N. R. Pogson

Norman Robert Pogson
Born	March 23, 1829(1829-03-23) Nottingham, England
Died	June 23, 1891(1891-06-23) (aged 62) Chennai, India
Nationality	English
Fields	astronomy

Asteroids discovered: 8
42 Isis	May 23, 1856
43 Ariadne	April 15, 1857
46 Hestia	August 16, 1857
67 Asia	April 17, 1861
80 Sappho	May 2, 1864
87 Sylvia	May 16, 1866
107 Camilla	November 17, 1868
245 Vera	February 6, 1885

Sir Norman Robert Pogson KBE (March 23, 1829 in Nottingham – June 23, 1891 in Chennai, India) was an English astronomer.

By the time he was 18 years old, he had computed the orbits of two comets. He became an assistant at Radcliffe Observatory in Oxford, England in 1851. In 1860 he travelled to Madras, India, becoming the government astronomer. At the Madras Observatory he produced the Madras Catalogue of 11,015 stars. He also discovered eight asteroids and six variable stars.

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 100^1/5 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.

In 1868 and 1871, Pogson joined the Indian solar eclipse expeditions. In 1872, he observed an object (recorded as X/1872 X1) which he believed to be a return of Biela's Comet.

During his career he discovered a total of eight asteroids and 21 variable stars. He headed the Madras Observatory for 30 years until his death.

Honours

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

References

• Magnitudes of Thirty-six of the Minor Planets for the first day of each month of the year 1857, N. Pogson, MNRAS 17 pp 12 1856 in which Pogson first introduced his magnitude system

• A link on his works: http://adszip.cfa.harvard.edu/ui/abs/1968ASPL...10..145J/similar

External links

• Norman Robert Pogson - Irineu Gomes Varella (Portuguese)
• http://dhinakarrajaram.blogspot.com/2011/02/norman-robert-pogson-astronomer-great.html