Supernova presolar grains

The second interesting feature of this isotope is that minuscule grains of silicon carbide extracted from meteorites have been found to be very rich in calcium-44, as mentioned earlier. They have been identified with presolar grains that condensed in the ejecta of supernovas during their first few years of expansion. Could it be that supernovas have been throwing sand in our eyes Data gathered by the ISO (Infrared Space Observatory), yet another experiment with strong participation by the French CEA, clearly demonstrates that new dust condensed inside the Cas A remnant very soon after explosion of the supernova that caused it. °... 

Titanium-44 decays by electron capture via 44Sc to 44Ca with a half-life of 60 years. Its half-life is too short for it to have played any role in the solar system. Titanium-44 is produced by explosive nucleosynthesis and it is useful as an indicator of the supernova source for a subset of 44Ca-rich presolar grains. 

Presolar grains Supernova condensates, called SUNOCONs, are presolar grains that condensed from the expanding supernova interior gas. The Ca/ Ca ratio is... 

Because V has but a single abundant isotope, its isotopic composition is not measurable within presolar material. However, extinct 49V with a halflife of 330 days has been shown to have been alive in presolar grains from supernovae at the time of their condensation (see 49Ti). 

The cosmic chemical memory interpretation was advanced by the writer as a superior way to think of these isotopic anomalies. This picture argued that the early solar system was not hot enough to vaporize the entirety of most solids but only their volatile parts and portions of their refractory Ca-and-Al-rich minerals. The refractory parts had survived to that time from their earlier condensation as stardust and were fused into the CAI assemblages found today in the meteorites. That fusion occurred while the gas that was vaporized from a dust-rich presolar mixture recondensed as the main minerals of the CAIs. The refractory cores, being stardust that had condensed even earlier within individual stars and supernovae, contain the isotope ratios from those distinct sources. When these cores were fused into the CAIs found today, the chemistry remembered the isotope ratios of the source presolar grains, so thatsolar-system rocks (CAIs) remembered their isotopic parentage. Hence the name cosmic chemical memory. See l60 for a fuller account of the historical role played by the experimental discovery of l60-rich minerals within the CAIs, and of how the memory of l60-richness was saved. 

Evidence of neutron-burst nucleosynthesis has been found most convincingly from the isotopic study of presolar grains. Many that were made within supernovae contain, in addition to their other telltale compositions, the evidence of the rapid burst of free neutrons. Interestingly, this is what occurs in an atomic bomb. The testing of these weapons gave the first inkling of something that is common in the universe. 

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