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Register a new userThe Link Between the Local Bubble and Radioisotopic Signatures on Earth
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Traces of 2-3 Myr old 60Fe were recently discovered in a manganese crust and in lunar samples. We have found that this signal is extended in time and is present in globally distributed deep-sea archives. A second 6.5-8.7 Myr old signature was revealed in a manganese crust. The existence of the Local Bubble hints to a recent nearby supernova-activity starting 13 Myr ago. With analytical and numerical models generating the Local Bubble, we explain the younger 60Fe-signature and thus link the evolution of the solar neighborhood to terrestrial anomalies.
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The discovery of radionuclides like 60Fe with half-lives of million years in deep-sea crusts and sediments offers the unique possibility to date and locate nearby supernovae. We want to quantitatively establish that the 60Fe enhancement is the result of several supernovae which are also responsible for the formation of the Local Bubble, our Galactic habitat. 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 60Fe 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. The models are able to reproduce both the timing and the intensity of the 60Fe 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 60Fe (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 Earths orbit sometimes even twice as a result of reflection from the Local Bubbles outer shell, or, alternatively, through the supershell of the Local Bubble itself, injecting the 60Fe content of all previous supernovae at once, but over a longer time range.
Young stars and planets both grow by accreting material from the proto-stellar disks. Planetary structure and formation models assume a common origin of the building blocks, yet, thus far, there is no direct conclusive observational evidence correlating the composition of rocky planets to their host stars. Here we present evidence of a chemical link between rocky planets and their host stars. The iron-mass fraction of the most precisely characterized rocky planets is compared to that of their building blocks, as inferred from the atmospheric composition of their host stars. We find a clear and statistically significant correlation between the two. We also find that this correlation is not one-to-one, owing to the disk-chemistry and planet formation processes. Therefore rocky planet composition depends on the chemical composition of the proto-planetary disk and contains signatures about planet formation processes.
The goal of the Ariel space mission is to observe a large and diversified population of transiting planets around a range of host star types to collect information on their atmospheric composition. The planetary bulk and atmospheric compositions bear the marks of the way the planets formed: Ariels observations will therefore provide an unprecedented wealth of data to advance our understanding of planet formation in our Galaxy. A number of environmental and evolutionary factors, however, can affect the final atmospheric composition. Here we provide a concise overview of which factors and effects of the star and planet formation processes can shape the atmospheric compositions that will be observed by Ariel, and highlight how Ariels characteristics make this mission optimally suited to address this very complex problem.
We explored the statistical and compositional link between Chelyabinsk meteoroid and potentially hazardous asteroid (86039) 1999 NC43 to investigate their proposed relation proposed by Boroviv{c}ka et al. (2013). Using detailed computation we confirm that the orbit of the Chelyabinsk impactor is anomalously close to 1999 NC43. We find about (1-3) x 10-4 likelihood of that to happen by chance. Taking the standpoint that the Chelyabinsk impactor indeed separated from 1999 NC43 by a cratering or rotational fission event, we run a forward probability calculation, which is an independent statistical test. However, we find this scenario is unlikely at the about (10-3 -10-2) level. We also verified compositional link between Chelyabinska and 1999NC43. Mineralogical analysis of Chelyabinsk (LL chondrite) and (8) Flora (the largest member of the presumed LL chondrite parent family) shows that their olivine and pyroxene chemistries are similar to LL chondrites. Similar analysis of 1999 NC43 shows that its olivine and pyroxene chemistries are more similar to L chondrites than LL chondrites (like Chelyabinsk). We also took photometric observations of 1999 NC43 over 54 nights during two apparitions (2000, 2014). The lightcurve of 1999 NC43 resembles simulated lightcurves of tumblers in Short-Axis Mode with the mean wobbling angle 20-30 deg. While, a mechanism of the non-principal axis rotation excitation is unclear, we can rule out the formation of asteroid in disruption of its parent body as a plausible cause, as it is unlikely that the rotation of an asteroid fragment from catastrophic disruption would be nearly completely halted. Considering all these facts, we find the proposed link between the Chelyabinsk meteoroid and the asteroid 1999 NC43 to be unlikely.
The paper aims to study relation between the distributions of the young stellar objects (YSOs) of different ages and the gas-dust constituents of the S254-S258 star-formation complex. This is necessary to study the time evolution of the YSO distribution with respect to the gas and dust compounds which are responsible for the birth of the young stars. For this purpose we use correlation analysis between different gas, dust and YSOs tracers. We compared the large-scale CO, HCO$^+$, near-IR extinction, and far-IR {it Herschel} maps with the density of YSOs of the different evolutionary Classes. The direct correlation analysis between these maps was used together with the wavelet-based spatial correlation analysis. This analysis reveals a much tighter correlation of the gas-dust tracers with the distribution of Class I YSOs than with that of Class II YSOs. We argue that Class I YSOs which were initially born in the central bright cluster S255-IR (both N and S parts) during their evolution to Class II stage ($sim$2 Myr) had enough time to travel through the whole S254-S258 star-formation region. Given that the region contains several isolated YSO clusters, the evolutionary link between these clusters and the bright central S255-IR (N and S) cluster can be considered. Despite the complexity of the YSO cluster formation in the non-uniform medium, the clusters of Class II YSOs in the S254-258 star-formation region can contain objects born in the different locations of the complex.
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