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==History== | ==History== | ||
Helium is the only element to have been discovered extraterrestrially before being found on Earth, specifically in the Sun. A bright yellow spectral line (''λ'' = 587.49 nm) was first observed by French astronomer [[Jules Janssen]] during the eclipse of 18 August 1868, which Janssen observed from Guntur in India, and independently by [[Norman Lockyer]] in London on 20 October 1868.<ref>{{citation | title = Sir Norman Lockyer, 1836–1920 | url = http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1921ApJ....53..233C&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf | last = Cortie | first = A. L. | journal = Astrophys. J. | year = 1921 | volume = 53 | issue = 4 | pages = 233–48}}.</ref><ref>{{citation | url = http://www.wired.com/thisdayintech/2009/08/dayintech_0818/ | publisher = wired.com | accessdate = 2010-03-18 | title = Aug. 18, 1868: Helium Discovered During Total Solar Eclipse | date = August 18, 2009 | first = Hadley | last = Leggett}}.</ref><ref>{{citation | journal = C. R. Hebd. Acad. Sci. Paris | volume = 67 | year = 1868 | pages = 836–41 | url = http://gallica.bnf.fr/ark:/12148/bpt6k3024c.image.r=comptes-rendus+hebdomadaires+Acad%C3%A9mie+des+Sciences.f836.langFR}}.</ref> Lockyer, together with English chemist [[Edward Frankland]], showed that the line could not be explained by any known element, and proposed the name helium, from the Greek {{Polytonic|ἥλιος}} (''helios'', the Sun). | Helium is the only element to have been discovered extraterrestrially before being found on Earth, specifically in the Sun. A bright yellow spectral line (''λ'' = 587.49 nm) was first observed by French astronomer [[Jules Janssen]] during the eclipse of 18 August 1868, which Janssen observed from Guntur in India, and independently by [[Norman Lockyer]] in London on 20 October 1868.<ref>{{citation | title = Sir Norman Lockyer, 1836–1920 | url = http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1921ApJ....53..233C&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf | last = Cortie | first = A. L. | journal = Astrophys. J. | year = 1921 | volume = 53 | issue = 4 | pages = 233–48}}.</ref><ref>{{citation | url = http://www.wired.com/thisdayintech/2009/08/dayintech_0818/ | publisher = wired.com | accessdate = 2010-03-18 | title = Aug. 18, 1868: Helium Discovered During Total Solar Eclipse | date = August 18, 2009 | first = Hadley | last = Leggett}}.</ref><ref>{{citation | journal = C. R. Hebd. Acad. Sci. Paris | volume = 67 | year = 1868 | pages = 836–41 | url = http://gallica.bnf.fr/ark:/12148/bpt6k3024c.image.r=comptes-rendus+hebdomadaires+Acad%C3%A9mie+des+Sciences.f836.langFR}}.</ref> Lockyer, together with English chemist [[Edward Frankland]], showed that the line could not be explained by any known element, and proposed the name helium, from the Greek {{Polytonic|ἥλιος}} (''helios'', the Sun). | ||
| + | |||
| + | ==Occurrence and production== | ||
| + | {| class="wikitable" align=right width=22em | ||
| + | |- | ||
| + | ! Country | ||
| + | ! Production<br/>km<sup>3</sup> | ||
| + | |- | ||
| + | | [[United States]] | ||
| + | | 122* | ||
| + | |- | ||
| + | | [[Algeria]] | ||
| + | | 24 | ||
| + | |- | ||
| + | | [[Qatar]] | ||
| + | | 15 | ||
| + | |- | ||
| + | | [[Russia]] | ||
| + | | 7 | ||
| + | |- | ||
| + | | [[Poland]] | ||
| + | | 2.5 | ||
| + | |- | ||
| + | | colspan=2 | Estimates for 2009 from the<br/>U.S. Geological Survey | ||
| + | |- | ||
| + | | colspan=2 | <small>*U.S. figure includes 42 million<br/>cubic metres withdrawn from the<br/>federal government stockpile.</small> | ||
| + | |- | ||
| + | |} | ||
| + | Helium is the second most common element in the Universe (after [[hydrogen]]), accounting for 23% of all atoms. However, the Earth's gravitational field is not strong enough to retain helium in the atmosphere for long periods, and all the Earth's primordial helium is believed to have escaped. The helium currently present on Earth has been formed from the [[alpha decay]] of radioactive nuclides: most of this helium escapes to the atmosphere and then into space, but some of it can be trapped underground by impermeable rock formations, often associated with [[natural gas]] deposits. | ||
| + | |||
| + | The commercial production of helium is based around its extraction from natural gas, which is economically viable when the helium fraction is greater than about 0.3%. The [[United States]] has historically been the predominant producer, although its ''de novo'' production is declining and [[Algeria]] and [[Qatar]] are gaining importance. | ||
==References== | ==References== | ||
{{reflist}} | {{reflist}} | ||
Revision as of 09:57, 18 March 2010
Helium (symbol: He) is a chemical element, the lightest of the noble gases.
History
Helium is the only element to have been discovered extraterrestrially before being found on Earth, specifically in the Sun. A bright yellow spectral line (λ = 587.49 nm) was first observed by French astronomer Jules Janssen during the eclipse of 18 August 1868, which Janssen observed from Guntur in India, and independently by Norman Lockyer in London on 20 October 1868.[1][2][3] Lockyer, together with English chemist Edward Frankland, showed that the line could not be explained by any known element, and proposed the name helium, from the Greek ἥλιος (helios, the Sun).
Occurrence and production
| Country | Production km3 |
|---|---|
| United States | 122* |
| Algeria | 24 |
| Qatar | 15 |
| Russia | 7 |
| Poland | 2.5 |
| Estimates for 2009 from the U.S. Geological Survey | |
| *U.S. figure includes 42 million cubic metres withdrawn from the federal government stockpile. | |
Helium is the second most common element in the Universe (after hydrogen), accounting for 23% of all atoms. However, the Earth's gravitational field is not strong enough to retain helium in the atmosphere for long periods, and all the Earth's primordial helium is believed to have escaped. The helium currently present on Earth has been formed from the alpha decay of radioactive nuclides: most of this helium escapes to the atmosphere and then into space, but some of it can be trapped underground by impermeable rock formations, often associated with natural gas deposits.
The commercial production of helium is based around its extraction from natural gas, which is economically viable when the helium fraction is greater than about 0.3%. The United States has historically been the predominant producer, although its de novo production is declining and Algeria and Qatar are gaining importance.
References
- ↑ Cortie, A. L. Sir Norman Lockyer, 1836–1920. Astrophys. J. 1921, 53 (4), 233–48, <http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1921ApJ....53..233C&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf>.
- ↑ Leggett, Hadley Aug. 18, 1868: Helium Discovered During Total Solar Eclipse; wired.com, August 18, 2009, <http://www.wired.com/thisdayintech/2009/08/dayintech_0818/>. (accessed 18 March 2010).
- ↑ C. R. Hebd. Acad. Sci. Paris 1868, 67, 836–41, <http://gallica.bnf.fr/ark:/12148/bpt6k3024c.image.r=comptes-rendus+hebdomadaires+Acad%C3%A9mie+des+Sciences.f836.langFR>.
