scholarly journals Solar Elemental Abundances

2020 ◽  
Author(s):  
Katharina Lodders
Keyword(s):  
Solar System ◽  
Chemical Evolution ◽  
Molecular Cloud ◽  
The Sun ◽  
Galactic Chemical Evolution ◽  
Dwarf Star ◽  
Dwarf Stars ◽  
Elemental Abundances ◽  
System Composition ◽  
Solar Composition

Solar elemental abundances, or solar system elemental abundances, refer to the complement of chemical elements in the entire Solar System. The Sun contains more than 99% of the mass in the solar system and therefore the composition of the Sun is a good proxy for the composition of the overall solar system. The solar system composition can be taken as the overall composition of the molecular cloud within the interstellar medium from which the solar system formed 4.567 billion years ago. Active research areas in astronomy and cosmochemistry model collapse of a molecular cloud of solar composition into a star with a planetary system and the physical and chemical fractionation of the elements during planetary formation and differentiation. The solar system composition is the initial composition from which all solar system objects (the Sun, terrestrial planets, gas giant planets, planetary satellites and moons, asteroids, Kuiper-belt objects, and comets) were derived. Other dwarf stars (with hydrostatic hydrogen-burning in their cores) like the Sun (type G2V dwarf star) within the solar neighborhood have compositions similar to the Sun and the solar system composition. In general, differential comparisons of stellar compositions provide insights about stellar evolution as functions of stellar mass and age and ongoing nucleosynthesis but also about galactic chemical evolution when elemental compositions of stellar populations across the Milky Way Galaxy is considered. Comparisons to solar composition can reveal element destruction (e.g., Li) in the Sun and in other dwarf stars. The comparisons also show element production of, for example, C, N, O, and the heavy elements made by the s-process in low to intermediate mass stars (3–7 solar masses) after these evolved from their dwarf-star stage into red giant stars (where hydrogen and helium burning can occur in shells around their cores). The solar system abundances are and have been a critical test composition for nucleosynthesis models and models of galactic chemical evolution, which aim ultimately to track the production of the elements heavier than hydrogen and helium in the generation of stars that came forth after the Big Bang 13.4 billion years ago.

Exoplanetary oxygen fugacities from polluted white dwarf stars

2019 ◽  
Vol 15 (S357) ◽  
pp. 28-32
Author(s):  
Alexandra E. Doyle ◽  
Beth Klein ◽  
Ben Zuckerman ◽  
Hilke E. Schlichting ◽  
Edward D. Young
Keyword(s):  
Solar System ◽  
Oxygen Fugacity ◽  
White Dwarf ◽  
Terrestrial Planets ◽  
Dwarf Stars ◽  
Elemental Abundances ◽  
White Dwarf Stars ◽  
Solar Composition

AbstractThe intrinsic oxygen fugacity of a planet profoundly influences a variety of its geochemical and geophysical aspects. Most rocky bodies in our solar system formed with oxygen fugacities approximately five orders of magnitude higher than that corresponding to a hydrogen-rich gas of solar composition. Here we derive oxygen fugacities of extrasolar rocky bodies from the elemental abundances in 15 white dwarf (WD) stars polluted by accretion of rocks. We find that the intrinsic oxygen fugacities of rocks accreted by the WDs are similar to those of terrestrial planets and asteroids in our solar system. This result suggests that at least some rocky exoplanets are geophysically and geochemically similar to Earth.

scholarly journals Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

2016 ◽  
Vol 113 (8) ◽  
pp. 2011-2016 ◽  
Author(s):  
Elishevah M. M. E. Van Kooten ◽  
Daniel Wielandt ◽  
Martin Schiller ◽  
Kazuhide Nagashima ◽  
Aurélien Thomen ◽  
...  
Keyword(s):  
Solar System ◽  
Thermal Processing ◽  
Molecular Cloud ◽  
Decay Product ◽  
Isotopic Signature ◽  
Carbonaceous Chondrites ◽  
Outer Solar System ◽  
Precursor Material ◽  
System Composition ◽  
Cloud Material

The short-lived 26Al radionuclide is thought to have been admixed into the initially 26Al-poor protosolar molecular cloud before or contemporaneously with its collapse. Bulk inner Solar System reservoirs record positively correlated variability in mass-independent 54Cr and 26Mg*, the decay product of 26Al. This correlation is interpreted as reflecting progressive thermal processing of in-falling 26Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last addition of stellar-derived 26Al has not been identified yet but may be preserved in planetesimals that accreted in the outer Solar System. We show that metal-rich carbonaceous chondrites and their components have a unique isotopic signature extending from an inner Solar System composition toward a 26Mg*-depleted and 54Cr-enriched component. This composition is consistent with that expected for thermally unprocessed primordial molecular cloud material before its pollution by stellar-derived 26Al. The 26Mg* and 54Cr compositions of bulk metal-rich chondrites require significant amounts (25–50%) of primordial molecular cloud matter in their precursor material. Given that such high fractions of primordial molecular cloud material are expected to survive only in the outer Solar System, we infer that, similarly to cometary bodies, metal-rich carbonaceous chondrites are samples of planetesimals that accreted beyond the orbits of the gas giants. The lack of evidence for this material in other chondrite groups requires isolation from the outer Solar System, possibly by the opening of disk gaps from the early formation of gas giants.

scholarly journals Oxygen isotopic heterogeneity in the early Solar System inherited from the protosolar molecular cloud

2020 ◽  
Vol 6 (42) ◽  
pp. eaay2724
Author(s):  
Alexander N. Krot ◽  
Kazuhide Nagashima ◽  
James R. Lyons ◽  
Jeong-Eun Lee ◽  
Martin Bizzarro
Keyword(s):  
Solar System ◽  
Molecular Cloud ◽  
Limited Range ◽  
Terrestrial Planets ◽  
Carbonaceous Chondrites ◽  
The Sun ◽  
Early Solar System ◽  
Isotopic Heterogeneity ◽  
Oxygen Isotopic ◽  
O 24

The Sun is 16O-enriched (Δ17O = −28.4 ± 3.6‰) relative to the terrestrial planets, asteroids, and chondrules (−7‰ < Δ17O < 3‰). Ca,Al-rich inclusions (CAIs), the oldest Solar System solids, approach the Sun’s Δ17O. Ultraviolet CO self-shielding resulting in formation of 16O-rich CO and 17,18O-enriched water is the currently favored mechanism invoked to explain the observed range of Δ17O. However, the location of CO self-shielding (molecular cloud or protoplanetary disk) remains unknown. Here we show that CAIs with predominantly low (26Al/27Al)0, <5 × 10−6, exhibit a large inter-CAI range of Δ17O, from −40‰ to −5‰. In contrast, CAIs with the canonical (26Al/27Al)0 of ~5 × 10−5 from unmetamorphosed carbonaceous chondrites have a limited range of Δ17O, −24 ± 2‰. Because CAIs with low (26Al/27Al)0 are thought to have predated the canonical CAIs and formed within first 10,000–20,000 years of the Solar System evolution, these observations suggest oxygen isotopic heterogeneity in the early solar system was inherited from the protosolar molecular cloud.

scholarly journals Carbon and oxygen in metal-poor halo stars

2019 ◽  
Vol 622 ◽  
pp. L4 ◽  
Author(s):  
A. M. Amarsi ◽  
P. E. Nissen ◽  
M. Asplund ◽  
K. Lind ◽  
P. S. Barklem
Keyword(s):  
Chemical Evolution ◽  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Galactic Chemical Evolution ◽  
Elemental Abundances ◽  
Halo Stars ◽  
Effective Temperatures ◽  
Population Iii Stars ◽  
Hydrodynamic Effects ◽  
First Time

Carbon and oxygen are key tracers of the Galactic chemical evolution; in particular, a reported upturn in [C/O] towards decreasing [O/H] in metal-poor halo stars could be a signature of nucleosynthesis by massive Population III stars. We reanalyse carbon, oxygen, and iron abundances in 39 metal-poor turn-off stars. For the first time, we take into account 3D hydrodynamic effects together with departures from local thermodynamic equilibrium (LTE) when determining both the stellar parameters and the elemental abundances, by deriving effective temperatures from 3D non-LTE Hβ profiles, surface gravities from Gaia parallaxes, iron abundances from 3D LTE Fe II equivalent widths, and carbon and oxygen abundances from 3D non-LTE C I and O I equivalent widths. We find that [C/Fe] stays flat with [Fe/H], whereas [O/Fe] increases linearly up to 0.75 dex with decreasing [Fe/H] down to −3.0 dex. Therefore [C/O] monotonically decreases towards decreasing [C/H], in contrast to previous findings, mainly because the non-LTE effects for O I at low [Fe/H] are weaker with our improved calculations.

scholarly journals 11. The Role of Protoplanets in the Formation of the Solar System

1977 ◽  
Vol 39 ◽  
pp. 569-571
Author(s):  
I. P. Williams
Keyword(s):  
Solar System ◽  
Refractory Material ◽  
The Sun ◽  
Resisting Medium ◽  
Solar Composition ◽  
Roche Limit ◽  
Natural Outcome

A likely origin of the asteroids (and possibly, of the comets?) is the natural outcome of the following scenario that we propose for the formation of the planets. Protoplanets of similar mass and solar composition will segregate in three different ways: For those far enough from the sun (like Uranus and Neptune), the segregation of icy grains releases enough energy to drive the remaining gases to infinity. For all other planets, the segregation of refractory material only does not release enough energy to disrupt the protoplanet; however, while spiraling inwards in a resisting medium, the terrestrial protoplanets cross their Roche limit and lose their gaseous outer layers. Asteroids (or comets) could therefore originate from the disruption of protoplanets before the settling of their refractory (or icy) grains is completed.

Volatile loss, Differentiation and Collisions: Key to the Composition of Rocky Exoplanets

2020 ◽  
Author(s):  
Amy Bonsor ◽  
John Harrison ◽  
Oliver Shorttle ◽  
Philip Carter ◽  
Mihkel Kama ◽  
...  
Keyword(s):  
Solar System ◽  
Chemical Evolution ◽  
White Dwarf ◽  
Thermal Processing ◽  
White Dwarfs ◽  
Bulk Composition ◽  
Galactic Chemical Evolution ◽  
Common Process ◽  
Planetary Bodies ◽  
Volatile Loss

&lt;p&gt;&lt;strong&gt;Volatile loss, Differentiation and Collisions: Key to the Composition of Rocky Exoplanets&lt;/strong&gt;&lt;/p&gt; &lt;p&gt;Many of the key characteristics and geology of our planet Earth today were determined during the planet&amp;#8217;s formation. What about rocky exoplanets? How does rocky planet formation determine the properties, composition, geology and ultimately, presence of life on rocky exoplanets?&lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt; &lt;p&gt;In this talk I will discuss projects that investigate the link between rocky planet formation and the composition of rocky exoplanets. This work utilises unique observations that provide us with the bulk composition of rocky exoplanetary material. These observations come from the old, faint remnants of stars like our Sun, known as white dwarfs.&lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt; &lt;p&gt;White dwarfs should have clean hydrogen or helium atmospheres. This means that planetary bodies as small as asteroids can show up in the white dwarf&amp;#8217;s atmosphere. Metallic species such as Fe, Mg or Ca provide the bulk composition of the accreted body. Several thousand polluted white dwarfs are now known.&lt;/p&gt; &lt;p&gt;Models indicate that outer planetary systems, like our Solar System beyond Mars, should survive the star&amp;#8217;s evolution to the white dwarf phase. Scattering is a common process, and any bodies that are scattered inwards, a bit like sun-grazing comets in our Solar System, would show up in the white dwarf atmosphere.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;What determines the composition of the rocky exoplanetary bodies accreted by white dwarfs?&lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160;&lt;/span&gt;&lt;/strong&gt;&lt;/p&gt; &lt;p&gt;Models presented in Harrison et al, 2018, 2020 (submitted) find that the abundances observed in the atmospheres of white dwarfs can be explained by three key processes, notably galactic chemical evolution, loss of volatiles (thermal processing) and large scale melting&lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160; &lt;/span&gt;which leads to the segregation of material between the core, mantle and crust. Galactic chemical evolution determines the initial composition of the planet forming material. Thermal processing determines the loss of volatiles, be that CO and other gases, water, or moderate volatile species such as Na. Collisions between planetary bodies that have differentiated to form a core can lead to fragments dominated by core-rich or mantle-rich material.&lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Core-Mantle differentiation is a common process in exoplanetary systems&lt;/strong&gt;&lt;/p&gt; &lt;p&gt;High abundances of siderophile (iron-loving) compared to lithophile (silicate loving) speeches in some polluted white dwarfs indicate that accretion of a planetary body composed primarily of material from a planetary core (or alternatively mantle). Harrison et al, 2020, based on data from Hollands et al, 2017, 2018, present several examples of systems with extreme abundances, core-rich, mantle-rich or crust-rich.&lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt; &lt;p&gt;Bonsor et al, 2020 concludes that most polluted white dwarfs (&gt;60%) have accreted the fragment of a differentiated exoplanetesimal.&lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Post-Nebula volatilisation in exoplanetary bodies&lt;/strong&gt;&lt;/p&gt; &lt;p&gt;Mn and Na trace the loss of volatiles in planetary bodies. The difference in behaviour of Mn and Na under oxidising/reducing conditions makes them a strong indicator of the conditions prevalent when volatile loss occurred. Mn/Na for the Moon/Mars indicate post-Nebula volatile loss&lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160; &lt;/span&gt;(Siebert et al, 2018). Harrison et al, 2020, in prep, provides the first evidence of post-nebula volatilisation in exoplanetary bodies utilising the Mn/Na abundances of polluted white dwarfs.&lt;span class=&quot;Apple-converted-space&quot;&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt;

scholarly journals Comments

1990 ◽  
Vol 123 ◽  
pp. 417-419
Author(s):  
Fred Hoyle
Keyword(s):  
Magnetic Field ◽  
Solar System ◽  
Molecular Cloud ◽  
The Sun ◽  
Ultimate Explanation ◽  
Word Origin ◽  
Entire Universe ◽  
A Chain ◽  
The Magnetic Field

The word 'origin' is one of the most widely used in science. Yet it seems to me to be always used either improperly or ineffectively. Ineffective uses have a derivative quality about them. As an example, suppose we ask: What was the 'origin' of the magnetic field of the Sun? The best answer I suppose is that the magnetic field of the Sun was formed by the compression of a magnetic field that was present already in the gases of the molecular cloud in which the Sun and Solar System were formed some 4.5 X 109 years ago. But what then was the 'origin' of the field in the molecular cloud? It was present already in the gases from which our galaxy was formed, one might suggest. A further displacement then takes us to the manner of 'origin' of t he entire universe, so that no ultimate explanation has really been given. The problem has only been displaced along a chain until it passes into a mental fog through which some claim to see clearly but through which others, including myself, do not see at all.

Developing an astrophysical line list for Keck/Nirspec observations of red giants in the Galactic centre

2017 ◽  
Vol 13 (S334) ◽  
pp. 372-373 ◽  
Author(s):  
B. Thorsbro ◽  
N. Ryde ◽  
R. M. Rich ◽  
M. Schultheis ◽  
T. K. Fritz ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Wavelength Region ◽  
Galactic Centre ◽  
Red Giants ◽  
The Sun ◽  
Galactic Chemical Evolution ◽  
Line List ◽  
Stellar Spectroscopy ◽  
Near Ir ◽  
The Galaxy

AbstractA major avenue in the study of the Galaxy is the investigation of stellar populations and Galactic chemical evolution by stellar spectroscopy. Due to the dust obscuration, stars in the centre of the Galaxy can only be observed in the near-IR wavelength region. However, existing line lists in this wavelength region are demonstratively not of good enough quality for use in stellar spectroscopy. In response to this, we have developed an empirical astrophysical line list in the K-band based on modelling against the Sun and testing against Arcturus. Of ca. 700 identified interesting lines about 570 lines have been assigned empirically determined values.

Presolar Stardust in the Solar System: Implications for Nucleosynthesis and Galactic Chemical Evolution

2008 ◽  
Author(s):  
Larry R. Nittler ◽  
Takuma Suda ◽  
Takaya Nozawa ◽  
Akira Ohnishi ◽  
Kiyoshi Kato ◽  
...  
Keyword(s):  
Solar System ◽  
Chemical Evolution ◽  
Galactic Chemical Evolution
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