Observing Comet 12P/Pons-Brooks

Observing Comet 12P/Pons-Brooks By: Syed Mohammad Baqir (Lecturer in physics and astronomer) Comets Comets are very small objects, only few km wide, orbiting Sun. They are mostly concentrated where obits of all planets finish. After orbit of Neptune a large number of comets circle Sun, this region of solar system is called Kuiper Belt. Another concentration of comets is very far away from Sun, approximately 2 light years, called Oort Cloud. Comets from these concentrations often change their original orbits and fall inwards, 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 outer regions of solar system. But if they are influenced by gravity of outer planets, their paths might change into elliptical ones and they become periodic comets. Now they repeat their visits to inner solar system. Very first periodic comet which was identified was Halley’s comet and hence it is given name 1P/Halley. It is also the most famous comet as it is bright enough to be seen with unaided eye and completes its orbit after 76 years. Its last visit to inner solar system was in 1986 and now will be in mid-2061. Then among many periodic comets there is another one called 12P/Pons Brooks which is still in inner solar system as I am writing this article. Two days back it passed closest to Sun (called perihelion) and now heading back to outer solar system. It was observed by astronomers all over world and I did too. Comet 12P/Pons Brooks Comet was discovered by two astronomers separately back in 19th century and that is why is named after both of them, Jean-Louis Pons and William Robert Brooks. It orbits sun after every 71 years. This time when it came to inner part of solar system, astronomers all over the world saw it. From those areas which had clear skies, it was visible to unaided eye (without any telescope or binoculars) but from city areas having 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 image of comet which I took myself. Comet is about the size of 30 km and on its closest it passed 0.78 AU from Sun (Earth-Sun distance is considered 1 AU). At its closest approach to sun it was moving at 47 km/s speed! On closest approach to Earth on 21st April 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 which were discovered as periodic ones. Sudden Brightness increase As comets approach sun they are heated by solar radiations and they evaporate their material uniformly. But occasional jets of gases and other material also emerge from comet’s surface like jets. These jet effects are unpredictable and may not happen to a comet often and in some cases may happen more often. In case of comet 12P, it apparently had a jet on one of its side and as comet was rotating this jet came towards that side where it reflected sunlight more than normal. Comet’s brightness than increased every time. Graph given here shows how its brightness increased in jumps. We measure brightness of comets and other celestial objects on a scale called magnitude. Low the value is brighter the object is. Naked eye visibility starts from magnitude 6. Higher magnitude objects can only be seen in telescopes. Venus shines at -3.5 magnitude, Moon at -12 and Sun at -27! Comet for public As most of comets are not bright enough that they become unaided eye objects so common people don’t notice them. This comet was one of those comets which came and went without public attention but in other occasions in past there were bright enough comets which common people saw. As not everyone has knowledge of astronomy so they made many stories behind appearance of comets like they cause floods, earthquakes, killing of animals etc. Another bright enough to be seen without any telescopic aid comet is coming and will be visible in oct 2024. Look skies towards west after sunset from 1 to 15 oct 2024. 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.