Calculation of the enrichment of the giant planet envelopes during the “late heavy bombardment” (original) (raw)
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Data Archiving and Networked Services (DANS), 2020
The chemical composition of planetary atmospheres has long been thought to store information regarding where and when a planet accretes its material. Predicting this chemical composition theoretically is a crucial step in linking observational studies to the underlying physics that govern planet formation. As a follow-up to a study of hot Jupiters in our previous work, we present a population of warm Jupiters (semi-major axis between 0.5-4 AU) extracted from the same planetesimal formation population synthesis model as used in our previous work. We compute the astrochemical evolution of the protoplanetary disks included in this population to predict the carbon-to-oxygen (C/O) and nitrogen-to-oxygen (N/O) ratio evolution of the disk gas, ice, and refractory sources, the accretion of which greatly impacts the resulting C/O and N/O in the atmosphere of giant planets. We confirm that the main sequence (between accreted solid mass and atmospheric C/O) we found previously is largely reproduced by the presented population of synthetic warm Jupiters. And as a result, the majority of the population fall along the empirically derived mass-metallicity relation when the natal disk has solar or lower metallicity. Planets forming from disks with high metallicity ([Fe/H] > 0.1) result in more scatter in chemical properties which could explain some of the scatter found in the mass-metallicity relation. Combining predicted C/O and N/O ratios shows that Jupiter does not fall among our population of synthetic planets, suggesting that it likely did not form in the inner 5 AU of the solar system before proceeding into a Grand Tack. This result is consistent with recent analysis of the chemical composition of Jupiter's atmosphere which suggests that it accreted most of its heavy element abundance farther than tens of AU away from the Sun. Finally we explore the impact of different carbon refractory erosion models, including the location of the carbon erosion front. Shifting the erosion front has a major impact on the resulting C/O ratio of Jupiter and Neptune-like planets, but warm Saturns see a smaller shift in C/O, since their carbon and oxygen abundances are equally impacted by gas and refractory accretion.
Determination of the Minimum Masses of Heavy Elements in the Envelopes of Jupiter and Saturn
The Astrophysical Journal, 2009
We report the orbital distribution of the trans-Neptunian comets discovered during the first discovery year of the Canada-France Ecliptic Plane Survey (CFEPS). CFEPS is a Kuiper Belt object survey based on observations acquired by the Very Wide component of the Canada-France-Hawaii Telescope Legacy Survey (LS-VW). The first year's detections consist of 73 Kuiper Belt objects, 55 of which have now been tracked for three years or more, providing precise orbits. Although this sample size is small compared to the world-wide inventory, because we have an absolutely calibrated and extremely well-characterized survey (with known pointing history) we are able to de-bias our observed population and make unbiased statements about the intrinsic orbital distribution of the Kuiper Belt. By applying the (publically available) CFEPS Survey Simulator to models of the true orbital distribution and comparing the resulting simulated detections to the actual detections made by the survey, we are able to rule out several hypothesized Kuiper Belt object orbit distributions. We find that the main classical belt's so-called 'cold' component is confined in semimajor axis (a) and eccentricity (e) compared to the more extended "hot" component; the cold component is confined to lower e and does not stretch all the way out to the 2:1 resonance but rather depletes quickly beyond a = 45 AU. For the cold main classical belt population we find a robust population estimate of N (H g < 10) = 50 ± 5 × 10 3 and find that the hot component of the main classical belt represents ∼60% of the total population. The inner classical belt (sunward of the 3:2 mean-motion resonance) has a population of roughly 2000 trans-Neptunian objects with absolute magnitudes H g < 10, and may not share the inclination distribution of the main classical belt. We also find that the plutino population lacks a cold low-inclination component, and so, the population is somewhat larger than recent estimates; our analysis shows a plutino population of N (H g < 10) ∼ 25 +25 −12 × 10 3 compared to our estimate of the size of main classical Kuiper Belt population of N (H g < 10) ∼ (126 +50 −46 ) × 10 3 .
Connecting planet formation and astrochemistry
Astronomy and Astrophysics, 2019
To understand the role that planet formation history has on the observable atmospheric carbon-to-oxygen ratio (C/O) we have produced a population of astrochemically evolving protoplanetary disks. Based on the parameters used in a pre-computed population of growing planets, their combination allows us to trace the molecular abundances of the gas that is being collected into planetary atmospheres. We include atmospheric pollution of incoming (icy) planetesimals as well as the effect of refractory carbon erosion noted to exist in our own solar system. We find that the carbon and oxygen content of Neptune-mass planets are determined primarily through solid accretion and result in more oxygen-rich (by roughly two orders of magnitude) atmospheres than hot Jupiters, whose C/O are primarily determined by gas accretion. Generally we find a "main sequence" between the fraction of planetary mass accreted through solid accretion and the resulting atmospheric C/O; planets of higher solid accretion fraction have lower C/O. Hot Jupiters whose atmospheres have been chemically characterized agree well with our population of planets, and our results suggest that hot-Jupiter formation typically begins near the water ice line. Lower mass hot Neptunes are observed to be much more carbon rich (with 0.33 C/O 1) than is found in our models (C/O ∼ 10 −2), and suggest that some form of chemical processing may affect their observed C/O over the few billion years between formation and observation. Our population reproduces the general mass-metallicity trend of the solar system and qualitatively reproduces the C/O metallicity anti-correlation that has been inferred for the population of characterized exoplanetary atmospheres.
Astronomy & Astrophysics, 2006
Context. Nine extrasolar planets with masses between 110 and 430M ⊕ are known to transit their star. The knowledge of their masses and radii allows an estimate of their composition, but uncertainties on equations of state, opacities and possible missing energy sources imply that only inaccurate constraints can be derived when considering each planet separately. Aims. We seek to better understand the composition of transiting extrasolar planets by considering them as an ensemble, and by comparing the obtained planetary properties to that of the parent stars. Methods. We use evolution models and constraints on the stellar ages to derive the mass of heavy elements present in the planets. Possible additional energy sources like tidal dissipation due to an inclined orbit or to downward kinetic energy transport are considered. Results. We show that the nine transiting planets discovered so far belong to a quite homogeneous ensemble that is characterized by a mass of heavy elements that is a relatively steep function of the stellar metallicity, from less than 20 earth masses of heavy elements around solar composition stars, to up to ∼ 100 M ⊕ for three times the solar metallicity (the precise values being model-dependant). The correlation is still to be ascertained however. Statistical tests imply a worst-case 1/3 probability of a false positive. Conclusions. Together with the observed lack of giant planets in close orbits around metal-poor stars, these results appear to imply that heavy elements play a key role in the formation of close-in giant planets. The large masses of heavy elements inferred for planets orbiting metal rich stars was not anticipated by planet formation models and shows the need for alternative theories including migration and subsequent collection of planetesimals.
HAT-P-26b: A Neptune-mass exoplanet with a well-constrained heavy element abundance
Science (New York, N.Y.), 2017
A correlation between giant-planet mass and atmospheric heavy elemental abundance was first noted in the past century from observations of planets in our own Solar System and has served as a cornerstone of planet-formation theory. Using data from the Hubble and Spitzer Space Telescopes from 0.5 to 5 micrometers, we conducted a detailed atmospheric study of the transiting Neptune-mass exoplanet HAT-P-26b. We detected prominent H2O absorption bands with a maximum base-to-peak amplitude of 525 parts per million in the transmission spectrum. Using the water abundance as a proxy for metallicity, we measured HAT-P-26b's atmospheric heavy element content ([Formula: see text] times solar). This likely indicates that HAT-P-26b's atmosphere is primordial and obtained its gaseous envelope late in its disk lifetime, with little contamination from metal-rich planetesimals.
Icarus, 1999
We report on numerical simulations exploring the dynamical stability of planetesimals in the gaps between the outer Solar System planets. We search for stable niches in the Saturn/Uranus and Uranus/Neptune zones by employing 10,000 massless particlesmany more than previous studies in these two zones-using highorder optimized multistep integration schemes coupled with roundoff error minimizing methods. An additional feature of this study, differing from its predecessors, is the fact that our initial distributions contain particles on orbits which are both inclined and noncircular. These initial distributions were also Gaussian distributed such that the Gaussian peaks were at the midpoint between the neighboring perturbers. The simulations showed an initial transient phase where the bulk of the primordial planetesimal swarm was removed from the Solar System within 10 5 years. This is about 10 times longer than we observed in our previous Jupiter/Saturn studies. Next, there was a gravitational relaxation phase where the particles underwent a random walk in momentum space and were exponentially eliminated by random encounters with the planets. Unlike our previous Jupiter/Saturn simulation, the particles did not fully relax into a third Lagrangian niche phase where long-lived particles are at Lagrange points or stable niches. This is either because the Lagrangian niche phase never occurs or because these simulations did not have enough particles for this third phase to manifest. In these simulations, there was a general trend for the particles to migrate outward and eventually to be cleared out by the outermost planet in the zone. We confirmed that particles with higher eccentricities had shorter lifetimes and that the resonances between the jovian planets "pumped up" the eccentricities of the planetesimals with low-inclination orbits more than those with higher inclinations. We estimated the expected lifetime of particles using kinetic theory and even though the time scale of the Uranus/Neptune simulation was 380 times longer than our previous Jupiter/Saturn simulation, the planetesimals in the Uranus/Neptune zone were cleared out more quickly than those in the Saturn/Uranus zone because of the positions of resonances with the jovian planets. These resonances had an even greater effect than random gravitational stirring in the winnowing process and confirm that all the jovian planets are necessary in long simulations. Even though we observed several long-lived zones near 12.5, 14.4, 16, 24.5, and 26 AU, only two particles remained at the end of the 10 9 -year integration: one near the 2 : 3 Saturn resonance, and the other near the Neptune 1 : 1 resonance. This suggests that niches for planetesimal material in the jovian planets are rare and may exist either only in extremely narrow bands or in the neighborhoods of the triangular Lagrange points of the outer planets.
arXiv (Cornell University), 2020
The observational detection of a localized reduction in the small planet occurrence rate, sometimes termed a gap, is an exciting discovery because of the implications for planet evolutionary history. This gap appears to define a transition region in which sub-Neptune planets are believed to have lost their H/He envelope, potentially by photoevaporation or core powered mass loss, and have thus been transformed into bare cores terrestrial planets. Here we investigate the transition between sub-Neptunes and super-Earths using a real sample of observed small close-in planets and applying envelope evolution models of the H/He envelope together with the mass-radius diagram and a photoevaporation model. We find that photoevaporation can explain the H/He envelope loss of most super-Earths in 100Myr, although an additional loss mechanism appears necessary in some planets. We explore the possibility that these planets families have different core mass and find a continuum in the primordial population of the strongly irradiated super-Earths and the sub-Neptunes. Our analysis also shows that close-orbiting sub-Neptunes with R<3.5 R ⊕ typically lose ∼ 30% of their primordial envelope.
The Astrophysical Journal, 2014
We study the stars of the binary system 16 Cygni to determine with high precision their chemical composition. Knowing that the component B has a detected planet of at least 1.5 Jupiter masses, we investigate if there are chemical peculiarities that could be attributed to planet formation around this star. We perform a differential abundance analysis using high resolution (R=81,000) and high S/N (∼700) CFHT/ESPaDOnS spectra of the 16 Cygni stars and the Sun; the latter was obtained from light reflected of asteroids. We determine differential abundances of the binary components relative to the Sun and between components A and B as well. We achieve a precision of σ 0.005 dex and a total error ∼0.01 dex for most elements. The effective temperatures and surface gravities found for 16 Cyg A and B are T eff = 5830±7 K, log g= 4.30±0.02 dex, and T eff = 5751±6 K, log g= 4.35±0.02 dex, respectively. The component 16 Cyg A has a metallicity ([Fe/H]) higher by 0.047±0.005 dex than 16 Cyg B, as well as a microturbulence velocity higher by 0.08 km s −1 . All elements show abundance differences between the binary components, but while the volatile difference is about 0.03 dex, the refractories differ by more and show a trend with condensation temperature, which could be interpreted as the signature of the rocky accretion core of the giant planet 16 Cyg Bb. We estimate a mass of about 1.5-6 M ⊕ for this rocky core, in good agreement with estimates of Jupiter's core.
1997
We repo~t on numerical simulations exploring the dynamical stability of planetesirnals in the gaps between the outer solar system planets. We reconsider the existence of st able niches in the Saturn/ [Jranus and Uranus/Neptune zones by employing 10,000 massless particles-many more than l)revious studies in these two zones----using high-order optimized multi-step integration schemes coupled with roundoff error minimizing methods. An additional feature of this study, differing from its predecessors, is the fact that our initial distributions contain particles on orbits which are both inclined and non-circular. '1'hese initial distributions were also .gaussian distributed such that the gaussian peaks were at the midpoint between the neighboring perturbers. The sinmlations showed an initial transient phase where the bulk of the primordial planetesirnal swarm was removed from the solar system within 105 years. This is about 10 times longer than we observed in our previous Jupiter/Saturn studies. Next, there was a gravitational relaxation phase where the particles underwent a random walk in momentum space, and were exponentially eliminated by random encounters with the planets. Unlike our previous Jupiter/Saturn simulation, the particles did not fully relax into a Lagrange points or stable niches. or because these simulations did third Lagrangian niche phase where long-lived particles are at 'I'his is either because the Lagrangian niche phase never occurs, not have enough particles for this third phase to manifest. In these simulations, there was a general trend for the particles to migrate outward, and eventually 1. Alarnos, NM 87.54.5. to be cleared out by the outermost planet, in the zone. tVe confirmed that particles with higher eccentricities had shorter lifetimes. and that the resonances between the .Jovian planets '"pumped up" the eccentricities of the planetesimals with low-inclination orbits more inclinations. This resulted in longer lifetimes for the particles with a large estimated the expected lifetime of particles using kinetic theory and even than those with higher initial inclination. We though the time scale of the Uranus/Neptune simulation was 380 times longer than our previous Jupiter/Saturn sinlulation, the planetesimals in the Uranus/ .Nept une zone were cleared out more quickly than those in the Saturn/Uranus zone because of the positions of resonances with the Jovian planets. l'hese resonances had an even greater effect than random gravitational stirring in the winnowing process and confirm that all the Jovian planets are necessary in long simulations. Even though we observed several long lived zones at 12.5, 14.4, 16, 24..5 and 26 .4 U, only two particles remained at the cnd of the 10 9 year integration: one near the 2:3 Saturn resonance, and the other near the Neptune 1:1 resonance. This suggests that niches for planetesirnal material in the Jovian planets are rare and may exist either only in extremely narrow bands, or in the neighborhoods of the triangular Lagrange points of the outer planets.
Formation of heavy element rich giant planets by giant impacts
Proceedings of The International Astronomical Union, 2007
We have performed the smoothed particle hydrodynamic (SPH) simulations of collisions between two gas giant planets. Changes in masses of the ice/rock core and the H/He envelope due to the collisions are investigated. The main aim of this study is to constrain the origin and probability of a class of extrasolar hot Jupiters that have much larger cores and/or higher