Helium gets its name directly from the Greek word helios, meaning “sun,” because it was detected in sunlight nearly three decades before anyone found it on Earth. During a total solar eclipse in 1868, astronomers noticed a bright yellow spectral line that did not match any known element. The mysterious line was attributed to a hypothetical new element, and the name “helium” stuck even after the gas was finally isolated in a laboratory in 1895. It remains the only element on the periodic table first identified not on our planet but in a star.
The 1868 Eclipse That Changed Chemistry
On August 18, 1868, a total solar eclipse was visible from parts of India and Southeast Asia. The French astronomer Pierre Jules César Janssen traveled to Guntur, India, to observe the sun’s chromosphere, the thin, glowing layer just above its visible surface. By spreading the chromosphere’s light through a prism, Janssen could see the individual wavelengths emitted by the hot gases there. He spotted a vivid yellow line that sat close to, but distinctly apart from, the well-known pair of sodium lines called D1 and D2. This new line would come to be called D3.
Back in England, the astronomer Joseph Norman Lockyer independently observed the same line in October 1868 using a new technique that allowed him to study the chromosphere without waiting for an eclipse. Lockyer and Janssen had no way of contacting each other quickly, and their reports arrived at the French Academy of Sciences within days of one another. The academy struck a medal honoring both men for essentially the same discovery. The D3 line did not correspond to any element that chemists had catalogued, and Lockyer, working with the chemist Edward Frankland, proposed that it belonged to a new element unique to the sun. It was Frankland and Lockyer who suggested the name “helium,” drawing on helios to mark its solar origin.
A Solar Element That Nobody Believed In
Calling something an element based solely on a single spectral line seen in the sun was a bold claim, and many scientists were unconvinced. Spectroscopy was still a relatively young tool, and the idea that the sun could harbor an element completely absent from Earth struck plenty of chemists and physicists as unlikely. Some researchers argued the D3 line was simply hydrogen behaving oddly under extreme solar temperatures and pressures. Others suspected it was a misidentified artifact of the observation itself.
The hypothetical element helium floated in a kind of scientific limbo for over a quarter century. It was “fairly well known” in scientific circles yet treated as unproven, a curiosity of solar physics rather than a confirmed addition to the list of elements.1Annals of Science. The Solar Element: A Reconsideration of Helium’s Early History Lockyer continued to champion it, but without a sample to weigh, smell, or react with other substances, most chemists kept helium at arm’s length. It is worth noting that the periodic table itself was still being organized during this period; Mendeleev published his first version in 1869, just a year after the D3 line was spotted. There was no obvious slot for a lightweight, seemingly inert gas in those early arrangements of the elements.
Finding Helium on Earth
The breakthrough came from an unexpected direction. In 1895, the Scottish chemist William Ramsay was investigating a mineral called cleveite, a uranium-bearing ore. When he dissolved cleveite in acid, it released a gas. Running that gas through a spectroscope, Ramsay saw the same D3 line that Lockyer and Janssen had seen in the sun’s chromosphere. Helium was not just a solar element after all; it had been sitting in Earth’s rocks all along, trapped by the radioactive decay of uranium and thorium.
Interestingly, Ramsay’s discovery “owed little or nothing to Lockyer’s solar element.”1Annals of Science. The Solar Element: A Reconsideration of Helium’s Early History Ramsay had not set out to find helium; he stumbled onto it while studying nitrogen in minerals. For a brief period, there was genuine uncertainty about whether the gas from the mineral and the element inferred from the sun were even the same thing. Careful spectral comparison settled the question: the D3 line matched perfectly. The solar element and the terrestrial gas were one substance.
Ramsay went on to discover an entire family of unreactive gases, including neon, argon, krypton, and xenon, which together with helium formed a whole new group on the periodic table and reshaped the understanding of how electrons hold atoms together.2PubMed Central. Sir William Ramsay and the noble gases The column of noble gases on the far right of the periodic table exists because of this era of discovery, and helium sits at its top.
Why the Sun Really Is Full of Helium
The name turned out to be more fitting than its coiners could have imagined. Lockyer and Frankland chose “helium” because they thought the element might exist only in the sun. They had no way of knowing that the sun is, in fact, a helium factory. Deep in the solar core, hydrogen nuclei fuse together under crushing pressure and extreme heat, and the end product of that fusion is helium. About 99 percent of the sun’s energy comes from this process, known as the proton-proton chain, which converts roughly 600 million tons of hydrogen into helium every second.3Nature. Comprehensive measurement of pp-chain solar neutrinos
This is not a minor side reaction. The proton-proton chain is the dominant energy source of the sun, and the neutrinos it emits have been directly measured by detectors on Earth, confirming that the fusion of hydrogen into helium accounts for nearly all of the sun’s luminosity.4Nature. Neutrinos from the primary proton–proton fusion process in the Sun Every photon of sunlight that warms your skin ultimately traces back to a reaction that created a helium nucleus. The sun has been doing this for about 4.6 billion years, and roughly a quarter of its mass is now helium, up from the roughly one-quarter it started with from the gas cloud that formed the solar system. Most stars follow a similar pattern: they burn hydrogen into helium for the bulk of their lifetimes.
Why Helium Is So Rare on Earth
Given that helium is the second most abundant element in the observable universe, it is surprisingly scarce in Earth’s atmosphere, making up only about five parts per million of the air you breathe. Two main factors explain the discrepancy.
First, Earth was never able to hold onto much primordial helium. When the planet formed, it was too small and too warm to gravitationally capture and retain large quantities of light gases. Hydrogen and helium both escaped into space during Earth’s early history, which is why our atmosphere is dominated by heavier molecules like nitrogen and oxygen instead. Even today, helium atoms that reach the upper atmosphere can gain enough energy to exceed escape velocity and drift off into space. Research on the mechanisms of helium loss has examined how helium ions interact with nitrogen, oxygen, and other atmospheric gases in charge-exchange reactions that strip electrons and launch neutral helium atoms upward fast enough to leave the planet entirely.5Planetary and Space Science. Helium escape from the Earth’s atmosphere: The charge exchange mechanism revisited
Second, almost all of the helium found on Earth today is not left over from the planet’s formation. It is freshly made, atom by atom, through the radioactive decay of heavy elements like uranium and thorium buried in Earth’s crust and mantle. When these elements undergo alpha decay, each alpha particle is essentially a helium-4 nucleus. Over geological time, some of this helium migrates upward through rock and accumulates in underground pockets, often alongside natural gas. This is where commercial helium comes from: it is extracted from certain natural gas wells, particularly in the United States, Qatar, and Algeria. The gas is genuinely non-renewable on human timescales. Once released into the atmosphere, it gradually drifts upward and is lost to space.
The Practical Consequences of a Finite Supply
Because Earth’s helium comes from slow radioactive decay rather than from some vast reservoir, the global supply is limited and has been subject to periodic shortages. Helium is essential in ways most people do not think about. Liquid helium is the coldest readily available cryogenic fluid, and it is indispensable for cooling the superconducting magnets inside MRI machines, particle accelerators, and quantum computing labs. It is also used in semiconductor manufacturing, deep-sea diving gas mixtures, rocket engine purging, and leak detection in industrial systems. Party balloons account for a relatively small fraction of total helium consumption, but they have become a cultural symbol of the gas.
The unusual origin story matters here. Unlike nitrogen or oxygen, which can be pulled from the atmosphere in virtually unlimited quantities, helium must be captured from the ground before it escapes. Once a helium-bearing gas field is tapped and the helium is vented rather than captured, that helium is gone for good on any human timescale. Several nations have established strategic helium reserves, and prices have spiked during shortage periods, creating real headaches for hospitals that depend on MRI technology and for physicists running experiments at temperatures near absolute zero.
Helium as a Tool for Studying Other Stars and Planets
The story of helium’s discovery has come full circle in a way Lockyer might have appreciated. Just as astronomers in the 1860s used spectral lines to detect helium in the sun, modern astronomers use a specific helium absorption line to study planets orbiting other stars. When an exoplanet passes in front of its host star, some of the starlight filters through the planet’s atmosphere. If that atmosphere contains helium, the helium absorbs light at a characteristic near-infrared wavelength around 10,833 angstroms. By measuring how much light is absorbed at that wavelength during a transit, researchers can learn about the composition and extent of the exoplanet’s upper atmosphere, including whether it is actively losing gas to space.
The strength of the helium signal depends not just on the exoplanet itself but also on the star it orbits. Stars with different levels of activity and different coronal compositions pump out different amounts of extreme ultraviolet radiation, which is what excites the helium in the planet’s atmosphere in the first place. Research has found that the relationship between a star’s extreme ultraviolet output and its X-ray luminosity changes depending on the star’s coronal chemistry, and accounting for this reduces the scatter in predictions of how strong a planet’s helium absorption signal should be.6Oxford Academic. Helium absorption in exoplanet atmospheres is connected to stellar coronal abundances In other words, understanding the star helps you understand the planet, which is a nice echo of the original helium story: understanding the sun’s light told us something fundamental about what elements exist.
Other Elements Named After Celestial Objects
Helium is not the only element whose name points skyward, though it is the only one first discovered in a star. Selenium comes from the Greek selene (moon), named by the chemist Jöns Jacob Berzelius in 1817 because it was chemically similar to tellurium, which had already been named after the Latin tellus (earth). The pairing was intentional: earth and moon, sitting together in the periodic table. Cerium was named after the dwarf planet Ceres, which had been discovered just two years before the element was isolated in 1803. Palladium was named after the asteroid Pallas, and uranium after the planet Uranus.
But helium’s case stands apart because the connection is not just a poetic tribute. The element genuinely was identified in the sun first, and the sun genuinely is where most of the helium in the solar system was produced. The name does not merely honor a celestial body; it records a historical fact about where humanity first encountered the substance. That makes helium’s name one of the more honest labels on the periodic table, a small reminder that the ground beneath your feet is not always the first place to look when searching for the building blocks of matter.