Table: Gross Solar and Primordial Cosmic Compositions by Mass Fraction
___________________________________________________________________________
Substance Traditional G-1998 A-2009 Primordial
Solar Solar Solar Cosmic
Fiducial Fiducial
___________________________________________________________________________
H 0.73 0.7120 0.7154 0.75
He 0.25 0.2701 0.2703 0.25
Z 0.02 0.0180 0.0142 10**(-3) (counting D, He-3,
and Li-7 as a metals)
10**(-9) (counting Li-7 only
as a metal)
___________________________________________________________________________
    Notes:
- The
solar composition
in the
Table
is the calculated
primordial solar nebula composition,
NOT the
composition of the present-day
solar photosphere
which has been altered by
transport processes
in the
Sun.
- Fiducial here means the values
are round numbers
representative of actual result values which have more
digits and
some uncertainty.
- Keywords:
D (deuterium, H-2),
H (hydrogen),
He (helium),
He-3,
Li (lithium),
Li-7,
mass fraction,
metal,
substance,
Z (metalliticity).
- Recall that metals
in astro-jargon
are elements
that are NOT
hydrogen
and helium and that
Z (metalliticity)
is the total mass fraction
of the metals.
- The mass fractions
are believed to much the same for
stars,
the interstellar medium (ISM),
and the
intergalactic medium (IGM)
throughout the
observable universe
and cosmic time.
However,
metalliticity at
the present cosmic time
varies wildly from the primordial values given above to of order a few percent.
However, the relative abundances of the
metals
is believed to be approximately constant.
Thus, the general
stellar composition
and
cosmic composition
are approximately
solar composition,
except for variations in the total
metalliticity.
- References:
Asplund et al. (2009, p. 46, A-2009),
Grevesse & Sauval (1998, G-1998),
(but see Asplund et al. (2009, p. 46)
for values),
Table: Solar Composition,
Wikipedia: Big Bang:
Primordial cosmic composition
(which explicitly gives
primordial cosmic
composition (fiducial values by mass fraction:
0.75 H, 0.25 He-4, 0.001 D, 0.0001 He-3, 10**(-9) Li-7)),
Wikipedia:
Cosmic composition,
Wikipedia:
Solar composition.
- The leading metals in the
Solar composition
mass fraction are:
oxygen (O),
carbon (C),
iron (Fe),
neon (Ne),
silicon (Si),
nitrogen (N),
magnesium (Mg),
sulfur (S)
(see Table: Solar Composition).
- The difference between the
G-1998
and
A-2009
solar metallicity (Z_☉)
values is the
solar abundance problem.
Both the G-1998
and
A-2009 values are obtained mainly
by modeling
the solar atmosphere:
the newer value being supposedly an improvement on the older value.
However,
helioseismology favors
G-1998 value,
and so suggests there is some
systematic error
with the A-2009 value
(Gough 2019).
The solar abundance problem is a significant
despite metals being
a trace abundance because their large
opacity gives them
a large effect on
solar structure and thus
on the modeling
of the Sun.
Hopefully, a measurement
of the
neutrino
flux from
the CNO cycle
in the Sun's core
will provide circa 2019
a high accuracy/precision
value of
Z_☉,
and lead to
a resolution of the
solar abundance problem.
The measurement will be done
by the Borexino Collaboration (2007--).
Since the
Z_☉
is used as an input in calculating the
absolute metallicity
of all other stars, obtaining
a high accuracy/precision
value of
Z_☉
is important for all astronomy
and in particular
cosmichemical evolution.
    Local file: