French astronomer · 1824–1907
Pierre Janssen
Pierre Janssen saw helium before anyone knew it existed. During a total solar eclipse in India in 1868 he recorded a bright yellow line in the Sun’s spectrum that matched no element on Earth.
How Helium was found
On 18 August 1868 Janssen travelled to Guntur, India, to watch a total eclipse through a spectroscope. He studied the solar prominences, the red flames around the Sun’s edge, and noticed a yellow line close to, but not quite matching, the familiar lines of sodium.
The prominences were so bright that he realised he could study them without an eclipse, and did so the next day. Norman Lockyer in England reached the same idea independently. Their reports reached the French Academy of Sciences the same day, and a medal was struck showing both men.
Shared the credit
The discovery is credited jointly to these scientists.
Life and career
Born 1824 · Died 1907
Janssen was born in Paris and was lame from a childhood accident. He studied mathematics and physics and became a specialist in solar spectroscopy, travelling the world for eclipses.
In 1870, during the siege of Paris, he escaped the city by balloon to reach an eclipse in Algeria. He founded the Meudon observatory near Paris and, in his seventies, built an observatory on the summit of Mont Blanc.
Also known for
- Founder of the Meudon astrophysical observatory
- Method for observing solar prominences without an eclipse
Discovered in the same era
Other elements identified within ten years of 1868.