arXiv subjects

Paul Wiegert

Publications and source records attributed to Paul Wiegert.

At least 19 recordsLinked to original sources

arXiv2025

Model Predictions for the 2025 October Draconid Outburst

The October Draconid meteor shower, produced by comet 21P/Giacobini-Zinner, is notorious for rare but intense outbursts, some exceeding rates of about 10 000 meteors per hour. In 2025, Earth will encounter young trails ejected by the comet in 2005 and 2012, producing a meteor outburst and providing a rare opportunity to probe their structure and benchmark meteoroid stream models. We present predictions from three independent dynamical models (NIMS, MSFC, Sisyphus), calibrated against updated activity profiles including the newly observed 2019 and 2024 outbursts. All simulations predict enhanced activity on 2025 October 8, dominated by faint meteors (m < 0.01 g; +4 mag and fainter) primarily detectable by radar. Our best estimate is a radar outburst near 15:00 - 16:00 UT, driven mainly by the 2012 trail with a possible minor contribution from 2005. The 2025 Draconids may represent one of the strongest radar dominated outbursts of the decade. Coordinated observing campaigns, especially radar measurements across the Northern Hemisphere and optical coverage from Asia, will be essential to validate these forecasts, constrain the dust environment of comet 21P, and improve future predictions of young meteoroid trails.

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arXiv2025

Catastrophic disruption of asteroid 2023 CX1 and implications for planetary defense

Mitigation of the threat from airbursting asteroids requires an understanding of the potential risk they pose for the ground. How asteroids release their kinetic energy in the atmosphere is not well understood due to the rarity of significant impacts. Ordinary chondrites, in particular L chondrites, represent a frequent type of Earth-impacting asteroids. Here, we present the first comprehensive, space-to-lab characterization of an L chondrite impact. Small asteroid 2023 CX1 was detected in space and predicted to impact over Normandy, France, on 13 February 2023. Observations from multiple independent sensors and reduction techniques revealed an unusual but potentially high-risk fragmentation behavior. The nearly spherical 650 $\pm$ 160 kg (72 $\pm$ 6 cm diameter) asteroid catastrophically fragmented around 28 km altitude, releasing 98% of its total energy in a concentrated region of the atmosphere. The resulting shockwave was spherical, not cylindrical, and released more energy closer to the ground. This type of fragmentation increases the risk of significant damage at ground level. These results warrant consideration for a planetary defense strategy for cases where a >3-4 MPa dynamic pressure is expected, including planning for evacuation of areas beneath anticipated disruption locations.

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arXiv2025

The Potential Danger to Satellites due to Ejecta from a 2032 Lunar Impact by Asteroid 2024 YR4

On 2032 December 22 the 60 m diameter asteroid 2024 YR4 has a 4% chance of impacting the Moon. Such an impact would release 6.5 MT TNT equivalent energy and produce a ~1 km diameter crater. We estimate that up to 10^8 kg of lunar material could be liberated in such an impact by exceeding lunar escape speed. Depending on the actual impact location on the Moon as much as 10% of this material may accrete to the Earth on timescales of a few days. The lunar ejecta-associated particle fluence at 0.1 - 10 mm sizes could produce upwards of years to of order a decade of equivalent background meteoroid impact exposure to satellites in near-Earth space late in 2032. Our results demonstrate that planetary defense considerations should be more broadly extended to cis-lunar space and not confined solely to near-Earth space.

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arXiv2025

A limit on the mass of the Taurid Resonant Swarm at sub-100 meter sizes

We report on a pencil-beam survey of the Taurid Swarm, a possible concentration of bodies in the Taurid meteoroid stream associated with the 7:2 mean-motion resonance with Jupiter. Canada-France-Hawaii Telescope MegaCam observations reaching apparent magnitudes of 24.5 in the gri filter were taken over three nights. Rates of motion on the sky allowed for the quick elimination of main-belt objects from the over 1000 moving sources seen. Eight candidates with on-sky rates of motion consistent with Taurids were detected, but seven were subsequently shown to be non-Taurids (Hungarias, Mars-crossers, etc). One object might be a 60 m class Taurid but not enough data was collected and its orbit remains ambiguous. Our results are consistent with no Taurid Swarm members observed, and an upper limit of fewer than 3e3 - 3e4 objects down to H=25.6 +/- 0.3 (diameter of 34-76 m assuming a 2P/Encke-like albedo) at the 95% confidence level. While meteor observations have confirmed the Taurid Swarm's existence at meter and smaller sizes, our results indicate that the current mass budget of the swarm at 100 m sizes does not require an outsize parent to explain it.

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arXiv2025

An Upper Limit on the Interstellar Meteoroid Flux at Video Sizes from the Global Meteor Network

Material arriving at our solar system from the Galaxy may be detected at Earth in the form of meteors ablating in our atmosphere. Here we report on a search for interstellar meteors within the highest-quality events in the Global Meteor Network (GMN) database. No events were detected that were conclusively hyperbolic with respect to the Sun; however, our search was not exhaustive and examined only the top 57% of events, with a deeper examination planned for future work. This study's effective meteoroid mass limit is 6.6 +/- 0.8 x 10^{-5} kg (5 millimeter diameter at a density of 1000 kg m^{-3}). Theoretical rates of interstellar meteors at these sizes range from 3 to 200 events globally per year. The highest rates can already be largely excluded by this study, while at the lowest rates GMN would have to observe for 25 more years to be 50% confident of seeing at least one event. GMN is thus well positioned to provide substantial constraints on the interstellar population at these sizes over the coming years. This study's results are statistically compatible with a rate of interstellar meteors at the Earth at less than 1 per million meteoroid impacts at Earth at millimeter sizes, or a flux rate of less than 8 +/- 2 x 10^{-11} per sq. km per hour at the 95% confidence level.

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arXiv2025

A Planet as the Possible Cause of the HD 181327 Debris Disk Asymmetry

The debris disk around HD 181327 shows a significant asymmetry in its surface brightness profile when viewed in visible light. Observations from the Hubble Space Telescope STIS instrument show an arc of approximately 90 degrees of higher optical depth at a distance of 84 au from the star. We find that a 2-5 Jupiter-mass planet on a circular orbit at 62 au can produce and maintain a similar feature if the collisional lifetime of dust in the disk is at least 25 kiloyears, and smaller mass planets can produce similar results on longer timescales. We also find that the surface brightness asymmetry is much less pronounced at larger particle sizes, which may account for the fact that observations of HD181327 at longer wavelengths have not reported such an arc. We predict that if a planet is producing the arc in question, the planet is along the line joining the star to the feature, and make some estimates of its observability.

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arXiv2024

Telescope-to-Fireball Characterization of Earth Impactor 2022 WJ1

Comparing how an asteroid appears in space to its ablation behavior during atmospheric passage and finally to the properties of associated meteorites represents the ultimate probe of small near-Earth objects. We present observations from the Lowell Discovery Telescope and from multiple meteor camera networks of 2022 WJ1, an Earth impactor which was disrupted over the North American Great Lakes on 19 November 2022. As far as we are aware, this is only the second time an Earth impactor has been specifically observed in multiple passbands prior to impact to characterize its composition. The orbits derived from telescopic observations submitted to the Minor Planet Center (MPC) and ground-based meteor cameras result in impact trajectories that agree to within 40 meters, but no meteorites have been found as of yet. The telescopic observations suggest a silicate-rich surface, and thus a moderate-to-high albedo, which results in an estimated size for the object of just D = 40 - 60 cm. Modeling the fragmentation of 2022 WJ1 during its fireball phase also suggests an approximate half-meter original size for the object as well as an ordinary chondrite-like strength. These two lines of evidence both support that 2022 WJ1 was likely an S-type condritic object and the smallest asteroid compositionally characterized in space. We discuss how best to combine telescopic and meteor camera datasets, how well these techniques agree, and what can be learned from studies of ultra-small asteroids.

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arXiv2024

On the sensitivity of Apophis' 2029 Earth approach to small asteroid impacts

Apophis' current trajectory takes it safely past our planet at a distance of several Earth radii on 2029 April 13. Here the possibility is considered that Apophis could collide with a small asteroid, like the ones that frequently and unpredictably strike Earth, and the resulting perturbation of its trajectory. The probability of an impact that could significantly displace Apophis relative to its keyholes is found to be less than 1 in $10^6$, requiring a delta-v greater than 0.3 mm/s, while for an impact that could significantly displace Apophis compared to its miss distance in 2029 it is less than 1 in $10^9$, requiring a delta-v greater than 5 cm/s. These probabilities are below the usual thresholds considered by asteroid impact warning systems. Apophis is in the daytime sky and unobservable from mid-2021 to 2027. It will be challenging to determine from single night observations in 2027 if Apophis has moved on the target plane enough to enter a dangerous keyhole, as the deviation from the nominal ephemeris might be only a few tenths of an arcsecond. An impending Earth impact would, however, be signalled clearly in most cases by deviations of tens of arcseconds of Apophis from its nominal ephemeris in 2027. Thus most of the impact risk could be retired by a single observation of Apophis in 2027, though a minority of cases present some ambiguity and are discussed in more detail. Charts of the on-sky position of Apophis under different scenarios are presented for quick assessment by observers.

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arXiv2024

Encounter circumstances of asteroid 99942 Apophis with the catalogue of known asteroids

Asteroid 99942 Apophis will pass near the Earth in April 2029. Expected to miss our planet by a safe margin, that could change if Apophis' path was perturbed by a collision with another asteroid in the interim. Though the statistical chance of such a collision is minuscule, the high risk associated with Apophis motivates us to examine even this very unlikely scenario. In this work, we identify encounters between known asteroids and Apophis up to April 2029. Here we show that Apophis will encounter the 1300 meter diameter asteroid 4544 Xanthus in December 2026. Their Minimum Orbit Intersection Distance (MOID) is less than 10,000 km, with Xanthus passing that closest point just four hours after Apophis. Though a direct collision is ruled out, the encounter is close enough that material accompanying Xanthus (if any) could strike Apophis. We also identify other asteroid encounters that deserve monitoring.

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arXiv2022

Direct measurement of decimeter-sized rocky material in the Oort cloud

The Oort cloud is thought to be a reservoir of icy planetesimals and the source of long-period comets (LPCs) implanted from the outer Solar System during the time of giant planet formation. The abundance of rocky ice-free bodies is a key diagnostic of Solar System formation models as it can distinguish between ``massive" and ``depleted" proto-asteroid belt scenarios and thus disentangle competing planet formation models. Here we report a direct observation of a decimeter-sized ($\sim2$ kg) rocky meteoroid on a retrograde LPC orbit ($e \approx 1.0$, i = $121^{\circ}$). During its flight, it fragmented at dynamic pressures similar to fireballs dropping ordinary chondrite meteorites. A numerical ablation model fit produces bulk density and ablation properties also consistent with asteroidal meteoroids. We estimate the flux of rocky objects impacting Earth from the Oort cloud to be $1.08^{+2.81}_{-0.95} \mathrm{meteoroids/10^6 km^2/yr}$ to a mass limit of 10 g. This corresponds to an abundance of rocky meteoroids of $\sim6^{+13}_{-5}$\% of all objects originating in the Oort cloud and impacting Earth to these masses. Our result gives support to migration-based dynamical models of the formation of the Solar System which predict that significant rocky material is implanted in the Oort cloud, a result not explained by traditional Solar System formation models.

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arXiv2022

NEOSSat Observations of Three Transiting Hot Jupiters

The Near Earth Object Surveillance Satellite (NEOSSat) is a Canadian-led 15 cm Earth-orbiting telescope originally designed to detect asteroids near the Sun. Its design is however also suitable for the observation of exoplanetary transits of bright stars. We used the NEOSSat platform to perform followup observations of several Transiting Exoplanets Survey Satellite (TESS) targets, both as a demonstration of NEOSSat capabilities for exoplanetary science and improve the orbital ephemerides and properties of these exoplanet systems. We are able to recover / confirm the orbital properties of such targets to within mutual error bars, demonstrating NEOSSat as a useful future contributor to exoplanetary science.

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arXiv2020

Exomoon Candidates from Transit Timing Variations: Eight Kepler systems with TTVs explainable by photometrically unseen exomoons

If a transiting exoplanet has a moon, that moon could be detected directly from the transit it produces itself, or indirectly via the transit timing variations it produces in its parent planet. There is a range of parameter space where the Kepler Space Telescope is sensitive to the TTVs exomoons might produce, though the moons themselves would be too small to detect photometrically via their own transits. The Earth's Moon, for example, produces TTVs of 2.6 minutes amplitude by causing our planet to move around their mutual centre of mass. This is more than Kepler's short-cadence interval of 1 minute and so nominally detectable (if transit timings can be measured with comparable accuracy), even though the Moon's transit signature is only 7% that of Earth's, well below Kepler's nominal photometric threshold. Here we examine several Kepler systems, exploring the hypothesis that an exomoon could be detected solely from the TTVs it induces on its host planet. We compare this with the alternate hypothesis that the TTVs are caused by an non-transiting planet in the system. We examine 13 Kepler systems and find 8 where both hypotheses explain the observed TTVs equally well. Though no definitive exomoon detection can be claimed on this basis, the observations are nevertheless completely consistent with a dynamically stable moon small enough to fall below Kepler's photometric threshold for transit detection, and these systems warrant further observation and analysis.

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arXiv2020

Modeling the past and future activity of the Halleyids meteor showers

We present a new numerical model of the eta-Aquariid and Orionid meteor showers. The model investigates the origin, variability and age of the eta-Aquariid and Orionid apparitions from 1985 to the present day, in order to forecast their activity over the next several decades. Through the numerical integration of millions of simulated meteoroids and a custom-made particle weighting scheme, we model the characteristics of every eta-Aquariid and Orionid apparition between 1985 and 2050. The modeled showers are calibrated using 35 years of meteor observations including the showers activity profiles and interannual variability. Our model reproduces the general characteristics of the present-day eta-Aquariids, and part of the Orionid activity. Simulations suggest that the age of the eta-Aquariids somewhat exceeds 5000 years, while a greater fraction of the Orionids are composed of older material. The 1:6 mean-motion resonance with Jupiter plays a major role in generating some (but not all) Halleyid stream outbursts. We find consistent evidence for a periodicity of 11.8 years in both the observations and modeled maximum meteor rates for the Orionids. A weaker evidence of a 10.7 year period in the peak activity for the eta-Aquariids needs to be investigated with future meteor observations. The extension of our model to future years predicts no significant Orionid outburst through 2050 and four significant eta-Aquariid outbursts in 2023, 2024, 2045 and 2046.

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arXiv2020

Estimating trajectories of meteors: an observational Monte Carlo approach -- I. Theory

It has recently been shown by Egal et al. (2017) that some types of existing meteor in-atmosphere trajectory estimation methods may be less accurate than others, particularly when applied to high precision optical measurements. The comparative performance of trajectory solution methods has previously only been examined for a small number of cases. Besides the radiant, orbital accuracy depends on the estimation of pre-atmosphere velocities, which have both random and systematic biases. Thus it is critical to understand the uncertainty in velocity measurement inherent to each trajectory estimation method. In this first of a series of two papers, we introduce a novel meteor trajectory estimation method which uses the observed dynamics of meteors across stations as a global optimization function and which does not require either a theoretical or empirical flight model to solve for velocity. We also develop a 3D observational meteor trajectory simulator that uses a meteor ablation model to replicate the dynamics of meteoroid flight, as a means to validate different trajectory solvers. We both test this new method and compare it to other methods, using synthetic meteors from three major showers spanning a wide range of velocities and geometries (Draconids, Geminids, Perseids). We determine which meteor trajectory solving algorithm performs better for: all-sky, moderate field of view, and high-precision narrow-field optical meteor detection systems. The results are presented in the second paper in this series. Finally, we give detailed equations for estimating meteor trajectories and analytically computing meteoroid orbits, and provide the Python code of the methodology as open source software.

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arXiv2020

On the delivery of DART-ejected material from asteroid (65803) Didymos to Earth

The DART spacecraft is planned to impact the secondary of the binary asteroid (65803) Didymos in 2022, to assess deflection strategies for planetary defense. The impact will create a crater and release asteroidal material, some of which will escape the Didymos system. Because the closest point of approach of Didymos to Earth's orbit is only 6 million km (about 16 times the Earth-Moon distance), some ejected material will make its way sooner or later to our planet, and the observation of these particles as meteors would increase the scientific payout of the DART mission. The DART project may also represent the first human-generated meteoroids to reach Earth, and a test case for human activity on asteroids and its eventual contribution to the meteoroid environment and spacecraft impact risk. This study examines the amount and timing of the delivery of meteoroids from Didymos to near-Earth space. Very little DART-ejected material will reach our planet, and most only after thousands of years. But some material, the smallest particles and/or those ejected at the highest velocities could be delivered to Earth-crossing trajectories almost immediately, though at very low fluxes. Timing and radiant directions for material reaching the Earth are calculated, though the detection of substantial numbers would indicate more abundant and/or faster ejecta than is expected. The DART impact will also create a new meteoroid stream, though probably not a very dense one. However, larger, more capable asteroid impactors could create meteoroid streams in which the particle flux exceeds that naturally occurring in the Solar System, with implications for spacecraft safety.

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arXiv2020

The Dynamics of Interstellar Asteroids and Comets within the Galaxy: an Assessment of Local Candidate Source Regions for 1I/`Oumuamua and 2I/Borisov

The low velocity of interstellar asteroid 1I/'Oumuamua with respect to our galaxy's Local Standard of Rest implies it is young. Adopting the young age hypothesis, we assess possible origin systems for this interstellar asteroid and for 2I/Borisov, though the latter's higher speed means it is unlikely to be young. First, their past trajectories are modelled under gravitational scattering by galactic components ('disk heating') to assess how far back one can trace them. The stochastic nature of disk heating means that a back-integration can only expect to be accurate to within 15 pc and 2 kms$^{-1}$ at -10 Myr, dropping steeply to 400 pc and 10 kms$^{-1}$ at -100 Myr, sharply limiting our ability to determine a precise origin. Nevertheless, we show `Oumuamua's origin system is likely currently within 1 kpc of Earth, in the local Orion Arm. Second, we back-integrate 'Oumuamua's trajectory to assess source regions, emphasizing young systems and moving groups. Though disk heating allows for only a statistical link to source regions, `Oumuamua passed through a considerable subset of the Carina and Columba moving groups when those groups were forming. This makes them perhaps the most plausible source region, if 'Oumuamua was ejected during planet formation or via intra-cluster interactions. We find three stars in the Ursa Major group, one brown dwarf, and seven other stars to have plausible encounters with 2I/Borisov, within 2 pc and 30 kms$^{-1}$. These encounters' high relative speeds mean none are likely to be the home of 2I/Borisov.

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arXiv2020

Supercatastrophic disruption of asteroids in the context of SOHO comet, fireball and meteor observations

Granvik et al. (2016) report an absence of asteroids on orbits with perihelia near the Sun that they attribute to the 'supercatastrophic disruption' of these bodies. Here we investigate whether there is evidence for this process among other bodies with similarly low perihelia: near-Earth asteroids, SOHO comets, as well as meter-sized and millimeter-sized meteoroids. We determine no known near-Earth asteroids have past (last 10^4 years) histories residing significantly inside the Granvik et al. (2016) limit, indirectly supporting the disruption hypothesis. The exception is asteroid (467372) 2004 LG which spent 2500 years within this limit, and thus presents a challenge to that theory. Phaethon has a perihelion distance hovering just above the limit and may be undergoing slow disruption, which may be the source of its dust complex. We find that the rate at which ungrouped SOHO comets are observed is consistent with expected rates for the injection of small (25 m) class asteroids into the near-Sun region and suggest that this fraction of the SOHO-observed comet population may in fact be asteroidal in origin. We also find that there is an absence of meter-sized bodies with near-Sun perihelia but an excess of millimeter-sized meteoroids. This implies that if near-Sun asteroids disrupt, they do not simply fragment into meter-sized chunks but disintegrate ultimately into millimeter-sized particles. We propose that the disruption of near-Sun asteroids as well as the anomalous brightening and destruction processes that affect SOHO comets occur through meteoroid erosion, that is, the removal of material through impacts by high-speed near-Sun meteoroids.

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arXiv2019

Estimating trajectories of meteors: an observational Monte Carlo approach -- II. Results

In the first paper of this series we examined existing methods of optical meteor trajectory estimation and developed a novel method which simultaneously uses both the geometry and the dynamics of meteors to constrain their trajectories. We also developed a simulator which uses an ablation model to generate realistic synthetic meteor trajectories which we use to test meteor trajectory solvers. In this second paper, we perform simulation validation to estimate radiant and velocity accuracy which may be achieved by various meteor observation systems as applied to several meteor showers. For low-resolution all-sky systems, where the meteor deceleration is generally not measurable, the multi-parameter fit method assuming a constant velocity better reproduces the radiant and speed of synthetic meteors. For moderate field of view systems, our novel method performs the best at all convergence angles, while multi-parameter fit methods generally produce larger speed errors. For high-resolution, narrow field of view systems, we find our new method of trajectory estimation reproduces radiant and speed more accurately than all other methods tested. The ablation properties of meteoroids are commonly found to be the limiting factor in velocity accuracy. We show that the true radiant dispersion of meteor showers can be reliably measured with moderate field of view (or more precise) systems provided appropriate methods of meteor trajectory estimation are employed. Finally, we compare estimated and real angular radiant uncertainty and show that for the solvers tested the real radiant error is on average underestimated by a factor of two.

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