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[en] In the search for habitable planets, the ultimate aspiration is finding an extraterrestrial technical civilization. We already lost a half of century for an active search for extraterrestrial civilizations. Should we lose another half? If all civilizations in the Universe are only recipients and not message-sending civilizations, then no SETI (Search for Extraterrestrial Intelligence) searches make any sense. Detecting only leaked radio signals is a hard job with present resources. Fear from the extraterrestrials is unfounded, having in mind physical difficulties and requirements of the interstellar travel. If possible extraterrestrial civilizations are more advanced than ours then they can pick up life signs from Earth easier than we can from their planets at present. Here we propose a scientifically based METI (Messaging to Extraterrestrial Intelligence) program.
[en] Comets are important “eyewitnesses” of Solar System formation and evolution. Important tests to determine the chemical composition and to study the physical processes in cometary nuclei and coma need data in the UV range of the electromagnetic spectrum. Comprehensive and complete studies require additional ground-based observations and in situ experiments. We briefly review observations of comets in the ultraviolet (UV) and discuss the prospects of UV observations of comets and exocomets with space-borne instruments. A special reference is made to the World Space Observatory-Ultraviolet (WSO-UV) project.
[en] It is shown that a number of superfast, with periods d, exoplanets revolve around parent stars with periods, near-commensurate with and/or , where the exoplanet resonance timescale s agrees fairly well with the period s of the so-called “cosmic oscillation” (the probability that the two timescales would coincide by chance is near ; the period was discovered first in the Sun, and later on—in other objects of Cosmos). True nature of the exoplanet resonance is unknown.
[en] We discuss the detection in the Outer Solar System Origins Survey (OSSOS) of two objects in Neptune’s distant 9:1 mean motion resonance at semimajor axis a ≈ 130 au. Both objects are securely resonant on 10 Myr timescales, with one securely in the 9:1 resonance’s leading asymmetric libration island and the other in either the symmetric or trailing asymmetric island. These objects are the largest semimajor axis objects with secure resonant classifications, and their detection in a carefully characterized survey allows for the first robust resonance population estimate beyond 100 au. The detection of these objects implies a 9:1 resonance population of 1.1 × 104 objects with H r < 8.66 (D ≳ 100 km) on similar orbits (95% confidence range of ∼(0.4–3) × 104). Integrations over 4 Gyr of an ensemble of clones spanning these objects’ orbit-fit uncertainties reveal that they both have median resonance occupation timescales of ∼1 Gyr. These timescales are consistent with the hypothesis that these objects originate in the scattering population but became transiently stuck to Neptune’s 9:1 resonance within the last ∼1 Gyr of solar system evolution. Based on simulations of a model of the current scattering population, we estimate the expected resonance sticking population in the 9:1 resonance to be 1000–4500 objects with H r < 8.66; this is marginally consistent with the OSSOS 9:1 population estimate. We conclude that resonance sticking is a plausible explanation for the observed 9:1 population, but we also discuss the possibility of a primordial 9:1 population, which would have interesting implications for the Kuiper Belt’s dynamical history.
[en] We demonstrate that, while the proposed Gravitational Dark-force Theory (of Nyambuya (New Astron. 67:1, 2019b) here-in Paper II) predicts an extra-anomalous apsidal precession for Solar planets due to the gravitational dark-force on the orbits of these planets, the predicted extra-anomalous apsidal precession is so small—so much that—it can not account for the observed extra-anomalous apsidal precession of Solar planets. This null result is important in that it informs us that whatever may be the cause of the extra-anomalous apsidal precession, it is not the proposed gravitational dark-force.
[en] 1I/‘Oumuamua is the first of likely many small bodies of extrasolar origin to be found in the solar system. These interstellar objects (ISOs) are hypothesized to have formed in extrasolar planetary systems prior to being ejected into interstellar space and subsequently arriving at the solar system. This paper discusses necessary considerations for tracing ISOs back to their parent stars via trajectory analysis and places approximate limits on doing so. Results indicate that the capability to backtrace ISOs beyond the immediate solar neighborhood is presently constrained by the quality of stellar astrometry, a factor poised for significant improvement with upcoming Gaia data releases. Nonetheless, prospects for linking 1I or any other ISO to their respective parent stars appear unfavorable on an individual basis due to gravitational scattering from random stellar encounters, which limit traceability to the past few tens of millions of years. These results, however, do not preclude the possibility of occasional success, particularly after considering the potential for observational bias favoring the discovery of younger ISOs, together with the anticipated rise in the ISO discovery rate under forthcoming surveys.
[en] Aside from recording stellar nucleosynthesis, a few elements in presolar grains can also provide insights into the galactic chemical evolution (GCE) of nuclides. We have studied the carbon, silicon, iron, and nickel isotopic compositions of presolar silicon carbide (SiC) grains from asymptotic giant branch (AGB) stars to better understand GCE. Since only the neutron-rich nuclides in these grains have been heavily in uenced by the parent star, the neutron-poor nuclides serve as GCE proxies. Using CHILI, a new resonance ionization mass spectrometry (RIMS) instrument, we measured 74 presolar SiC grains for all iron and nickel isotopes. With the CHARISMA instrument, 13 presolar SiC grains were analyzed for iron isotopes. All grains were also measured by NanoSIMS for their carbon and silicon isotopic compositions. A comparison of the measured neutron-rich isotopes with models for AGB star nucleosynthesis shows that our measurements are consistent with AGB star predictions for low-mass stars between half-solar and solar metallicity. Furthermore, our measurements give an indication on the 22Ne(,n)25Mg reaction rate. In terms of GCE, we nd that the GCE-dominated iron and nickel isotope ratios, 54Fe/56Fe and 60Ni/58Ni, correlate with their GCE-dominated counterpart in silicon, 29Si/28Si. The measured GCE trends include the Solar System composition, showing that the Solar System is not a special case. However, as seen in silicon and titanium, many presolar SiC grains are more evolved for iron and nickel than the Solar System. This con rms prior ndings and agrees with observations of large stellar samples that a simple age-metallicity relationship for GCE cannot explain the composition of the solar neighborhood.
[en] We report the discovery and dynamical analysis of 2015 BP, an extreme Trans-Neptunian Object detected detected by the Dark Energy Survey at a heliocentric distance of 55 AU and absolute magnitude Hr= 4.3. The current orbit, determined from a 1110-day observational arc, has semi-major axis 450 AU, eccentricity 0.92 and inclination 54 degrees. With these orbital elements, 2015 BP is the most extreme TNO discovered to date, as quantified by the reduced Kozai action, which is is a conserved quantity at fixed semi-major axis for axisymmetric perturbations. We discuss the orbital stability and evolution of this object in the context of the known Solar System, and find that 2015 BP displays rich dynamical behavior, including rapid diffusion in semi-major axis and more constrained variations in eccentricity and inclination. We also consider the long term orbital stability and evolutionary behavior within the context of the Planet Nine Hypothesis, and find that BP adds to the circumstantial evidence for the existence of this proposed new member of the Solar System, as it would represent the first member of the population of high-i, -shepherded TNOs.
[en] Type Ia supernovae (SNeIa), used as one of the standard candles in astrophysics, are believed to form when the mass of the white dwarf approaches Chandrasekhar mass limit. However, observations in last few decades detected some peculiar SNeIa, which are predicted to be originating from white dwarfs of mass much less than the Chandrasekhar mass limit or much higher than it. Although the unification of these two sub-classes of SNeIa was attempted earlier by our group, in this work, we, for the first time, explain this phenomenon in terms of just one property of the white dwarf which is its central density. Thereby we do not vary the fundamental parameters of the underlying gravity model in the contrary to the earlier attempt. We effectively consider higher order corrections to the Starobinsky-f(R) gravity model to reveal the unification. We show that the limiting mass of a white dwarf is ∼ M⊙ for central density ρc ∼ 1.4×108 g/cc, while it is ∼ 2.8M⊙ for ρc ∼1.6× 1010 g/cc under the same model parameters. We further confirm that these models are viable with respect to the solar system test. This perhaps enlightens very strongly the long standing puzzle lying with the predicted variation of progenitor mass in SNeIa.
[en] The theoretical interpretation of dark matter direct detection experiments is hindered by uncertainties of the microphysics governing the dark matter-nucleon interaction, and of the dark matter density and velocity distribution inside the Solar System. These uncertainties are especially relevant when confronting a detection claim to the null results from other experiments, since seemingly conflicting experimental results may be reconciled when relaxing the assumptions about the form of the interaction and/or the velocity distribution. We present in this paper a halo-independent method to calculate the maximum number of events in a direct detection experiment given a set of null search results, allowing for the first time the scattering to be mediated by an arbitrary combination of various interactions (concretely we consider up to 64). We illustrate this method to examine the compatibility of the dark matter interpretation of the three events detected by the silicon detectors in the CDMS-II experiment with the null results from XENON1T and PICO-60.