Related papers: Comet Hazard to the Earth

Giant planets are tens to thousands of times as massive as the Earth, and many times as large. Most of their volumes are occupied by hydrogen and helium, the primary constituents of the protostellar disks from which they formed.…

The Kuiper Belt of our solar system is a source of short-period comets that may have delivered water and other volatiles to Earth and the other terrestrial planets. However, the distribution of water and other volatiles in extrasolar…

The origin of hot Jupiters -- gas giant exoplanets orbiting very close to their host stars -- is a long-standing puzzle. Planet formation theories suggest that such planets are unlikely to have formed in-situ but instead may have formed at…

Terrestrial planets grew in a series of similar-sized collisions that swept up most of the next-largest bodies. Theia was accreted by the Earth to form the Moon according to the theory. Planetesimals likewise may have finished their…

During the last stages of the terrestrial planet formation, planets grow mainly through giant-impacts with large planetary embryos. The Earth's Moon was suggested to form through one of these impacts. However, since the proto-Earth has…

The majority of the transiting planets discovered by the Kepler mission (called super-Earths here, includes the so-called 'sub-Neptunes') orbit close to their stars. As such, photoevaporation of their hydrogen envelopes etch sharp features…

During orbital migration of a giant extrasolar planet via ejection of planetesimals (Murray et al.~1998), inner mean motion resonances can be strong enough to cause planetesimals to graze or impact the star. We integrate numerically the…

Impacts from icy and rocky bodies have helped shape the composition of solar system objects, for example the Earth-Moon system, or the recent impact of comet Shoemaker-Levy 9 with Jupiter. It is likely that such impacts also shape the…

Planet migration is the process by which a planet's orbital radius changes in time. The main agent for causing gas giant planet migration is the gravitational interaction of the young planet with the gaseous disk from which it forms. We…

A new effect of total neutrino conversion is possible when neutrino propagates through multi-layer medium of nonperiodic constant density layers. The effect can take place in the oscillations in the Earth of the Earth-core-crossing solar…

Outer satellites of the planets have distant, eccentric orbits that can be highly inclined or even retrograde relative to the equatorial planes of their planets. These irregular orbits cannot have formed by circumplanetary accretion and are…

We present a model to account for the observed debris disks around young white dwarfs and the presence of metal-lines in their spectra. Stellar evolution models predict that the mass-loss on the AGB will be pulsed; furthermore, observations…

We present several lines of evidence based on different kinds of observations to conclude that rotational fission has likely occurred for a fraction of the known Trans-Neptunian Objects (TNOs). It is also likely that a number of binary…

The widespread prevalence of close-in, nearly coplanar super-Earth- and sub-Neptune-sized planets in multiple-planet systems was one of the most surprising results from the Kepler mission. By studying a uniform sample of Kepler "multis"…

The orbital architecture of the Solar System is thought to have been sculpted by a dynamical instability among the giant planets. During the instability a primordial outer disk of planetesimals was destabilized and ended up on…

Short period planets are subject to intense energetic irradiations from their stars. It has been shown that this can lead to significant atmospheric mass-loss and create smaller mass planets. Here, we analyse whether the evaporation…

Many exoplanets in close-in orbits are observed to have relatively high eccentricities and large stellar obliquities. We explore the possibility that these result from planet-planet scattering by studying the dynamical outcomes from a large…

Planets in close-in orbits interact magnetically and tidally with their host stars. These interactions lead to a net torque that makes close-in planets migrate inward or outward depending on their orbital distance. We compare systematically…

Mini-Neptunes and volatile-poor super-Earths coexist on adjacent orbits in proximity to host stars such as Kepler-36 and Kepler-11. Several post-formation processes have been proposed for explaining the origin of the compositional…

Asymmetric debris discs have been found around stars other than the Sun; asymmetries are sometimes attributed to perturbations induced by unseen planets. The presence or absence of asymmetries in our own trans-Neptunian belt remains…