Historedia
Person

Jules Janssen

Events
2
Episodes
5
Years
1868–1874

Every event in Historedia whose sources name Jules Janssen, with the role they cite and all of that event’s episodes. This is not a biography, and mentions are grouped by name, so two people with the same name can share this page.

Events and episodes

  1. Janssen detects an unknown solar spectral line

    1868

    Role: French astronomer

    1. 1868 · Solar eclipse observation siteInitial Detection Attribution

      The first detection of the spectral line signature is attributed to Rayet, Pogson, and Herschel, with Janssen confirming the observation.

    2. 18 August 1868 · Guntur, British IndiaJanssen's Observation

      Janssen observed a bright yellow line in the solar chromosphere during the total eclipse at Guntur, British India, on 18 August 1868.

    3. 20 October 1868 · LondonLockyer's Identification

      Lockyer observed the yellow line from London in October 1868 and identified it as an unknown solar element.

  2. Passage de Vénus photographic sequence

    1874

    Role: Astronomer and inventor of the photographic revolver

    1. 1874 · Place of invention not specifiedInstrument Invention

      Janssen invented the photographic revolver in 1874, the instrument that originated chronophotography.

    2. 9 December 1874 · Japan (no exact site named; outside allowed places)Transit Observation

      Janssen observed the 1874 transit of Venus in Japan, the event the Passage de Vénus photographs are associated with.

Sources

  1. Pierre Janssen Wikipedia, revision of 2026-08-12
  2. Passage de Vénus Wikipedia, revision of 2026-09-20