Time-resolved 2-million-year-old supernova activity discovered in Earth’s microfossil record

Ludwig, Peter; Bishop, S.; Egli, Ramón; Chernenko, Valentyna; Deneva, Boyana; Faestermann, T.; Famulok, Nicolai; Fimiani, L.; Gómez-Guzmán, J.M.; Hain, Karin; Korschinek, G.; Hanzlik, Marianne; Merchel, Silke; Rugel, G.

doi:10.1073/pnas.1601040113

Cited by 94 publications

(106 citation statements)

References 111 publications

(243 reference statements)

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“…Similar signatures have been found in lunar samples [6] and in microfossil records [7]. These excesses would seem to indicate that the Solar System passed through the debris field of multiple supernova events in the last 10 million years, as discussed in [8].…”

Section: Arxiv:161200006v2 [Nucl-ex] 2 Mar 2017supporting

confidence: 73%

Activity measurement of Fe60 through the decay of Co60m and confirmation of its half-life

et al. 2017

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The half-life of the neutron-rich nuclide, 60 Fe has been in dispute in recent years. A measurement in 2009 published a value of (2.62 ± 0.04) × 10 6 years, almost twice that of the previously accepted value from 1984 of (1.49 ± 0.27) × 10 6 years. This longer half-life was confirmed in 2015 by a second measurement, resulting in a value of (2.50 ± 0.12) × 10 6 years. All three half-life measurements used the grow-in of the γ-ray lines in 60 Ni from the decay of the ground state of 60 Co (t 1/2 =5.27 years) to determine the activity of a sample with a known number of 60 Fe atoms. In contrast, the work presented here measured the 60 Fe activity directly via the 58.6 keV γ-ray line from the short-lived isomeric state of 60 Co (t 1/2 =10.5 minutes), thus being independent of any possible contamination from long-lived 60g Co. A fraction of the material from the 2015 experiment with a known number of 60 Fe atoms was used for the activity measurement, resulting in a half-life value of (2.72 ± 0.16) × 10 6 years, confirming again the longer half-life. In addition, 60 Fe/ 56 Fe isotopic ratios of samples with two different dilutions of this material were measured with Accelerator Mass Spectrometry (AMS) to determine the number of 60 Fe atoms. Combining this with our activity measurement resulted in a half-life value of (2.69 ± 0.28) × 10 6 years, again agreeing with the longer half-life.

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Section: Arxiv:161200006v2 [Nucl-ex] 2 Mar 2017supporting

confidence: 73%

Activity measurement of Fe60 through the decay of Co60m and confirmation of its half-life

et al. 2017

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“…They were able to extract 60 Fe from magnetofossils and quantify abundances using a mass spectrometer. Further analysis recently reported by [186] confirms the direct detection of live 60 Fe atoms contained within secondary iron oxides, including magnetofossils, which are fossilized chains of magnetite crystals produced by magnetoactive bacteria. They suggest that the 60 Fe signal begins 2.6 -2.8 Myr ago, peaks around 2.2 Myr earlier and terminates around 1.7 Myr earlier, consistent with the time periods deduced from other data such as deep-ocean crusts and lunar samples.…”

Section: Fe Radioisotope Observations As Indicators Of Nearby Supesupporting

confidence: 65%

Effect of Supernovae on the Local Interstellar Material

Frisch¹,

Dwarkadas²

2016

Handbook of Supernovae

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A range of astronomical data indicates that ancient supernovae created the galactic environment of the Sun and sculpted the physical properties of the interstellar medium near the heliosphere. In this paper we review the characteristics of the local interstellar medium that have been affected by supernovae. The kinematics, magnetic field, elemental abundances, and configuration of the nearest interstellar material support the view that the Sun is at the edge of the Loop I superbubble, which has merged into the low density Local Bubble. The energy source for the higher temperature X-ray emitting plasma pervading the Local Bubble is uncertain. Winds from massive stars and nearby supernovae, perhaps from the Sco-Cen Association, may have contributed radioisotopes found in the geologic record and galactic cosmic ray population. Nested supernova shells in the Orion and Sco-Cen regions suggest spatially distinct sites of episodic star formation. The heliosphere properties vary with the pressure of the surrounding interstellar cloud. A nearby supernova would modify this pressure equilibrium and thereby severely disrupt the heliosphere as well as the local interstellar medium.

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“…In order to prove this hypothesis, they analysed magnetofossils of a sediment core from the eastern equatorial Pacific. The results (Ludwig et al 2016) indeed show a comparatively weaker 60 Fe signal in layers spanning a time range of about 1 Myr, with the maximum again located at 2.2 Myr ago.…”

Section: Introductionmentioning

confidence: 66%

Numerical studies on the link between radioisotopic signatures on Earth and the formation of the Local Bubble

Schulreich

Breitschwerdt

Feige

et al. 2017

A&A

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Context. The discovery of radionuclides like 60 Fe with half-lives of million years in deep-sea crusts and sediments offers the unique possibility to date and locate nearby supernovae. Aims. We want to quantitatively establish that the 60 Fe enhancement is the result of several supernovae which are also responsible for the formation of the Local Bubble, our Galactic habitat. Methods. We performed three-dimensional hydrodynamic adaptive mesh refinement simulations (with resolutions down to subparsec scale) of the Local Bubble and the neighbouring Loop I superbubble in different homogeneous, self-gravitating environments. For setting up the Local and Loop I superbubble, we took into account the time sequence and locations of the generating core-collapse supernova explosions, which were derived from the mass spectrum of the perished members of certain stellar moving groups. The release of 60 Fe and its subsequent turbulent mixing process inside the superbubble cavities was followed via passive scalars, where the yields of the decaying radioisotope were adjusted according to recent stellar evolution calculations. Results. The models are able to reproduce both the timing and the intensity of the 60 Fe excess observed with rather high precision, provided that the external density does not exceed 0.3 cm −3 on average. Thus the two best-fit models presented here were obtained with background media mimicking the classical warm ionised and warm neutral medium. We also found that 60 Fe (which is condensed onto dust grains) can be delivered to Earth via two physical mechanisms: either through individual fast-paced supernova blast waves, which cross the Earth's orbit sometimes even twice as a result of reflection from the Local Bubble's outer shell, or, alternatively, through the supershell of the Local Bubble itself, injecting the 60 Fe content of all previous supernovae at once, but over a longer time range.

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Time-resolved 2-million-year-old supernova activity discovered in Earth’s microfossil record

Cited by 94 publications

References 111 publications

Activity measurement of Fe60 through the decay of Co60m and confirmation of its half-life

Activity measurement of Fe60 through the decay of Co60m and confirmation of its half-life

Effect of Supernovae on the Local Interstellar Material

Numerical studies on the link between radioisotopic signatures on Earth and the formation of the Local Bubble

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