相关论文: Formation of a Propeller Structure by a Moonlet in…

Several stars show deep transits consistent with discs of roughly 1 Solar radius seen at moderate inclinations, likely surrounding planets on eccentric orbits. We show that this configuration arises naturally as a result of planet-planet…

The accurate determination of Saturn's gravitational coefficients by Cassini could provide tighter constrains on Saturn's internal structure. Also, occultation measurements provide important information on the planetary shape which is often…

Stellar multiple systems play a pivotal role in cluster dynamics and stellar evolution, leading to intense astronomical phenomena like X-ray binaries, gamma-ray bursts, Type Ia supernova, and stellar mergers, which are prime sources of…

Narrow eccentric planetary ringlets have sharp edges, sizable eccentricity gradients, and a confinement mechanism that prevents radial spreading due to ring viscosity. Most proposed ringlet confinement mechanisms presume that there are one…

We discuss the formation of globules in planetary nebulae, typified by those observed in the Helix Nebula. We show that the properties of the globules, their number, mass, separation, and overall geometry strongly support a scenario in…

For its beautiful rings, active atmosphere and mysterious magnetic field, Saturn is a fascinating planet. It also holds some of the keys to understanding the formation of our Solar System and the evolution of giant planets in general. While…

Since 2004, the images obtained by Cassini spacecraft's on-board cameras have revealed the existence of several small satellites in the Saturn system. Some of these small satellites are embedded in arcs of particles. While these satellites…

We describe a model that accounts for the complex morphology of spiral density waves raised in Saturn's rings by the co-orbital satellites, Janus and Epimetheus. Our model may be corroborated by future Cassini observations of these…

Giant planets are expected to form within circumstellar disks, which shape their formation history and the local environment. Here, we consider the formation and structure of circumplanetary disks that arise during the late stages of giant…

The core-accretion mechanism for gas giant formation may be too slow to create all observed gas giant planets during reasonable gas disk lifetimes, but it has yet to be firmly established that the disk instability model can produce…

The mechanism through which meter-sized boulders grow to km-sized planetesimals in protoplanetary discs is a subject of active research, since it is critical for planet formation. To avoid spiralling into the protostar due to aerodynamic…

In a previous paper (Hedman and Nicholson 2013), we developed tools that allowed us to confirm that several of the waves in Saturn's rings were likely generated by resonances with fundamental sectoral normal modes inside Saturn itself. Here…

The Monoceros Ring (MRi) structure is an apparent stellar overdensity that has been postulated to entirely encircle the Galactic plane and has been variously described as being due to line-of-sight effects of the Galactic warp and flare or…

The secular perturbations exerted by an inclined satellite orbiting in a gap in a broad planetary ring tends to excite the inclinations of the nearby ring particles, and the ring's self-gravity can allow that disturbance to propagate away…

We have analyzed the highest-quality images to be obtained by Cassini of Saturn's main rings after the Saturn Orbit Insertion (SOI) and before the Ring Grazing Orbits (RGO) and Grand Finale (GF). These images are comparable to those of SOI…

A kinky and clumpy ringlet shares orbit with the moon Pan in the center of the 320-km wide Encke gap in Saturn's rings (Porco et al., 2005). The ringlet is mainly composed of micron-sized particles (Showalter, 1991, Hedman et al., 2011),…

The origin and long-term evolution of Saturn's rings is still an unsolved problem in modern planetary science. In this chapter we review the current state of our knowledge on this long-standing question for the main rings (A, Cassini…

Context. Protoplanetary discs are formed due to the fragmentation and collapse of giant molecular cloud cores. The physical properties and structure of a formed disc are of great importance when studying the onset of planet formation…

The radio lobes of the radio galaxy Hercules A contain intriguing ring-like structures concentric with the jet axis. To investigate the occurrence of such features, we have used hydrodynamic simulations of jets with a range of Mach numbers…

Stars form from the gravitational collapse of turbulent, magnetized molecular cloud cores. Our non-ideal MHD simulations reveal that the intrinsically anisotropic magnetic resistance to gravity during the core collapse naturally generates…