Pons' eye view... Science

The greatest comet discoverer

Do you have an eye for comets? Then you'll love this one...   | Photo Credit: Minoru Yoneto

Have you ever seen a comet pass by? Comets are celestial objects primarily consisting of ice and dust, which often develop a bright tail when passing near the sun. They have been observed and recorded since ancient times. If you remember the occasion in which you saw the comet, and, better still, the configuration of the night sky at that moment, then you must be like Jean-Louis Pons.

Born to a poor family in 1761, Pons hardly had any formal education in his formative years. In fact, for the first 28 years of his life, there was little or no indication of what Pons was to become - the most successful discoverer of comets in the history of astronomy.

The beginning of his astronomical career was humble, as he started out as a concierge (janitor) with the Marseilles observatory in 1789. It was here that he was instructed on astronomy, by the observers and directors at the establishment. Within no time, Pons had learnt the art himself and was allowed to do observations with the instruments.

Photo: Wikimedia Commons

Photo: Wikimedia Commons  

Pons’ particular strength lied in the fact that he could remember in detail the star fields that he observed, enabling him to recognise the changes in the observed area. Coupled with excellent eyesight and the patience for practical observations, Pons was soon on the way to greatness.

On July 11, 1801, Pons logged his first discovery of a comet, which he had to share with Charles Messier, who found it a day later. Coincidentally, Pons’ first comet discovery turned out to be the last for Messier, himself a distinguished astronomer.

Pons was named astronomer adjoint in 1813 and became assistant director at the Marseilles observatory by 1818. In 1818, Pons discovered three small tailless comets — a feat that won him the Lalande Prize awarded by the Academie des Sciences.

Pons also suspected that one of these three comets was the same as one discovered in 1805, prompting him to suggest to Johann Franz Encke that he look into it. Encke calculated its elements and found it to have a period of only 1,208 days or 3.3 years — a revelation in an age when all known comets had an orbital period of over 70 years.

Based on his calculations, Encke predicted that this comet would next make its appearance in 1822. The predicted return was observable only in the southern hemisphere and was seen by Karl Rumker in Australia.

Even though Encke himself referred to this comet as ‘Pons’ Comet’, it is known now as ‘Encke’s Comet’. The Astronomical Society in London awarded Encke with a gold medal in that year, while Pons and Rumker received silver medals. Pons though, received his silver medal for discovering two other comets.

He won the Lalande Prize two more times - in 1821 and 1827. Including two prolific stretches when he found five comets in eight months (February-September 1808) and five in 12 months (August 1826 - August 1827), Pons took the total number of comets he discovered or co-discovered to 37.

Failing eyesight, however, meant that Pons lost his position of first announcer of comets in 1827. He completely stopped observing in the first months of 1831, months before his death in October.


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Printable version | Nov 29, 2021 7:28:16 PM | https://www.thehindu.com/in-school/sh-science/The-greatest-comet-discoverer/article14483319.ece

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