers are puzzled as to why “the whole surface doesn’t explode like crazy,” Schleicher said.
The observations suggest that ice has covered most of the surface, or the ice has evaporated, leaving only dirt behind, but astronomers “are not quite sure which of these mechanisms is running the show,” he said.
However, the comet’s outbursts appear to have stopped, and it has not shown any explosive activity since February, Carretta said.
Astronomers have been watching Pons-Brooks in hopes of revealing more details about its spin rate, or the rate 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 from the comet speed it up or slow it down.
An overlapping series of events likely contributed to Pons-Brooks’ distinctive appearance, but it could also be due to our perspective on the comet, Carretta said.
“These are three-dimensional objects,” Carretta said. “When we make images of the night sky, we make them in a limited range of colors, all flattened in two dimensions. It will make things that might make perfect sense to you if you could get on and walk around and see it from a few different points of view look a lot more complicated than they really are.
