Recruited by Deslandres as an astronomer at l’observatoire de Paris, Bosler discovered in 1908 in the spectrum of Comet Morehouse the spectral lines of ionized nitrogen, which was the first evidence of that element in comets. Much of his research was on the physical properties and orbits of comets. He made a report on progress in astrophysics in the United States for the 1910 annual report of the Smithsonian Institution. In 1912, he showed in his doctoral dissertation (supervised by Henri Poincaré) that the Sun’s magnetic field, by means of the intermediary of the solar wind, explains many aspects of cometary tails, the aurora borealis and aurora australis, solar storms and telluric currents. During a solar eclipse in 1914, Bosler observed in the corona a spectral band “nouvelle, intense et unique” which he suggested was spectral evidence for coronium; however, in the 1930s subsequent research showed that the cause was a highly ionized form of iron. In 1916, he published an analysis of the circular form of lunar craters as caused by the impact of meteors.
In 1923 Bosler was named director of Marseille Observatory, a post he occupied until his retirement in 1948. Simultaneously with his directorship, he taught at the University of Marseille from 1923 to 1948. Bosler made important contributions to the theory of the evolution of stars and published the first textbook in French that dealt with the then recent discoveries of Hubble and the work on optical phenomena of such physicists as Michelson, Fabry and Perot.
- Les théories modernes du soleil (1910)
- L’évolution des étoiles (1923)
- Cours d’astronomie (1928)
- Fehrenbach, Charles (1975). "Jean Bosler (1878-1973)". L'Astronomie. 89: 220. Bibcode:1975LAstr..89..220F.
- "Recent progress in astrophysics in the United States". Annual Report of the Smithsonian Institution for 1910. Government Printing Office. 1911. pp. 357–370.
- Jean Bosler in the German National Library