arXiv subjects

David Nesvorný

Publications and source records attributed to David Nesvorný.

At least 37 records · Page 2Linked to original sources

arXiv2023

Debiased population of very young asteroid families

We use observations from the Catalina Sky Survey (CSS) to determine the bias-corrected population of small members in four very young families down to sizes equivalent to several hundred meters. Using the most recent catalog of known asteroids, we identified members from four young families for which the population has grown appreciably over recent times. A large fraction of these bodies have also been detected by CSS. We used synthetic populations of asteroids, with their magnitude distribution controlled by a small number of parameters, as a template for the bias-corrected model of these families. Applying the known detection probability of the CSS observations, we could adjust these model parameters to match the observed (biased) populations in the young families. In the case of three families, Datura, Adelaide, and Rampo, we find evidence that the magnitude distribution transitions from steep to shallow slopes near $300$ to $400$ meters. Conversely, the Hobson family population may be represented by a single power-law model. The Lucascavin family has a limited population; no new members have been discovered over the past two decades. We consider a model of parent body rotational fission with the escaping secondary tidally split into two components (thereby providing three members within this family). In support of this idea, we find that no other asteroid with absolute magnitude $H\leq 18.3$ accompanies the known three members in the Lucascavin family. A similar result is found for the archetypal asteroid pair Rheinland--Kurpfalz.

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arXiv2023

Dynamical feasibility of (3) Juno as a parent body of the H chondrites

We test the hypothesis that (3) Juno is a parent body of the H chondrites with dynamical modeling of an asteroid-family-forming impact and comparison to current observational data. Using a dynamical model that includes the Yarkovsky force on a simulated Juno family and a simplified cosmic ray exposure age model we examine the expected distribution of Juno family members in both the main belt and near-Earth orbits over 300 Myrs and the cosmic ray exposure distribution for fragments exiting the main belt via the 3:1J, 5:2J, and 8:3J mean motion resonances. We find that the smallest modeled ($D<$10 m) family members of (3) Juno cannot be directly responsible for the observed H chondrite flux and that the breakup of larger family members creates an CRE distribution that resembles the measured H chondrite CRE distribution but is still unable to adequately explain the significant number of H chondrites with CRE ages of 6-8 Myrs. A similar model was performed for the asteroid (6) Hebe, another parent body candidate, and produced a CRE age distribution that is inconsistent with the measured H chondrite CRE ages. We also find from our dynamical models that we can expect $<$7 km-scale Juno family members in near-Earth orbits in the present day, consistent with the recent discovery of the shock-darkened H chondrite-like asteroid (52768) 1998 OR$_{2}$.

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arXiv2023

Not So Fast Kepler-1513: A Perturbing Planetary Interloper in the Exomoon Corridor

Transit Timing Variations (TTVs) can be induced by a range of physical phenomena, including planet-planet interactions, planet-moon interactions, and stellar activity. Recent work has shown that roughly half of moons would induce fast TTVs with a short period in the range of two-to-four orbits of its host planet around the star. An investigation of the Kepler TTV data in this period range identified one primary target of interest, Kepler-1513 b. Kepler-1513 b is a $8.05^{+0.58}_{-0.40}$ $R_\oplus$ planet orbiting a late G-type dwarf at $0.53^{+0.04}_{-0.03}$ AU. Using Kepler photometry, this initial analysis showed that Kepler-1513 b's TTVs were consistent with a moon. Here, we report photometric observations of two additional transits nearly a decade after the last Kepler transit using both ground-based observations and space-based photometry with TESS. These new transit observations introduce a previously undetected long period TTV, in addition to the original short period TTV signal. Using the complete transit dataset, we investigate whether a non-transiting planet, a moon, or stellar activity could induce the observed TTVs. We find that only a non-transiting perturbing planet can reproduce the observed TTVs. We additionally perform transit origami on the Kepler photometry, which independently applies pressure against a moon hypothesis. Specifically, we find that Kepler-1513 b's TTVs are consistent with an exterior non-transiting $\sim$Saturn mass planet, Kepler-1513 c, on a wide orbit, $\sim$5$\%$ outside a 5:1 period ratio with Kepler-1513 b. This example introduces a previously unidentified cause for planetary interlopers in the exomoon corridor, namely an insufficient baseline of observations.

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arXiv2023

A race against the clock: Constraining the timing of cometary bombardment relative to Earth's growth

Comets are considered a potential source of inner solar system volatiles, but the timing of this delivery relative to that of Earth's accretion is still poorly understood. Measurements of xenon isotopes in comet 67P/Churyumov-Gerasimenko revealed that comets partly contributed to the Earth's atmosphere. However, there is no conclusive evidence of a significant cometary component in the Earth's mantle. These geochemical constraints would favour a contribution of comets mainly occurring after the last stages of Earth's formation. Here, we evaluate whether dynamical simulations satisfy these constraints in the context of an Early Instability model. We perform dynamical simulations of the solar system, calculate the probability of collision between comets and Earth analogs component embryos through time and estimate the total cometary mass accreted in Earth analogs as a function of time. While our results are in excellent agreement with geochemical constraints, we also demonstrate that the contribution of comets on Earth might have been delayed with respect to the timing of the instability, due to a stochastic component of the bombardment. More importantly, we show that it is possible that enough cometary mass has been brought to Earth after it had finished forming so that the xenon constraint is not necessarily in conflict with an Early Instability scenario. However, it appears very likely that a few comets were delivered to Earth early in its accretion history, thus contributing to the mantle's budget. Finally, we compare the delivery of cometary material on Earth to Venus and Mars. These results emphasize the stochastic nature of the cometary bombardment in the inner solar system.

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arXiv2023

Shape models and spin states of Jupiter Trojans: Testing the streaming instability formation scenario

The leading theory for the origin of Jupiter Trojans (JTs) assumes that JTs were captured to their orbits near the Lagrangian points of Jupiter during the early reconfiguration of the giant planets. The natural source region for the majority of JTs would then be the population of planetesimals born in a massive trans-Neptunian disk. If true, JTs represent the most accessible stable population of small Solar System bodies that formed in the outer regions of the Solar System. For this work, we compiled photometric datasets for about 1000 JTs and applied the convex inversion technique in order to assess their shapes and spin states. We obtained full solutions for $79$ JTs, and partial solutions for an additional $31$ JTs. We found that the observed distribution of the pole obliquities of JTs is broadly consistent with expectations from the streaming instability, which is the leading mechanism for the formation of planetesimals in the trans-Neptunian disk. The observed JTs' pole distribution has a slightly smaller prograde vs. retrograde asymmetry (excess of obliquities $>130^\circ$) than what is expected from the existing streaming instability simulations. However, this discrepancy can be plausibly reconciled by the effects of the post-formation collisional activity. Our numerical simulations of the post-capture spin evolution indicate that the JTs' pole distribution is not significantly affected by dynamical processes such as the eccentricity excitation in resonances, close encounters with planets, or the effects of nongravitational forces. However, a few JTs exhibit large latitude variations of the rotation pole and may even temporarily transition between prograde- and retrograde-rotating categories.

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arXiv2022

Comets and Planetesimal Formation

In this chapter, we review the processes involved in the formation of planetesimals and comets. We will start with a description of the physics of dust grain growth and how this is mediated by gas-dust interactions in planet-forming disks. We will then delve into the various models of planetesimal formation, describing how these planetesimals form as well as their resulting structure. In doing so, we focus on and compare two paradigms for planetesimal formation: the gravitational collapse of particle over-densities (which can be produced by a variety of mechanisms) and the growth of particles into planetesimals via collisional and gravitational coagulation. Finally, we compare the predictions from these models with data collected by the Rosetta and New Horizons missions and that obtained via observations of distant Kuiper Belt Objects.

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arXiv2022

The Transition from the Kuiper Belt to the Jupiter-Family (Comets)

Kuiper Belt Objects, or more generally Trans-Neptunian Objects (TNOs), are planetesimals found beyond the orbit of Neptune. Some TNOs evolve onto Neptune-crossing orbits and become Centaurs. Many Centaurs, in turn, reach Jupiter-crossing orbits and become Jupiter-family comets (JFCs). TNOs are the main source of the JFCs. TNOs offer a different window than the JFCs, of more primordial bodies and over a different size and temperature range. It is in that context that this chapter is written. Here we discuss the dynamical pathways taken from the trans-Neptunian region to the JFCs, and the most important properties of TNOs that relate to the JFC population, including considerations of their origins, compositions, morphologies, and size distributions. We relate these properties to the JFCs whenever possible. We reflect on a few key outstanding issues regarding our incomplete knowledge of TNOs as they pertain to the Centaurs and JFC populations. We finish with a short discussion of notable new and upcoming facilities and the impacts they will have regarding these outstanding questions.

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arXiv2022

Trapping (sub-)Neptunes similar to TOI-216b at the inner disk rim: Implications for the disk viscosity and the Neptunian desert

[Abridged] The occurrence rate of observed sub-Neptunes has a break at 0.1 au, which is often attributed to a migration trap at the inner rim of protoplanetary disks where a positive co-rotation torque prevents inward migration. We argue that conditions in inner disk regions are such that sub-Neptunes are likely to open gaps, lose the support of the co-rotation torque as their co-rotation regions become depleted, and the trapping efficiency then becomes uncertain. We study what it takes to trap such gap-opening planets at the inner disk rim. We performed 2D locally isothermal and non-isothermal hydrodynamic simulations of planet migration. A viscosity transition was introduced in the disk to (i) create a density drop and (ii) mimic the viscosity increase as the planet migrated from a dead zone towards a region with active magneto-rotational instability (MRI). We chose TOI-216b as a Neptune-like upper-limit test case, but we also explored different planetary masses, both on fixed and evolving orbits. For planet-to-star mass ratios $q\simeq(4$-$8)\times10^{-5}$, the density drop at the disk rim becomes reshaped due to a gap opening and is often replaced with a small density bump centered on the planet's corotation. Trapping is possible only if the bump retains enough gas mass and if the co-rotation region becomes azimuthally asymmetric, with an island of librating streamlines that accumulate a gas overdensity ahead of the planet. The overdensity exerts a positive torque that can counteract the negative torque of spiral arms. In our model, efficient trapping depends on the $α$ viscosity and its contrast across the viscosity transition. In order to trap TOI-216b, $α_{\mathrm{DZ}}=10^{-3}$ in the dead zone requires $α_{\mathrm{MRI}}\gtrsim5\times10^{-2}$ in the MRI-active zone. If $α_{\mathrm{DZ}}=5\times10^{-4}$, $α_{\mathrm{MRI}}\gtrsim7.5\times10^{-2}$ is needed.

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arXiv2022

Implications for the collisional strength of Jupiter Trojans from the Eurybates family

In this work, we model the collisional evolution of the Jupiter Trojans and determined under which conditions the Eurybates-Queta system survives. We show that the collisional strength of the Jupiter Trojans and the age of the Eurybates family and by extension Queta are correlated. The collisional grinding of the Jupiter Trojan population over 4.5 Gy results in a size-frequency distribution (SFD) that remains largely unaltered at large sizes (>10 km) but is depleted at small sizes (10 m to 1 km). This results in a turnover in the SFD, the location of which depends on the collisional strength of the material. It is to be expected that the Trojan SFD bends between 1 and 10 km. Based on the SFD of the Eurybates family, we find that the family was likely the result of a catastrophic impact onto a 100 km rubble pile target. This corresponds to objects with a rather low collisional strength (10 times weaker than that of basaltic material studied in Benz & Asphaug1999). Assuming this weak strength, and an initial cumulative slope of the size frequency distribution of 2.1 between diameters of 2 m and 100 km when the Trojans were captured, the existence of Queta, the satellite of Eurybates, implies an upper limit for the family age of 3.7 Gy. Alternatively, we demonstrate that an unconventional collisional strength with a minimum at 20 m is a plausible candidate to ensure the survival of Queta over the age of the Solar System. Finally, we show how different collisional histories change the expected number of craters on the targets of the Lucy mission and that Lucy will be able to differentiate between them.

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arXiv2022

HD 28109 hosts a trio of transiting Neptunian planets including a near-resonant pair, confirmed by ASTEP from Antarctica

We report on the discovery and characterisation of three planets orbiting the F8 star HD~28109, which sits comfortably in \tess's continuous viewing zone. The two outer planets have periods of $\rm 56.0067 \pm 0.0003~days$ and $\rm 84.2597_{-0.0008}^{+0.0010}~days$, which implies a period ratio very close to that of the first-order 3:2 mean motion resonance, exciting transit timing variations (TTVs) of up to $\rm 60\,mins$. These two planets were first identified by \tess, and we identified a third planet in the \textcolor{black}{\tess photometry} with a period of $\rm 22.8911 \pm 0.0004~days$. We confirm the planetary nature of all three planetary candidates using ground-based photometry from Hazelwood, ASTEP and LCO, including a full detection of the $\rm \sim9\,h$ transit of HD~28109 c from Antarctica. The radii of the three planets are \textcolor{black}{$\rm R_b=2.199_{-0.10}^{+0.098} ~R_{\oplus}$, $\rm R_c=4.23\pm0.11~ R_{\oplus}$ and $\rm R_d=3.25\pm0.11 ~R_{\oplus}$}; we characterise their masses using TTVs and precise radial velocities from ESPRESSO and HARPS, and find them to be $\rm M_b=18.5_{-7.6}^{+9.1}~M_{\oplus}$, $\rm M_c=7.9_{-3.0}^{+4.2}~M_{\oplus}$ and $\rm M_d=5.7_{-2.1}^{+2.7}~M_{\oplus}$, making planet b a dense, massive planet while c and d are both under-dense. We also demonstrate that the two outer planets are ripe for atmospheric characterisation using transmission spectroscopy, especially given their position in the CVZ of JWST. The data obtained to date are consistent with resonant (librating) and non-resonant (circulating) solutions; additional observations will show whether the pair is actually locked in resonance or just near-resonant.

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arXiv2022

Exogenous delivery of water to Mercury

Radar and spacecraft observations show the permanently shadowed regions around Mercury's North Pole to contain water ice and complex organic material. One possible source of this material are impacts by interplanetary dust particles (IDPs), asteroids, and comets. We have performed numerical simulations of the dynamical evolution of asteroids and comets over the few Myr and checked for their impacts with Mercury. We use the N-body integrator RMVS/Swifter to propagate the Sun and the eight planets from their current positions. We add comets and asteroids to the simulations as massless test particles, based on their current orbital distributions. Asteroid impactors are assigned a probability of being water-rich (C-class) based on the measured distribution of taxonomic types. For comets, we assume a constant water fraction. For IDPs, we use a dynamical meteoroid model to compute the dust flux on Mercury. Relative to previous work on asteroid and comet impacts (Moses et al. 1999), we leverage 20 years of progress in minor body surveys. Immediate post-impact ejection of impactor material into outer space is taken into account as is the migration efficiency of water across Mercury's surface to the polar cold traps. We find that asteroids deliver $\sim 1 \times 10^{3}$ kg/yr of water to Mercury, comets deliver $\sim 1 \times 10^{3}$ kg/yr and IDPs deliver $\sim 16 \times 10^{3}$ kg/yr within a factor of several. Over a timescale of $\sim 1$ Gyr, this is enough to deliver the minimum amount of water required by the radar and MESSENGER observations. While other sources of water on Mercury are not ruled out by our analysis, we show that they are not required to explain the currently available observational lower limits.

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arXiv2022

Thermal processing of Jupiter Family Comets during their chaotic orbital evolution

Evidence for cometary activity beyond Jupiter and Saturn's orbits -- such as that observed for Centaurs and long period comets -- suggests that the thermal processing of comet nuclei starts long before they enter the inner Solar System, where they are typically observed and monitored. Such observations raise questions as to the depth of unprocessed material, and whether the activity of JFCs can be representative of any primitive material. Here we model the coupled thermal and dynamical evolution of Jupiter Family Comets (JFCs), from the moment they leave their outer Solar System reservoirs until their ejection into interstellar space. We apply a thermal evolution model to a sample of simulated JFCs obtained from dynamical simulations (arXiv:1706.07447) that successfully reproduce the orbital distribution of observed JFCs. We show that due to the stochastic nature of comet trajectories toward the inner solar system, all simulated JFCs undergo multiple heating episodes resulting in significant modifications of their initial volatile contents. A statistical analysis constrains the extent of such processing. We suggest that primordial condensed hypervolatile ices should be entirely lost from the layers that contribute to cometary activity observed today. Our results demonstrate that understanding the orbital (and thus, heating) history of JFCs is essential when putting observations in a broader context.

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arXiv2021

Col-OSSOS: Probing Ice Line/Color Transitions within the Kuiper Belt's Progenitor Populations

Dynamically excited objects within the Kuiper belt show a bimodal distribution in their surface colors, and these differing surface colors may be a tracer of where these objects formed. In this work we explore radial color distributions in the primordial planetesimal disk and implications for the positions of ice line/color transitions within the Kuiper belt's progenitor populations. We combine a full dynamical model of the Kuiper belt's evolution due to Neptune's migration with precise surface colors measured by the Colours of the Outer Solar System Origins Survey in order to examine the true color ratios within the Kuiper belt and the ice lines within the primordial disk. We investigate the position of a dominant, surface color changing ice-line, with two possible surface color layouts within the initial disk; (1) inner neutral surfaces and outer red, and (2) inner red surfaces and outer neutral. We performed simulations with a primordial disk that truncates at 30 au. By radially stepping the color transition out through 0.5 au intervals we show that both disk configurations are consistent with the observed color fraction. For an inner neutral, outer red primordial disk we find that the color transition can be at $28^{+2}_{-3}$ au at a 95% confidence level. For an inner red, outer neutral primordial disk the color transition can be at $27^{+3}_{-3}$ au at a 95% confidence level.

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arXiv2021

iSyMBA: A Symplectic Massive Bodies Integrator with Planets Interpolation

A planetary instability occurring at time $<100$ My after formation of the giant planets in our solar system can be responsible for some characteristics of the inner solar system. However, the actual influence of the instability on the terrestrial planet formation is not well understood. The simulations of terrestrial planet formation are very CPU-expensive, and this limits the exploration of different instability scenarios. To include the effects of the giant planets instability in the simulations of terrestrial planets formation in a feasible way, we approach the problem in two steps. First, we model and record an evolution of the giant planets that replicates the present outer solar system in the end. Then, we use that orbital record, properly interpolated, as the input for a second step to simulate its effects on the terrestrial planet formation. For this second step, we developed iSyMBA, a symplectic massive bodies algorithm, where ``i'' stands for interpolation. iSyMBA is a very useful code to accurately evaluate the effects of planetary instabilities on minor body reservoirs, while accounting for close encounters among massive objects. We provide a detailed description of how iSyMBA was developed and implemented to study terrestrial planet formation. Adapting iSyMBA for other problems that demand interpolation from previous simulations can be done following the method described here.

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arXiv2021

The young Hobson family: Possible binary parent body and low-velocity dispersal

Asteroid families with ages younger than $1$ Myr offer an interesting possibility of studying the outcomes of asteroid disruptions that are little modified by subsequent evolutionary processes. We analyze a very young asteroid family associated with (18777) Hobson in the central part of the main belt. We aim at (i) understanding its peculiar size distribution, and (ii) setting an upper limit on the characteristic dispersal velocity at subkilometer sizes corresponding to the smallest visible Hobson members. We identified the Hobson family using an up-to-date asteroid catalog. A significant increase in the number of its known members allowed us to study their size distribution and compare it with computer simulations of catastrophic disruptions. Backward orbital integrations of the heliocentric orbits allowed us to confirm the previously suggested age of Hobson and helped to estimate limits of the ejection speed. The Hobson family has an unusual size distribution: two nearly equal-size bodies, followed by a population of smaller asteroids, whose distribution takes a characteristic power law. There are two possibilities to explain these data. Either a canonical impact onto a single parent body, requiring fine-tuned impact conditions that have not been studied so far, or an unconventional model for the parent object of the Hobson family, namely a binary with $\simeq 7-9$ km primary and a $\simeq 2.5$ km secondary. In the latter case, the primary was disrupted, leaving behind the largest remnant (18777) Hobson and a suite of subkilometer asteroids. The second largest asteroid, (57738) 2001 UZ160, is the nearly intact satellite of the parent binary. The excellent convergence of nominal orbits of Hobson members sets an upper limit of $\simeq (10-20)$ m s$^{-1}$ for the initial dispersal velocity of the known members, which is consistent with both formation models.

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arXiv2021

Can a jumping-Jupiter trigger the Moon's formation impact?

We investigate the possibility that the Moon's formation impact was triggered by an early dynamical instability of the giant planets. We consider the well-studied "jumping Jupiter" hypothesis for the solar system's instability, where Jupiter and Saturn's semi-major axes evolve in step-wise manner from their primordially compact architecture to their present locations. Moreover, we test multiple different configurations for the primordial system of terrestrial planets and the Moon-forming projectile, with particular focus on the almost equal masses impact. We find that the instability/migration of the giant planets excites the orbits of the terrestrial planets through dynamical perturbations, thus allowing collisions between them. About 10% of the simulations lead to a collision with the proto-Earth which resulted in a final configuration of the terrestrial system that reproduces, to some extent, its present architecture. Most of these collisions occur in the hit-and-run domain, but about 15% occur in the partial accretion regime, with the right conditions for a Moon-forming impact. In most of the simulations, there is a delay of more than ~20 My between the time of the instability and the Moon-forming impact. This supports the occurrence of an early instability (< 10 My} after dissipation of the gas in the proto-planetary disk), compatible with the time of the Moon-forming impact (30-60 My) inferred from cosmochemical constraints. In general, the final states of the inner solar system in our simulations show an excess of Angular Momentum Deficit, mostly attributed to the over-excitation of Mercury's eccentricity and inclination.

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arXiv2021

Astrocladistics of the Jovian Trojan Swarms

The Jovian Trojans are two swarms of small objects that share Jupiter's orbit, clustered around the leading and trailing Lagrange points, L$_4$ and L$_5$. In this work, we investigate the Jovian Trojan population using the technique of astrocladistics, an adaptation of the `tree of life' approach used in biology. We combine colour data from WISE, SDSS, Gaia DR2 and MOVIS surveys with knowledge of the physical and orbital characteristics of the Trojans, to generate a classification tree composed of clans with distinctive characteristics. We identify 48 clans, indicating groups of objects that possibly share a common origin. Amongst these are several that contain members of the known collisional families, though our work identifies subtleties in that classification that bear future investigation. Our clans are often broken into subclans, and most can be grouped into 10 superclans, reflecting the hierarchical nature of the population. Outcomes from this project include the identification of several high priority objects for additional observations and as well as providing context for the objects to be visited by the forthcoming \textit{Lucy} mission. Our results demonstrate the ability of astrocladistics to classify multiple large and heterogeneous composite survey datasets into groupings useful for studies of the origins and evolution of our Solar system.

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arXiv2020

Migration of gap-opening planets in 3D stellar-irradiated accretion disks

Context. The origin of giant planets at moderate separations $\simeq$$1$$-$$10$ au is still not fully understood because numerical studies of Type II migration in protoplanetary disks often predict a decay of the semi-major axis that is too fast. According to recent 2D simulations, inward migration of a gap-opening planet can be slowed down or even reversed if the outer gap edge becomes heated by irradiation from the central star, and puffed up. Aims. Here we study how stellar irradiation reduces the disk-driven torque and affects migration in more realistic 3D disks. Methods. Using 3D hydrodynamic simulations with radiation transfer, we investigated the static torque acting on a single gap-opening planet embedded in a passively heated accretion disk. Results. Our simulations confirm that a temperature inversion is established at the irradiated outer gap edge and the local increase of the scale height reduces the magnitude of the negative outer Lindblad torque. However, the temperature excess is smaller than assumed in 2D simulations and the torque reduction only becomes prominent for specific parameters. For the viscosity $α=10^{-3}$, the total torque is reduced for planetary masses ranging from $0.1$ to $0.7$ Jupiter mass, with the strongest reduction being by a factor of $-0.17$ (implying outward migration) for a Saturn-mass planet. For a Jupiter-mass planet, the torque reduction becomes stronger with increasing $α$ (the torque is halved when $α=5\times10^{-3}$). Conclusions. We conclude that planets that open moderately wide and deep gaps are subject to the largest torque modifications and their Type II migration can be stalled due to gap edge illumination. We then argue that the torque reduction can help to stabilize the orbits of giant planets forming at $\gtrsim$$1$ au.

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