Norman Lockyer identifies the D3 spectral line and proposes helium
- When
- 1868
- Where
- London; Unknown
- Episodes
- 3
In 1868, Norman Lockyer observed a prominent yellow spectral line in the solar spectrum that could not be explained by known materials. He proposed it was caused by an unknown solar element, later named helium. This inference followed an earlier observation by Pierre Janssen during the August 1868 eclipse. Lockyer's work established the basis for identifying helium as a distinct element.
Episodes
- Observation of the D3 Line
Lockyer observed a prominent yellow line in the solar spectrum from London, concluding it was caused by an unknown solar element.
- Janssen's Eclipse Observation
Pierre Janssen observed the yellow line during the total solar eclipse of August 18, 1868.
- Naming of Helium
Lockyer named the proposed unknown element helium, derived from the Greek word for the Sun.
Background and detail
Background. Norman Lockyer, an English scientist and astronomer, is credited with discovering helium alongside Pierre Janssen. In 1868, a prominent yellow line was observed in a spectrum taken near the edge of the Sun. This line could not be explained as due to any material known at the time, leading to the hypothesis of an unknown solar element.
Independent Verification. An observation of the new yellow line had been made earlier by Janssen at the 18 August 1868 solar eclipse. Both Janssen's and Lockyer's communications regarding the independent findings were presented to the French Academy of Sciences on October 26, 1868.
People involved
- Norman Lockyer · Astronomer who observed the D3 line and proposed helium
- Pierre Janssen · French scientist who independently observed the spectral line during the 1868 eclipse
Sources
- Norman Lockyer Wikipedia, revision of 2026-09-23
- Helium Wikipedia, revision of 2026-10-01
- Solar eclipse of August 18, 1868 Wikipedia, revision of 2026-08-22
Machine-drafted from the cited Wikipedia passages and checked by a reviewing model, not by a human editor. Every passage cites the revision it was written from; dates and places follow those passages.