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[en] A relatively massive and moderately eccentric disk of trans-Neptunian objects (TNOs) can effectively counteract apse precession induced by the outer planets, and in the process shepherd highly eccentric members of its population into nearly stationary configurations that are antialigned with the disk itself. We were sufficiently intrigued by this remarkable feature to embark on an extensive exploration of the full spatial dynamics sustained by the combined action of giant planets and a massive trans-Neptunian debris disk. In the process, we identified ranges of disk mass, eccentricity, and precession rate that allow apse-clustered populations that faithfully reproduce key orbital properties of the much-discussed TNO population. The shepherding disk hypothesis is, to be sure, complementary to any potential ninth member of the solar system pantheon, and could obviate the need for it altogether. We discuss its essential ingredients in the context of solar system formation and evolution, and argue for their naturalness in view of the growing body of observational and theoretical knowledge about self-gravitating disks around massive bodies, extra-solar debris disks included.
[en] Modern studies of the early solar system routinely invoke the possibility of an orbital instability among the giant planets triggered by gravitational interactions between the planets and a massive exterior disk of planetesimals. Previous works have suggested that this instability can be substantially delayed (about hundreds of megayears) after the formation of the giant planets. Bodies in the disk are typically treated in a semi-active manner, wherein their gravitational force on the planets is included, but interactions between the planetesimals are ignored. We perform N-body numerical simulations using
GENGA, which makes use of GPUs to allow for the inclusion of all gravitational interactions between bodies. Although our simulated Kuiper Belt particles are more massive than the probable masses of real primordial Kuiper Belt objects, our simulations indicate that the self-stirring of the primordial Kuiper Belt is very important to the dynamics of the giant planet instability. We find that interactions between planetesimals dynamically heat the disk and typically prevent the outer solar system’s instability from being delayed by more than a few tens of megayears after giant planet formation. Longer delays occur in a small fraction of systems that have at least 3.5 au gaps between the planets and planetesimal disk. Our final planetary configurations match the solar system at a rate consistent with other previous works in most regards. Pre-instability heating of the disk typically yields final Jovian eccentricities comparable to the modern solar system’s value, which has been a difficult constraint to match in past works.
[en] The varying solar output is affected by the Sun’s activity and associated phenomena. Predictions of solar and geomagnetic activity are important for various technologies, including the operation of low-earth-orbiting satellites, electric power transmission grids, geophysical exploration and high-frequency radio communications. Annual averages of geomagnetic activity in cycle 23 were found to be large in comparison with other cycles. The dramatic variability from one cycle to the other in these parameters gives us unique opportunity to understand the physics of various associated phenomena. In this paper, we have analysed the solar cycles 22 and 23 and compared them with solar cycle 24 on the basis of 10.7 radio flux, sunspot number (Rz), solar flare index, cosmic ray intensity and interplanetary and geomagnetic parameters. (author)
[en] We point out serious shortcomings of a very recent article (Iorio in Astrophys. Space Sci. 364:126, 2019) wrongly claiming that the current precision with which we know orbits of planets in the Solar System rules out the possibility of gravitational polarization of the quantum vacuum. The main mistake is that the Sun and a planet are considered as an isolated binary system completely neglecting the existence of other planets and their crucial contribution to the gravitational polarization of the quantum vacuum.
[en] The modified gravitational theory by Hajdukovic, based on the idea that quantum vacuum contains virtual gravitational dipoles, predicts, among other things, anomalous secular precessions of the planets of the Solar System as large as ≃700–6,000 milliarceconds per century. We demonstrate that they are ruled out by several orders of magnitude by the existing bounds on any anomalous orbital secular rates obtained with the EPM and INPOP ephemerides.
[en] Micheli et al. (Nature 559:223, 2018) reported that a seven-parameter fit to the orbit of 1I/2017 U1 ‘Oumuamua indicated a non-gravitational acceleration in the anti-Solar direction, and attributed it to recoil from comet-like outgassing. The implied gas to dust ratio is at least 100 times greater than that of known Solar System comets. The reported collapse of the scatter of nearly contemporaneous coordinate residuals upon inclusion of the non-gravitational term in the orbital fits is difficult to understand. There are grounds for skepticism.
[en] Inner Oort cloud objects (IOCs) are trans-Plutonian for their entire orbits. They are beyond the strong gravitational influences of the known planets, yet close enough to the Sun that outside forces are minimal. Here we report the discovery of the third known IOC after Sedna and 2012 VP113, called 2015 TG387. This object has a perihelion of 65 ± 1 au and semimajor axis of 1170 ± 70 au. The longitude of perihelion angle, , for 2015 TG387 is between that of Sedna and 2012 VP113 and thus similar to the main group of clustered extreme trans-Neptunian objects (ETNOs), which may be shepherded into similar orbital angles by an unknown massive distant planet called Planet X, or Planet Nine. The orbit of 2015 TG387 is stable over the age of the solar system from the known planets and Galactic tide. When including outside stellar encounters over 4 Gyr, 2015 TG387's orbit is usually stable, but its dynamical evolution depends on the stellar encounter scenarios used. Surprisingly, when including a massive Planet X beyond a few hundred au on an eccentric orbit that is antialigned in longitude of perihelion with most of the known ETNOs, we find that 2015 TG387 is typically stable for Planet X orbits that render the other ETNOs stable as well. Notably, 2015 TG387's argument of perihelion is constrained, and its longitude of perihelion librates about 180° from Planet X’s longitude of perihelion, keeping 2015 TG387 antialigned with Planet X over the age of the solar system.
[en] The condition, for determining the Hill stability of a coplanar four-body system, is analyzed for the particular situation where the mass of a body is much greater than the other three. In this case, the criterion can be expressed in a closed form, which makes it easier to judge the stability of a system or predict the stable regions described by physical and orbital parameters. The criterion is applied to nine known four-body systems in our Solar System. Besides, the situations where a passing star moving on a parabolic or hyperbolic orbit encounters a triple system are considered. The Hill stability of all extrasolar triple systems are investigated during encounters of a passing star.
[en] Detection of cosmic ray fluxes makes it possible to study dynamics of the interplanetary magnetic field and gain information about processes that occur both on the solar surface and in the entire Solar system. The main variations in the cosmic ray intensity are 27-day variations and Forbush effects. These variations are caused by complex spatial solar-plasma formations resulting from various processes on the solar surface and propagating in space with widely varying velocities. The data recorded by the PAMELA magnetic spectrometer on board the Resurs-DK1 satellite in 2006–2016 are used.
[en] In our Galaxy, around 1 to 2 supernovae (SN) explode over the course of 100 years. Such a titanic event happened during the last 10 Million years close to our solar system, so to speak on our doorstep. The ejected debris has entered our solar- system, and a fraction lodged on our Earth and on the Moon. Clear signals are long-living radioisotopes, which do not exist naturally or at low amounts on Earth; such as 60Fe (t1/2 = 2.6 Ma). After a short summary of measurement results of 60Fe, performed at TU-Munich and at ANU (Canberra), I will present first indications of another supernova-formed radioisotope in deep-sea crusts, 53Mn (t1/2 = 3.7 Ma). The, so called, local fluff (local interstellar cloud), presently imbedding the solar system, could originate from these close-by SNe, hence should comprise 60Fe that enters the solar system now. Search in 500 kg snow from the Antarctica reveals a signal of 60Fe that supports a recent SN-origin of the local fluff. The time slot where we found 60Fe deposition in crusts and sediments, coincide with a drop in Earth’s temperature, that happened between 2 or 3 Million years before now, and it enforced glaciations on the Earth. These glaciations are considered the cause for the evolution and development of mankind. Possible correlations will be discussed. (author)