When and Where Was Helium Discovered? The Story of a Solar Element

Helium was first identified in the Sun in 1868. French astronomer Jules Janssen observed its spectral line during a solar eclipse, and English scientist Norman Lockyer later identified the same line independently. Helium was not confirmed on Earth until 1895, when chemist William Ramsay found it in gas released from a uranium-bearing mineral.

The discovery began with a yellow line in sunlight that did not match any element then known on Earth. Its position was close to the yellow lines produced by sodium, but the difference was clear enough to suggest a new source. The line became the first evidence for an element detected in space before it was found on Earth.

The solar discovery in 1868

During the total solar eclipse of August 18, 1868, Janssen studied the Sun’s chromosphere, a layer of its atmosphere visible during an eclipse. He recorded a yellow spectral line near the sodium lines. Its wavelength was about 587.5 nanometers, according to Encyclopaedia Britannica.

A spectrum separates light into its component wavelengths. Each element produces a characteristic pattern of lines, so scientists can use a spectrum to identify substances in a distant source. The unfamiliar yellow line suggested that the Sun contained an element absent from the reference spectra available at the time.

Lockyer observed the line independently later that year with chemist Edward Frankland. They concluded that it came from a new element and named it helium, from helios, the Greek word for the Sun Royal Society of Chemistry. Janssen and Lockyer are both associated with the discovery because their observations and analysis helped establish the line as evidence of a new element.

How helium was found on Earth

For nearly three decades, helium was known from its solar spectrum but had not been identified in a terrestrial sample. That changed in 1895. William Ramsay treated cleveite, a uranium-bearing mineral, with acid and collected the gas it released. Its spectrum contained the yellow helium line, linking the gas to the element identified in the Sun Royal Society of Chemistry.

The mineral held helium produced through radioactive decay. Uranium decay releases alpha particles, which are helium nuclei. After gaining electrons, these nuclei become helium atoms. Some atoms remain trapped in minerals until a process such as Ramsay’s experiment releases them.

Per Teodor Cleve and Nils Abraham Langlet independently confirmed the terrestrial discovery in 1895. Their results helped establish that the helium detected in the Sun and the gas found in minerals were the same element Encyclopaedia Britannica.

One example: the yellow line

The yellow line shows how scientists could identify an element without collecting a sample from the place where it appeared. Sodium also produces yellow spectral lines, so the line’s color alone was not enough. Its measured position differed from sodium’s lines. When Ramsay later found a matching line in gas from cleveite, that comparison supported the identification of helium on Earth.

Why the discovery began with spectroscopy

Spectroscopy made the solar discovery possible. When an atom emits or absorbs light, it produces lines at particular wavelengths. Scientists compare those lines with known patterns to identify elements. The method allows them to study distant objects by analyzing their light.

In 1868, the yellow line near sodium posed a specific question: did it belong to a known element, or did it point to an unknown one? Janssen’s and Lockyer’s observations supplied evidence for the second explanation. Ramsay’s experiment later gave scientists a terrestrial sample whose spectrum could be compared with the solar observation.

The discovery remains unusual because the order was reversed: helium was identified in the Sun before it was isolated on Earth. Its later detection in a mineral connected an astronomical observation to laboratory chemistry.

Key Takeaways

• Helium was first identified in the Sun in 1868, during observations of a solar eclipse.
• Jules Janssen observed the line, and Norman Lockyer independently identified it as evidence of a new element with Edward Frankland.
• The clue was a yellow spectral line near 587.5 nanometers that did not match the known sodium lines.
• William Ramsay found helium on Earth in 1895 in gas released from cleveite, a uranium-bearing mineral.
• Helium was identified in space before it was confirmed on Earth.