death_date death_place birth_place citizenship nationality fields workplaces birth_date known_for image article_title name alma_mater
13 september 1936 göttingen erfurt , saxony german german mineralogist astrophysical institute potsdam 11 january 1865 discovering interstellar medium . johannes franz hartmann.jpg johannes franz hartmann
 johannes franz hartman university of leipzig
johannes franz hartmann

johannes franz hartmann -lrb- january 11 , 1865 -- september 13 , 1936 -rrb- was a german physicist and astronomer .
in 1904 , while studying the spectroscopy of delta orionis he noticed that most of the spectrum had a shift , except the calcium lines , which he interpreted as indicating the presence of interstellar medium he was the director of the observatorio astronómico de la plata from november 1922 to may 1934 .
he oriented the work of the observatory towards astrophysics .
he discovered three asteroids .
his doctorate was from the university of leipzig in 1891 on lunar eclipses .
