Comets are celestial travelers, often described as “dirty snowballs,” that orbit the Sun and display a glowing cloud of gas and dust, known as a coma, and sometimes a bright tail. These icy bodies are relics from the solar system’s formation. One such object, Comet 12P/Pons-Brooks, has recently captured attention due to its unusual, recurring shape and explosive nature, earning it the moniker, “The Devil’s Comet.”
Core Identity and Discovery
The object is formally designated 12P/Pons-Brooks, marking it as the twelfth comet recognized with a short-period orbit. Its classification as a Halley-type periodic comet means its elliptical orbit takes between 20 and 200 years to complete, with this specific comet returning approximately every 71 years. The comet bears the names of two prominent comet hunters: Jean-Louis Pons, who first conclusively spotted it in 1812, and William Brooks, who independently rediscovered it during its next return in 1883.
The comet possesses a large nucleus, an icy core estimated to be between 17 and 30 kilometers in diameter. Its physical makeup consists of a mixture of dust, rock, and various frozen gases, including water ice and more volatile compounds. The nucleus is likely larger than that of Halley’s Comet, suggesting a significant reservoir of material.
The Cryovolcanic Engine
The nickname, “The Devil’s Comet,” stems from the object’s unique and recurrent explosive behavior, a phenomenon known as cryovolcanism. This process is driven by internal pressure that builds up as the comet nears the Sun. Solar radiation penetrates the surface layers of the nucleus, warming and vaporizing volatile compounds such as carbon monoxide and nitrogen ice trapped beneath the crust.
As these frozen gases turn into vapor, the pressure inside the nucleus increases until the icy shell ruptures. This causes a sudden eruption that blasts a mixture of gas and fine ice particles, often referred to as cryomagma, into space. Such an event, known as an outburst, can cause the comet’s brightness to increase by a factor of up to 100 times in a single day. The resulting cloud of material, or coma, rapidly expands to enormous sizes.
A large outburst in 2023 created an asymmetrical, horseshoe-like shape in the expanding coma. This distinct, bifurcated appearance resembled a pair of horns, which immediately led to the adoption of the “Devil’s Comet” nickname. The comet’s distinctive green color is attributed to the presence of diatomic carbon molecules in the coma, which glow when exposed to sunlight. These eruptions are a signature feature of 12P/Pons-Brooks.
Tracking and Viewing Opportunities
The comet’s recent passage brought it closest to the Sun, or perihelion, on April 21, 2024, the time when it shone at its brightest for this return. During this period, the comet was best viewed low on the western horizon just after sunset, as its proximity to the Sun made it a twilight object. Observers were generally advised to use binoculars or a small telescope for a clearer view of the fuzzy, glowing coma.
Following its perihelion, the comet continued its journey, making its closest approach to Earth on June 2, 2024, though at a significant distance of approximately 232 million kilometers. After this date, 12P/Pons-Brooks began its retreat back into the outer solar system. The 2024 apparition represents a once-in-a-lifetime chance for most people to see this comet, as it will not return until the next expected perihelion on August 15, 2095.