The Nucleosynthesis of Chemical Elements Outline

TheThe NucleosynthesisNucleosynthesis ofof ChemicalChemical ElementsElements

Dr. Adriana Banu, Cyclotron Institute February 23, Saturday Morning Physics’08

Outline

History of chemical elements

Origin of chemical elements

Stellar nucleosynthesis

Explosive nucleosynthesis

Summary From AristotletoMendeleyev • History of chemical elements Modern “Alchemy” • History of chemical elements In searchofthe buildingblocksoftheuniverse… re Curie Marie Curie Marie ⇒ ⇒ Pierre Curie A. H.Becquerel water 1896 Becquerel discovers discovers Becquerel 1896 fire Greek philosophers 3 typesobserved: emission ofradiationfromatoms (Helium) α , β 4 buildingblocks

and and radioactivity

γ Periodic Tableof Elements 1896 Mendeleyev air earth : radioactivity “transmutation” (chemical elements) 92 buildingblocks The NobelPrizeinPhysics1903 18 th -19 atomic theoryrevived and pureelements betweendistinction compounds th century Lavoisier, Dalton, … century Lavoisier,Dalton, History of chemical elements MassesandBindingEnergy Nuclear • History of chemical elements Chart oftheNuclides • Nuclides thathavethesame A chemicalelementisuniquelyidentifiedbytheatomicnumber needtounderstandthephysicsofnuclei • Z m(Z,N) =massofnucleus with m It isderivedfromthestrongnuclearforce. dissasemble anucleusintoprotonsandneutrons. to The bindingenergyistherequired elements p = protonmass,m NZM ~ 7000expectedtoexist ~ 270stablesonly! ~ 3000currentlyknownnuclides ),( n = neutronmass, N p Z NmZm protons and 118 118 118 Z but different 50 50 n −+= Sn Sn Sn BE N neutrons N explaintheoriginofchemical 68 are calledisotopes M • in nuclei: BE~MeV in • atoms: BE~eV in • enormous energy storedin nuclei! enormous energy constituents ! potential energythanits A boundsystemhasalower Color Key: β fission Spontaneous α β Stable positive nucl - + particle emission emission emission < Σ m BE p binding energy(BE) + Σ m Z n ⇓ : ! M(Z,N) Z A Energy Δ X E = N Δ M·c 2 Thanks to E=mc2, tiny amounts of mass convert into huge energy release… He-4 (2 protons + 2 neutrons)

⇒

Radium-226 Radon-222 (88 protons + 138 neutrons) (86 protons + 136 neutrons)

1 kg of radium would be converted into 0.999977 kg of radon and alpha particles.

The loss in mass is only 0.000023 kg.

Energy = mc2 = mass x (speed of light)2 = 0.000023 x (3 x 108)2 = 2.07 x 1012 joules. Equivalent to the energy from over 400 tonnes of TNT!!! 1 kg Ra (nuclear) ↔ 4*105 kg TNT (chemical) • Nuclear Reactions • origin of chemical elements • origin of stellar energies

A1 A2 A3 A4 Z1X + Z2 Y ⇒ Z3 A + Z4 B

A1 + A2 = A3 + A4 (mass numbers) Conservation laws: Z1 + Z2 = Z3 + Z4 (atomic numbers)

Amount of energy liberated in a nuclear reaction (Q-value):

Qval = [(m1 + m2) – (m3 + m4)]c2 definition

initial final

Qval > 0: exothermic process (release of energy) in stars

History of chemical elements Qval < 0: endothermic process (absorption of energy) History of chemical elements Stability andBindingEnergyCurve • History of chemical elements Modern “Alchemy”: • elemental transmutationbecause Fission the sameelementasoriginal the resultingfragmentsarenot and Nuclear fusionoccurs nuclei. fusion >0 Qval fusion naturally instars! are aformof ula fusionandfission nuclear fusion <0 Qval called nucleiis nucleus issplitintosmaller whichalarge The processthrough Fusion fission >0 Qval fission is areverseprocess. . Origin of chemical elements AbundanceoftheElements • 10 7 ordersofmagnitudelessabundant! why doesonekilogramofgoldcostsomuch -1 Fe why when how where synthesized? + proper Au morethanonek ties (itshines…) stellar (Sun) spectra, cosmicrays... (Sun)spectra, stellar meteorites, Moon, Earth, Data sources: • almost flat distributionbeyondFe flat almost • •peak exponential decrease upto Fe near• Fe• • D, Li,Be,Bunder-abundant • •C • • span 12orders-of-magnitude • Features: He ~23% H ~75% C the fourthmost abundant O the thirdmost abundant → U ~2%(“metals”) ilogram ofiron? Primordial nucleosynthesis BigBangNucleosynthesis • Origin of chemical elements What IstheOriginofElements? • of neutron captures… of neutron gap through sequence No way all elementsformed fromprotonsandneutrons • A=5 Mass stabilitygapat Alpher, Bethe &Gamow (“ BBN nucleosynthesis: themakingofelementsthroughnuclearreactions The NobelPrizeinPhysics1967 sequence of n-captures and sequence of and n-captures Big-Bang nucleosynthesis Phys. Rev.73(1948)803 and to bridgethe A=8 soon aftertheBigBang !!! Which oneiscorrect? β • • • αβγ decays (temperature anddensityfellbelowthoserequired 2 resulted inmassabundancesof resulted BBN stoppedbyfurtherexpansionandcooling occurred within the first 3 minutes of the 3minutesof thefirst occurred within Li andBe, Li Universe aftertheprimordialquark-gluonplasma for nuclearfusion) froze outtoformneutronsandprotons H (0.003%), ”) A =8 Burbidge, Fowler&Hoyle(B 3 He (0.004%), trace amounts(10 trace He (0.004%), The NobelPrizeinPhysics1983 well defined stagesofstellarevolution Rev. Mod.Phys.29(1957)547 elements synthesised inside thestars inside synthesised elements no other heavyelements no other A =5 Stellar nucleosynthesis nuclear processes 1 H (75%), 4 -10 He (23%) %) of %) 2 FH) , After that, very little happened in nucleosynthesis for a long time.

temperature and density too small !!!

It required galaxy and star formation via gravitation to advance the synthesis of heavier elements.

matter coalesces to higher temperature and density…

Because in stars the reactions involve mainly charged particles, stellar nucleosynthesis is a slow process.

• Stellar life cycle

BIRTH Interstellar gas gravitational contraction Stars

+ metals DEATH element explosion thermonuclear mixing reactions

abundance distribution ⇔

¾ energy production ¾ stability against collapse ¾ synthesis of “metals” Stellar nucleosynthesis Stellar nucleosynthesis HeliumBurning: • Stellar nucleosynthesis HydrogenBurning • almost95%of allstarsspendtheirlivesburningtheHincore(including • • • our Sun): nucleus with8nucleons heavy elements in stars BBN producednoelementsheavierthanLi 4 He + 12 α C formationsetthestageforentirenucleosynthesisof 4 How isCarbonsynthesizedinstars? He 8 ( α Be unstable τ T ~6*10 ↔ ~ 10 8 Be -16 s) 8 K and α Carbon formation ρ ~ 2*10 5 gcm due totheabsenceofastable -3 8 Be + 4 He ↔ 12 C Stellar nucleosynthesis uptoIron Nucleosynthesis • Stellar nucleosynthesis HeliumBurning: • A massivestarneartheendofitslifetimehas“onionring”structure • became possible… Oxygen productionispossibleandCarbon-basedlife Reaction rateisverysmall Oxygen productionfromcarbon: Carbon consumption! 12 C + 4 He Oxygen formation → ⇒ 12 16 energy via nuclear fusion ! stars cannolonger convert mass into 20 20 major ash: Oxygen burning Carbon burning Neon burning Silicon burning 16 C + Ne + Ne +γ not allCisburned,but O + O + 12 C 16 4 He O -> -> -> 23 -> 20 16 γ Fe Na Ne O 28 24 31 Si + ⇒ Mg P + + ⇒ 4 ⇒ + ⇒ + He 1 4

H +2.2MeV He +4.6MeV ρ 1.2*10 T ~ + 4 1

He +10MeV

ρ H +7.7MeV

T ~ 3*10 T ~ ~ 4*10

ρ T ~ 1.5*10 T ~ ρ T ~ 6*10 T ~ γ ~ 10 ~ 10 ~ 2*10 8 6 7 gcm gcm gcm 9 9 5 8 K K K gcm 9 -3 K -3 -3 -3 Explosive nucleosynthesis RapidNeutronCapture:r-process • Explosive nucleosynthesis beyond Iron Nucleosynthesis • entailsasuccessionof • responsibleforthecreationofabouthalf • nucleosynthesisoccurringincore-collapsesupernovae • • -rcs:ncesnhssbymeansof s-process: nucleosynthesis during He-burning (thesource forneutrons: h te rdmnn mechanism fortheproduction ofheavyelements isthe the otherpredominant ¾ ¾ Then, abetadecayoccurs,andinthe Fast neutroncaptureuntilthenuclear Z rapid neutron seed The r-processschematic capture rapid neutron capturesonironseednuclei force isunabletobindanextraneutron force new chaintheneutroncapturecontinues slow of neutron-richnucleiheavierthanFe 13 C( β neutron captures occursinstars -decay α,n) 16 O and N 22 Ne( α,n) 25 Mg)) Overview of main astrophysical processes

M.S. Smith and K.E. Rehm, Ann. Rev. Nucl. Part. Sci, 51 (2001) 91-130

• Messages to take away

What you have learned about the abundance of elements: Summary

charged-particle mainly neutron induced reaction capture reaction Both occur during quiescent and explosive stages of stellar evolution

involve mainly STABLE NUCLEI involve mainly UNSTABLE NUCLEI Summary Messagestotakeaway • sufficient quantities. applications. Presenttechniquesare unabletoproducethemin nothing aboutandwhichwillhold manysurprisesand There are~4000more(unstable) nucleiwhichweknow (unstable) nuclei. reactions betweenthemwehave produced ~3000more There are~270stablenucleiinthe Universe.Bystudying theyprovidetheenergyinstar • theyproducedalltheelements wedependon. • Nuclear reactionsplayacrucialroleintheUniverse: Instead ofConclusions: and the nextgeneration ofscientists ( some of you?!) It willbethenext generationofaccelerators of this exciting research field. which will completethe work s includingthatoftheSun. why not