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For very fast spinning black holes with a>0.9953 the orbital velocity of a test particle unexpectly shows a positive radial gradient for low orbits, an effect of GR which has been overlooked so far. For a=0.99616 the maximum radial change…
The main-sequence solar-type star HD69830 has an unusually large amount of dusty debris orbiting close to three planets found via the radial velocity technique. In order to explore the dynamical interaction between the dust and planets, we…
We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope (UKIRT), of the Local Group spiral galaxy M33 (Triangulum). The main aim was to identify stars in the very final stage of their evolution, and for which the…
Stars with masses between roughly 1 and 8~$M_\odot$ end their lives on the asymptotic giant branch (AGB), when intense mass loss takes place. The outflows are generally accepted to be driven by radiation pressure acting on dust grains that…
Porosity is a key characteristic of the regolith on the surface of small bodies. The porosity of the regolith on the surface of asteroids is changed by applied pressure, and the relationship between pressure and porosity depends on the…
Deep SCUBA observations of NGC 1275 at 450 micron and 850 micron along with the application of deconvolution algorithms have permitted us to separate the strong core emission in this galaxy from the fainter extended emission around it. The…
Context. Recent observations of dust ejections from active asteroids, including (3200) Phaethon, have drawn considerable interest from planetary astronomers studying the generation and removal of small dust particles on asteroids. Aims. In…
New long-term Very Long Baseline Array observations of the well-known jet in the M87 radio galaxy at 43 GHz show that the jet experiences a sideways shift with an approximately 8-10 yr quasi-periodicity. Such jet wobbling can be indicative…
We study the effect of rotation on the spectrum of bound states for dust cores that source (quantum) black holes found in Eur. Phys. J. C 82 (2022) 10. The dust ball is assumed to spin rigidly with sufficiently slow angular velocity that…
Conditions for regolith landslides to occur on spinning, gravitating spheroidal asteroids and their aftermath are studied. These conditions are developed by application of classical granular mechanics stability analysis to the asteroid…
We present a study of the newly-discovered main-belt comet P/2008 R1 (Garradd), an object with the dynamical characteristics of an asteroid and the physical characteristics of a comet. Photometry sets a limit to the effective radius of the…
We present thermal infrared observations of the active asteroid (and Geminid meteoroid stream parent) 3200 Phaethon using the Very Large Telescope. The images, at 10.7 micron wavelength, were taken with Phaethon at its closest approach to…
In a multi-wavelength study of thermal emission and scattered light images we analyse the dust properties and structure of the debris disc around the A1-type main sequence star 49~Cet. As a basis for this study, we present new scattered…
Precise-Doppler experiments suggest that a massive (m sin i=0.86 M_J) planet orbits at semimajor axis a=3.4 AU around Epsilon Eridani, a nearby star with a massive debris disk. The dynamical perturbations from such a planet would mold the…
We investigate the dust and gas distribution in the disk around HD 142527 based on ALMA observations of dust continuum, 13CO(3-2), and C18O(3-2) emission. The disk shows strong azimuthal asymmetry in the dust continuum emission, while gas…
Conventional meteoroid theory assumes that the dominant mode of ablation is by evaporation following intense heating during atmospheric flight. In this paper we consider the question of whether sputtering may provide an alternative…
The structural coefficient of restitution describes the kinetic energy dissipation upon low-velocity (~0.1 m/s) impact of a small asteroid lander, MASCOT, against a hard, ideally elastic plane surface. It is a crucial worst-case input for…
Early-type galaxies exhibit thermal and molecular resonance emission from dust that is shed and heated through stellar mass loss as a subset of the population moves through the AGB phase of evolution. Because this emission can give direct…
We employed recent Gaia/DR2 data to investigate the dynamical status of the nearby (300 pc), old (2.5 Gyr) open cluster Ruprecht~147. We found prominent leading and trailing tails of stars along the cluster orbit, which demonstrates that…
We present subarcsecond observations at 2.7 and 1.4 mm of a sample of massive young stellar objects made with the BIMA millimetre array. For most sources the continuum emission on the smallest scales at 2.7 mm is dominated by free-free…