Cosmological lithium problem: Difference between revisions

Revision as of 07:51, 20 July 2022

Revision as of 11:30, 21 September 2022

Line 2:

In [[astronomy]], the '''lithium problem''' or '''lithium discrepancy''' refers to the discrepancy between the primordial [[Abundance of the chemical elements|abundance]] of [[lithium]] as inferred from observations of metal-poor ([[Stellar population|Population II]]) [[Stellar halo|halo stars]] in our galaxy and the amount that should theoretically exist due to [[Big Bang nucleosynthesis]]+[[Wilkinson Microwave Anisotropy Probe|WMAP]] cosmic baryon density predictions of the [[Cosmic microwave background|CMB]]. Namely, the most widely accepted models of the Big Bang suggest that three times as much primordial lithium, in particular [[lithium-7]], should exist. 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>{{cite journal |last1=Hou |first1=S. Q. |last2=He |first2=J.J. |last3=Parikh |first3=A. |last4=Kahl |first4=D. |last5=Bertulani |first5=C.A. |last6=Kajino |first6=T. |last7=Mathews |first7=G.J. |last8=Zhao |first8=G. |date=2017 |title=Non-extensive statistics to the cosmological lithium problem |journal=The Astrophysical Journal |volume=834 |issue=2 |pages= 165|doi=10.3847/1538-4357/834/2/165 |bibcode=2017ApJ...834..165H |arxiv=1701.04149 |s2cid=568182 }}</ref> The discrepancy is highlighted in a so-called "Schramm plot", named in honor of astrophysicist [[David Schramm (astrophysicist)|David Schramm]], which depicts these primordial abundances as a function of cosmic baryon content from standard [[Big Bang nucleosynthesis|BBN]] predictions.

[[File:Schramm plot BBN review 2019.png|thumb|400px|This "Schramm plot"<ref>{{cite journal | last1=Tanabashi | first1=M. | last2=Hagiwara | first2=K. | last3=Hikasa | first3=K. | last4=Nakamura | first4=K. | last5=Sumino | first5=Y. | last6=Takahashi | first6=F. | last7=Tanaka | first7=J. | last8=Agashe | first8=K. | last9=Aielli | first9=G. | last10=Amsler | first10=C. | display-authors=5|collaboration=Particle Data Group| title=Review of Particle Physics | journal=Physical Review D | publisher=American Physical Society (APS) | volume=98 | issue=3 | date=2018-08-17 | issn=2470-0010 | doi=10.1103/physrevd.98.030001 | page=030001| bibcode=2018PhRvD..98c0001T |doi-access=free}} and 2019 update.</ref> depicts primordial abundances of ⁴He, D, ³He, and ⁷Li as a function of cosmic baryon content from standard BBN predictions. CMB predictions of ⁷Li (narrow vertical bands, at 95% [[confidence level|CL]]) and the BBN D&nbsp;+&nbsp;⁴He concordance range (wider vertical bands, at 95% CL) should overlap with the observed light element abundances (yellow boxes) to be in agreement. This occurs in ⁴He and is well constrained in D, but is not the case for ⁷Li, where the observed Li observations lie a factor of 3−4 below the BBN+WMAP prediction.]]

==Origin of lithium==

Line 37:

|}

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 |bibcode=2018PhRvD..98c0001T |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=C. H.|last2=Broecker|first2=W. S.|year=2012}}</ref>

Line 69:

[[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=M. |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">{{cite web|title=The Cosmic Explosions That Made the Universe|url=http://www.bbc.com/earth/story/20170220-the-cosmic-explosions-that-made-the-universe|last=Woo|first=M.|date=21 Feb 2017|website=earth|publisher=BBC|url-status=live|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|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|df=dmy-all}}</ref> One proposed model is that lithium produced during a star's youth sinks beneath the star's atmosphere (where it is obscured from direct observation) due to effects the authors describe as "turbulent mixing" and "diffusion," which are suggested to increase or accumulate as the star ages.<ref>{{Cite journal |last1=Richard |first1=O. |last2=Michaud |first2=G. |last3=Richer |first3=J. |date=2005-01-20 |title=Implications of WMAP Observations on Li Abundance and Stellar Evolution Models |url=https://doi.org/10.1086/426470 |journal=The Astrophysical Journal |language=en |volume=619 |issue=1 |pages=538–548 |doi=10.1086/426470 |arxiv=astro-ph/0409672 |bibcode=2005ApJ...619..538R |s2cid=14299934 |issn=0004-637X}}</ref> Spectroscopic observations of stars in [[NGC 6397]], a metal-poor globular cluster, are consistent with an inverse relation between lithium abundance and age, but a theoretical mechanism for diffusion has not been formalized.<ref>{{Cite journal |last1=Korn |first1=A. J. |last2=Grundahl |first2=F. |last3=Richard |first3=O. |last4=Barklem |first4=P. S. |last5=Mashonkina |first5=L. |last6=Collet |first6=R. |last7=Piskunov |first7=N. |last8=Gustafsson |first8=B. |date=August 2006 |title=A probable stellar solution to the cosmological lithium discrepancy |url=https://www.nature.com/articles/nature05011 |journal=Nature |language=en |volume=442 |issue=7103 |pages=657–659 |doi=10.1038/nature05011 |pmid=16900193 |arxiv=astro-ph/0608201 |bibcode=2006Natur.442..657K |s2cid=3943644 |issn=1476-4687}}</ref> 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>

[[File:Nova Centauri 2013 ESO.jpg|thumb|[[Nova Centauri 2013]] is the first in which evidence of lithium has been found.<ref>{{cite web|title=First Detection of Lithium from an Exploding Star|url=http://www.eso.org/public/news/eso1531/|accessdate=29 July 2015|url-status=dead|archiveurl=https://web.archive.org/web/20150801001700/http://www.eso.org/public/news/eso1531/|archivedate=1 August 2015|df=dmy-all}}</ref>]]

Line 89:

|arxiv = 0911.4198

|s2cid=388656

|quote=<span style="font-family:LatinModern;"><small>... confirm the peculiar behaviour of Li in the effective temperature range 5600–5900 K ... We found that the immense majority of planet host stars have severely depleted lithium ... At higher and lower temperatures planet-host stars do not appear to show any peculiar behaviour in their Li abundance.</small></span>}}</ref> The Sun's surface layers have less than 1% the lithium of the original formation [[Formation and evolution of the Solar System#Formation|protosolar gas clouds]] despite the surface convective zone not being quite hot enough to burn lithium.<ref name = "Israelian"/> It is suspected that the gravitational pull of planets might enhance the churning up of the star's surface, driving the lithium to hotter cores where [[lithium burning]] occurs.<ref name="Discover"/><ref name = "Israelian"/> The absence of lithium could also be a way to find new planetary systems.<ref name="Discover"/> However, this claimed relationship has become a point of contention in the planetary astrophysics community, being frequently denied<ref name="BaumannRamírez2010">{{cite journal|last1=Baumann|first1=P.|last2=Ramírez|first2=I.|last3=Meléndez|first3=J.|last4=Asplund|first4=M.|last5=Lind|first5=K.|display-authors=2|title=Lithium depletion in solar-like stars: no planet connection|journal=Astronomy and Astrophysics|volume=519|year=2010|pages=A87|issn=0004-6361|doi=10.1051/0004-6361/201015137|arxiv=1008.0575 |bibcode=2010A&A...519A..87B |doi-access=free}}</ref><ref name="RamírezFish2012">{{cite journal|last1=Ramírez|first1=I.|last2=Fish|first2=J. R.|last3=Lambert|first3=D. L.|last4=Allende Prieto|first4=C.|display-authors=2|title=Lithium abundances in nearby FGK dwarf and subgiant stars: internal destruction, galactic chemical evolution, and exoplanets|journal=The Astrophysical Journal|volume=756|issue=1|year=2012|pages=46|issn=0004-637X|doi=10.1088/0004-637X/756/1/46|arxiv=1207.0499 |bibcode=2012ApJ...756...46R |hdl=2152/34872|s2cid=119199829 |hdl-access=free}}</ref> but also supported.<ref name="FigueiraFaria2014">{{cite journal|last1=Figueira|first1=P.|last2=Faria|first2=J. P.|last3=Delgado-Mena|first3=E.|last4=Adibekyan|first4=V. Zh.|last5=Sousa|first5=S. G.|last6=Santos|first6=N. C.|last7=Israelian|first7=G.|display-authors=2|title=Exoplanet hosts reveal lithium depletion|journal=Astronomy & Astrophysics|volume=570|year=2014|pages=A21|issn=0004-6361|doi=10.1051/0004-6361/201424218|doi-access=free}}</ref><ref name="Delgado MenaIsraelian2014">{{cite journal|last1=Delgado Mena|first1=E.|last2=Israelian|first2=G.|last3=González Hernández|first3=J. I.|last4=Sousa|first4=S. G.|last5=Mortier|first5=A.|last6=Santos|first6=N. C.|last7=Adibekyan|first7=V. Zh.|last8=Fernandes|first8=J.|last9=Rebolo|first9=R.|last10=Udry|first10=S.|last11=Mayor|first11=M.|display-authors=2|title=Li depletion in solar analogues with exoplanets|journal=Astronomy & Astrophysics|volume=562|year=2014|pages=A92|issn=0004-6361|doi=10.1051/0004-6361/201321493|doi-access=free}}</ref>

===Higher than expected lithium in metal-poor stars===

Line 116:

Changing [[fundamental constants]] can be one possible solution, and it implies that first, atomic transitions in metals residing in high-[[redshift]] regions might behave differently from our own. Additionally, Standard Model couplings and particle masses might vary; third, variation in nuclear physics parameters is needed.<ref name="fields11" />

Nonstandard cosmologies indicate variation of the baryon to photon ratio in different regions. One proposal is a result of large-scale inhomogeneities in cosmic density, different from homogeneity defined in the [[cosmological principle]]. However, this possibility requires a large amount of observations to test it.<ref>{{Cite journal|last1=Holder|first1=Gilbert P.|last2=Nollett|first2=Kenneth M.|last3=van Engelen|first3=Alexander|date=June 2010|title=On Possible Variation in the Cosmological Baryon Fraction|journal=Astrophysical Journal|language=en|volume=716|issue=2|pages=907–913|doi=10.1088/0004-637X/716/2/907|arxiv=0907.3919 |bibcode=2010ApJ...716..907H |issn=0004-637X|doi-access=free}}</ref>

== See also ==