Interstellar planets

Лекция посвящена изучению роли гравитационного рассеяния в эволюции планетных систем. В рамках этого механизма объясняется происхождение облака Оорта и свободных от родительской звезды астероидов, комет и планет (АКП).The lecture is devoted to the study of the role of gravitational scattering in the evolution of planetary systems. This mechanism explains the origin of the Oort cloud and free asteroids, comets, and planets (ACPs) from the parent star

Interstellar Planets and Comets: Origin Mechanisms, Discovery Ways, and Statistics

We consider mechanisms of origin and detection of interstellar planets and comets.Рассмотрены механизмы образования и обнаружения межзвездных планет и комет

Extremely Wide “Binary Stars”

В кратком обзоре ставится проблема эволюционной связи центральных околоядерных S-звезд и сверхскоростных звезд (СЗ), которые в недалеком прошлом были компонентами общей родительской двойной звезды, до ее захвата в галактический центр, населенный сверхмассивной черной дырой (СМЧД). Представляет интерес взаимной «реконструкции» популяций S-звезд и СЗ, рассчитанных в рамках классического сценария Хиллза, по принципу дополнения их наблюдательных данных. Обсуждается возможность «восстановления» из наблюдений S-СЗ-пар в Галактике.In a brief review, the problem of the evolutionary relationship between central near-nuclear S-stars and hypervelocity stars (HVS), which in the recent past were components of a parent binary star, before its capture into the galactic center inhabited by a supermassive black hole (SMBH), is posed. Of interest is the mutual ”reconstruction” of populations of S stars and HVS calculated within the framework of the classic Hills scenario, based on the principle of supplementing their observational data. The possibility of ”recovery” from observations of S-HVS-pairs in the Galaxy is discussed

On the Scenario of the Moon Formation

Рассматривается задача гравитационного захвата околосолнечной Луны как возможный вариант образования спутника Земли. В модели трех тел (Солнце, Земля, Луна) производится отбор кривых сближений Луны и Земли, допускающих пересечение сферы Хилла Земли. Такие варианты повторяются в модели N-тел для оценки влияния приливных сил на перекачку орбитального момента Луны (P M orb) относительно Земли в ее собственный (P M s ∼ 10−6P M orb), что не приводит к захвату в короткой шкале времени ∼ 100 лет. Как показывает моделирование, захват Луны за одно сближение реализуется при учете небольшого (≈ 0.05 % от орбитальной скорости Луны) ее «притормаживания» за счет, например, столкновения с астероидом.The problem of gravitational capture of the Moon as near-sun planet is considered as a possible variant of the formation of the Earth satellite. In the model of three bodies (Sun, Earth, Moon), the Moon and Earth approaching trajectories are selected, allowing the intersection of the Earth’s Hill sphere. Such variants are repeated in the N-body model to assess the effect of tidal forces on the transfer of the orbital moment of the Moon (P M orb) relative to the Earth into its own (P M s ∼ 10−6P M orb), which does not lead to capture in a short timescale ∼ 100 years. It was shown that the capture of the Moon in one approach is realized if one takes into account a small (≈ 0.05 % of the orbital velocity of the Moon) “braking” due, for example, to a collision with an asteroid

Survival Probability for a Hypervelocity Star in Close Neighborhood of a Supermassive Black Hole

We present the results of numerical simulation on the probability of formation of a Hypervelocity Star (HVS) in the scenario of dynamic capture of a close binary system by the central black hole in the Galaxy and on the probability of its survival in the strong tidal field in the vicinity of the black hole. The results have been obtained for a series of pericentric distances. We applied a two-level numerical simulation implemented at first in the framework of the three-body problem used for evaluation of the HVS ejection velocity and then as an N-body approach that allowed us to establish the final status of the star: the degree of its destruction and mass loss. Probability estimations are based on a statistical ensemble of 10 000 initial configurations of the close binary with respect to the orbital phase of the components as well as to the inclination of the binary orbit to the plane of the orbit around the super-massive black hole and on the ensemble of 50 configurations for the three-body and N-body approaches, respectively

Ejection of Stars with Relativistic Velocities

We present the results of numerical simulations performed in terms of modified Hills' scenario involving two supermassive black holes (SMBHs). In contrast to the classic Hills scenario (Hills 1988), here one component of the ordinary stellar binary system is replaced with a SMBH that provides a kinetic resource for ejecting a star (the secondary component of the binary) with relativistic velocity (RVS). We examine the conditions that favor relativistic ejections of stars, depending on the pericentric approach, the mass ratio of two SMBHs, and the orbital configuration of the binary system. Applying the simple criteria helped us to sort out the results of numerical simulations by the outcome: conservation of the orbital configuration of the binary system, dynamic recapture of the star by the central SMBH, emission of hypervelocity stars (HVSs), and RVS ejection. In the framework of N-body simulations we estimate the probability for a star to survive in the cross-field of two SMBHs during the ejection with relativistic velocity, and discuss the probability of the detection of RVSs in our Galaxy in the cases where such stars are generated in distant interacting galaxies undergoing a merger of their central parts occupied by SMBHs

Kinematics of a planetary system near a Supermassive Black Hole

We simulate the dynamic capture of a planetary system in the vicinity of a Supermassive Black Hole in order to study the spectrum of scattering velocities of small space bodies depending on the initial configuration, variations in the angle between the near-stellar and “near-hole” orbital planes and pericentric distance. The relevance of this problem is discussed in connection with the high observed frequency of tidal destruction of stars and the problem of the formation of free interstellar planets, including high-velocity class.В работе моделируется динамический захват планетной системы в окрестность сверхмассивной черной дыры (СМЧД) с целью изучения спектра скоростей рассеяния малых космических тел в зависимости от начальной конфигурации, вариации угла между околозвездной и «околодырной» орбитальными плоскостями и перицентрического сближения. Обсуждается актуальность данной задачи в связи с высокой наблюдаемой частотой приливных разрушений звезд и проблемой образования свободных межзвездных планет, включая класс сверхскоростных

Mitochondrial genome diversity on the Central Siberian Plateau with particular reference to the prehistory of northernmost Eurasia.

The Central Siberian Plateau was the last geographic area in Eurasia to become habitable by modern humans after the Last Glacial Maximum (LGM). Through a comprehensive dataset of mitochondrial DNA (mtDNA) genomes retained in the remnats of earlier ("Old") Siberians, primarily the Ket, Tofalar, and Todzhi, we explored genetic links between the Yenisei-Sayan region and Northeast Eurasia (best represented by the Yukaghir) over the last 10,000 years. We generated 218 new complete mtDNA sequences and placed them into compound phylogenies with 7 newly obtained and 70 published ancient mitochondrial genomes. We have considerably extended the mtDNA sequence diversity (at the entire mtDNA genome level) of autochthonous Siberians, which remain poorly sampled, and these new data may have a broad impact on the study of human migration. We compared present-day mtDNA diversity in these groups with complete mitochondrial genomes from ancient samples from the region and placed the samples into combined genealogical trees. The resulting components were used to clarify the origins and expansion history of mtDNA lineages that evolved in the refugia of south-central Siberia and beyond, as well as multiple phases of connection between this region and distant parts of Eurasia