On the Oxygen Isotopic Composition of the Solar System

Abstract

The 18 O/ 17 O ratio of the solar system is 5.2 while that of the interstellar medium (ISM) and young stellar objects is ∼4. This difference cannot be explained by pollution of the Sun's natal molecular cloud by 18 O-rich supernova ejecta because (1) the necessary B-star progenitors live longer than the duration of star formation in molecular clouds, (2) the delivery of ejecta gas is too inefficient and the amount of dust in supernova ejecta is too small compared to the required pollution (2% of total mass or ∼20% of oxygen), and (3) the predicted amounts of concomitant short-lived radionuclides (SLRs) conflicts with the abundances of 26 Al and 41 Ca in the early solar system. Proposals for the introduction of 18 O-rich material must also be consistent with any explanation for the origin of the observed slope-one relationship between 17 O/ 16 O and 18 O/ 16 O in the high-temperature components of primitive meteorites. The difference in 18 O/ 17 O ratios can be explained by enrichment of the ISM by the 17 O-rich winds of asymptotic giant branch (AGB) stars, the sequestration of comparatively 18 O-rich gas from star-forming regions into long-lived, low-mass stars, and a monotonic decrease in the 18 O/ 17 O ratio of interstellar gas. At plausible rates of star formation and gas infall, Galactic chemical evolution does not follow a slope-one line in a three-isotope plot, but instead moves along a steeper trajectory toward an 17 O-rich state. Evolution of the ISM and star-forming gas by AGB winds also explains the difference in the carbon isotope ratios of the solar system and ISM.

Corundum–hibonite inclusions and the environments of high temperature processing in the early Solar System

“…Despite the potentially complicated 26 Al history of the Solar System, such as late addition from other stars (Arnould et al, 2006;Wasserburg et al, 2006;Boss et al, 2008;Gaidos et al, 2009;Tatischeff et al, 2010;Gounelle and Meynet, 2012), there are well-documented systematic variations in initial 26 Al/ 27 Al ratios of certain highly-refractory CAIs. The morphology of hibonite-bearing inclusions correlates well with their Al-Mg systematics, with 26 Mg excesses typical of spinel-hibonite inclusions (SHIBs), yet lacking in platy crystals (PLACs; Ireland, 1988;Liu et al, 2009).…”

Atmospheres From Very Low-Mass Stars to Extrasolar Planets

“…Stellar model atmospheres assume scaled solar abundances for all elements relative to hydrogen. Additionally, some enrichment of α-process elements (C, O, Ne, Mg, Si, S, Ar, Ca, and Ti) resulting from a "pollution" of the star-forming gas by the explosion of a supernova is appropriate in the case of metalpoor subdwarfs of the Galactic thick disk, halo, and globular clusters, and the stars in the high stellar density environment towards the galactic center (Gaidos et al 2009). …”

Galactic chemical evolution and the oxygen isotopic composition of the solar system

“…More subtle influences of heterogeneity and noninstantaneous mixing might be detected in O‐isotopic compositions. Gaidos et al. (2009) used a two‐phase model analogous to Thomas et al.…”

“…2011). One major difference between these calculations and those of Gaidos et al. (2009) is the use of revised AGB star yields from Karakas (2010).…”