An object in this meaning is the same thing as an objective[?] or task[?]. It comes from old project terminology and refers to the act of actually performing something according to a plan, or rather "according to a project" (the word "project" used to mean "plan").
... to reach the South Pole and came further south than anyone before him
John Hanning Speke, (1827-1864), discovered Lake Victoria
Henry Morton Stanley, (1841-1904), found ...