Helium was first discovered not on Earth, but in the sun. During a solar eclipse in 1868, a French astronomer spotted an unfamiliar yellow line in the sun’s light spectrum that didn’t match any known element. It took nearly three decades before anyone found the same element on our planet.
A Yellow Line in the Sun’s Spectrum
On August 18, 1868, French astronomer Pierre Janssen traveled to Guntur, India, to observe a total solar eclipse. He pointed a spectroscope at the glowing layer of gas surrounding the sun (the chromosphere) and noticed something unexpected: a bright yellow spectral line that didn’t correspond to any element known at the time. The line sat close to the familiar yellow signature of sodium but was clearly distinct from it.
English astronomer Norman Lockyer independently observed the same mysterious yellow line and became convinced it represented an entirely new element. He coined the name “helium” after the Greek word for the sun, helios. Lockyer himself admitted he didn’t know whether this new substance would turn out to be a metal like calcium or a gas like hydrogen. For years, helium existed only as a spectral signature, an element known to science solely because of its fingerprint in sunlight.
First Detection on Earth
Helium remained a purely solar curiosity for over a decade. Then in 1882, Italian physicist Luigi Palmieri detected the same telltale spectral line while analyzing gases released from the lava of Mount Vesuvius. This was the first evidence that helium existed on Earth, though the finding didn’t lead to isolation of the element and attracted relatively little attention at the time.
Isolation From Uranium Ore
The real breakthrough came in 1895, when Scottish chemist William Ramsay extracted helium from a uranium mineral called cleveite. By heating the mineral and collecting the gas it released, Ramsay was able to confirm that the spectral lines matched those observed in the sun decades earlier. Helium was no longer just a solar constituent. It was a real, isolable substance.
Almost simultaneously, Swedish chemists Per Theodor Cleve and Nils Abraham Langlet independently found helium in the same mineral. Their parallel discoveries confirmed the result beyond doubt, but the quantities involved were tiny. Helium still seemed like an exotic rarity, interesting to chemists but with no practical significance.
From Rare Curiosity to Industrial Resource
That perception changed dramatically on December 7, 1905, when two University of Kansas chemists, Hamilton P. Cady and David F. McFarland, analyzed a sample of natural gas from a well near Dexter, Kansas. The gas from that well had puzzled locals because it wouldn’t burn. When Cady and McFarland ran it through a spectroscope, the yellow glow of helium flashed up immediately. The gas contained an astonishing 1.84% helium.
Over the following months, they analyzed more than 40 additional gas samples from across the region and found helium in many of them. By mid-1906, they reported having “a very unusual opportunity for obtaining helium in practically unlimited quantities.” When they published their complete findings in November 1907, Cady wrote that their work “assures the fact that helium is no longer a rare element, but a common element, existing in goodly quantity for uses that are yet to be found for it.” The Great Plains of the United States turned out to be sitting on enormous reserves of helium trapped in natural gas deposits.
Why Helium Is Rare in Earth’s Atmosphere
Given those underground reserves, it might seem strange that helium makes up only about 0.0005% of Earth’s atmosphere. The reason is simple physics: helium atoms are extremely light, the second lightest element after hydrogen. At the temperatures found in the upper atmosphere, helium atoms can reach speeds high enough to escape Earth’s gravitational pull entirely. Once helium reaches the open air, it drifts upward and eventually leaks into space. This process has been going on for billions of years.
The helium found in natural gas deposits has a completely different origin. It forms underground through radioactive decay. Uranium and thorium in Earth’s crust slowly break down over millions of years, releasing particles that capture electrons and become helium atoms. That helium gets trapped in rock formations alongside natural gas. Without those geological traps acting as sealed containers, the helium would simply float away. This is why nearly all commercial helium today comes from natural gas extraction, and why the supply is finite. Once released and not captured, it’s gone for good.
A Discovery That Spanned Decades
Unlike most elements, helium wasn’t discovered in a single moment. Its story stretches across 37 years, from Janssen’s eclipse observation in 1868 to Cady and McFarland’s natural gas analysis in 1905. Each step built on the last: an unexplained line in sunlight, a volcanic hint, isolation from radioactive minerals, and finally the realization that vast quantities had been hiding underground all along. The element named for the sun turned out to be woven into the geology beneath our feet.