Helium was discovered in the Sun before it was found on Earth.
That strange fact begins with the total solar eclipse of August 18, 1868. During the eclipse, French astronomer Pierre Janssen observed the Sun's outer atmosphere with a spectroscope, an instrument that spreads light into its component colors.
The eclipse made the observation possible. With the Sun's bright face blocked by the Moon, the Sun's prominences and chromosphere became easier to study. Janssen saw a bright yellow spectral line that did not match the familiar sodium lines.
That line pointed to something new.
Spectroscopy changed eclipse science
Before spectroscopy, eclipse observers could describe the shape, color, and brightness of the corona and prominences. Spectroscopy added a new question: what is the Sun made of?
Each chemical element leaves a pattern in light. These patterns act like fingerprints. By comparing light from the Sun with light from known materials in the laboratory, astronomers could identify elements at a distance.
During the 1868 eclipse in India, Janssen used this method on solar prominences. He noticed a yellow line near sodium's part of the spectrum, but not exactly where sodium should be.
That difference was small in wavelength, but huge in meaning.
Janssen, Lockyer, and a new element
Janssen continued working after the eclipse and found a way to observe the same solar line outside totality by isolating the relevant wavelength.
In England, Norman Lockyer independently observed the same yellow line later in 1868. Lockyer argued that it came from an element not yet known on Earth. He and chemist Edward Frankland suggested the name helium, from Helios, the Greek name associated with the Sun.
That was a bold idea. Scientists were used to discovering elements in earthly minerals, gases, and compounds. Helium reversed the usual order: first seen in sunlight, later isolated on Earth.
Terrestrial helium was not isolated until 1895, when William Ramsay found it in a uranium mineral.
Why an eclipse helped
The Sun's bright surface normally drowns out the faint light from prominences and the chromosphere. Totality removes that glare for a few minutes.
That brief interval is enough to reveal hidden layers of the Sun. It is the same basic principle behind eclipse observations of the corona: block the photosphere, and faint structures become visible.
The 1868 eclipse arrived at the right moment in scientific history. Spectroscopes had become powerful enough to turn colored light into chemical evidence. Eclipse expeditions gave astronomers a temporary natural laboratory.
What helium changed
Helium is now familiar: balloons, cryogenics, MRI machines, leak detection, deep-sea breathing mixtures, and solar physics all involve it in different ways. But its discovery was a reminder that the universe can reveal chemistry beyond Earth.
The Sun was no longer just a bright disk or a clock in the sky. It was a physical object with gases, temperatures, motions, and elements that could be studied from millions of kilometers away.
That shift helped create modern astrophysics.
A short eclipse, a long legacy
Totality in 1868 lasted only minutes, but the observations changed the periodic table.
The story also shows why eclipses are more than visual spectacles. They are rare observing conditions. When the Moon covers the Sun, the hidden becomes measurable: the corona, prominences, shadow edges, and in this case, a new element.
The next time you see a total eclipse image with pink prominences around the Moon's edge, remember that those same solar features helped reveal helium.
Sources and related guides
- Purdue Chemistry's history note on helium first observed during the 1868 eclipse summarizes Janssen, Lockyer, and the later isolation of helium on Earth.
- The Science History Institute's history of helium discovery explains Janssen's eclipse observations and Lockyer's independent work.
- Britannica's Joseph Norman Lockyer entry adds biographical context for Lockyer's solar spectroscopy.
- Related SolarWatch guides: the solar corona, eclipse contact times, how eclipse predictions work, and solar eclipse safety.
See it in SolarWatch
SolarWatch helps you plan the exact observing window when totality reveals the Sun's hidden atmosphere. Use local contact times to understand when the bright photosphere is covered and when filters must go back on.