Nucleosynthetic Activity of WR Stars: Implications for 26Al in the Galaxy and Isotopic Anomalies in Cosmic Rays and the Early Solar System

1991 ◽  
pp. 550-550 ◽  
Author(s):  
N. Prantzos
Keyword(s):  
Cosmic Rays ◽  
Solar System ◽  
Early Solar System ◽  
The Galaxy ◽  
Isotopic Anomalies

scholarly journals Nucleosynthetic Activity of WR Stars: Implications for 26Al in the Galaxy and Isotopic Anomalies in Cosmic Rays and the Early Solar System

1991 ◽  
Vol 143 ◽  
pp. 550-550 ◽  
Author(s):  
N. Prantzos
Keyword(s):  
Cosmic Rays ◽  
Solar System ◽  
Observational Data ◽  
Galactic Plane ◽  
Galactic Cosmic Rays ◽  
Early Solar System ◽  
The Galaxy ◽  
Isotopic Anomalies

The implications of the nucleosynthetic activity of WR stars are reassessed, in view of recent experimental and observational data. It is confirmed that WR stars may 1) contribute significantly (up to ~20%) to the ~3 M⊙ of 26Al detected in the galactic plane through its 1.8 MeV line, 2) be responsible for the isotopic anomalies of 22Ne and 25,26Mg, detected in galactic cosmic rays (GCR), and 3) be responsible for the inferred presence of 26Al and 107Pd in the early solar system (and, perhaps, some other nuclei as well).

The production of 26Al in the early solar system by oxygen rich cosmic rays

1997 ◽  
Vol 621 (1-2) ◽  
pp. 60-63 ◽  
Author(s):  
N.P.T. Bateman ◽  
D.W. Bardayan ◽  
Y.M. Butt ◽  
A.A. Chen ◽  
K.O. Yildiz ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Solar System ◽  
Early Solar System

Cosmic-ray nuclei up to 10 10 eV/u in the galaxy

1975 ◽  
Vol 277 (1270) ◽  
pp. 319-348 ◽  
Keyword(s):  
Cosmic Rays ◽  
Solar System ◽  
Cross Sections ◽  
Cosmic Ray ◽  
Interstellar Space ◽  
Heavy Nuclei ◽  
Hydrogen Atoms ◽  
Interstellar Gas ◽  
The Galaxy ◽  
Ionization Cross Sections

O f the nuclear cosmic rays arriving in the vicinity of Earth from interstellar space, more than 90% have energies less than 1010 eV /u.f Some effects of their modulation (including deceleration) in the Solar System are briefly discussed. The origin of particles at energies < 107 eV/u is still obscure. They could be due to stellar explosions or to solar emissions, or perhaps to interaction of interstellar gas with the solar wind. Between 108 and 1010 eV/u, the composition appears constant to ca. 30% within the statistics of available data. Cosmic rays traverse a mean path length of 6 g/cm 2 in a medium assumed to contain nine hydrogen atoms for each helium atom. Spallation reactions occurring in this medium result in enhancement of many cosmic-ray elements that are more scarce in the general abundances by several orders of magnitude. Cosmic-ray dwell time in the Galaxy seems to be < 107 years. The source composition of cosmic rays has been derived for elements with atomic numbers 1 ≤ Z ≤ 26. A comparison with abundances in the Solar System implies that the latter is richer in hydrogen and helium by a factor of ca. 20, in N and O by ca. 5, and in C by a factor of ca.2. Possible interpretations invoke (a) nucleosynthesis of cosmic rays in certain sources, e.g. supernovae, or (b) models of selective injection that depend, e.g. on ionization potentials or ionization cross sections. Calculated isotopic abundances of arriving cosmic rays are compared with the observed values now becoming available, and found to be in general agreement. Recent progress in probing the composition and spectrum of ultra-heavy nuclei is outlined.

Nucleosynthesis contributions to the solar nebula

1987 ◽  
Vol 323 (1572) ◽  
pp. 251-267 ◽  
Keyword(s):  
Solar System ◽  
Chemical Evolution ◽  
Solar Nebula ◽  
Rich Diversity ◽  
Model Predictions ◽  
The Galaxy ◽  
The Rich ◽  
Isotopic Anomalies

The discovery of isotopic anomalies in meteorites suggests that the Solar System is made of material from compositionally different and imperfectly mixed reservoirs. One of them, which comprises the bulk Solar System material, is considered to be made of the well-homogenized ashes of many nucleosynthesis events. Its composition can be studied through models of the chemical evolution of the Galaxy. The main nucleosynthetic agents responsible for that evolution are very briefly reviewed, as well as the level of reliability of the model predictions. The remaining reservoir(s) contain(s) isotopically anomalous material, which probably represents only a very minute fraction of the total Solar System material. The great astrophysical importance of the existence of such reservoirs is emphasized. Some selected examples are given to illustrate the rich diversity of potential nucleosynthetic mechanisms that possibly produced the isotopically anomalous material. The difficulties encountered and uncertainties involved in trying to interpret the array of anomalies within nucleosynthesis models are stressed, as well as the key importance of correlated anomalies.

scholarly journals Observational constraints on the likelihood of 26Al in planet-forming environments

2020 ◽  
Vol 644 ◽  
pp. L1
Author(s):  
Megan Reiter
Keyword(s):  
Solar System ◽  
Planet Formation ◽  
Radioactive Decay ◽  
High Mass ◽  
Mass Star ◽  
Early Solar System ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Galaxy ◽  
Order Of Magnitude

Recent work suggests that 26Al may determine the water budget in terrestrial exoplanets as its radioactive decay dehydrates planetesimals leading to rockier compositions. Here I consider the observed distribution of 26Al in the Galaxy and typical star-forming environments to estimate the likelihood of 26Al enrichment during planet formation. I do not assume Solar-System-specific constraints as I am interested in enrichment for exoplanets generally. Observations indicate that high-mass stars dominate the production of 26Al with nearly equal contributions from their winds and supernovae. Observed 26Al abundances are comparable to those in the early Solar System in the high-mass star-forming regions where most stars (and thereby most planets) form. These high abundances appear to be maintained for a few million years, which is much longer than the 0.7 Myr half-life. Observed bulk 26Al velocities are an order of magnitude slower than expected from winds and supernovae. These observations are at odds with typical model assumptions that 26Al is provided instantaneously by high velocity mass loss from supernovae and winds. The regular replenishment of 26Al, especially when coupled with the small age differences that are common in high-mass star-forming complexes, may significantly increase the number of star- and planet-forming systems exposed to 26Al. Exposure does not imply enrichment, but the order of magnitude slower velocity of 26Al may alter the fraction that is incorporated into planet-forming material. Together, this suggests that the conditions for rocky planet formation are not rare, nor are they ubiquitous, as small regions such as Taurus, that lack high-mass stars to produce 26Al may be less likely to form rocky planets. I conclude with suggested directions for future studies.

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