{"id":3268,"date":"2018-09-13T15:10:49","date_gmt":"2018-09-13T18:10:49","guid":{"rendered":"https:\/\/www.nachodelatorre.com.ar\/mosconi\/?p=3268"},"modified":"2018-09-13T15:10:49","modified_gmt":"2018-09-13T18:10:49","slug":"helio","status":"publish","type":"post","link":"https:\/\/www.fie.undef.edu.ar\/ceptm\/?p=3268","title":{"rendered":"Helio"},"content":{"rendered":"

El helio, el primero de la lista de los gases nobles, fue descubierto por primera vez hace 150 a\u00f1os, el 18 de agosto de 1868, por el astr\u00f3nomo franc\u00e9s Pierre Jules C\u00e9sar Janssen, durante un eclipse total de Sol. <\/span><\/span>Pese a ser el segundo elemento m\u00e1s abundante en el universo, debido a su baja densidad, el He que se forma en la Tierra es capaz de escapar r\u00e1pidamente a trav\u00e9s de la atm\u00f3sfera.<\/span><\/p>\n

have obtained one of the finest and least expected results\u2014Spectra of the stars!\u2014and beautiful spectra with colors and magnificent lines. Just one more step and the chemical composition of the universe will be revealed,\u201d\u00a0wrote astrophysicist Pierre Jules C\u00e9sar Janssen<\/a>\u00a0to his wife from an observatory in Italy in December 1862. Armed with the latest technology of the day and observations made by other Western astrophysicists, Janssen was determined to pry open the secrets of the galaxy.<\/p>\n

On August 18, 1868, Janssen managed to do just that. He became the first person to observe helium, an element never before seen on Earth, in the solar spectrum. At the time, though, Janssen didn\u2019t know what he\u2019d seen\u2014just that it was something new.<\/p>\n

The mid-1800s was an exciting time to peer at the heavens. A new instrument called a spectroscope was upending the field of astronomy. Similar in design to a telescope, the spectroscope worked like a super-powered prism, dispersing light into measurable wavelengths. An early model had allowed physicist Joseph Fraunhofer to observe the sun in the early 1800s, but he was\u00a0puzzled by black lines<\/a>\u00a0interrupting the normal colors. These black lines were named for Fraunhofer, even though he didn\u2019t understand what they were.<\/p>\n

That knowledge would come several decades later, with German researchers Gustav Kirchhoff and Robert Bunsen. In 1859, Bunsen and Kirchoff discovered that heating different elements produced bright lines of light in the spectroscope\u2014and those lines of light sometimes corresponded to the dark Fraunhofer lines.<\/p>\n

The scientists determined that the bright lines appeared when a hot gas was burned. For example, hydrogen burns orange, but when observed through a spectroscope, it becomes clear that the orange\u00a0is made up of multiple individual narrow wavelengths of light<\/a>. Similarly, the dark lines that Fraunhofer had discovered represented light being absorbed by a cooler element at the surface of the sun. \u201cThe two scientists found that every chemical element produces a unique spectrum,\u201d the\u00a0American Institute of Physics<\/a>\u00a0writes. \u201cThis provides a sort of \u2018fingerprint\u2019 which can confirm the presence of that chemical.\u201d<\/p>\n

By analyzing the emission spectra of specific elements in the lab, then turning their spectroscopes on the stars, researchers could make out the chemical composition of everything from our sun to the stars across the galaxy.<\/p>\n

 <\/p>\n

\"Solar_Automatic_Spectroscope.png\"

A spectroscope designed to look at the sun.\u00a0(Wikimedia Commons)<\/span><\/figcaption><\/figure>\n

\u201cBefore the spectroscope you had no idea what the sun was made of, or what stars are made of,\u201d says Deborah Warner, a curator in the division of medicine and science at the National Museum of American History. \u201cAll of a sudden there\u2019s this almost magical technique by which you can know the elements of these distant bodies. New elements are showing up right and left because you have this new tool.\u201d<\/p>\n

Janssen dove eagerly into this new form of light analysis. Though he lived in Paris, he traveled across Europe and Asia in search of optimal vantage points for observing the night sky. He also chased after eclipses, visiting Italy in February 1867 and then going all the way to Guntur, India, for the total solar eclipse of August 18, 1868. The French government and its national Academy of Sciences both funded this expedition, along with that of another Frenchman,\u00a0spending more than 75,000 francs<\/a>\u00a0for the two journeys.<\/p>\n

But the high cost would prove a worthy investment. On the day of the eclipse, armed with his spectroscope, Janssen saw something extraordinary: a bright yellow line whose wavelength didn\u2019t match with any known element. The spectrum came closest to the pattern made by sodium, but was distinct enough to merit its own category. It seemed that Janssen had discovered a new element, one never before seen on Earth.<\/p>\n

At the same time, Janssen uncovered a new way of observing the sun without the need of an eclipse, using a modified scope. He sent word of all this to the Academy of Sciences after the eclipse. But around the same time, the Academy received word from English astronomer Norman Lockyer that he\u2019d happened upon an invention that allowed him to view the sun without the eclipse, and had made a similar observation. With each man\u2019s work confirming the other\u2019s, it was hard to award definitive credit to either.\u00a0Astronomer Herv\u00e9 Faye suggested<\/a>\u00a0something of a compromise: \u201cInstead of trying to proportion the merit of the discovery, and consequently diminishing it, would it be better to attribute impartially the whole honor to both of these men of science, who, separated by some thousands of miles, have each been fortunate enough to reach the intangible and invisible by a method which is probably the most astonishing that the genius of observation has ever conceived?\u201d<\/p>\n

 <\/p>\n

\"Jules_Janssen_3-wr.jpg\"

French astrophysicist Pierre Jules Janssen traveled across the world in an attempt to understand the cosmos, and was the first to sight the wavelength pattern of helium in his spectroscope.\u00a0(Wikimedia Commons)<\/span><\/figcaption><\/figure>\n

The two researchers heartily agreed to share the honor of discovery, and later became close friends. But even with the excitement of their observation, questions remained. Most important among them: What exactly had Janssen and Lockyer seen? Not all scientists believed the observation, as Lockyer was soon to learn. Seeking proof to back up the claim that he\u2019d helped discover a new element, Lockyer went to English chemist Edward Frankland to attempt to reproduce the wavelength pattern in the lab. Frankland theorized it might be caused by hydrogen under extreme temperature and pressure, but they were unsuccessful in their attempts to recreate it.<\/p>\n

The skepticism over the possibility of an element existing in space but not on Earth is perhaps no surprise, given that it was the first of its kind. Science historians\u00a0James L. Marshall and Virginia R. Marshall write<\/a>, \u201cFrankland, perhaps cautious because of the many erroneous \u2018newly discovered elements\u2019 arising from the high resolution spectra now available, maintained that he did not want to have his name associated with this imaginary element,\u201d even after Lockyer went public, dubbing it \u201cHelium,\u201d after the Greek name for the sun.<\/p>\n

Not everyone was so skeptical. American scientist John William Draper extolled the discovery in 1876 in an address to the inaugural meeting of the American Chemical Society. \u201cI often look at the bright yellow ray emitted from the chromosphere of the sun, by that unknown element, helium, as the astronomers have ventured to call it. It seems trembling with excitement to tell its story, and how many unseen companions it has,\u201d\u00a0Draper said<\/a>.<\/p>\n

 <\/p>\n

\"Kirchhoffs_improved_spectroscope-wr.jpg\"

The spectroscope went through multiple iterations, and the scientists often tweaked the design on their own.(Wikimedia Commons)<\/span><\/figcaption><\/figure>\n

It wasn\u2019t until 1882 that a physicist spotted helium on Earth. Italian physicist Luigi Palmieri recorded the yellow spectral line in his data while\u00a0analyzing lava from Mount Vesuvius<\/a>. That discovery was later followed up by experiments conducted on the gas by Scottish chemist William Ramsay, and by 1895 researchers could definitively say that helium existed on Earth as well as in the sun. Ramsay went on to show helium was a product of the radioactive decay of radium, and placed it in relation to other elements on the periodic table.<\/p>\n

Today, helium is probably best known today as the gas that fills birthday balloons, but the gas also serves\u00a0important purposes<\/a>\u00a0in medical machinery (like MRI scanners) as well as in spacecraft and radiation monitors. It\u2019s also used in\u00a0computer parts, microscopes, air bags in cars<\/a>, and the\u00a0large hadron collider<\/a>\u00a0used in physics experiments. Plenty have worried about shortages of the element, but a large deposit found in Tanzania means we\u2019re likely\u00a0well-supplied for some time<\/a>.<\/p>\n

As for Janssen, he hardly rested on his laurels after spotting helium in the sun. Over the course of his long scientific career, he traveled to Peru, Switzerland, Japan, Algeria and elsewhere in his search to understand the cosmos. He even\u00a0escaped Paris in a hot-air balloon<\/a>\u00a0in 1870, when the city was under siege during the Franco-Prussian War. He fervently believed in his work,\u00a0once writing<\/a>, \u201cThe study of light will show us the physical organization of the system of the world.\u201d<\/p>\n

Fuente:<\/strong>\u00a0https:\/\/www.smithsonianmag.com<\/a><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

El helio, el primero de la lista de los gases nobles, fue descubierto por primera vez hace 150 a\u00f1os, el 18 de agosto de 1868,… <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[29,24],"tags":[],"_links":{"self":[{"href":"https:\/\/www.fie.undef.edu.ar\/ceptm\/index.php?rest_route=\/wp\/v2\/posts\/3268"}],"collection":[{"href":"https:\/\/www.fie.undef.edu.ar\/ceptm\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.fie.undef.edu.ar\/ceptm\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.fie.undef.edu.ar\/ceptm\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.fie.undef.edu.ar\/ceptm\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3268"}],"version-history":[{"count":0,"href":"https:\/\/www.fie.undef.edu.ar\/ceptm\/index.php?rest_route=\/wp\/v2\/posts\/3268\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.fie.undef.edu.ar\/ceptm\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3268"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.fie.undef.edu.ar\/ceptm\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3268"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.fie.undef.edu.ar\/ceptm\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3268"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}