Radionuclide formed by nucleosynthesis before formation of the Solar System
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An extinct radionuclide is a radionuclide that was formed by nucleosynthesis before the formation of the Solar System, about 4.6 billion years ago, but has since decayed to virtually zero abundance and is no longer detectable as a primordial nuclide. Extinct radionuclides were generated by various processes in the early Solar system, and became part of the composition of meteorites and protoplanets. All widely documented extinct radionuclides have half-lives shorter than 100 million years.[1]
Short-lived radioisotopes that are found in nature are continuously generated or replenished by natural processes, such as cosmic rays (cosmogenic nuclides), background radiation, or the decay chain or spontaneous fission of other radionuclides.
Short-lived isotopes that are not generated or replenished by natural processes are not found in nature, so they are known as extinct radionuclides. Their former existence is inferred from a superabundance of their stable or nearly stable decay products.
Examples of extinct radionuclides include iodine-129 (the first to be noted in 1960, inferred from excess xenon-129 concentrations in meteorites, in the xenon-iodine dating system), aluminium-26 (inferred from extra magnesium-26 found in meteorites), and iron-60.
The Solar System and Earth are formed from primordial nuclides and extinct nuclides. Extinct nuclides have decayed away, but primordial nuclides still exist in their original state (undecayed). There are 251 stable primordial nuclides, and remainders of 35 primordial radionuclides that have very long half-lives.
^Dauphas, N.; Chaussidon, M. (2011). "A perspective from extinct radionuclides on a young stellar object: the Sun and its accretion disk". Annual Review of Earth and Planetary Sciences. 39: 351–386. arXiv:1105.5172. Bibcode:2011AREPS..39..351D. doi:10.1146/annurev-earth-040610-133428. S2CID 37117614.
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An extinctradionuclide is a radionuclide that was formed by nucleosynthesis before the formation of the Solar System, about 4.6 billion years ago, but...
early solar system.[citation needed] Another example of short-lived extinctradionuclide dating is the 26 Al – 26 Mg chronometer, which can be used to estimate...
solar nebula but have long since decayed away completely are termed extinctradionuclides if they have no other means of being regenerated. Because primordial...
significant quantities of 236U, which has a shorter half-life and so is an extinctradionuclide, having long since decayed completely to 232Th. Further uranium-236...
radionuclides with half lives less than about 50 to 100 million years. Such nuclides are formed in supernovas, but are known as extinctradionuclides...
of about 105 years. Its existence in the early Solar System as an extinctradionuclide has been inferred from excesses of 41K: traces of 41Ca also still...
the half-life of 3.1×1022 years has been established. 60Fe is an extinctradionuclide of long half-life (2.6 million years). It is not found on Earth,...
System, but it has by now completely decayed away, making it an extinctradionuclide that is nevertheless still useful in dating the history of the early...
known isotope beyond curium, and long enough to study as a possible extinctradionuclide that would be produced by the r-process. The longest-lived isomer...
stable of which is 182Hf with a half-life of 8.9×106 years. This extinctradionuclide is used in hafnium–tungsten dating to study the chronology of planetary...
short-lived extinctradionuclides in the early Solar System. The extra presence of these stable radiogenic nuclides (such as xenon-129 from extinct iodine-129)...
far the most abundant. Nickel-60 is the daughter product of the extinctradionuclide 60 Fe (half-life 2.6 million years). Due to the long half-life of...
when it formed, should have decayed by now. Its past presence as an extinctradionuclide is detectable as an excess of its primordial, long-lived daughter...
dust in ice and sediment. Nickel-60 is the daughter product of the extinctradionuclide 60 Fe (half-life = 2.6 My). Because 60 Fe had such a long half-life...
it remains useful in radiometric dating in the Solar System as an extinctradionuclide. A 2012 paper revising the estimated half-life of 146Sm from 10.3(5)×107 y...
0×1016 years for the most stable one, the primordial 174Hf. The extinctradionuclide 182Hf has a half-life of 8.9±0.1 million years, and is an important...
composed primarily of 44Ca which is presumably the remains of the extinctradionuclide 44Ti, a titanium isotope that was formed in abundance in Type II...
using extinctradionuclides give only relative ages and have to be calibrated with radiometric dating techniques based on long-living radionuclides like...
06×1011 years and is used in samarium–neodymium dating. 146Sm is an extinctradionuclide, with the half-life of 1.03×108 years. There have been searches of...
within the expanding supernova interior, but would have become an extinctradionuclide (specifically 44Ca) after the time required for mixing with the interstellar...
has long decayed and is thus referred to as "extinct". Historically, 129I was the first extinctradionuclide to be identified as present in the early Solar...
composed primarily of 44Ca, which is presumably the remains of the extinctradionuclide titanium-44, a titanium isotope which is formed in abundance in Type...
Indicates spin with weak assignment arguments. Niobium-92 is an extinctradionuclide with a half-life of 34.7 million years, decaying predominantly via...
industrial or medical purposes. Each group of radionuclides, starting with the longest-lived primordial radionuclides, is sorted by decreasing half-life, but...
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