☄ Pons-Brooks 12P/Pons-Brooks

How to follow comet Pons-Brooks live

The panel above recomputes the position of Pons-Brooks every second in your browser: its distance from the Sun and from Earth, its position in the sky (right ascension and declination), and a live countdown to the next perihelion. It runs on the same kind of engine observatories use, a Kepler solver applied to the JPL osculating orbital elements, so the numbers are not a static snapshot, they keep ticking.

Just below, the top-down map of the Solar System shows exactly where Pons-Brooks is right now among the planets. You can fast-forward time with the day slider, zoom and pan, compare its distance to another body with a click, and press "Next event" to jump straight to perihelion. It is the most direct way to grasp the orbit of Pons-Brooks with no math at all.

Comet fact sheet

About Pons-Brooks

12P/Pons-Brooks is a Halley-type periodic comet classified as cryovolcanic: its nucleus releases gas and dust in violent, asymmetric outbursts rather than through passive sublimation alone. With an estimated diameter of roughly 30 km, it ranks among the largest nuclei known for short-to-long period comets. During its 2024 apparition it reached perihelion on 21 April and was visible to the naked eye from northern latitudes between February and May, with brightness outbursts that drew worldwide coverage.

The "devil comet" nickname came from 2023 photographs in which asymmetrically expelled coma material created a silhouette of two symmetric horns around the nucleus. The morphology resulted from two jets of cryogenic material projected through vents in the nucleus and pushed back by solar radiation pressure, creating an iconic visual effect that went viral on astronomy platforms and social media.

History and discovery

The comet was first observed by Jean-Louis Pons on 12 July 1812 from the Marseille Observatory. Pons, considered the greatest visual comet discoverer in history with more than 37 discoveries over his career, recorded the object as a fuzzy patch with no indication it was periodic. William Robert Brooks independently recovered the same object on 2 September 1883, unaware he was seeing a return of the comet catalogued by Pons. The link between the two observations was established later through celestial mechanics calculations, cementing the double name Pons-Brooks.

Historical records suggest the comet may have been sighted as far back as 1385 and 1457, though retroactive identification depends on orbital calculations carrying significant uncertainties. The 1954 return was the first followed with modern instruments, confirming the orbital period of approximately 71 years and the brightness-outburst behaviour that had already been documented in 1883.

The 2023-2024 apparition was the best-observed in the comet's history, benefiting from digital detection instruments, global amateur observation networks, and instant internet communication.

Orbit and returns

12P/Pons-Brooks follows an elliptical orbit with eccentricity 0.9547 and inclination 74.2 degrees to the ecliptic. Perihelion occurs at 0.781 AU from the Sun, just beyond Venus's orbit, while aphelion lies at roughly 33.7 AU in the outer Solar System between Neptune and the Kuiper Belt. The orbital period is about 71.3 years.

During aphelion the comet spends several decades at temperatures near -220 degrees Celsius, preserving its cryogenic volatiles such as CO, CO2 and methane. That deep freezing is what fuels the violent outbursts as the comet draws closer to the Sun.

Nucleus, coma and tail

The 12P/Pons-Brooks nucleus is estimated at roughly 30 km in diameter, notably larger than Halley's Comet at 15 km. That size places it among the largest cometary nuclei known for comets with periods under 200 years. The slow rotation rate of the nucleus, not yet precisely determined, is cited as a factor that allows internal gas pressure to build up before outbursts.

The cryovolcanic behaviour of 12P was studied in unprecedented detail during the 2023-2024 apparition. In each outburst, the nucleus ejected cryogenic material in preferential directions, creating asymmetric jets that solar radiation pressure pushed back. The "horn" morphology recorded in 2023 resulted from two symmetric jets projected through opposing vents in the nucleus, creating a bilobed silhouette around the bright central nucleus.

The coma at perihelion reached considerable angular diameter, with the characteristic green colour of active comets. The ion tail was documented at extensions of up to 2 degrees in February 2024, before perihelion. In April 2024, observers with high-sensitivity photographic equipment recorded both the dust and ion tails clearly.

The sky spectacle

The 2024 apparition was an event anticipated for years by the astronomy community, since the 71-year period is long enough that most observers had not seen the comet during the previous 1954 return. Northern hemisphere visibility was good from February to May 2024, with the comet moving through Andromeda, Pisces and Aries before perihelion.

The 21 April 2024 perihelion came two weeks after the total solar eclipse visible across North America on 8 April. Many observers had hoped to spot the comet during totality, but it was still too faint at that date. In the days following the eclipse, the comet brightened to magnitude 3.8 after the 3 April outburst, becoming visible to the naked eye under dark skies without instruments.

Science and observations

The 2023-2024 apparition generated substantial scientific output on the cryovolcanic mechanism of 12P/Pons-Brooks. Researchers published detailed data on the mass of particles ejected in each outburst, coma composition, and jet structure.

• Number of outbursts: 14 well-documented outbursts between June 2023 and April 2024 (heliocentric distances 4.26 to 0.85 AU), plus two additional post-perihelion outbursts in summer 2024. Historically, 3-4 magnitude outbursts were also recorded during the 1883 and 1954 apparitions.
• Horn mechanism: each outburst released cryogenic material that, pushed by solar radiation pressure, formed the characteristic bilobed morphology. High-resolution photometry showed the two lobes were symmetric and originated at opposing vents in the nucleus.
• Coma composition: long-slit spectroscopy during 2024 identified CN, C2, C3 and OH emissions in the coma, typical composition for Halley-type comets.
• Ejected mass: photometric calculations estimated each event ejected between 10 to the power of 8 and 10 to the power of 10 kg of material, equivalent to tens of millions of tonnes per outburst.
• CO and CO2: cryovolcanic activity was attributed primarily to volatilisation of CO and CO2, gases with very low sublimation points that remain frozen during the long aphelion and erupt when the comet draws close enough to the Sun.

Facts worth knowing

• The horn shape seen in 2023-2024 resulted from two symmetric lateral jets channelled through vents in the nucleus -- it is not a permanent physical feature of the comet.
• The 21 April 2024 perihelion came just two weeks after the total solar eclipse across North America on 8 April -- amateur astronomers had hoped to spot the comet during totality, but it was still too faint at that date.
• With a nucleus of ~30 km, 12P is notably larger than Halley's Comet at about 15 km, though both qualify as large-nucleus comets for their respective periods.
• Jean-Louis Pons discovered more than 37 comets over his career, the all-time record for visual discoveries by a single observer.
• The 2095 return will place perihelion near late June, with geometry potentially more favourable for southern hemisphere observers.
• In every documented apparition since 1812, the comet has produced at least one significant brightness outburst, confirming that cryovolcanic behaviour is a permanent, not accidental, feature of 12P.
• The term cryovolcanic, classifying comets that eject material through internal eruptions rather than passive sublimation alone, was popularised in part through study of 12P/Pons-Brooks during the 2023-2024 apparition.
• The richness of 2024 data on 12P is expected to inform the design of future flyby missions to cryovolcanic comets.

Other comets

See the full comet catalogue.