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{{short description|Discrepancy between the observed abundance of lithium produced in Big Bang nucleosynthesis and the amount that should theoretically exist.}}
In [[
==Origin of lithium==
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Lithium is also found in [[brown dwarf]] substellar objects and certain anomalous orange stars. Because lithium is present in cooler, less-massive brown dwarfs, but is destroyed in hotter [[red dwarf]] stars, its presence in the stars' spectra can be used in the "lithium test" to differentiate the two, as both are smaller than the Sun.<ref name=emsley/><ref>{{cite web|url=http://www.universetoday.com/24593/brown-dwarf/|archiveurl=https://web.archive.org/web/20110225032434/http://www.universetoday.com/24593/brown-dwarf/|archivedate=25 February 2011|title=Brown Dwarf |accessdate=17 November 2009 |last=Cain |first=Fraser |publisher=Universe Today}}</ref><ref>{{cite web|url=http://www-int.stsci.edu/~inr/ldwarf3.html |archive-url=https://archive.is/20130521055905/http://www-int.stsci.edu/~inr/ldwarf3.html |dead-url=yes |archive-date=21 May 2013 |title=L Dwarf Classification|accessdate=6 March 2013 | first =Neill | last = Reid | date = 10 March 2002}}</ref> Certain orange stars can also contain a high concentration of lithium. Those orange stars found to have a higher than usual concentration of lithium (such as [[Centaurus X-4]]) orbit massive objects—neutron stars or black holes—whose gravity evidently pulls heavier lithium to the surface of a hydrogen-helium star, causing more lithium to be observed.<ref name=emsley>{{Cite book|last=Emsley |first=John |title=Nature's Building Blocks |publisher=Oxford University Press |___location=Oxford|date=2001 |isbn=0-19-850341-5}}</ref>
==Proposed solutions==▼
===Less lithium in stars with planets===
This deficiency of lithium may in part be due to faster destruction than synthesis of <sup>7</sup>Li and its progenitor [[beryllium-7|<sup>7</sup>Be]] in [[nuclear reaction]]s, though no conclusive results on the reaction flow in Big Bang nucleosynthesis have been obtained. Newer theories involving physics beyond the [[standard model]], involving not well understood [[dark matter]], have also been proposed to explain the possible destruction of lithium, also inconclusively.<ref name=Bertulani>{{cite journal |last=Bertulani |first=C.A. |last2=Shubhchintak |last3=Mukhamedzhanov |first3=A.M. |title=Cosmological lithium problems |date=2018 |journal=The European Physical Journal Conferences |volume=184 |doi=10.1051/epjconf/201818401002 |arxiv=1802.03469}}</ref><ref name=MWoo>{{cite web |url=http://www.bbc.com/earth/story/20170220-the-cosmic-explosions-that-made-the-universe |title=The Cosmic Explosions That Made the Universe |last=Woo |first=Marcus |date=21 Feb 2017 |website=earth |publisher=BBC |access-date=21 Feb 2017 |quote=A mysterious cosmic factory is producing lithium. Scientists are now getting closer at finding out where it comes from |deadurl=no |archiveurl=https://web.archive.org/web/20170221214442/http://www.bbc.com/earth/story/20170220-the-cosmic-explosions-that-made-the-universe |archivedate=21 February 2017 |df=dmy-all }}</ref>▼
Stars without planets have 10 times the lithium as stars with planets in a sample of 500 stars.<ref name="Discover">{{cite journal |last1=Plait |first1=Phil |title=Want a planet? You might want to avoid lithium |date=Nov 11, 2009}}</ref> The sun has 1% of the amount of lithium in gas clouds. It is suspected that the gravitational pull of planets might churn up a star's surface driving the lithium to hotter cores where [[Lithium burning]] can take place.<ref name="Discover"/> The absence of lithium could also be a way to find new planetary systems.<ref name="Discover"/>
▲==Proposed solutions==
▲This deficiency of lithium may in part be due to faster destruction than synthesis of <sup>7</sup>Li and its progenitor [[beryllium-7|<sup>7</sup>Be]] in [[nuclear reaction]]s, though no conclusive results on the reaction flow in Big Bang nucleosynthesis have been obtained. Newer theories involving physics beyond the [[standard model]], involving not well understood [[dark matter]], have also been proposed to explain the possible destruction of lithium, also inconclusively.<ref name=Bertulani>{{cite journal |last=Bertulani |first=C.A. |last2=Shubhchintak |last3=Mukhamedzhanov |first3=A.M. |title=Cosmological lithium problems |date=2018 |journal=The European Physical Journal Conferences |volume=184 |doi=10.1051/epjconf/201818401002 |arxiv=1802.03469}}</ref><ref name=MWoo>{{cite web |url=http://www.bbc.com/earth/story/20170220-the-cosmic-explosions-that-made-the-universe |title=The Cosmic Explosions That Made the Universe |last=Woo |first=Marcus |date=21 Feb 2017 |website=earth |publisher=BBC |access-date=21 Feb 2017 |quote=A mysterious cosmic factory is producing lithium. Scientists are now getting closer at finding out where it comes from |deadurl=no |archiveurl=https://web.archive.org/web/20170221214442/http://www.bbc.com/earth/story/20170220-the-cosmic-explosions-that-made-the-universe |archivedate=21 February 2017 |df=dmy-all }}</ref>
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