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The majority of extrasolar planets discovered to date have significantly eccentric orbits, some if not all of which may have been produced through planetary migration. During this process, any planets interior to such an orbit would…
Coagulation theory predicts that micron-sized dust grains grow into pebbles which drift inward towards the star, when they reach sizes of mm-cm. When they cross the orbit of a planet, a fraction of these drifting pebbles will be accreted.…
Instabilities and strong dynamical interactions between multiple giant planets have been proposed as a possible explanation for the surprising orbital properties of extrasolar planetary systems. In particular, dynamical instabilities seem…
In a recent paper we proposed that the giant planets' primordial orbits may have been eccentric (~0.05), and used a suite of dynamical simulations to show outcomes of the giant planet instability that are consistent with their present-day…
For a hypothetical planet on a highly eccentric orbit, we have calculated the osculating orbital parameters and its closest approaches to Earth and Moon over a period of 750 kyr. The approaches which are close enough to influence the…
Over a hundred rocky planets orbiting Sun-like stars in very short orbital periods (<1 day) have been discovered by the Kepler mission. These planets, known as ultra-short-period (USP) planets, are unlikely to have attained their orbits in…
Over the course of 3.1 years we determined the position of Mars on 75 dates using a handheld cross staff and two to five bright reference stars of known right ascension and declination on each occasion. On average the observed positions of…
Contrary to Earth, which has a small orbital eccentricity, some exoplanets discovered in the insolation habitable zone (HZ) have high orbital eccentricities (e.g., up to an eccentricity of $\sim0.97$ for HD~20782~b). This raises the…
In recent years several planets have been discovered at wide orbits (>100 AU) around their host stars. Theoretical studies encounter difficulties in explaining their formation and origin. Here we propose a novel scenario for the production…
In this work, we study the continuation of a periodic orbit on a relatively large scale and discover the existence of convergence under certain conditions, which has profound significance in research on asteroids and can provide a total…
Distribution of eccentricities of very wide (up to 10 kau) low-mass binaries in the solar neighborhood is studied using the catalog of El-Badry and Rix (2018) based on Gaia. Direction and speed of relative motions in wide pairs contain…
A simple question of celestial mechanics is investigated: in what regions of phase space near a binary system can planets persist for long times? The planets are taken to be test particles moving in the field of an eccentric binary system.…
The capture of a compact object in a galactic nucleus by a massive black hole (MBH) is the best way to map space and time around it. Compact objects such as stellar black holes on a capture orbit with a very high eccentricity have been…
Numerical hydrodynamics calculations are performed to determine conditions under which giant planet eccentricities can be excited by parent gas disks. Unlike in other studies, Jupiter-mass planets are found to have their eccentricities…
All circumbinary planets currently detected are in orbits that are almost coplanar to the binary orbit. While misaligned circumbinary planets are more difficult to detect, observations of polar aligned circumbinary gas and debris disks…
Planets with non-zero obliquity and/or orbital eccentricity experience seasonal variations of stellar irradiation at local latitudes. The extent of the atmospheric response can be crudely estimated by the ratio between the orbital timescale…
With 16-month Kepler data, 14 long-period (40 d - 265 d) eclipsing binaries on highly eccentric orbits (minimum e between 0.5 and 0.85) are recognized from their closely separated primary and secondary eclipses (\Delta t_I,II = 3 d - 10 d).…
A number of irregular moons of the Jovian planets have recently been discovered. Most adequate way of their origin is capture, but detailed mechanism is unknown. A few possibilities are discussed: collisions, gas drag, tidal destruction of…
We investigate the spin behavior of close-in rocky planets and the implications for their orbital evolution. Considering that the planet rotation evolves under simultaneous actions of the torque due to the equatorial deformation and the…
The significant orbital eccentricities of most giant extrasolar planets may have their origin in the gravitational dynamics of initially unstable multiple planet systems. In this work, we explore the dynamics of two close planets on…