Ismail Bouillaud (Bullialdus; September 28, 1605 - November 25, 1694)

Ismail Bouillaud (or Boulliau, or latinized Bullialdus) was a French librarian, astronomer and priest, who was born in 1605 in Loudun where he studied, then traveling in Italy, Holland and Germany for buying books. He published Astronomia philolaica in 1645, supporting Kepler's elliptical orbits, and assuming an inverse-square force law for the first time.

He observed the Andromeda "Nebula" (M31) in 1661, but according to Allen (1899/1963), he expressedly mentioned that this "Nebula" had been observed 150 years earlier by some anonymous but expert astronomer. Nevertheless, Edmond Halley accounted the discovery of this object to him in his 1716 treat of Nebulae.

Because the "nebula" had not been documented by so many famous astronomers, Boulliau suspected that it might been variable, similar to Mira Ceti which he also studied, and attempted to calculate a period of variation - of 333 days, compared to the modern value of 332.

He died in 1694 in Paris.

The astronomical community has named a Moon crater to his honor: Bullialdus (20.7S, 22.2W, 60 km diameter, in 1935).



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