Cosmological lithium problem: Difference between revisions

Revision as of 04:59, 4 February 2020

Revision as of 00:48, 8 May 2020

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==Origin of lithium==

One dayMinutes after the Big Bang, the universe was made almost entirely of hydrogen and helium, with only very smalltrace amounts of lithium and beryllium, and negligibly small abundances of all heavier elements.<ref name="habitable"/>

===Lithium Synthesis in the Big Bang===

Big-bang nucleosynthesis produces both lithium-7 and beryllium-7, and indeed the latter dominates the primordial mass-7 production. On the other hand, the big bang produces lithium-6 at levels more than 1000 times smaller.

{{nuclide|link=yes|beryllium|7}} later decays via [[electron capture]] into {{nuclide|link=yes|lithium|7}},

so that the observable primordial lithium abundance essentially sums {{nuclide|link=yes|lithium|7}}+{{nuclide|link=yes|beryllium|7}}.

These isotopes

are produced by the reactions

<!--

H-3 + He-4 -> Li-7 + y

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

-->:{| border="0"

|- style="height:2em;"

|{{nuclide|link=yes|hydrogen|3}}&nbsp;||+&nbsp;||{{nuclide|link=yes|helium|4}}&nbsp;||→&nbsp;||{{nuclide|link=yes|lithium|7}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|Gamma}}

|- style="height:2em;"

|{{nuclide|link=yes|helium|3}}&nbsp;||+&nbsp;||{{nuclide|link=yes|helium|4}}&nbsp;||→&nbsp;||{{nuclide|link=yes|beryllium|7}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|Gamma}}

|- style="height:2em;"

|}

and destroyed by

<!--

H-3 + He-4 -> Li-7 + y

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

-->:{| border="0"

|- style="height:2em;"

|{{nuclide|link=yes|beryllium|7}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|neutron}}&nbsp;||→&nbsp;||{{nuclide|link=yes|lithium|7}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|proton}}

|- style="height:2em;"

|{{nuclide|link=yes|lithium|7}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|proton}}&nbsp;||→&nbsp;||{{nuclide|link=yes|helium|4}}&nbsp;||+&nbsp;||{{nuclide|link=yes|helium|4}}

|- style="height:2em;"

|}

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

}}</ref> The calculated abundance and ratio of ¹H and ⁴He is in agreement with data from 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>

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

{{See also|Lithium burning}}

LithiumIn stars, lithium-7 is made byin a [[proton-proton chain reaction]].

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

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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

}}</ref> The calculated abundance and ratio of ¹H and ⁴He is in agreement with data from 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|right|400px|Stable nuclides of the first few elements]]