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Supernova shrapnel slammed into meteorite

Scientists this week said they found microscopic shrapnel in a meteorite of a star they say exploded around the birth of our solar system 4.5 billion years ago.
The findings suggest that a supernova sprayed a mass of finely grained particles into the cloud of gas and dust that gave birth to the solar system 4.5 billion years ago,

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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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A meteorite found in the Sahara Desert has helped to pin down the age of the Solar System and shed light on how it may have formed.
The new estimate, which comes from measuring the ratios of lead isotopes inside the chondrite - an ancient stony meteorite - suggests that the Solar System is 4.568 billion years old. This is 0.3-1.9 million years older than some previous studies projected. The relatively small revision means that models of the gas and dust that gave rise to the Solar System should have around double the amount of a certain iron isotope, iron-60, than previously suggested.

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Davisite and Grossmanite
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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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RE: Solar supernova
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Did an Ancient Supernova Trigger the Solar System's Birth?

Aside from producing many of the elements that make up our planet and our bodies, the stellar cycle of birth and death appears to have spurred the formation of our solar system some 4.5 billion years ago. According to a new model outlined in a study in the July 1 issue of Astrophysical Journal Letters, a shock wave from an exploding massive star several light-years away probably triggered the collapse of the molecular cloud that would become our sun and planets.
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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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Star explosion explains why solar system is enriched in oxygen

That's the conclusion of a study that aimed to solve the mystery of why our solar system is enriched in a rare form of oxygen.
The study suggests that the sun and the material for what became the eight major planets formed in the vicinity of one or more supernovas and were enriched in the matter that stellar explosions left behind, including that strange type of oxygen.
Astronomers can probe the galaxy for signatures of different elements and their isotopes (atoms that have the same number of protons, but a different number of neutrons) to see how they vary from region to region. They have long known that the solar system has a peculiarly high ratio of the two rarest forms of oxygen, but haven't known exactly why.

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Solar system oxygen isotope ratios
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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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Solar supernova
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Title: 238U/235U Variations in Meteorites: Extant 247Cm and Implications for Pb-Pb Dating
Authors: G. A. Brennecka, S. Weyer, M. Wadhwa, P. E. Janney, J. Zipfel, A. D. Anbar

The 238U/235U isotope ratio has long been considered invariant in meteoritic materials (i.e., 137.88). This assumption is a cornerstone of the high-precision Pb-Pb dates that define the absolute age of the Solar System. Calcium-aluminium-rich inclusions of the Allende meteorite display variable 238U/235U ratios, ranging between 137.409±0.039 and 137.885±0.009. This range implies substantial uncertainties in the ages previously determined by Pb-Pb dating of CAIs, which may be overestimated by several million years. The correlation of U isotope ratios with proxies for Cm/U (i.e., Th/U and Nd/U) provides strong evidence that the observed variations of 238U/235U in CAIs were produced by the decay of extant 247Cm to 235U in the early Solar System, with an initial 247Cm/235U of ~ 1.1 to 2.4 x 10^-4.

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-- Edited by Blobrana on Friday 1st of January 2010 07:04:21 PM

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ASU researchers recalculate age of Solar System

Lead-lead (Pb-Pb) dating is among the most widely used radiometric dating techniques to determine the age of really old things, such as the age of the Earth or the Solar System. However, recent advances in instrumentation now allow scientists to make more precise measurements that promise to revolutionize the way the ages of some samples are calculated with this technique.
Radiometric dating can be used to determine the age of a wide range of natural and human-made materials. The comparison between the observed abundance of a naturally occurring radioactive isotope, such as uranium (U), and its decay products can be used to determine the age of a material, using known decay rates. The Pb-Pb dating technique has been used for decades under the assumption that the ratio of the 238U and 235U isotopes, both of which decay to different isotopes of Pb, is constant in the Solar System. This assumed value is built into the Pb-Pb age equation.

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