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It says that the they detected Pu-244 with a concentration of c244 = 0.15×10−18 g/g in bastnasite, making its concentration 4.5 billion years ago in similar minerals 255 times larger or 3.6×10-2 g/g, almost 5 times the pre-solar nebula abundance, relative to U-238, mentioned above. This seems erroneous and the differences in these estimates isn't explained. I sugest removing at least one of them. Crackhorace ( talk) 17 November 2016
@ Double sharp: I notice you edited in a mention of Sm-146 being primordial, but I don't see a source for it and can't find one myself. Could you enlighten me? Magic9mushroom ( talk) 14:45, 24 August 2017 (UTC)
@ Double sharp: So you're saying Sm-146 is not in fact primordial? I mean, certainly if Sm-146 is primordial Pu-244 would be the second-shortest-lived primordial; I'm more concerned with whether Sm-146 has or hasn't been confirmed to be primordial. Back-of-the-envelope calculations suggest there should be about 4 mg left in the entire Earth, so it's in the weird limbo where there is some but no conceivable experiment could detect it (a kilogram of natural samarium should contain about 9 atoms of Sm-246 and have about one decay every 10 million years). Magic9mushroom ( talk) 02:44, 25 August 2017 (UTC)
@ Magic9mushroom: Ah, I found a source (doi 10.1039/B608157F). It says that 146Sm should be primordial, as you note, but it should not be easy to find, especially because mass spectrometry is going to get swamped by the stable isobar 146Nd. So they propose here a method to effectively separate Nd from Sm and pin it down; but since even the detection of 244Pu is unconfirmed, we may have to wait a while to find 146Sm. They also suggest that a similar Hf–W separation should help to find 182Hf, which may be around from more recent nearby supernovae like 60Fe. So, perhaps we may finally get rid of these two borderline cases in the future, though I am not inclined to be as hopeful given that this paper is from 2006. Double sharp ( talk) 03:40, 25 August 2017 (UTC)
@ Double sharp: That paper still assumes a 100-million-year half-life, which means it's probably overestimating the abundance of Sm-146 in the present day.
I'm going to remove the mention of Sm-146 being detected from the Isotopes of niobium article, because it's not sourced there either and was edited by an IP from a sentence originally talking about Pu-244. I think this article could do with some cleanup as well; there's one paragraph stating unambiguously that Pu-244 is primordial and a second saying that it's disputed, which frankly stinks. And lastly, I think Isotopes of samarium should probably have the bit saying Sm-146 definitively isn't primordial reworded. Your thoughts on the latter two? Magic9mushroom ( talk) 06:35, 25 August 2017 (UTC)
...since even the detection of 244Pu is unconfirmed, ... according to User:Double sharp. Plutonium-239 is the most stable isotope known in any measurable quantity, and somebody's shooting billiards for 150 neutrons in the nucleus and it just doesn't happen at all, let alone stable for 80,000,000 years. 24.237.158.249 ( talk) 17:28, 11 January 2022 (UTC)
This article is rated Start-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | ||||||||||||||
|
|
|
This page has archives. Sections older than 730 days may be automatically archived by Lowercase sigmabot III when more than 3 sections are present. |
It says that the they detected Pu-244 with a concentration of c244 = 0.15×10−18 g/g in bastnasite, making its concentration 4.5 billion years ago in similar minerals 255 times larger or 3.6×10-2 g/g, almost 5 times the pre-solar nebula abundance, relative to U-238, mentioned above. This seems erroneous and the differences in these estimates isn't explained. I sugest removing at least one of them. Crackhorace ( talk) 17 November 2016
@ Double sharp: I notice you edited in a mention of Sm-146 being primordial, but I don't see a source for it and can't find one myself. Could you enlighten me? Magic9mushroom ( talk) 14:45, 24 August 2017 (UTC)
@ Double sharp: So you're saying Sm-146 is not in fact primordial? I mean, certainly if Sm-146 is primordial Pu-244 would be the second-shortest-lived primordial; I'm more concerned with whether Sm-146 has or hasn't been confirmed to be primordial. Back-of-the-envelope calculations suggest there should be about 4 mg left in the entire Earth, so it's in the weird limbo where there is some but no conceivable experiment could detect it (a kilogram of natural samarium should contain about 9 atoms of Sm-246 and have about one decay every 10 million years). Magic9mushroom ( talk) 02:44, 25 August 2017 (UTC)
@ Magic9mushroom: Ah, I found a source (doi 10.1039/B608157F). It says that 146Sm should be primordial, as you note, but it should not be easy to find, especially because mass spectrometry is going to get swamped by the stable isobar 146Nd. So they propose here a method to effectively separate Nd from Sm and pin it down; but since even the detection of 244Pu is unconfirmed, we may have to wait a while to find 146Sm. They also suggest that a similar Hf–W separation should help to find 182Hf, which may be around from more recent nearby supernovae like 60Fe. So, perhaps we may finally get rid of these two borderline cases in the future, though I am not inclined to be as hopeful given that this paper is from 2006. Double sharp ( talk) 03:40, 25 August 2017 (UTC)
@ Double sharp: That paper still assumes a 100-million-year half-life, which means it's probably overestimating the abundance of Sm-146 in the present day.
I'm going to remove the mention of Sm-146 being detected from the Isotopes of niobium article, because it's not sourced there either and was edited by an IP from a sentence originally talking about Pu-244. I think this article could do with some cleanup as well; there's one paragraph stating unambiguously that Pu-244 is primordial and a second saying that it's disputed, which frankly stinks. And lastly, I think Isotopes of samarium should probably have the bit saying Sm-146 definitively isn't primordial reworded. Your thoughts on the latter two? Magic9mushroom ( talk) 06:35, 25 August 2017 (UTC)
...since even the detection of 244Pu is unconfirmed, ... according to User:Double sharp. Plutonium-239 is the most stable isotope known in any measurable quantity, and somebody's shooting billiards for 150 neutrons in the nucleus and it just doesn't happen at all, let alone stable for 80,000,000 years. 24.237.158.249 ( talk) 17:28, 11 January 2022 (UTC)