The Element Found in the Sun: How an 1868 Eclipse Led to Helium

On the evening of August 12, 2026, as the Moon slid fully across the Sun over northern Spain, thousands of people on hillsides and beaches saw a small pink flame standing at the edge of the black disk. It looked like a tongue of fire. It was a solar prominence, a loop of glowing gas many times the size of Earth, held up by the Sun’s magnetic field. Most of that pink light comes from hydrogen. But hidden in the same glow is a faint yellow light that, in the summer of 1868, did not match anything known on Earth.

That yellow light belonged to helium, the only element found in space before anyone found it on the ground. Helium is now the gas in party balloons and the coolant inside most hospital MRI scanners. It keeps the magnets of the Large Hadron Collider colder than deep space and flushes the air out of chip factories. This year it has also been a casualty of war, with prices for some buyers roughly doubling after strikes on the plant in Qatar that supplied about a third of the world’s helium.

The usual story of how helium was found is short and tidy. A French astronomer in India and an English astronomer in London spotted the same strange yellow line at the same moment, their letters reached Paris on the same day, and science shared the credit. Almost every part of that story is a little bit wrong. The real version has a forgotten astronomer in a cyclone-battered port, a king who died after predicting an eclipse, an escape by balloon from a city under siege, a gas that would not burn in a Kansas field, and a teacupful of liquid that opened a new branch of physics.

The King of Siam’s Eclipse

The eclipse of August 18, 1868, was one of the longest of the century. Its path ran from Ethiopia and Yemen across India, Burma and Siam (now Thailand) to the islands of what is now Indonesia, and in some places the Sun stayed hidden for more than six minutes. It was also the first total eclipse since the German physicist Gustav Kirchhoff had shown, in 1859 and 1860, that the dark lines in the Sun’s spectrum are fingerprints of chemical elements. Pass light through a prism and each element in a hot gas glows at its own exact colors. For the first time, astronomers could carry a tool to an eclipse that might tell them what the Sun was made of.

Expeditions sailed from Britain, France and Germany. Some of the most eager watchers were already in Asia. King Mongkut of Siam, a former Buddhist monk with a deep interest in Western astronomy, had calculated the eclipse himself and found that totality would cross the coast at Wa Ko, a village on the narrow neck of land south of Bangkok. He built a camp there, invited the British governor of the Straits Settlements, Sir Harry Ord, and hosted a French astronomical party as his guests. The eclipse arrived where and when the king had said it would. It is still remembered in Thailand as the King of Siam’s eclipse, and August 18 is now Thailand’s National Science Day.

The triumph had a terrible cost. The camp sat in malarial country, and the king came home with fever. He died on October 1, 1868, six weeks after the eclipse, at the age of 63. His son Chulalongkorn, who also fell ill at Wa Ko, survived and became one of Siam’s great reforming kings.

A Yellow Line Near Sodium

The man usually given the starring role in 1868 was Pierre Jules César Janssen, a 44-year-old Parisian physicist who had been lame since a childhood accident and who spent the rest of his life climbing mountains and flying in balloons anyway. Janssen had already spent years studying the solar spectrum and had shown that some of its dark lines came not from the Sun but from water vapor in Earth’s air. Paris was then a capital of optical science, where Hippolyte Fizeau and Léon Foucault had lately clocked the speed of light on a laboratory bench. For the eclipse, the French government sent Janssen to Guntur, an inland town in what was then the Madras Presidency of British India.

On the morning of August 18, when the Moon covered the Sun over Guntur, Janssen aimed his spectroscope at two large prominences on the Sun’s edge and saw them break into a few bright lines of colored light. That alone was a discovery: it proved that prominences were glowing clouds of gas, not mountains on the Sun or tricks of light in Earth’s atmosphere. Among the bright lines was a yellow one close to the familiar pair of yellow lines made by sodium, which astronomers call D.

Janssen was so struck by how bright the lines were that he wondered whether he could see them without an eclipse at all. Clouds rolled in after totality, but the next morning, at about ten o’clock, he pointed his spectroscope at the edge of the uneclipsed Sun, tuned it to where the lines had been, and there they were. Prominences, which until then could be seen only for a few minutes during a total eclipse, could now be studied on any clear day. He kept watching them from Guntur for days afterward and wrote it all up in a letter to the French Academy of Sciences in Paris. In 1868, mail from southern India to France took about two months.

Janssen was not the only person who saw the yellow line. At least four other observers in the eclipse path noted it, including Georges Rayet with the French party in Siam and two British officers in India, Captain C.T. Haig and Lieutenant John Herschel, a son of the astronomer John Herschel. Most assumed it was sodium. And one observer, working almost alone on the coast, wrote down something more careful than anybody else.

The Man at Masulipatam

Norman Robert Pogson was the government astronomer at the Madras Observatory. He is best known today for Pogson’s ratio, the rule that makes a first-magnitude star exactly 100 times brighter than a sixth-magnitude star, which astronomers still use. In 1868 he was an Englishman stuck in India, out of favor with the astronomical establishment in London. The Royal Astronomical Society funded a well-equipped British expedition to Guntur under a surveyor, James Francis Tennant. Pogson was given nothing.

So he improvised. Masulipatam (now Machilipatnam), a port on the Bay of Bengal, lay in the path of totality and had been wrecked by a cyclone four years earlier. Pogson argued that it needed a weather station, set one up there, borrowed a spectroscope from the London astronomer William Huggins, recruited engineers from the telegraph and railway departments, and watched the eclipse. He described the yellow line in the prominences as lying “at or near D.” Nearly 80 years later the astrophysicist Subrahmanyan Chandrasekhar wrote that almost the whole story of helium depends on that distinction. Everyone else called the line sodium. Pogson left the door open to something new.

His report never reached a wide audience. In 1868 his wife was dying, his superiors in London had written him off, and he could only get his account printed privately in Madras with local government money. According to the astrophysicist Biman Nath, whose 2013 book The Story of Helium and the Birth of Astrophysics pieced the record back together, it was Pogson’s wording that later pushed Norman Lockyer to look hard at that yellow line. Nath also found that Janssen, in his own reports, never claimed to have seen the sign of a new element. What he announced was a new way to watch prominences in daylight.

“At Last!”

Joseph Norman Lockyer was a clerk at the War Office in London who had turned himself into one of Britain’s best-known amateur astronomers. Two years before the eclipse he had suggested that prominences might be seen without one if a spectroscope could spread the bright Sun into a long enough rainbow that the faint glowing lines of the prominences stood out against it. To do that he needed a stronger instrument. He ordered one from the London instrument maker John Browning, with seven prisms, and waited a long time for it.

The spectroscope was finished on October 16, 1868. Four days later, on October 20, Lockyer fixed it to his telescope at his home in West Hampstead, pointed it at the edge of the Sun and searched for the prominence lines. After a long search, the bright lines of a prominence came into view. “At last!” he later wrote of that moment. He then left the observatory to fetch his wife, Winifred, to confirm what he was seeing. Winifred Lockyer was a translator of French science books and a real partner in his work, and she would join him on an eclipse expedition to Sicily two years later.

Lockyer wrote to the Royal Society in London and to the French Academy. His letter arrived in Paris on October 26, the same day as Janssen’s long-delayed letter from India. Both were read at the Academy’s meeting that afternoon. The coincidence delighted the French, who were happy to share the glory with a British rival, and in 1872 the Academy commissioned a medal with the two men’s heads side by side, the words “Analyse des protubérances solaires, 18 août 1868” and Apollo driving his chariot across the sky. Janssen and Lockyer became lifelong friends.

What the two letters shared, though, was the daylight method for seeing prominences, not a new element. It was in the weeks that followed that Lockyer measured the yellow line carefully and found that it really did not sit where the sodium lines sit. He called it D3, to set it beside sodium’s D1 and D2. He then spent months with the chemist Edward Frankland in a London laboratory, trying to make hydrogen or any other known gas produce a line in the same spot by heating it, squeezing it and passing sparks through it. Nothing worked.

An Element With No Proof

Gradually Lockyer came to believe that the line belonged to an element nobody had found on Earth. He and Frankland chose a name from the Greek word for the Sun, helios. The ending was odd. Chemists normally give “-ium” endings to metals, such as sodium and potassium, and some suspect Lockyer thought the new substance might be a metal. Lockyer himself never seems to have used the word in print. The first time it appeared in public was in August 1871, when Lord Kelvin, as president of the British Association for the Advancement of Science, mentioned in his address in Edinburgh the bright yellow line and the name “helium” that Frankland and Lockyer had given it.

Many scientists thought the idea was reckless. There was no sample, no weight, no chemistry, only a line of light. Even Frankland later backed away from it in public. And the sky soon offered warnings. In August 1869, the American astronomers William Harkness and Charles Young saw a bright green line in the light of the Sun’s corona during an eclipse and put it down to another unknown element, coronium. Not long before, the English astronomer William Huggins had found green lines in the glowing gas clouds called nebulae and suggested an element called nebulium.

Both turned out to be mirages. In 1927 the American physicist Ira Bowen showed that the nebula lines came from ordinary oxygen that had lost two electrons, in a gas so thin that its atoms behaved in ways that cannot happen in a laboratory. His colleague Henry Norris Russell joked that nebulium had vanished into thin air. Around 1940, the German astronomer Walter Grotrian and the Swedish physicist Bengt Edlén showed that coronium was iron stripped of 13 of its 26 electrons, a sign that the Sun’s thin outer atmosphere is heated to more than a million degrees. Helium could easily have joined them on the list of lost elements. It did not, because of a chemist with a taste for odd problems.

Ramsay’s Gas From a Swedish Mineral

William Ramsay was a Scottish chemist at University College London. In 1894 he and the physicist Lord Rayleigh had discovered argon, an inert gas that makes up nearly 1 percent of air and had been sitting unnoticed in every breath anyone took. The find made Ramsay curious about gases that refuse to react with anything.

On February 1, 1895, the mineralogist Henry Miers wrote to tell him about the work of William Hillebrand of the U.S. Geological Survey. A few years earlier, Hillebrand had boiled a uranium mineral in acid and collected an inert gas that he took to be nitrogen, though it showed a few odd lines in a spectroscope. Ramsay wondered whether Hillebrand’s gas might be argon. He bought about a gram of a related Norwegian uranium mineral called cleveite, reportedly for three shillings and sixpence, and boiled it in acid.

The gas he collected did not show the lines of argon. Instead, through his spectroscope, Ramsay saw a brilliant yellow line, close to sodium but not on it. To be sure, he sent samples to the chemist and spectroscopist William Crookes and to Lockyer himself. Ramsay had first dubbed the new gas krypton, and Crookes sent back a famous telegram: “Crypton is Helium. Come and see it.” Ramsay’s announcement was read out in Paris on March 26, 1895. A few weeks later, two Swedish chemists working separately, Per Teodor Cleve and Nils Abraham Langlet, collected enough of the gas from cleveite to measure its atomic weight at about 4.

After 27 years, Lockyer’s element was real. Ramsay sent him a sample, and a tube of Ramsay’s helium from cleveite survives in the Science Museum in London. Ramsay went on to find neon, krypton and xenon with Morris Travers, and in 1904 he won the Nobel Prize in Chemistry for discovering the noble gases. Lockyer, by then Sir Norman, had founded the journal Nature in 1869 and edited it for half a century.

The discovery also solved a riddle about where Earth’s helium comes from. In 1903 Ramsay and Frederick Soddy showed that radium gives off helium as it decays, and in 1908 Ernest Rutherford and Thomas Royds proved that the alpha particles thrown out by radioactive atoms are helium nuclei. That was why helium was trapped inside uranium minerals. Almost all the helium on Earth has been made this way, a few atoms at a time, by uranium and thorium decaying in rock over billions of years. Helium in the air does not last. It is so light that it slowly leaks away into space, which is why the atmosphere holds only about 5 parts per million of it. The helium we use has to be mined, from the few places where rock has trapped it underground. (The Moon is a different case: the solar wind has sprinkled its soil with a rare light form of the element, helium-3, which some space agencies and companies dream of mining.)

The Gas That Wouldn’t Burn

One of those places turned out to be Kansas. In May 1903, drillers looking for natural gas near the small town of Dexter struck a well that roared out gas under such pressure that people called it a “howling gasser.” The town planned a celebration. A bale of hay was set alight and pushed into the stream of gas to light a great torch. Instead the burning hay went out. The mayor tried several more times, with the same result, and the disappointed crowd went home calling it “wind gas.”

The state geologist, Erasmus Haworth, had a steel cylinder filled with the gas and took it back to the University of Kansas in Lawrence. The gas turned out to be mostly nitrogen, with about 15 percent methane and a stubborn 12 percent that would not react with anything. In December 1905, the chemists Hamilton Cady and David McFarland soaked up the inert part with charcoal cooled in liquid air and found that 1.84 percent of the Dexter gas was helium. Before that, helium had been a laboratory curiosity drawn out of rare minerals a few bubbles at a time. Cady and McFarland went on to find it in natural gas wells across Kansas and beyond, and wrote that helium was “no longer a rare element.” The American Chemical Society made their lab a National Historic Chemical Landmark in 2000.

It was still a substance with no job. That changed with war. During the First World War the British physicist Sir Richard Threlfall suggested that the Allies could fill their observation balloons and airships with helium instead of hydrogen, which explodes in flame when a bullet hits it. The U.S. Navy paid for three small experimental plants, which produced about 200,000 cubic feet of fairly pure helium, more than had ever been collected anywhere. The war ended before it could be used, but on December 1, 1921, the Navy’s small blimp C-7 became the first airship to fly on helium, and in 1923 the giant rigid airship USS Shenandoah followed.

America’s Helium

The United States now held almost the entire world supply of a gas that could make airships safe, and it chose to keep it. Under the Helium Act of 1925, exports were effectively banned, and the federal Bureau of Mines took charge of production. The German Zeppelin company designed its great passenger airship Hindenburg to fly on helium but could not get any. It flew on hydrogen instead, and on May 6, 1937, it caught fire while landing at Lakehurst, New Jersey, killing 36 people.

Helium did not make airships safe from the weather, though. The Navy’s helium-filled USS Akron, one of the largest flying machines ever built, crashed into the Atlantic in a storm off New Jersey on April 4, 1933. Of the 76 men aboard, 73 died, most of them from drowning or the cold, more than in the Hindenburg disaster. The era of the giant airship was over within a few years.

The government kept the gas anyway. In 1929 the Bureau of Mines opened a helium plant on the Cliffside gas field near Amarillo, Texas. In the 1960s, worried about rocket programs and the Cold War, the government bought huge amounts of helium from private companies and pumped it back underground into the Cliffside rock dome through a pipeline that grew to more than 400 miles long, running across Kansas, Oklahoma and Texas. The Saturn V rockets of the Apollo era used helium to push fuel and purge their tanks. In 1968, to mark the centennial of Janssen’s and Lockyer’s 1868 observations, Amarillo put up a six-story stainless steel sculpture, the Helium Centennial Time Columns Monument, with four time capsules to be opened after 25, 50, 100 and 1,000 years.

By the 1990s the stockpile had left the government about $1.4 billion in debt, and Congress decided to get out of the helium business. The Helium Privatization Act of 1996 ordered the reserve sold down. The process took almost three decades. In June 2024 the Bureau of Land Management completed the sale of the whole Federal Helium System, including Cliffside and its pipeline, to the industrial gas company Messer, which had bid about $423 million.

A Teacup of Liquid

The other great story of helium is cold. Every gas turns to liquid if it is cooled enough, and in the late 1800s physicists raced to liquefy them all. Oxygen and nitrogen fell in the 1870s and 1880s, and hydrogen in 1898. Helium held out. It boils at about minus 269 degrees Celsius, only about 4 degrees above absolute zero, the coldest possible temperature.

The Dutch physicist Heike Kamerlingh Onnes built the most ambitious cold laboratory in the world at Leiden to beat it. On July 10, 1908, after cooling a supply of helium with liquid hydrogen and running it through his apparatus all day, his team saw a clear liquid collecting in the glass at about 7:30 in the evening. They had made roughly 60 cubic centimeters, about the volume of a small cup. For the next 15 years Leiden was the only place on Earth that could make liquid helium.

With it, Kamerlingh Onnes found something no one had predicted. In 1911 he cooled a thread of mercury in liquid helium and its electrical resistance suddenly dropped to zero. He had discovered superconductivity, and he won the 1913 Nobel Prize in Physics. In the late 1930s, Pyotr Kapitsa in Moscow and John Allen and Don Misener in Cambridge found that helium cooled below about 2.2 degrees above absolute zero turns into a superfluid that flows without any friction. It can seep through gaps too fine for any other liquid, climb up and over the walls of its container in a thin film and shoot up in a fountain when it is gently warmed. Nothing else on Earth behaves like it.

Those two discoveries are why helium matters so much now. Most MRI scanners use superconducting magnets made of special wire that only works when it is bathed in liquid helium. Cooling, mainly for MRI, is the largest single use of helium. The Large Hadron Collider at CERN, near Geneva, uses about 120 tonnes of helium to keep its superconducting magnets at 1.9 degrees above absolute zero, colder than the space between the stars. Helium is also used to make the silicon chips in phones and computers, to pull optical fibers and to protect welds, and divers mix it with oxygen to breathe at depth.

Helium in 2026

Because helium is collected as a by-product of natural gas, a few gas fields supply the world. The United States produced about 43 percent of the world’s helium in 2025. Qatar, where helium is separated out at the giant Ras Laffan gas complex, supplied roughly a third. Algeria and Russia are among the other big suppliers.

In March 2026, during the war between the United States and Iran, Iranian strikes hit Ras Laffan and production stopped. QatarEnergy declared force majeure, a legal notice that it could not meet its contracts, and warned that rebuilding the damaged units could take years. Shipping through the Strait of Hormuz, the narrow sea lane most Qatari helium has to pass through, was cut off. Spot prices for helium jumped within weeks. By October, a ceasefire had been agreed and extended, but the trade press reported that shipments were still disrupted and that spot prices were about double their prewar levels. Chip makers in South Korea and Taiwan, which relied heavily on Qatari helium, were among the hardest hit. Helium is hard to stockpile. It has to be shipped as a liquid at about 4 degrees above absolute zero, and it slowly boils away on the journey.

Hospitals have been trying to use less. Newer MRI scanners seal their helium in and need only a small fraction of what older machines used, and many research labs now recycle the gas instead of letting it escape. But the lesson of 1868 still holds. Helium is common in the universe and rare where we live. It makes up about a quarter of all the ordinary matter in the cosmos, most of it made in the first few minutes after the Big Bang, and it is the second most common element in the Sun. On Earth, every balloon of it is a gas that took billions of years to collect and that will drift off into space once it escapes.

What Happened to the Astronomers

Janssen never stopped. In 1870, when Prussian armies surrounded Paris, he planned to observe that December’s eclipse in Algeria. Lockyer arranged for the Prussians to offer him a safe-conduct pass through their lines, but Janssen refused it. Instead, early on December 2, he lifted off from the besieged city in a gas balloon named the Volta, filled with the city’s coal gas, and carrying his instruments. He landed hours later near the Atlantic coast, more than 200 miles away, and made his way to Algeria. On the day of the eclipse, the sky there was cloudy. So was the sky over Sicily, where Lockyer and Winifred had gone to watch it.

Janssen went on to invent a “photographic revolver” in 1874, a camera that took 48 pictures in 72 seconds to record the planet Venus crossing the face of the Sun. Many historians count it as an ancestor of the movie camera. He became the first director of the observatory at Meudon, outside Paris, published an atlas of more than 6,000 photographs of the Sun’s surface, and at the age of 69 had himself carried up Mont Blanc to build an observatory on the summit. He died in Paris on December 23, 1907.

Lockyer spent his later years on solar physics, on Nature and on a surprising sideline. In Egypt and at Stonehenge he measured how ancient temples and stone circles lined up with sunrise on key days of the year, and his 1894 book The Dawn of Astronomy helped start the field now called archaeoastronomy. He died in 1920. Pogson died in Madras in 1891, still in his post after 30 years and largely forgotten. His careful words about a yellow line near D were rescued by historians more than a century later.

The Next Eclipse

On August 2, 2027, the Moon’s shadow will cross Spain, North Africa and the Middle East in one of the longest total eclipses of the century. Near Luxor in Egypt, among the temples Lockyer once measured, the Sun will be hidden for about 6 minutes and 23 seconds, longer than at any easily reached spot on land until the year 2114. People who look at the edge of the Moon in those minutes, with the right filters before and after totality and with their bare eyes only during it, may see the same pink prominences Janssen saw at Guntur. Some will bring small spectroscopes, and in the pink glow they will find the yellow line of the gas that powers the scanners in their hospitals, which was found in the Sun 27 years before anyone found it on Earth.

Further reading