* Astronomy

Title: Neutron-rich chromium isotope anomalies in supernova nanoparticles
Authors: Nicolas Dauphas, Laurent Remusat, James Chen, Mathieu Roskosz, Dimitri Papanastassiou, Julien Stodolna, Yunbin Guan, Chi Ma, John Eiler

Neutron-rich isotopes with masses near that of iron are produced in type Ia and II supernovae. Traces of such nucleosynthesis are found in primitive meteorites in the form of variations in the isotopic abundance of 54Cr, the most neutron-rich stable isotope of chromium. The hosts of these isotopic anomalies must be presolar grains that condensed in the outflows of supernovae, offering the opportunity to study the nucleosynthesis of iron-peak nuclei in ways that complement spectroscopic observations and can inform models of stellar evolution. However, despite almost two decades of extensive search, the carrier of 54Cr anomalies is still unknown, presumably because it is fine-grained and is chemically labile. Here we identify in the primitive meteorite Orgueil the carrier of 54Cr-anomalies as nanoparticles, most likely spinels that show large enrichments in 54Cr relative to solar composition (54Cr/52Cr ratio >3.6xsolar). Such large enrichments in 54Cr can only be produced in supernovae. The mineralogy of the grains supports condensation in the O/Ne-O/C zones of a type II supernova, although a type Ia origin cannot be excluded. We suggest that planetary materials incorporated different amounts of these nanoparticles, possibly due to late injection by a nearby supernova that also delivered 26Al and 60Fe to the solar system. This idea explains why the relative abundance of 54Cr and other neutron-rich isotopes vary between planets and meteorites. We anticipate that future isotopic studies of the grains identified here will shed new light on the birth of the solar system and the conditions in supernovae. 

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New names of ancient minerals honour scientists

When the solar system was born 4.5 billion years ago, davisite and grossmanite were there.
These minerals were two of the first solids to form when an interstellar gas cloud collapsed to form the sun. Found in the Allende meteorite, they now carry the names of Andrew Davis and Lawrence Grossman, professors in geophysical sciences at the University of Chicago, in honour of their pioneering contributions to cosmochemistry.
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Runaway star may have spawned the solar system

The solar system may have been born inside the remains of a single star that ran away from its family, rather than from a tight-knit clan of stars. If so, it may be more unusual than previously thought.
Meteorites that contain bits of rock called calcium-aluminium-rich inclusions suggest that the solar system may have formed very quickly from the ashes of other stars. That's because the inclusions formed with the radioactive isotope aluminium-26, which is forged inside stars tens of times as massive as the sun and decays with a half-life of only 720,000 years.
Such massive stars tend to form in clusters, and they shed material in roiling winds that can cool down and seed planetary systems.
But Vincent Tatischeff of the National Centre for Scientific Research in Orsay, France, and colleagues suspect a massive star cluster would have been have been so hot that most of the Al-26 would have decayed before planets could congeal.

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Title: SOLAR SYSTEM OXYGEN ISOTOPE RATIOS RESULT FROM POLLUTION BY TYPE II SUPERNOVAE. 
Authors: E. D. Young, M. Gounelle, R. Smith, M. R. Morris, and K. M. Pontoppidan

For decades it has been known that solar system 18O/17O is peculiar with respect to Galactic values.  Rocks of the solar system have 18O/17O of approximately 5.2 while values for CO, OH, and HCO+ in giant molecular clouds across the Galaxy are consistently 3.5 ±0.3.  This difference cannot be explained by Galactic chemical evolution (GCE), which results in a constant 18O/17O with time, and a satisfactory explanation for the disparity has proven elusive. The standard view has been that there may be a systematic error between the absolute ratios obtained by radio astronomy and those measured by mass spectrometry, however the latter yield absolute oxygen isotope ratios accurate to fractions of per cent while the difference in question is 30%.  Systematic errors in the radio astronomy measurements can be addressed by measuring isotopologue ratios using a different method.
Here we report new infrared absorption measurements of oxygen isotope ratios in individual young stellar objects (YSOs) that confirm the previous radio observations of giant molecular cloud gas.  These new data show that the typical Galactic 18O/17O of ~3.5 is not only an average over the parsec scale but pertains to the scale of single YSOs as well.  These new, high-spatial-resolution data underscore the disparity between solar and extrasolar 18O/17O ratios.  We show that this discrepancy is best explained by ~30% pollution (atomic units) of the proto-solar molecular cloud by intermediate mass (~20M: ) type II supernovae ejecta.

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