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An unusual horned comet notable for a series of explosions, nicknamed the “devil’s comet,” will make its closest approach to Earth on Sunday around 3 a.m. ET.
While 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 seeing the fuzzy object through 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 movies when it is explosively active is still a puzzle to scientists. But the celestial object completes only one orbit around the sun about every 71 years, similar to Halley’s Comet, which makes the chances of observing it for close-up study a once-in-a-lifetime opportunity.
Given that the comet won’t pass by Earth again for decades, collective observations by astronomers could provide key insights into its true nature and behavior.
Officially known as Comet 12P/Pons-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 make its closest pass of Earth on Sunday, but it will be more than 143 million miles (230 million kilometers) from our planet and will not pose a threat. 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 has been steadily dimming for three to four weeks, Dr. Dave Schleicher, astronomer at the Lowell Observatory in Arizona.
“For people below the equator, the next few weeks and months could be the first good chance to see this thing since the 1950s,” said astronomer Dr. Teddy Kareta, 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 likely made many trips around the sun over thousands of years, long before astronomers to think of comets as anything other than “something weird in the atmosphere,” Schleicher said.
Astronomers estimate the massive comet to be 6.2 to 12.4 miles (10 to 20 kilometers) in diameter, 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 caught the attention of astronomers after exhibiting intriguing behavior that caused the comet to take on a horned appearance and fly into our solar system.
The comet has experienced a series of explosions over the past eight months, causing it to eject gas and dust. While such releases are not uncommon in comets, and a crescent or Pac-Man shape has been observed in others, it is difficult to say what is normal for Pons-Brooks.
“I would say it’s somewhat unusual in the number of explosions there have been,” Schleicher said. “On the other hand, it’s not like you have a good track record from the past to tell you what’s typical. And I suspect given the fairly large number of explosions that have occurred over the past eight months, that this is very clearly a common occurrence for Pons-Brooks.
Comets are chunks of dust, rock and ice, essentially frozen leftovers from the formation of the solar system. They also contain frozen elements such as carbon dioxide and carbon monoxide.
Comets heat up and glow as they approach the sun, and some of the frozen gases stored in comets don’t need to heat up much before they start turning into vapor, Schleicher said.
Theodore Kareta Observatory/Lowell
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 October 2023 image.
“We think the ultimate driver, of course, is solar heating,” he said. “The comet is coming in; it’s been in a deep freeze for years. The heat will move from the surface down to wherever the carbon dioxide or carbon monoxide ice is.”
Astronomers suspect that Pons-Brooks explosions have occurred in the course of repeated events, as heat vaporizes material inside the comet, which causes the pressure to rise and penetrate the surface. While a burst of gas would not be visible to telescopes, the dust it emits would create the type of events observed by Pons-Brooks, Schleicher said.
Scientists have traced the jets of material observed being ejected from the comet during its explosion to two source regions on its surface. Astronomers are puzzled as to why “the whole surface isn’t going crazy,” Schleicher said.
The observations imply that the ice has crusted over much of the surface, or the ice has evaporated, leaving only debris behind, but astronomers “are not entirely sure which of these mechanisms is driving 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 have been 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 jets of material ejected from the comet are speeding it up or slowing it down.
An overlapping series of events likely contributed to Pons-Brooks’ distinctive appearance, but it could also be due to our view of the comet, Kareta said.
“These are three-dimensional objects,” Kareta said. “When we take images of the night sky, we get them in a limited range of colors, all flattened in two dimensions. It’s going to make things that might make perfect sense to you, if you’re able to go up and walk around and see it from a few different angles, look a lot more complicated than they really are.”
