Comet 12P/Pons-Brooks, the “Devil’s Comet”

On July 21, 1812, a French astronomer named Jean Louis Pons was observing a remote region of the night sky when he found, on the border of two very dark constellations, Camelopardalis and Lynx, a comet of magnitude 6.5 (the magnitude indicates the degree of brightness of a celestial object: the lower the magnitude value, the brighter it is).

Pons described his discovery in his journal entries as a shapeless object with no tail. However, just over three weeks later, the comet reached naked-eye visibility and, at the end of August, it had a magnitude of 4.5 and a tail of significant extension. Observations continued until September, when the comet plunged into the southern sky, out of sight of most northern observers.

Several astronomers tried to calculate the comet's orbit and all the results indicated that it was of a periodic comet that traveled around the Sun in a highly elliptical cycle with a period of approximately 65 to 75 years.

Representation made of comet Pons-Brooks in 1884.Source: Public Domain

In fact, 71 years later, the same comet was seen again on the night of September 2, 1883, when American comet observer William R. Brooks accidentally found it. Initially, the comet was quite faint – at magnitude 10.0 – and was thought to be a new comet until the first orbital calculations showed that it was identical to Comet Pons. The comet soon became visible to the naked eye on November 20 and brightened to a magnitude of 3.0.

After this new appearance of the comet, other orbital calculations were made and showed that the comet has a period of approximately 71.3 years and would return in 1953-1954, which in fact happened.

Today, it is known that this comet, called 12P/Pons-Brooks, is a Halley-type comet that during its closest approach to the Sun, or perihelion, reaches approximately 0.78 astronomical units (116 million kilometers) , while at its furthest point, or aphelion, it reaches a distance of about 17.2 astronomical units (2.5 billion kilometers).

Comet Rosetta, example of a periodic comet.Source: Rolando Ligustri

If you did the math in your head from the last time he was observed in 1953, already understand that 12P/Pons-Brooks will return in 2024 and can be seen from both hemispheres of the planet with the help of small telescopes and/or binoculars.

In this passage, it is expected to reach its maximum brightness during the month of April.

Its closest approach to Earth is expected to occur in early April, a moment that will present a unique opportunity for amateur and enthusiast astronomers to observe it in the night sky. However, because the comet's brightness is often unpredictable, there is no guarantee that it will be visible without the use of instruments.

Comet 12P/Pons-Brooks in 2023.Source: Comet Chasers/Richard Miles

So far, 12P/Pons-Brooks has been monitored since June 2020 by the Lowell Discovery Telescope in Arizona. When first sighted, the comet was magnitude 23.0 and has since increased in brightness to about magnitude 10.0, making it a target for moderately large telescopes.

On July 20, 2020, an unexpected burst of brightness again caused it to briefly become about 100 times brighter and, similar to what was seen in 1884, Its coma expanded to resemble what some consider to be the horns of a demon, which is why it became known as “the Devil’s Comet.”.

The exact cause of the explosion is unknown, but it is speculated that it was caused by a fissure in the comet's nucleus, due to the accumulation of gas – carbon monoxide and dioxide – inside it.

Current location of comet 12P/Pons-Brooks in the constellation Cygnus (February 5, 2024).Source: Sky Live

Comet 12P/Pons-Brooks is currently in the constellation Cygnus, at an approximate distance of 280 million kilometers from Earth and at the end of February it is expected to be at magnitude 7.0.

On the nights of March 30 and 31, 12P/Pons-Brooks will pass very close to Aries' brightest star, Hamal. This star will be useful as a reference for finding the comet. After that, The comet will fade into the sunset glow during April and reach perihelion on April 21, beginning the best time for Southern Hemisphere observers. Its brightness will gradually become dimmer in the months of May and June.