Norman Pogson

Norman Robert Pogson (Nottingham, March 23, 1829 - Chennai, June 23, 1891) was a British astronomer.

Biography

At the age of 18 Pogson had already calculated the orbits of two comets. In 1851 he began working as an assistant at the Radcliffe Observatory in Oxford and in 1860 he moved to Madras (India) where he served as government astronomer and directed the Madras Observatory until his death. Throughout his career he discovered eight asteroids and 21 variable stars.

His greatest contribution to astronomy was observing that in the system of expressing the apparent magnitude of stars proposed by Hipparchus of Nicaea, stars of the first magnitude are around one hundred times brighter than those of the sixth magnitude. In 1856 he proposed adopting this system in which each decrease in the apparent magnitude scale represents a decrease in brightness equal to the fifth root of 100 (≈ 2.512), a constant called Pogson's ratio:

The apparent magnitude of stars is given by the following formula:

m₁ - m₂ = -2.5 log₁₀ (laughs)L₁ / L₂)

where m is the apparent magnitude and L is the luminosity, for stars 1 and 2.

Eponymy

• The Pogson lunar crater carries this name in his memory.
• In his honor was also named the asteroid (1830) Pogson.

Awards and recognitions

• 1856 Lalande Prize together with Jean Chacornac for the discovery of asteroid 42 Isis on May 23, 1856.