Halley's Comet's Cousin: Unveiling the Secrets of 12P/Pons-Brooks

Comets are very small objects, only a few kilometers wide, orbiting the Sun. They are mostly concentrated where the orbits of all planets finish.

Comets are very small objects, only a few kilometers wide, orbiting the Sun. They are mostly concentrated where the orbits of all planets finish. After the orbit of Neptune, a large number of comets circle the Sun; this region of the solar system is called the Kuiper Belt. Another concentration of comets is very far away from the Sun, approximately 2 light-years away, called the Oort Cloud.

Comets from these concentrations often change their original orbits and fall inward, towards inner planets. When comets start their inward motion, they might be on parabolic paths, which will make them swing around the Sun and then head back to the outer regions of the solar system. But if they are influenced by the gravity of outer planets, their paths might change into elliptical ones, and they might become periodic comets. Now they repeat their visits to the inner solar system.

The very first periodic comet that was identified was Halley’s comet, and hence it is given the name 1P/Halley. It is also the most famous comet, as it is bright enough to be seen with an unaided eye and completes its orbit after 76 years. Its last visit to the inner solar system was in 1986, and now it will be in mid-2061.

Then, among many periodic comets, there is another one called 12P/Pons Brooks, which is still in the inner solar system as I am writing this article. Two days ago, it passed closest to the Sun (called the perihelion) and is now heading back to the outer solar system. It was observed by astronomers all over the world, and I did too.

Comet 12P/Pons Brooks

The comet was discovered by two astronomers separately back in the 19th century, and that is why it is named after both of them, Jean-Louis Pons and William Robert Brooks. It orbits the Sun  every 71 years. This time, when it came to the inner part of the solar system, astronomers all over the world saw it.

From those areas with clear skies, Comet 12P/Pons Brooks was visible to the unaided eye (without any telescope or binoculars), but from city areas with pollution and dust, it was visible in camera images with long exposure times and in binoculars and telescopes.

I also observed the comet and took many snaps. When comets are heated, they develop a tail of dust and gas, which gives comets their main beauty. This comet was not having much longer tail but tail was visible in images. Here I share an image of a comet that I took myself.

The comet is about 30 km in size, and at its closest, it passed 0.78 AU from the Sun (the Earth-Sun distance is considered 1 AU). At its closest approach to the Sun, it was moving at 47 km/s! On its closest approach to Earth on April 21, 2024, it was at 1.55 AU. With no chances of collision, this comet gave astronomers a chance to observe it in good detail, as it is one of those initial comets that were discovered as periodic ones.

Sudden brightness increases

As comets approach the Sun, they are heated by solar radiation, and they evaporate their material uniformly. But occasional jets of gases and other material also emerge from a comet’s surface, like jets. These jet effects are unpredictable and may not happen to a comet often, and in some cases, they may happen more often.

In the case of comet 12P/Pons Brooks, it apparently had a jet on one of its sides, and as the comet was rotating, this jet came towards that side, where it reflected sunlight more than normal. The comet’s brightness increased every time. The graph given here shows how its brightness increased in jumps.

We measure the brightness of comets and other celestial objects on a scale called magnitude. The lower the value, the brighter the object is. Naked eye visibility starts at magnitude 6. Higher-magnitude objects can only be seen through telescopes. Venus shines at -3.5 magnitude, the Moon at -12, and the Sun at -27!

Comet for the public

As most comets are not bright enough, they become unaided eye objects, so people don’t notice them. This comet was one of those that came and went without public attention, but on other occasions in the past, there were bright enough comets that common people saw. As not everyone has knowledge of astronomy, there are many stories behind the appearance of comets, like how they cause floods, earthquakes, the killing of animals, etc.

Another bright enough to be seen without any telescopic aid comet is coming and will be visible in October 2024. From October 1 to 15, 2024, look towards the west after sunset.

Also we are expecting this comet will not only be bright but infact very bright. It is going to be one of the brightest in many years. This comet is called C/2023 A3 (Tsuchinshan-ATLAS). It will also be appearing on that part of sky where there will be Venus to welcome it. Keep an eye on it. Here is expected sight of this comet as computer have predicted.

Thanks. Keep watching universe and enthusiasm must not die.