Ay, for twere absurd

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Ay, for twere absurd To think that nature in
the earth bred gold Perfect i the instant
Something went before. There must be remote
matter. Ben Jonson, The Alchemist, 1610
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Stars and the Abundances of the Elements
Katharina Lodders, Washington University Saint
Louis, USA
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Why are we interested in the abundances and the
distribution of the elements? Its the stuff we
are made of Constitution of (baryonic) matter,
numbers and amounts of stable elements/isotopes C
omposition and formation of the solar system,
planetary compositions other solar
systems Origin of the elements in stars, element
abundance distributions are critical tests for
nucleosynthesis models Clues about the basic
make-up and origins of matter
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Aristotle's periodic table of the elements
Air
Fire
Water
Earth
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The periodic table of the elements 2300 years
later
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11 chemical elements known in antiquity
Fe, Cu, Ag, Au, Hg, C, Sn, Pb, As, Sb, S
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What is meant by abundance
Solar abundances present-day observable
composition of Sun, mainly
photosphere also sunspots, solar flares, solar
wind Solar system abundances composition at
birth of solar system ISM/molecular cloud
composition 4.6 billion years ago proto-solar
abundances Li, D, short-lived radioactive
nuclides 26Al, 129I long-lived (still present)
radioactive nuclides 87Rb, 235U, 238U,
232Th Cosmic abundances there is no generic
cosmic composition avoid use of cosmic
abundances many dwarfs stars are similar in
composition as Sun, but amount of elements
heavier than He (metallicity) changes with time
and varies across Milky Way Galaxy,

other galaxies
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Abundance is a relative quantity Most commonly
used abundance scales compare the number of atoms
of an element to a fixed (normalized) number of
atoms of a reference element , (H or
Si) Astronomical abundance scale normalized to
H, the most-abundant element in the universe set
to eH 1012 atoms gives the number of atoms
of an element per one trillion H
atoms converted to log scale A(H) log eH
12 abundances are measured relative to H,
e.g., N(Fe)/N(H), so log eFe log N(Fe)/N(H)
12 used for H-rich systems stars,
ISM Cosmochemical abundance scale normalized
to Si, the most abundant cation in rock, set to
N(Si) 106 atoms gives the number of atoms of
an element per one million Si atoms used for
planetary modeling, meteorites
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HUGE RANGE IN VALUES
The atomic abundances of the elements in the
solar system vary over 12 orders of magnitude
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Where do the abundance numbers come
from? Earths crust Meteorites Solar
photospheric spectrum solar wind, solar energetic
particles Other solar system objects gas-giant
planets, comets, meteors Spectra of other dwarf
stars (B stars) Interstellar medium Planetary
Nebulae (PN) Galactic Cosmic Rays (GCR) Also
presolar grains found in meteorites
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Elie de Beaumont, 1847 59 out of 83 stable
long-lived elements are known 16 abundant
elements common to different crustal rocks, ore
veins, mineral ocean waters, meteorites,
organic matter H, Na, K, Mg, Ca, Al, C,
Si, N, P, O, S, F, Cl, Mn, Fe only
later spectral analysis invented
1860s Mendeleevs periodic table 1869
GluconiumBe, DidymiumNdPr, ColumbiumNb
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There are 16 abundant elements common to
different crustal rocks, ore veins, mineral
ocean waters, meteorites, organic matter
This identity shows that the surface of the
Earth encloses in all its parts everything that
is essential for the existence of organized
beings... ... one sees that nature has provided
not only a settlement but also the conservation
of this indispensable harmony. The aging Earth
will never cease to furnish all the elements to
the organized beings necessary for their
existence Elie de Beaumont, 1847
GluconiumBe, DidymiumNdPr, ColumbiumNb
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Extend search for chemical elements to other
celestial objects I.A. Kleiber, 1885 68 elements
are known periodic table is established Compar
e Earths crust Meteorites Comets Meteors Sun Oth
er stars Composition of celestial objects is not
random Helium found in 1868 but not plotted, no
other noble gases known at the time
First Periodic Table with Cosmochemistry
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Abundances in the Earths crust igneous
rocks Clarke 1898, Harkins 1917 Quantitative
analyses limited to abundant Elements
(wet.chem) Light elements with atomic numbers
up to that of Fe (26) are abundant, heavier
elements are rare Notable exceptions light
elements Li, Be, B (3-5) are also quite rare
photo K. Lodders
3-3.6 billion year old crust in Bangalore, India
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Composition of the Earths crust Clarke 1898,
Harkins 1917
What controls the abundances of the
elements? Check abundances as a function of
atomic number or mass
Crust no discernable trends of abundance with
atomic number or atomic weight ? Abundances were
modified from the initial solar system element
mixture during Earths formation and
differentiation
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Earths crust abundances available material
that can be analyzed in the lab but not
representative for composition of entire Earth
Earth materials are distributed between core,
silicate mantle and crust elements follow
geochemical affinities metallic elements Fe,
Ni, Co, Au, Ir, move into the core
oxide and silicate rock-forming elements go
into silicate mantle and crust
Mg, Si, Al, Ca, Ti, REE
Crust has elements with large ionic radii
that enter silicate melts and are
incompatible in silicate mantle
minerals olivine, pyroxene Si,
Al, Ca, K, Na, REE, U, Th Earth is also not
representative for solar system
composition Element fractionations started during
formation of planetesimals from molecular cloud
material processed in the protoplanetary
accretion disk (solar nebula) ?
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Before the solar system forms stars feed gas and
dust to a molecular cloud
Molecular cloud composition 4.6 billion years ago
gives the solar system composition
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Meter to km size planetesimals begin to form
mixtures of silicates, metal and sulfides that
may have been processed subsequently on their
parent asteroids
chondrites
Planetesimals grow to larger asteroids and
planets which experienced melting
achondrites iron meteorites
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Molecular cloud composition 4.6 billion years
ago solar system composition
Earths crust Good place to live, bad place to
determine solar system abundances
Earths crust today
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Chondritic Meteorites Chondrites contain
mineral phases that most closely resemble the
original solids that were present in the solar
nebula TRY THESE FOR ABUNDANCES of
non-volatile elements Many types of chondrites
contain round silicate spheres called
chondrules Chondrite groups Ordinary
chondrites H, L, LL Enstatite chondrites
EH, EL Carbonaceous chondrites CI, CM, CV,
CO, CK, CR, CH
Bjurboele L/LL3 chondrite
Chondrules in the Tieschitz ordinary chondrite
Check meteoritic abundance distributions
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Abundances vs. atomic number
Harkins 1917 Use average abundances from
meteorites no photospheric abundances
yet Even-numbered elements are more abundant
than their odd-numbered neighbors Li, B, Be
(3-5) are below scale, C (6) low because of
volatility, but still more abundant than odd
numbered neighbors B (5) or N (7) Abundances
peak again at Fe (26) Abundances of elements
heavier than Fe (26) are quite low
Harkins discovery graph of the odd-even effect
in elemental abundances
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Elemental abundances of CI chondrites match those
in the Sun (exceptions volatile elements H, C, N,
O, noble gases)
Photo Le Muséum National d'Histoire Naturelle,
Paris
Orgueil meteorite
CI stands for carbonaceous chondrite of Ivuna
type 5 observed CI chondrite falls Alais 1806 (6
kg), Ivuna 1938 (0.7 kg), Orgueil 1864 (14 kg),
Revelstoke 1965 (1 g), Tonk 1911 (10 g)
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Sun holds more than 99 of the solar systems
mass Composition of Sun should be good
approximation for solar system as a whole First
done by H.N Russell in 1929
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• Element determinations in the Sun
• 66 elements out of 83 naturally occurring
  elements identified in the photosphere
• all stable elements up to atomic number 83 (Bi)
• plus radioactive Th and U
• 30 35 elements well determined in photosphere
• Determined in photosphere with larger
  uncertainties
• gt 0.10 dex (factor 1.3)
• Li, Be, B, N, Sc, Cr, Ni, Zn, Ga, Rh, Cd,
  In, Nd, Tb, Ho, Tm, Yb, Lu, Os, Pt
• gt 0.05 dex (factor 1.12)
• Mg, Al, Si, Ti, Fe, Co, Nb, Ru, Ba, Ce,
  Pr, Dy, Er, Hf, Pb
• Difficult to determine (line blends, low
  abundance)
• Ag, In, Sn, Sb, W, Au, Th, U As, Se, Br,
  Te I, Cs, Ta, Re, Hg, Bi
• He detected but difficult to quantify from
  spectra
• He, Ne, Ar, Kr, Xe found in solar wind
• Determined from Sun-spot spectra, relatively
  uncertain F, Cl, Tl

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Comparison of photospheric and CI chondritic
abundances (both scales normalized to Si106
atoms
Good correlation for many heavy elements (11
line) Meteorites depleted in elements that form
volatile compounds Noble gases, CO,
CH4, N2, H2O Photosphere depleted in
Li Abundances of missing rock-forming elements
in photosphere can be derived from CI-chondrites
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The state of solar system elemental abundances as
of 2003
Lodders 2003
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nuclear properties control abundances, not
chemical (electron shell) properties
peaks of elements with tightly bound nuclei
Fe-peak most tightly bound nuclei
Li, Be, B fragile
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H, He (Li) produced in big-bang Elements heavier
than He produced in stars Nucleosynthesis in the
stellar core depends on a stars initial mass
Low-mass stars with masses less than 8 times the
Suns mass dwarf stars, Sun main-sequence H
to He for 11 billion years
(Bethe, Weizaecker 1930s) On the red giant
branches He to C,O for 110
million years
(AGB, carbon stars Merrill
1952, Tc) No more nucleosynthesis, white dwarfs
Light stars live long and produce mainly Helium,
C and O, but also Li, F, and several elements
heavier than iron (e.g., Sr, Ba)
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Nucleosynthesis models for red giant stars have
become testable through the analysis of presolar
grains found in meteorites. These dust grains
captured the stars nucleosynthesis products when
they formed in the stellar winds
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H, He (Li) produced in big-bang Elements heavier
than He are produced in stars Nucleosynthesis in
the stellar core depends on a stars initial mass
Low-mass stars like the Sun (less than 8 times
the Suns mass) dwarf star Sun, main-sequence
H to He for 11 billion years On the red giant
branches He to C for 110 million
years No more nucleosynthesis, white dwarfs
Massive stars above 8 times the Suns
mass e.g., 15 solar-mass star main sequence H
to He for 8 million years Red/blue supergiant
stage He to C and O for 1.2 million
years C to Ne and Mg for 1 thousand years O
and Ne to Si and S 0.6-1.3 years Si and S to
Fe, Ni 12 days Supernova few
seconds B2FH 1957, Cameron 1957
Light stars live longer and produce mainly
Helium, C and O Massive stars have short lives
and produce essentially all the abundant elements
up to Fe
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Shells containing the principal products of the
nucleosynthesis stages in massive stars are
detected in SN remnants through X ray
emissions Cas-A Broadband, Si, Ca, Fe Chandra
X-ray observatory
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The elements heavier than iron e.g., Sr, Ba, Au,
Pb, U
Production of elements heavier than iron requires
input of energy, no more fusion reactions of
lighter elements The heavy elements are built-up
by neutron capture on pre-existing nuclides such
as iron 2 different possibilities Slow neutron
capture during alternate H shell and He-shell
burning in
red giant stars slow compared to the
beta-decay rates of the interim produced
radioactive nuclides. These decay to a stable
atom before another neutron is captured Rapid
neutron capture during supernova
explosions rapid compared to the beta decay
rates of the interim produced radioactive
nuclides Different isotopes of the heavy
elements are preferentially made by either the S
or R process ? contribution of SN and giant
stars to solar system element mixture
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Ba
Au Pb
Sr
U, Th
Low-intermediate giant stars
---------Massive stars ------
Where the heavy elements in our solar system come
from
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Supernovae produce most of the abundant elements
heavier than He C, N, O, Mg, Si, Fe,
R rated R process SN also contribute to
elements heavier than iron
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H from big bang, maybe up to half of all C and N
from giant stars, all other major elements made
in massive stars going supernova
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We are supernova
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For more information and reprints of our
work please visit the Planetary Chemistry
laboratorys webpage at http//solarsystem.wustl.
edu
for solar abundances see Lodders 2003,
Astrophysical Journal 591(2) 1220-1247, Solar
system abundances and condensation temperatures
of the elements. for a compilation of various
physical and chemical data on solar system
objects see Lodders, K. Fegley, B. 1998, The
Planetary Scientist's Companion, Oxford Univ.
Press, pp. 384 for a less technical description
see Lodders, K. Fegley, B., 2008/2009,
Chemistry of the Solar System, Royal Society of
Chemistry, coming soon to a bookstore near you