A5082952271- Astro and Planetary Science
- Planetary Science and Exploration
- Stellar, planetary, and galactic studies
- Isotope Analysis in Ecology
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Atmospheric Ozone and Climate
- Adaptive optics and wavefront sensing
- Astrophysics and Star Formation Studies
- Particle Dynamics in Fluid Flows
- Space Exploration and Technology
- Astronomical Observations and Instrumentation
- Dust and Plasma Wave Phenomena
- Space Science and Extraterrestrial Life
- Aeolian processes and effects
- Laser-induced spectroscopy and plasma
- History and Developments in Astronomy
- Space exploration and regulation
- Earthquake Detection and Analysis
- Atmospheric aerosols and clouds
- Geological and Geochemical Analysis
- Nuclear Physics and Applications
- Historical and Architectural Studies
Planetary Science Institute
2019-2024
University of Namur
2023
Massachusetts Institute of Technology
2015-2022
Moscow Institute of Thermal Technology
2021
South African Radio Astronomy Observatory
2016-2020
Astronomical Observatory
2017
University of the Western Cape
2016
Northern Arizona University
2016
University of Colorado Boulder
2000-2002
Laboratory for Atmospheric and Space Physics
2000-2002
Photoelectric charging measurements are presented of dust grains in vacuum for isolated and near a photoemissive surface. Isolated reach positive-equilibrium floating potential, dependent upon the work function particle, which causes emitted electrons to be returned. Grains dropped past photoemitting surface negative potential sum collected currents is zero. The particles tested 90-106 microm diameter composed Zn, Cu, graphite, glass.
Experiments are performed pertaining to the charging of single dust particles in space due three effects: (1) photoemission, (2) collection electrons from a photoemissive surface, and (3) triboelectric charging. The tested 90–106 μm diameter include JSC‐1 (lunar regolith simulant) JSC‐Mars‐1 (Martian simulant). Isolated conducting grains (Zn, Cu, graphite) illuminated by ultraviolet light reach positive equilibrium floating potential (a few volts) that depends upon work function particle....
Dusty regolith particles accumulate charge through grain‐grain contact and with various surfaces. These processes affect vertical horizontal transport may cause electrical discharges in dust storms. We report the results of a simple experimental setup used to investigate charging properties two planetary analog samples: lunar (JSC‐1) Martian (JSC‐Mars‐1) simulants. In these experiments, are brought into surfaces known work functions (metals: Co, Ni, Au, Pt, silica glass), resulting charges...
Dust grains have been observed to levitate above the surface of Moon and as spokes in Saturn's rings. In order gain a better understanding these observations, we performed levitation experiments on dust low‐density plasma. Plasma sheath potential profiles, measured by an emissive probe, are used determine spatial dependence electric force grain sheath. The height agrees with values calculated using orbital‐motion‐limited charging theory balance equations. Levitating were also exposed...
Two narrow and dense rings (called C1R C2R) were discovered around the Centaur object (10199) Chariklo during a stellar occultation observed on 2013 June 3. Following this discovery, we planned observations of several occultations by Chariklo's system in order to better characterize physical properties ring main body. Here, use 12 successful occulations between 2014 2016. They provide profiles (physical width, opacity, edge structure) constraints radii pole position. Our new are currently...
Abstract The discovery of two thin rings around the ∼ 250 km sized Centaur Chariklo was first its kind, and their formation evolutionary mechanisms are not well understood. Here, we explore a single shepherd satellite as mechanism to confine Chariklo’s rings. We also investigate impact such perturber on reaccretion, which is likely process for material located outside Roche limit. have modified N -body code that developed Saturn’s model system. Exploration reasonable parameter space...
Abstract Ultrahot Jupiters (UHJs) are likely doomed by tidal forces to undergo orbital decay and eventual disruption their stars, but the timescale over which this process unfolds is unknown. We present results from a long-term project monitor UHJ transits. recovered WASP-12 b’s rate of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>P</mml:mi> </mml:mrow> <mml:mo>̇</mml:mo> </mml:mover> <mml:mo>=</mml:mo>...
We use data from five stellar occultations observed between 2013 and 2016 to constrain Chariklo's size shape, the ring reflectivity. consider four possible models for Chariklo (sphere, Maclaurin spheroid, tri-axial ellipsoid Jacobi ellipsoid) we a Bayesian approach estimate corresponding parameters. The spherical model has radius $R=129\pm3$ km. equatorial polar radii $a=b=143^{+3}_{-6}$ km $c=96^{+14}_{-4}$ km, respectively, with density $970^{+300}_{-180}$ kg m$^{-3}$. ellipsoidal semiaxes...
After the discovery of rings around largest known Centaur object, (10199) Chariklo, we carried out observation campaigns stellar occultations produced by second-largest (2060) Chiron, to better characterize its physical properties and presence material on surroundings. We predicted successfully observed two Chiron. These observations were used constrain size shape fitting elliptical limbs with equivalent surface radii in agreement radiometric measurements. Constraints Chiron are reported for...
Abstract We present evidence, via a large survey of 191 new spectra along with previously published spectra, divide in the 3 μ m spectral properties low-albedo asteroid population. One group (“sharp types,” or STs, band centers <3 m) has shape consistent carbonaceous chondrite meteorites, while other (“not sharp NSTs, bands centered >3 is not represented meteorite literature but as abundant STs among objects. Both groups are most taxonomic classes, and, except limited cases,...
Abstract Gaussian process (GP) regression is a nonparametric Bayesian approach that has been used successfully in various astronomical domains, especially time-domain astronomy. The most common applications are the smoothing of data for interpolation and detection periodicities. ability to create unbiased data-driven models without predefined physical model can be major advantage over conventional methods. Prior knowledge included by setting boundary conditions or constraining hyperparameter...
We present Mookodi (meaning "rainbow" in Sesotho), a multipurpose instrument with low-resolution spectrograph mode and multi-filter imaging for quick-reaction astronomical observations. The instrument, mounted on the 1-m Lesedi telescope at South African Astronomical Observatory Sutherland (South Africa), is based rapid acquisition of transients (SPRAT) operation 2-m Liverpool Telescope La Palma (Canary Islands, Spain). Similar to SPRAT, has resolution R≈350 an operating wavelength range...
Abstract The area in the Reiner Gamma swirl studied by Weirich et al. for topographic correlations also displays with Hapke-model-derived single-scattering albedo, surface roughness, and particle scattering properties unit. albedo associate compositional variations plagioclase FeO content photometric roughness show a rougher on-swirl, implying potentially more porous on-swirl compared to off-swirl. This suggests are dominated differences not structural differences, such as compaction....
Abstract The Moon's bright albedo markings, known as swirls, are defined by broad, bright, on‐swirl areas separated darker off‐swirl lanes. Their formation mechanism has long been debated and is key for understanding the processing of lunar surface, mobility soil particles, effects space environment on planetary surfaces. Here we present, first time, evidence that these features do not necessarily cross surface without regard to topography or local terrain. Within portions Mare Ingenii...
Abstract A stellar occultation of Gaia DR3 2646598228351156352 by the Centaur (2060) Chiron was observed from South African Astronomical Observatory on 2018 November 28 UT. Here we present a positive detection material surrounding 74-inch telescope for this event. Additionally, global atmosphere is ruled out at tens microbars level several possible atmospheric compositions. There are multiple 3 σ drops in light curve: three during immersion and two emersion. Occulting located between 242 270...
We report on the extensively upgraded Cassegrain spectrograph South African Astronomical Observatory (SAAO) 1.9-m telescope. The introduction of new collimator and camera optics, a detector controller, rear-of-slit viewing to facilitate acquisition, instrument control quick-look data-reduction software (to take advantage entire system now being governed by programmable logic controller) has revolutionized this workhorse Africa's second largest optical improvement in throughput over previous...
ABSTRACT The centaur (2060) Chiron exhibits outgassing behaviour and possibly hosts a ring system. On 2011 November 29, occulted fairly bright star (R ∼ 15 mag) as observed from the 3-m NASA Infrared Telescope Facility (IRTF) on Mauna Kea 2-m Faulkes North (FTN) at Haleakala. Data were taken visible wavelength images simultaneous, low-resolution, near-infrared (NIR) spectra. Here, we present detailed examination of light-curve features in optical data an analysis NIR We place lower limit...
SpUpNIC (Spectrograph Upgrade: Newly Improved Cassegrain) is the extensively upgraded Cassegrain Spectrograph on South African Astronomical Observatory's 74-inch (1.9-m) telescope. The inverse-Cassegrain collimator mirrors and woefully inefficient Maksutov-Cassegrain camera optics have been replaced, along with CCD SDSU controller. All moving mechanisms are now governed by a programmable logic controller, allowing remote configuration of instrument via an intuitive new graphical user...
We present here the c-o colors for identified Flora, Vesta, Nysa-Polana, Themis, and Koronis family members within historic data set (2015-2018) of Asteroid Terrestrial-impact Last Alert System (ATLAS). The Themis families are known to be relatively pure C- S-type Bus-DeMeo taxonomic families, respectively, extracted color from ATLAS broadband c- o-filters these two is used demonstrate that a sufficient parameter distinguish between taxonomies. Vesta Nysa-Polana display mixture taxonomies...
Evolved stars near the tip of red giant branch (TRGB) show solar-like oscillations with periods spanning hours to months and amplitudes ranging from $\sim$1 mmag $\sim$100 mmag. The systematic detection resulting photometric variations ground-based telescopes would enable application asteroseismology a much larger more distant sample than is currently accessible space-based such as \textit{Kepler} or ongoing Transiting Exoplanet Survey Satellite (\textit{TESS}) mission. We present an...
We present here multi-band photometry for over 2000 Main-belt asteroids. For each target we report the probabilistic taxonomy using measured V-R and V-I colors in combination with a machine-learning generated decision surface color-color space. Through this method classify >85% of our targets as one four main Bus-DeMeo complexes: S-, C-, X-, or D-type. Roughly third have known associated dynamic family 69 families represented data. Within uncertainty results show no discernible difference...