Cosmological lithium problem: Difference between revisions

Revision as of 12:26, 10 July 2019

Revision as of 22:48, 18 July 2019

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==Origin of lithium==

One day after the Big Bang, the universe was made almost entirely of hydrogen and helium, with only very small amounts of thelithium next three elements—lithium (Li),and beryllium (Be), and boron (B).<ref name="habitable"/>

===The P-P II branch===

{{See also|Lithium burning}}

Lithium-7 is made by a [[proton-proton chain reaction]].

[[File:Proton-Proton II chain reaction.svg|thumb|Proton–proton II chain reaction]]

Lithium is made by a proton-proton chain reaction.

[[File:Proton-Proton II chain reaction.svg|thumb|Proton–proton II chain reaction]]

{{See also|Lithium burning}}

<!-- Autogenerated using Phykiformulae 0.11 by [[User:SkyLined]]

He-3 + He-4 -> Be-7 + y

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The P-P II branch is dominant at temperatures of 14 to {{val|23|u=MK}}.

The amount of lithium generated in the Big Bang can be calculated.<ref>{{cite journal | bibcode= 1985ARA&A..23..319B | title= Big bang nucleosynthesis – Theories and observations | last1= Boesgaard | first1=A. M. | last2= Steigman | first2= G. | volume= 23 |date= 1985 | pages= 319–378 | journal= Annual Review of Astronomy and Astrophysics |id=A86-14507 04–90 |___location=Palo Alto, CA | doi= 10.1146/annurev.aa.23.090185.001535}}</ref> [[Hydrogen-1]] is the most abundant [[nuclide]], comprising roughly 92% of the atoms in the Universe, with [[helium-4]] second at 8%. Other isotopes including ²H, ³H, ³He, ⁶Li, ⁷Li, and ⁷Be are much rarer; the estimated abundance of primordial lithium is 10⁻¹⁰ relative to hydrogen.<ref name=23bbn>{{cite book |last1=Tanabashi |first1=M. |display-authors=et al. |editor-last1=Fields |editor-first1=B.D. |editor-last2=Molaro |editor-first2=P. |editor-last3=Sarkar |editor-first3=S. |title=The Review |date=2018 |chapter=Big-bang nucleosynthesis |journal=Physical Review D |volume=98 |pages=377–382 |doi=10.1103/PhysRevD.98.030001 |url=https://pdg.lbl.gov/2019/reviews/rpp2018-rev-bbang-nucleosynthesis.pdf

Models}}</ref> ofThe thecalculated collisionsabundance thatand wouldratio haveof occurred¹H foundand that⁴He thereis wouldin haveagreement beenwith one helium atom for every ten hydrogen atoms, which agrees withdata thefrom observations of young stars.<ref name="habitable">{{cite book |isbn=978-0691140063|title=How to Build a Habitable Planet: The Story of Earth from the Big Bang to Humankind|last1=Langmuir|first1=Charles Herbert|last2=Broecker|first2=Wallace S.|year=2012}}</ref>

Models of the collisions that would have occurred found that there would have been one helium atom for every ten hydrogen atoms, which agrees with the observations of young stars.<ref name="habitable">{{cite book |isbn=978-0691140063|title=How to Build a Habitable Planet: The Story of Earth from the Big Bang to Humankind|last1=Langmuir|first1=Charles Herbert|last2=Broecker|first2=Wallace S.|year=2012}}</ref>

[[File:Stable nuclides H to B.png|thumb|centerright|800px400px|Stable nuclides Hof tothe Bfirst few elements]]

==Observed abundance of lithium==

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Despite the low theoretical abundance of lithium, the actual observable amount is less than the calculated amount by a factor of 3-4.<ref name=fields11>{{cite journal |last=Fields |first=B.D. |date=2011 |title=The primordial lithium problem |journal=Annual Review of Nuclear and Particle Science |volume=61 |pages=47–68 |doi=10.1146/annurev-nucl-102010-130445 |arxiv=1203.3551}}</ref> This contrasts with the observed abundance of isotopes of [[hydrogen]] (¹H and [[deuterium|²H]]) and [[helium]] ([[helium-3|³He]] and [[helium-4|⁴He]]) that are consistent with predictions.<ref name=HouStats/>

[[Image:SolarSystemAbundances.svg|thumb|center|800px|Abundances of the chemical elements in the Solar System. Hydrogen and helium are most common, residuals within the paradigm of the Big Bang.<ref>{{cite book |last1=Stiavelli |first1=Massimo |year=2009 |title=From First Light to Reionization the End of the Dark Ages |url=https://books.google.com/books?id=iCLNBElRTS4C&pg=PA8 |page=8 |publisher=[[Wiley-VCH]] |___location=Weinheim, Germany |isbn=9783527627370|bibcode=2009fflr.book.....S }}</ref> Li, Be and B are rare because they are poorly synthesized in the Big Bang and also in stars; the main source of these elements is [[cosmic ray spallation]].]]

Older stars seem to have less lithium than they should, and some younger stars have much more.<ref name="MWoo"/> The lack of lithium in older stars is apparently caused by the "mixing" of lithium into the interior of stars, where it is destroyed,<ref name=cld>{{Cite news |url=http://www.universetoday.com/476/why-old-stars-seem-to-lack-lithium/ |title=Why Old Stars Seem to Lack Lithium |date=16 August 2006 |author=Cain, Fraser |deadurl=no |archiveurl=https://web.archive.org/web/20160604044857/http://www.universetoday.com/476/why-old-stars-seem-to-lack-lithium/ |archivedate=4 June 2016 |df=dmy-all }}</ref> while lithium is produced in younger stars. Though it [[lithium burning|transmutes]] into two atoms of [[helium]] due to collision with a [[proton]] at temperatures above 2.4 million degrees Celsius (most stars easily attain this temperature in their interiors), lithium is more abundant than current computations would predict in later-generation stars.<ref name=emsley/><ref name="Cain">{{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>

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==Proposed solutions==

Numerous studies have been conducted in search of an explanation for this deficiency of lithium, all inconclusive.<ref name=coc>{{cite journal |last=Coc |first=A. |last2=Uzan |first2=J.-P. |last3=Vangioni |first3=E. |title=Standard big bang nucleosynthesis and primordial CNO abundances after Planck |date=2014 |journal=Journal of Cosmology and Astroparticle Physics |volume=2014 |doi=10.1088/1475-7516/2014/10/050 |arxiv=1403.6694}}</ref> One theory suggests that the lithium problem may be partially caused by faster destruction than synthesis of ⁷Li and its progenitor [[beryllium-7|⁷Be]] 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=EPJ Web of Conferences |volume=184 |pages=01002 |doi=10.1051/epjconf/201818401002 |arxiv=1802.03469|bibcode=2018EPJWC.18401002B }}</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> However, one new theory posits that strangeon dark matter (a hypothetical mix of [[strange matter|strange]] and dark matter) may be responsible for the destruction of ⁷Be before it decays to ⁷Li, as the low [[nuclear binding energy]] of ⁷Be renders it susceptible to destruction upon collision with strangeons.<ref name=Xu19>{{cite arxiv |last=Xu |first=R. |title=Trinity of strangeon matter |date=2019 |arxiv=1904.11153}}</ref>

==See also==