N. R. Pogson
|Norman Robert Pogson|
Sir N.R. Pogson KBE
23 March 1829|
|Died||23 June 1891
|Notable awards||Lalande Prize (1856)|
Norman Robert Pogson, CIE (23 March 1829 – 23 June 1891) was an English astronomer who worked in India at the Madras observatory. He discovered several minor planets, made observations on comets and deduced a mathematical scale of stellar magnitudes with the ratio of two successive magnitudes being the fifth root of hundred (~2.512) and referred to as Pogson's ratio.
Youth and education
Norman was born in Nottingham, the son of George Owen Pogson, a hosiery manufacturer, lace dealer and commission agent, "with enough income to support an extended family", and his wife, Mary Ann. It was intended that he should follow his father into business, and he was accordingly sent for "commercial education", but he was fascinated by science, and his mother supported and encouraged this interest. His early education was largely informal. He left school at 16, intending to teach mathematics. At the age of eighten, he calculated with the help of J.R. Hind of the Royal Astronomical Society, the orbits of two comets. He was introduced to astronomy through George Bishop's Observatory at Regent's Park. He took an interest in comets and studied Iris, a minor planet that had been recently discovered. He was engaged as an assistant at the Radcliffe Observatory in 1852; a new Heliometer had been installed there in 1850. However, in 1846 he commenced training in astronomy at the South Villa Observatory in Regent's Park in London.
|Asteroids discovered: 8|
|42 Isis||23 May 1856|
|43 Ariadne||15 April 1857|
|46 Hestia||16 August 1857|
|67 Asia||17 April 1861|
|80 Sappho||2 May 1864|
|87 Sylvia||16 May 1866|
|107 Camilla||17 November 1868|
|245 Vera||6 February 1885|
After working as an assistant at the South Villa Observatory in 1851, he moved to the Radcliffe Observatory in Oxford in 1852. He received the Lalande medal upon his discovery of the minor planet Isis. His Oxford period was spent studying variable stars and other routine research. In 1854 he helped Sir George Airy conduct an experiment to determine the density of the earth. Pogson was appointed as director at the Hartwell Observatory belonging to John Lee in 1859. He published around fourteen papers from 1859 to 1860 in the Monthly Notices of the Royal Astronomical Society, mostly on variable stars and on minor planets. Sir Charles Wood appointed him as government astronomer for Madras in October 1860.
Reaching India in 1861 and working at the Madras Observatory he worked tirelessly, discovering a planet Asia. In the next seven years he found five minor planets and seven variable stars. He worked on the Madras Catalogue of 11,015 stars based on 51,101 observations (until 1887). This work is unpublished. Despite Pogson's isolation he had at the time of his death discovered 134 stars, 106 variable stars, 21 possible variable stars and 7 possible supernovae. Pogson also made special expeditions, observing a total solar eclipse on 18 August 1868 at Masulipatnam and making spectrometric studies. He observed and commented on the spectral line associated with Helium, then yet to be discovered.
His most notable contribution was to note that in the stellar magnitude system introduced by the Greek astronomer Hipparchus, stars of the first magnitude were a hundred times as bright as stars of the sixth magnitude. Pogson's suggestion in 1856 was to make this a standard; thus, a first magnitude star is 1001/5 or about 2.512 times as bright as a second magnitude star. This fifth root of 100 is known as Pogson's Ratio.
The magnitude relation is given as follows:
- m1 - m2 = -2.5 log10 (L1 / L2)
where m is the stellar magnitude and L is the luminosity, for stars 1 and 2.
One of Pogson's assistants was Chintamani Raghunatha Chary. He worked for many years with Pogson and his retirement in 1878 was a blow to Pogson. Pogson also got into increasing difficulties with his collaborators in England as well as the bureacuracy in India. George Airy, who had admired Pogson once became increasingly unsupportive and downright dismissive of Pogson's applications for help from the government as well as to help him return to England. Pogson on his part had been stubborn in not supporting a southern-sky survey.
Pogson was married in London in 1849 to Elizabeth Jane Ambrose, by whom he had 11 children. She died on 5 November 1869. He was married again, in Madras on 25 October 1883, to Edith Louisa Stopford Sibley, daughter of Charles W. Sibley of the 64th regiment and a widow, aged 33, by whom he had a further three children: Frederick Vere (born in 1885), Edith Vera (born in 1886; died in infancy) and Edith Gladys (born in 1889).
The asteroid Vera, first discovered by Pogson on 6 February 1885, was named at the suggestion of his wife, Edith Pogson.
Pogson's daughter, Elizabeth Isis Pogson (born on 28 September 1852), served as his assistant at the Madras observatory from 1873 to 1881. She went on to become meteorological reporter for Madras. First proposed for a Fellowship of the Royal Astronomical Society in 1886, she was finally admitted to that honour in 1920.
The following celestial features are named after him:
- Asteroid 1830 Pogson.
- The crater Pogson on the Moon.
- Asteroid 42 Isis is believed to be named after his daughter, Elizabeth Isis Pogson
- "Pogson, Norman Robert". Dictionary of National Biography. London: Smith, Elder & Co. 1885–1900.
- Reddy, V.; Snedegar, K.; Balasubramanian, R. K. (2007). "Scaling the magnitude: the fall and rise of N. R. Pogson". Journal of the British Astronomical Association 117 (5): 237–245.
- Jones, D. (1967). "Norman Pogson and the Definition of Stellar Magnitude". Astronomical Society of the Pacific Leaflets 10 (469): 145–152.
- Williams, Thomas R.; Saladyga, Michael (2011). Advancing Variable Star Astronomy: The Centennial History of the American Association of Variable Star Observers. Cambridge University Press. p. 6.
- Nath, Biman B. (2013). "The Folklore and Reality of the Discovery of Helium". Astronomers' Universe: 249–268. doi:10.1007/978-1-4614-5363-5_13.
- Pogson, N. "Magnitudes of Thirty-six of the Minor Planets for the first day of each month of the year 1857". Monthly Notices of the Royal Astronomical Society 17: 12–15.
- Marriage registered in Pancras Registration District in the first quarter of 1850. FamilySearch.org, "India, Marriages, 1792–1948"; "India, Births and Baptisms, 1786–1947".
- L.D. Schmadel (2012) Dictionary of Minor Planet Names (sixth edition). p. 35.
- Principal Probate Registry, Calendar of the Grants of Probate and Letters of Administration made in the Probate Registries of the High Court of Justice in England (1947), p. 473.
- Hockey, T. (editor-in-chief), Biographical Encyclopedia of Astronomers (vol. II, M–Z) (2007), p. 920.
- FamilySearch.org, "England Births and Christenings, 1538–1975".