View source for Isotopes of iron

{{Short description|none}}
{{Infobox iron isotopes}}
Natural [[iron]] ({{sub|26}}Fe) consists of four stable [[isotope]]s: 5.845% {{sup|54}}Fe (possibly radioactive with [[half-life]] >{{val|4.4|e=20}} years),<ref name="Fe54decay">{{cite journal |last1=Bikit |first1=I. |last2=Krmar |first2=M. |last3=Slivka |first3=J. |last4=Vesković |first4=M. |last5=Čonkić |first5=Lj. |last6=Aničin |first6=I. |title=New results on the double β decay of iron |journal=Physical Review C |date=1998 |volume=58 |issue=4 |pages=2566–2567 |doi=10.1103/PhysRevC.58.2566|bibcode=1998PhRvC..58.2566B }}</ref> 91.754% {{sup|56}}Fe, 2.119% {{sup|57}}Fe and 0.286% {{sup|58}}Fe. There are 28 known radioisotopes and 8 [[nuclear isomer]]s, the most stable of which are {{sup|60}}Fe (half-life 2.6&nbsp;million years) and {{sup|55}}Fe (half-life 2.7 years).

Much of the past work on measuring the isotopic composition of iron has centered on determining {{sup|60}}Fe variations due to processes accompanying [[nucleosynthesis]] (i.e., [[meteorite]] studies) and ore formation. In the last decade however, advances in [[mass spectrometry]] technology have allowed the detection and quantification of minute, naturally occurring variations in the ratios of the [[stable isotope]]s of iron. Much of this work has been driven by the [[Earth science|Earth]] and [[planetary science]] communities, though applications to biological and industrial systems are beginning to emerge.<ref>{{cite journal |author=N. Dauphas |author2=O. Rouxel |year=2006 |title=Mass spectrometry and natural variations of iron isotopes |journal=[[Mass Spectrometry Reviews]] |volume=25 |issue= 4|pages=515–550 |doi=10.1002/mas.20078 |pmid=16463281|bibcode=2006MSRv...25..515D }}</ref>

== List of isotopes ==
{{Anchor|Iron-47m}}

<!--Please delete anchor(s) from the list above or table below if adding a dedicated isotope section(s).-->

{{Isotopes table
|symbol=Fe
|refs=NUBASE2020, AME2020 II
|notes=m, unc(), mass#, hl#, spin(), spin#, daughter-st, EC, IT, n, p 
}}
|-id=Iron-45
| rowspan=4|<sup>45</sup>Fe
| rowspan=4 style="text-align:right" | 26
| rowspan=4 style="text-align:right" | 19
| rowspan=4|45.01547(30)#
| rowspan=4|2.5(2)&nbsp;ms
| 2[[proton emission|p]] (70%)
| <sup>43</sup>Cr
| rowspan=4|3/2+#
| rowspan=4|
| rowspan=4|
|-
| [[beta decay|β<sup>+</sup>]], p (18.9%)
| <sup>44</sup>Cr
|-
| β<sup>+</sup>, 2p (7.8%)
| <sup>43</sup>V
|-
| β<sup>+</sup> (3.3%)
| <sup>45</sup>Mn
|-id=Iron-46
| rowspan=3|<sup>46</sup>Fe
| rowspan=3 style="text-align:right" | 26
| rowspan=3 style="text-align:right" | 20
| rowspan=3|46.00130(32)#
| rowspan=3|13.0(20)&nbsp;ms
| β<sup>+</sup>, p (78.7%)
| <sup>45</sup>Cr
| rowspan=3|0+
| rowspan=3|
| rowspan=3|
|-
| β<sup>+</sup> (21.3%)
| <sup>46</sup>Mn
|-
| β<sup>+</sup>, 2p?
| <sup>44</sup>V
|-id=Iron-47
| rowspan=2|<sup>47</sup>Fe
| rowspan=2 style="text-align:right" | 26
| rowspan=2 style="text-align:right" | 21
| rowspan=2|46.99235(54)#
| rowspan=2|21.9(2)&nbsp;ms
| β<sup>+</sup>, p (88.4%)
| <sup>46</sup>Cr
| rowspan=2|7/2−#
| rowspan=2|
| rowspan=2|
|-
| β<sup>+</sup> (11.6%)
| <sup>47</sup>Mn
|-id=Iron-48
| rowspan=2|<sup>48</sup>Fe
| rowspan=2 style="text-align:right" | 26
| rowspan=2 style="text-align:right" | 22
| rowspan=2|47.980667(99)
| rowspan=2|45.3(6)&nbsp;ms
| β<sup>+</sup> (84.7%)
| <sup>48</sup>Mn
| rowspan=2|0+
| rowspan=2|
| rowspan=2|
|-
| β<sup>+</sup>, p (15.3%)
| <sup>47</sup>Cr
|-id=Iron-49
| rowspan=2|<sup>49</sup>Fe
| rowspan=2 style="text-align:right" | 26
| rowspan=2 style="text-align:right" | 23
| rowspan=2|48.973429(26)
| rowspan=2|64.7(3)&nbsp;ms
| β<sup>+</sup>, p (56.7%)
| <sup>48</sup>Cr
| rowspan=2|(7/2−)
| rowspan=2|
| rowspan=2|
|-
| β<sup>+</sup> (43.3%)
| <sup>49</sup>Mn
|-id=Iron-50
| rowspan=2|<sup>50</sup>Fe
| rowspan=2 style="text-align:right" | 26
| rowspan=2 style="text-align:right" | 24
| rowspan=2|49.9629880(90)
| rowspan=2|152.0(6)&nbsp;ms
| β<sup>+</sup>
| <sup>50</sup>Mn
| rowspan=2|0+
| rowspan=2|
| rowspan=2|
|-
| β<sup>+</sup>, p?
| <sup>49</sup>Cr
|-id=Iron-51
| <sup>51</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 25
| 50.9568551(15)
| 305.4(23)&nbsp;ms
| β<sup>+</sup>
| <sup>51</sup>Mn
| 5/2−
|
|
|-id=Iron-52
| <sup>52</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 26
| 51.94811336(19)
| 8.275(8)&nbsp;h
| β<sup>+</sup>
| <sup>52</sup>Mn
| 0+
|
|
|-id=Iron-52m
| rowspan=2 style="text-indent:1em" | <sup>52m</sup>Fe
| rowspan=2 colspan="3" style="text-indent:2em" | 6960.7(3)&nbsp;keV
| rowspan=2|45.9(6)&nbsp;s
| β<sup>+</sup> (99.98%)
| <sup>52</sup>Mn
| rowspan=2|12+
| rowspan=2|
| rowspan=2|
|-
| [[isomeric transition|IT]] (0.021%)
| <sup>52</sup>Fe
|-id=Iron-53
| <sup>53</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 27
| 52.9453056(18)
| 8.51(2)&nbsp;min
| β<sup>+</sup>
| <sup>53</sup>Mn
| 7/2−
|
|
|-id=Iron-53m
| style="text-indent:1em" | <sup>53m</sup>Fe
| colspan="3" style="text-indent:2em" | 3040.4(3)&nbsp;keV
| 2.54(2)&nbsp;min
| IT
| <sup>53</sup>Fe
| 19/2−
|
|
|-
| <sup>54</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 28
| 53.93960819(37)
| colspan=3 align=center|'''[[Observationally Stable]]'''{{refn|group=n|Believed to decay by β<sup>+</sup>β<sup>+</sup> to '''<sup>54</sup>Cr''' with a half-life of over 4.4×10<sup>20</sup> [[Annum|a]]<ref name="Fe54decay"/>}}
| 0+
| 0.05845(105)
| 
|-id=Iron-54m
| style="text-indent:1em" | <sup>54m</sup>Fe
| colspan="3" style="text-indent:2em" | 6527.1(11)&nbsp;keV
| 364(7)&nbsp;ns
| IT
| '''<sup>54</sup>Fe'''
| 10+
|
|
|-
| [[Iron-55|<sup>55</sup>Fe]]
| style="text-align:right" | 26
| style="text-align:right" | 29
| 54.93829116(33)
| 2.7562(4)&nbsp;y
| [[Electron capture|EC]]
| '''<sup>55</sup>Mn'''
| 3/2−
|
|
|-
| [[Iron-56|<sup>56</sup>Fe]]<ref group="n">Lowest mass per nucleon of all nuclides; End product of stellar [[nucleosynthesis]]</ref>
| style="text-align:right" | 26
| style="text-align:right" | 30
| 55.93493554(29)
| colspan=3 align=center|'''Stable'''
| 0+
| 0.91754(106)
| 
|-
| <sup>57</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 31
| 56.93539195(29)
| colspan=3 align=center|'''Stable'''
| 1/2−
| 0.02119(29)
| 
|-
| <sup>58</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 32
| 57.93327358(34)
| colspan=3 align=center|'''Stable'''
| 0+
| 0.00282(12)
| 
|-id=Iron-59
| <sup>59</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 33
| 58.93487349(35)
| 44.500(12)&nbsp;d
| β<sup>−</sup>
| '''<sup>59</sup>Co'''
| 3/2−
|
|
|-
| <sup>60</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 34
| 59.9340702(37)
| 2.62(4)×10<sup>6</sup>&nbsp;y
| β<sup>−</sup>
| <sup>60</sup>Co
| 0+
| [[trace radioisotope|trace]]
|
|-id=Iron-61
| <sup>61</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 35
| 60.9367462(28)
| 5.98(6)&nbsp;min
| β<sup>−</sup>
| <sup>61</sup>Co
| (3/2−)
|
|
|-id=Iron-61m
| style="text-indent:1em" | <sup>61m</sup>Fe
| colspan="3" style="text-indent:2em" | 861.67(11)&nbsp;keV
| 238(5)&nbsp;ns
| IT
| <sup>61</sup>Fe
| 9/2+
|
|
|-id=Iron-62
| <sup>62</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 36
| 61.9367918(30)
| 68(2)&nbsp;s
| β<sup>−</sup>
| <sup>62</sup>Co
| 0+
|
|
|-id=Iron-63
| <sup>63</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 37
| 62.9402727(46)
| 6.1(6)&nbsp;s
| β<sup>−</sup>
| <sup>63</sup>Co
| (5/2−)
|
|
|-id=Iron-64
| <sup>64</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 38
| 63.9409878(54)
| 2.0(2)&nbsp;s
| β<sup>−</sup>
| <sup>64</sup>Co
| 0+
|
|
|-id=Iron-65
| rowspan=2|<sup>65</sup>Fe
| rowspan=2 style="text-align:right" | 26
| rowspan=2 style="text-align:right" | 39
| rowspan=2|64.9450153(55)
| rowspan=2|805(10)&nbsp;ms
| β<sup>−</sup>
| <sup>65</sup>Co
| rowspan=2|(1/2−)
| rowspan=2|
| rowspan=2|
|-
| β<sup>−</sup>, [[neutron emission|n]]?
| <sup>64</sup>Co
|-id=Iron-65m1
| style="text-indent:1em" | <sup>65m1</sup>Fe
| colspan="3" style="text-indent:2em" | 393.7(2)&nbsp;keV
| 1.12(15)&nbsp;s
| β<sup>−</sup>?
| <sup>65</sup>Co
| (9/2+)
|
|
|-id=Iron-65m2
| style="text-indent:1em" | <sup>65m2</sup>Fe
| colspan="3" style="text-indent:2em" | 397.6(2)&nbsp;keV
| 418(12)&nbsp;ns
| IT
| <sup>65</sup>Fe
| (5/2+)
|
|
|-id=Iron-66
| rowspan=2|<sup>66</sup>Fe
| rowspan=2 style="text-align:right" | 26
| rowspan=2 style="text-align:right" | 40
| rowspan=2|65.9462500(44)
| rowspan=2|467(29)&nbsp;ms
| β<sup>−</sup>
| <sup>66</sup>Co
| rowspan=2|0+
| rowspan=2|
| rowspan=2|
|-
| β<sup>−</sup>, n?
| <sup>65</sup>Co
|-id=Iron-67
| rowspan=2|<sup>67</sup>Fe
| rowspan=2 style="text-align:right" | 26
| rowspan=2 style="text-align:right" | 41
| rowspan=2|66.9509300(41)
| rowspan=2|394(9)&nbsp;ms
| β<sup>−</sup>
| <sup>67</sup>Co
| rowspan=2|(1/2-)
| rowspan=2|
| rowspan=2|
|-
| β<sup>−</sup>, n?
| <sup>66</sup>Co
|-id=Iron-67m1
| style="text-indent:1em" | <sup>67m1</sup>Fe
| colspan="3" style="text-indent:2em" | 403(9)&nbsp;keV
| 64(17)&nbsp;μs
| IT
| <sup>67</sup>Fe
| (5/2+,7/2+)
|
|
|-id=Iron-67m2
| style="text-indent:1em" | <sup>67m2</sup>Fe
| colspan="3" style="text-indent:2em" | 450(100)#&nbsp;keV
| 75(21)&nbsp;μs
| IT
| <sup>67</sup>Fe
| (9/2+)
|
|
|-id=Iron-68
| rowspan=2|<sup>68</sup>Fe
| rowspan=2 style="text-align:right" | 26
| rowspan=2 style="text-align:right" | 42
| rowspan=2|67.95288(21)#
| rowspan=2|188(4)&nbsp;ms
| β<sup>−</sup>
| <sup>68</sup>Co
| rowspan=2|0+
| rowspan=2|
| rowspan=2|
|-
| β<sup>−</sup>, n?
| <sup>67</sup>Co
|-id=Iron-69
| rowspan=3|<sup>69</sup>Fe
| rowspan=3 style="text-align:right" | 26
| rowspan=3 style="text-align:right" | 43
| rowspan=3|68.95792(22)#
| rowspan=3|162(7)&nbsp;ms
| β<sup>−</sup>
| <sup>69</sup>Co
| rowspan=3|1/2−#
| rowspan=3|
| rowspan=3|
|-
| β<sup>−</sup>, n?
| <sup>68</sup>Co
|-
| β<sup>−</sup>, 2n?
| <sup>67</sup>Co
|-id=Iron-70
| rowspan=2|<sup>70</sup>Fe
| rowspan=2 style="text-align:right" | 26
| rowspan=2 style="text-align:right" | 44
| rowspan=2|69.96040(32)#
| rowspan=2|61.4(7)&nbsp;ms
| β<sup>−</sup>
| <sup>70</sup>Co
| rowspan=2|0+
| rowspan=2|
| rowspan=2|
|-
| β<sup>−</sup>, n?
| <sup>69</sup>Co

|-id=Iron-71
| rowspan=3|<sup>71</sup>Fe
| rowspan=3 style="text-align:right" | 26
| rowspan=3 style="text-align:right" | 45
| rowspan=3|70.96572(43)#
| rowspan=3|34.3(26)&nbsp;ms
| β<sup>−</sup>
| <sup>71</sup>Co
| rowspan=3|7/2+#
| rowspan=3|
| rowspan=3|
|-
| β<sup>−</sup>, n?
| <sup>70</sup>Co
|-
| β<sup>−</sup>, 2n?
| <sup>69</sup>Co
|-id=Iron-72
| rowspan=3|<sup>72</sup>Fe
| rowspan=3 style="text-align:right" | 26
| rowspan=3 style="text-align:right" | 46
| rowspan=3|71.96860(54)#
| rowspan=3|17.0(10)&nbsp;ms
| β<sup>−</sup>
| <sup>72</sup>Co
| rowspan=3|0+
| rowspan=3|
| rowspan=3|
|-
| β<sup>−</sup>, n?
| <sup>71</sup>Co
|-
| β<sup>−</sup>, 2n?
| <sup>70</sup>Co
|-id=Iron-73
| rowspan=3|<sup>73</sup>Fe
| rowspan=3 style="text-align:right" | 26
| rowspan=3 style="text-align:right" | 47
| rowspan=3|72.97425(54)#
| rowspan=3|12.9(16)&nbsp;ms
| β<sup>−</sup>
| <sup>73</sup>Co
| rowspan=3|7/2+#
| rowspan=3|
| rowspan=3|
|-
| β<sup>−</sup>, n?
| <sup>72</sup>Co
|-
| β<sup>−</sup>, 2n?
| <sup>71</sup>Co
|-id=Iron-74
| rowspan=3|<sup>74</sup>Fe
| rowspan=3 style="text-align:right" | 26
| rowspan=3 style="text-align:right" | 48
| rowspan=3|73.97782(54)#
| rowspan=3|5(5)&nbsp;ms
| β<sup>−</sup>
| <sup>74</sup>Co
| rowspan=3|0+
| rowspan=3|
| rowspan=3|
|-
| β<sup>−</sup>, n?
| <sup>73</sup>Co
|-
| β<sup>−</sup>, 2n?
| <sup>72</sup>Co
|-id=Iron-75
| rowspan=3|<sup>75</sup>Fe
| rowspan=3 style="text-align:right" | 26
| rowspan=3 style="text-align:right" | 49
| rowspan=3|74.98422(64)#
| rowspan=3|9#&nbsp;ms<br>[>620&nbsp;ns]
| β<sup>−</sup>?
| <sup>75</sup>Co
| rowspan=3|9/2+#
| rowspan=3|
| rowspan=3|
|-
| β<sup>−</sup>, n?
| <sup>74</sup>Co
|-
| β<sup>−</sup>, 2n?
| <sup>73</sup>Co
|-id=Iron-76
| <sup>76</sup>Fe
| style="text-align:right" | 26
| style="text-align:right" | 50
| 75.98863(64)#
| 3#&nbsp;ms<br>[>410&nbsp;ns]
| β<sup>−</sup>?
| <sup>76</sup>Co
| 0+
|
|
{{Isotopes table/footer}}

==Iron-54==
{{sup|54}}Fe is observationally stable, but theoretically can decay to {{sup|54}}Cr, with a half-life of more than {{val|4.4|e=20}} years via [[double electron capture]] (εε).<ref name="Fe54decay"/>

==Iron-56==
{{main|Iron-56}}
{{sup|56}}Fe is the most abundant isotope of iron. It is also the isotope with the lowest mass per nucleon, 930.412 MeV/c{{sup|2}}, though not the isotope with the highest [[nuclear binding energy]] per nucleon, which is [[nickel-62]].<ref>{{cite journal |url=https://ui.adsabs.harvard.edu/abs/1995AmJPh..63..653F/abstract |journal=[[American Journal of Physics]]|bibcode=1995AmJPh..63..653F|title=The atomic nuclide with the highest mean binding energy|last1=Fewell|first1=M. P.|year=1995|volume=63|issue=7|page=653|doi=10.1119/1.17828}}</ref> However, because of the details of how nucleosynthesis works, {{sup|56}}Fe is a more common endpoint of fusion chains inside [[supernova]]e, where it is mostly produced as {{sup|56}}Ni. Thus, {{sup|56}}Ni is more common in the universe, relative to other [[Metallicity|metals]], including {{sup|62}}Ni, {{sup|58}}Fe and {{sup|60}}Ni, all of which have a very high binding energy.

The high nuclear binding energy of {{sup|56}}Fe represents the point where further nuclear reactions become energetically unfavorable. Therefore it is among the heaviest elements formed in [[stellar nucleosynthesis]] reactions in massive stars. These reactions fuse lighter elements like magnesium, silicon, and sulfur to form heavier elements. Among the heavier elements formed is {{sup|56}}Ni, which subsequently decays to [[Isotopes of cobalt|{{sup|56}}Co]] and then {{sup|56}}Fe.

== Iron-57 ==
{{sup|57}}Fe is widely used in [[Mössbauer spectroscopy]] and the related [[nuclear resonance vibrational spectroscopy]] due to the low natural variation in energy of the 14.4&nbsp;keV nuclear transition.<ref>
{{cite web
 |author=R. Nave
 |title=Mossbauer Effect in Iron-57
 |url=http://hyperphysics.phy-astr.gsu.edu/Hbase/Nuclear/mossfe.html
 |work=[[HyperPhysics]]
 |publisher=Georgia State University
 |access-date=2009-10-13
}}</ref> 
The transition was famously used to make the first definitive measurement of [[gravitational redshift]], in the 1960 [[Pound–Rebka experiment]].<ref>{{cite journal|last=Pound| first=R. V.|author2=Rebka Jr. G. A. | date= April 1, 1960| title=Apparent weight of photons| journal=[[Physical Review Letters]]| volume=4| issue=7|  pages=337–341| doi = 10.1103/PhysRevLett.4.337| bibcode=1960PhRvL...4..337P| doi-access=free}}</ref>

== Iron-58 ==
Iron-58 can be used to combat anemia and low iron absorption, to metabolically track iron-controlling human genes, and for tracing elements in nature.<ref>{{Cite web |title=Iron-58 Metal Isotope |url=https://www.americanelements.com/iron-58-metal-isotope-13968-47-3 |access-date=2023-06-28 |website=American Elements |language=en}}</ref><ref name=":0" /> Iron-58 is also an assisting reagent in the synthesis of superheavy elements.<ref name=":0">{{Cite web |last=Vasiliev |first=Petr |title=Iron-58, Iron-58 Isotope, Enriched Iron-58, Iron-58 Metal |url=https://www.buyisotope.com/iron-58-isotope.php |access-date=2023-06-28 |website=www.buyisotope.com |language=en}}</ref>

== Iron-60 ==
'''Iron-60''' has a half-life of 2.6&nbsp;million years,<ref>{{cite journal|title=New Measurement of the {{sup|60}}Fe Half-Life |journal=[[Physical Review Letters]] |volume=103 |issue= 7|pages=72502 |doi=10.1103/PhysRevLett.103.072502|pmid=19792637 |bibcode=2009PhRvL.103g2502R|year=2009|last1=Rugel|first1=G.|last2=Faestermann|first2=T.|last3=Knie|first3=K.|last4=Korschinek|first4=G.|last5=Poutivtsev|first5=M.|last6=Schumann|first6=D.|last7=Kivel|first7=N.|last8=Günther-Leopold|first8=I.|last9=Weinreich|first9=R.|last10=Wohlmuther|first10=M.|url=https://www.dora.lib4ri.ch/psi/islandora/object/psi%3A17743 }}</ref><ref>{{cite web|title=Eisen mit langem Atem|url=http://www.scienceticker.info/2009/08/27/eisen-mit-langem-atem/#more-5677|date=27 August 2009|work=scienceticker|access-date=22 May 2010|archive-date=3 February 2018|archive-url=https://web.archive.org/web/20180203071537/http://www.scienceticker.info/2009/08/27/eisen-mit-langem-atem/#more-5677|url-status=dead}}</ref> but was thought until 2009 to have a half-life of 1.5&nbsp;million years. It undergoes [[beta decay]] to [[cobalt-60]], which then decays with a half-life of about 5 years to stable nickel-60. Traces of iron-60 have been found in lunar samples.

In phases of the meteorites ''Semarkona'' and ''Chervony Kut'', a correlation between the concentration of {{sup|60}}[[Nickel|Ni]], the [[granddaughter isotope]] of {{sup|60}}Fe, and the abundance of the stable iron isotopes could be found, which is evidence for the existence of {{sup|60}}Fe at the time of formation of the Solar System. Possibly the energy from the decay of {{sup|60}}Fe contributed, together with the energy from the decay of the radionuclide [[Aluminium-26|{{sup|26}}Al]], to the remelting and [[planetary differentiation|differentiation]] of [[asteroid]]s after their formation 4.6&nbsp;billion years ago. The abundance of {{sup|60}}Ni in [[wikt:extraterrestrial|extraterrestrial]] material may also provide further insight into the origin of the [[Solar System]] and its early history.

Iron-60 found in fossilized bacteria in sea floor sediments suggest there was a supernova near the Solar System about 2&nbsp;million years ago.<ref>{{cite journal|last1=Belinda Smith|title=Ancient bacteria store signs of supernova smattering|journal=Cosmos|date=Aug 9, 2016|url=https://cosmosmagazine.com/space/ancient-bacteria-store-signs-of-supernova-smattering}}</ref><ref>{{cite journal|last1=Peter Ludwig|display-authors=etal|title=Time-resolved 2-million-year-old supernova activity discovered in Earth's microfossil record|journal=[[PNAS]]|volume=113|issue=33|pages=9232–9237|date=Aug 16, 2016|doi=10.1073/pnas.1601040113|pmid=27503888|pmc=4995991|arxiv=1710.09573|bibcode=2016PNAS..113.9232L|doi-access=free}}</ref> Iron-60 is also found in sediments from 8&nbsp;million years ago.<ref>{{cite journal|last1=Colin Barras|title=Fires may have given our evolution a kick-start|journal=[[New Scientist]]|volume=236|issue=3147|pages=7|date=Oct 14, 2017|url=https://www.newscientist.com/article/mg23631474-400-exploding-stars-could-have-kickstarted-our-ancestors-evolution/|bibcode=2017NewSc.236....7B|doi=10.1016/S0262-4079(17)31997-8}}</ref> In 2019, researchers found interstellar {{sup|60}}Fe in [[Antarctica]], which they relate to the [[Local Interstellar Cloud]].<ref name="Interstellar Iron">{{cite journal |title=Interstellar {{sup|60}}Fe in Antarctica |first1=Dominik |last1=Koll |first2=al. |last2=et. |journal=Physical Review Letters |year=2019 |volume=123 |issue=7 |pages=072701 |doi=10.1103/PhysRevLett.123.072701|pmid=31491090 |bibcode=2019PhRvL.123g2701K |s2cid=201868513 |hdl=1885/298253 |hdl-access=free }}</ref>

The distance to the [[supernova]] of origin can be estimated by relating the amount of iron-60 intercepted as Earth passes through the expanding supernova ejecta. Assuming that the material ejected in a supernova expands uniformly out from its origin as a sphere with surface area 4πr{{sup|2}}. The fraction of the material intercepted by the Earth is dependent on its cross-sectional area (πR{{sup|2}}{{sub|Earth}}) as it passes through the expanding debris. Where M{{sub|ej}} is the mass of ejected material.<math display="block">M_{\text {Fraction intercepted }}=\frac{\pi R_{\text {Earth }}^{2}}{4 \pi r^{2}} M_{e j}</math>Assuming the intercepted material is distributed uniformly across the surface of the Earth (4πR{{sup|2}}{{sub|Earth}}), the mass surface density (Σ{{sub|ej}}) of the supernova ejecta on Earth is: <math display="block">
\Sigma_{e j}=\frac{M_{\text {Fraction intercepted }}}{A_{\text {surface,Earth }}}=\frac{M_{e j}}{16 \pi r^2}</math>The number of {{sup|60}}Fe atoms per unit area found on Earth can be estimated if the typical amount of {{sup|60}}Fe ejected from a supernova is known. This can be done by dividing the surface mass density (Σ{{sub|ej}}) by the atomic mass of {{sup|60}}Fe. <math display="block">
N_{60}=\left(\frac{M_{e j, 60} / m_{60}}{16 \pi r^2}\right)
</math>The equation for N{{sup|60}} can be rearranged to find the distance to the supernova.<math display="block">

r=\sqrt{\frac{M_{e j, 60}}{16 \pi m_{60} N_{60}}}
</math>An example calculation for the distance to the supernova point of origin is given below. This calculation uses speculative values for terrestrial {{sup|60}}Fe atom surface density (N{{sub|60}} ≈ 4 × 10{{sup|11}} atoms/m{{sup|2}}) and a rough estimate of the mass of {{sup|60}}Fe ejected by a supernova (10{{sup|-5}} M{{sub|☉}}). <math display="block">

r=\sqrt{\frac{10^{-5} M_{\odot}}{16 \pi\left(60 m_p\right) N_{60}}}

</math><math display="block">

r=3 \times 10^{18} m=100 p c

</math>More sophisticated analyses have been reported that take into consideration the [[flux]] and deposition of {{sup|60}}Fe as well as possible interfering background sources.<ref>{{Cite journal |last=Ertel |first=Adrienne F. |last2=Fry |first2=Brian J. |last3=Fields |first3=Brian D. |last4=Ellis |first4=John |date=20 April 2023 |title=Supernova Dust Evolution Probed by Deep-sea 60Fe Time History |url=https://doi.org/10.3847/1538-4357/acb699 |journal=The Astrophysical Journal |volume=947 |issue=2 |pages=58-83 |via=The Institute of Physics (IOP)}}</ref> 

Cobalt-60, the decay product of iron-60, emits 1.173&nbsp;MeV and 1.333&nbsp;MeV as it decays. These gamma-ray lines have long been important targets for [[gamma-ray astronomy]], and have been detected by the gamma-ray observatory [[INTEGRAL]]. The signal traces the [[Galactic plane]], showing that {{sup|60}}Fe synthesis is ongoing in our Galaxy, and probing [[Nucleosynthesis|element production]] in massive stars.<ref>{{Cite journal |last1=Harris |first1=M. J. |last2=Knödlseder |first2=J. |last3=Jean |first3=P. |last4=Cisana |first4=E. |last5=Diehl |first5=R. |last6=Lichti |first6=G. G. |last7=Roques |first7=J. -P. |last8=Schanne |first8=S. |last9=Weidenspointner |first9=G. |date=2005-04-01 |title=Detection of γ-ray lines from interstellar 60Fe by the high resolution spectrometer SPI |url=https://ui.adsabs.harvard.edu/abs/2005A&A...433L..49H |journal=Astronomy and Astrophysics |volume=433 |issue=3 |pages=L49–L52 |doi=10.1051/0004-6361:200500093 |arxiv=astro-ph/0502219 |bibcode=2005A&A...433L..49H |issn=0004-6361}}</ref><ref>{{Cite journal |last1=Wang |first1=W. |last2=Siegert |first2=T. |last3=Dai |first3=Z. G. |last4=Diehl |first4=R. |last5=Greiner |first5=J. |last6=Heger |first6=A. |last7=Krause |first7=M. |last8=Lang |first8=M. |last9=Pleintinger |first9=M. M. M. |last10=Zhang |first10=X. L. |date=2020-02-01 |title=Gamma-Ray Emission of 60Fe and 26Al Radioactivity in Our Galaxy |journal=The Astrophysical Journal |volume=889 |issue=2 |pages=169 |doi=10.3847/1538-4357/ab6336 |doi-access=free |arxiv=1912.07874 |bibcode=2020ApJ...889..169W |issn=0004-637X}}</ref>

== References ==
{{Reflist}}

Isotope masses from:
*{{NUBASE 2003}}

Isotopic compositions and standard atomic masses from:
*{{CIAAW2003}}
*{{CIAAW 2005}}

Half-life, spin, and isomer data selected from:
*{{NUBASE 2003}}
*{{NNDC}}
*{{CRC85|chapter=11}}

==Further reading==
*{{cite book
 |author=J. M. Nielsen
 |year=1960
 |title=The Radiochemistry of Iron
 |url=http://library.lanl.gov/cgi-bin/getfile?rc000015.pdf
 |publisher=[[United States National Academy of Sciences|National Academy of Sciences]]/[[United States National Research Council|National Research Council]]
}}

{{Navbox element isotopes}}

[[Category:Isotopes of iron| ]]
[[Category:Iron]]
[[Category:Lists of isotopes by element|Iron]]