scholarly journals Why do warm Neptunes present nonzero eccentricity?

2020 ◽  
Vol 635 ◽  
pp. A37 ◽  
Author(s):  
A. C. M. Correia ◽  
V. Bourrier ◽  
J.-B. Delisle
Keyword(s):  
Planetary Systems ◽  
Atmospheric Tides ◽  
Tidal Dissipation ◽  
Bodily Tides ◽  
Orbital Periods

Most Neptune-mass planets in close-in orbits (orbital periods less than a few days) present nonzero eccentricity, typically around 0.15. This is somehow unexpected, as these planets undergo strong tidal dissipation that should circularize their orbits in a timescale shorter than the age of the system. In this paper we discuss some mechanisms that can oppose to bodily tides, namely, thermal atmospheric tides, evaporation of the atmosphere, and excitation from a distant companion. In the first two cases, the eccentricity can increase consistently, while in the last one, the eccentricity can only be excited for a limited amount of time (that may nevertheless exceed the age of the system). We show the limitations of these different mechanisms and how some of them could, depending on specific properties of the observed planetary systems, account for their presently observed eccentricities.

scholarly journals Quantization of Planetary Systems and its Dependency on Stellar Rotation

2011 ◽  
Vol 28 (3) ◽  
pp. 177-201 ◽  
Author(s):  
Jean-Paul A. Zoghbi
Keyword(s):  
Gravitational Instability ◽  
Rotation Period ◽  
Planetary Systems ◽  
Stellar Rotation ◽  
Tidal Dissipation ◽  
Half Integer ◽  
Pure Chance ◽  
Rotation Periods ◽  
Planetary Orbits ◽  
Orbital Periods

AbstractWith the discovery of now more than 500 exoplanets, we present a statistical analysis of the planetary orbital periods and their relationship to the rotation periods of their parent stars. We test whether the structural variables of planetary orbits, i.e. planetary angular momentum and orbital period, are ‘quantized’ in integer or half-integer multiples of the parent star's rotation period. The Solar System is first shown to exhibit quantized planetary orbits that correlate with the Sun's rotation period. The analysis is then expanded over 443 exoplanets to statistically validate this quantization and its association with stellar rotation. The results imply that the exoplanetary orbital periods are highly correlated with the parent star's rotation periods and follow a discrete half-integer relationship with orbital ranks n = 0.5, 1.0, 1.5, 2.0, 2.5, etc. The probability of obtaining these results by pure chance is p < 0.024. We discuss various mechanisms that could justify this planetary quantization, such as the hybrid gravitational instability models of planet formation, along with possible physical mechanisms such as the inner disc's magnetospheric truncation, tidal dissipation, and resonance trapping. In conclusion, we statistically demonstrate that a quantized orbital structure should emerge from the formation processes of planetary systems and that this orbital quantization is highly dependent on the parent star's rotation period.

scholarly journals Tidally induced stellar oscillations: converting modelled oscillations excited by hot Jupiters into observables

2020 ◽  
Vol 500 (2) ◽  
pp. 2711-2731
Author(s):  
Andrew Bunting ◽  
Caroline Terquem
Keyword(s):  
Radial Velocity ◽  
Orbital Period ◽  
Planetary Systems ◽  
Velocity Signal ◽  
Convective Flux ◽  
Hot Jupiters ◽  
Stellar Oscillations ◽  
Orbital Periods ◽  
Hot Jupiter

ABSTRACT We calculate the conversion from non-adiabatic, non-radial oscillations tidally induced by a hot Jupiter on a star to observable spectroscopic and photometric signals. Models with both frozen convection and an approximation for a perturbation to the convective flux are discussed. Observables are calculated for some real planetary systems to give specific predictions. The photometric signal is predicted to be proportional to the inverse square of the orbital period, P−2, as in the equilibrium tide approximation. However, the radial velocity signal is predicted to be proportional to P−1, and is therefore much larger at long orbital periods than the signal corresponding to the equilibrium tide approximation, which is proportional to P−3. The prospects for detecting these oscillations and the implications for the detection and characterization of planets are discussed.

Tidal Interactions Between Planets and Host Stars

2020 ◽  
Author(s):  
Gordon Ogilvie
Keyword(s):  
Angular Momentum ◽  
Large Scale ◽  
Solid Mechanics ◽  
Hydrodynamic Instability ◽  
The Body ◽  
Tidal Dissipation ◽  
Tidal Interactions ◽  
Exoplanetary Systems ◽  
Short Period ◽  
Orbital Periods

Hundreds of planets are already known to have orbits only a few times wider than the stars that host them. The tidal interaction between a planet and its host star is one of the main agents shaping the observed distributions of properties of these systems. Tidal dissipation in the planet tends make the orbit circular, as well as synchronizing and aligning the planet’s spin with the orbit, and can significantly heat the planet, potentially affecting its size and structure. Dissipation in the star typically leads to inward orbital migration of the planet, accelerating the star’s rotation, and in some cases destroying the planet. Some essential features of tidal evolution can be understood from the basic principles that angular momentum and energy are exchanged between spin and orbit by means of a gravitational field and that energy is dissipated. For example, most short-period exoplanetary systems have too little angular momentum to reach a tidal equilibrium state. Theoretical studies aim to explain tidal dissipation quantitatively by solving the equations of fluid and solid mechanics in stars and planets undergoing periodic tidal forcing. The equilibrium tide is a nearly hydrostatic bulge that is carried around the body by a large-scale flow, which can be damped by convection or hydrodynamic instability, or by viscoelastic dissipation in solid regions of planets. The dynamical tide is an additional component that generally takes the form of internal waves restored by Coriolis and buoyancy forces in a rotating and stratified fluid body. It can lead to significant dissipation if the waves are amplified by resonance, are efficiently damped when they attain a very short wavelength, or break because they exceed a critical amplitude. Thermal tides are excited in a planetary atmosphere by the variable heating by the star’s radiation. They can oppose gravitational tides and prevent tidal locking, with consequences for the climate and habitability of the planet. Ongoing observations of transiting exoplanets provide information on the orbital periods and eccentricities as well as the obliquity (spin–orbit misalignment) of the star and the size of the planet. These data reveal several tidal processes at work and provide constraints on the efficiency of tidal dissipation in a variety of stars and planets.

scholarly journals The Impact of Stellar Clustering on the Observed Multiplicity and Orbital Periods of Planetary Systems

2021 ◽  
Vol 911 (1) ◽  
pp. L16
Author(s):  
Steven N. Longmore ◽  
Mélanie Chevance ◽  
J. M. Diederik Kruijssen
Keyword(s):  
Planetary Systems ◽  
Orbital Periods ◽  
The Impact

scholarly journals Scaling laws to understand tidal dissipation in fluid planetary layers and stars

2014 ◽  
Vol 9 (S310) ◽  
pp. 29-32
Author(s):  
Pierre Auclair-Desrotour ◽  
Stéphane Mathis ◽  
Christophe Le Poncin-Lafitte
Keyword(s):  
Thermal Diffusivity ◽  
Scaling Laws ◽  
Planetary Systems ◽  
Viscous Friction ◽  
Local Model ◽  
Tidal Dissipation ◽  
Tidal Waves ◽  
Secular Evolution ◽  
Structure And Dynamics ◽  
Internal Parameters

AbstractTidal dissipation is known as one of the main drivers of the secular evolution of planetary systems. It directly results from dissipative mechanisms that occur in planets and stars' interiors and strongly depends on the structure and dynamics of the bodies. This work focuses on the mechanism of viscous friction in stars and planetary layers. A local model is used to study tidal dissipation. It provides general scaling laws that give a qualitative overview of the different possible behaviors of fluid tidal waves. Furthermore, it highlights the sensitivity of dissipation to the tidal frequency and the roles played by the internal parameters of the fluid such as rotation, stratification, viscosity and thermal diffusivity that will impact the spins/orbital architecture in planetary systems.

scholarly journals Planetary Systems and Stellar Multiplicity

1977 ◽  
Vol 33 ◽  
pp. 175-187
Author(s):  
Su-Shu Huang
Keyword(s):  
Planetary System ◽  
Genetic Difference ◽  
Surrounding Medium ◽  
Planetary Systems ◽  
Rotating Disk ◽  
Central Star ◽  
Dust Particles ◽  
Basic Point ◽  
Multiple Systems ◽  
Orbital Periods

AbstractIn this paper we have discussed the origin of planetary systems on one hand and binary and multiple stars on the other. First we show that phenomenological differences between these two kinds of celestial objects are due to their genetic difference. The basic point is that formation of a planetary system around a star has to be a minor event in the life history of the star while formation of a binary or multiple system has to be an event that is important equally to all components of the system. Thus the planetary system evolves from a rotating disk of gaseous and dust particles that comes into being after the star has already been there. It is therefore reasonable to suggest that the rotating disk results from transfer of angular momentum from the central star to the surrounding medium which is likely a residue left over in the process of formation of the central star.Binary and multiple systems cannot be formed in this way because they do not show the characteristics of having come out of a rotating disk. The dominant mechanism of their formation is that they were formed naturally as they are, each from perhaps a single condensation in the interstellar medium. However such a single mechanism of formation cannot satisfactorily explain the observed spread of binaries in mean separations between two components (or equivalently orbital periods). But the disagreement may be removed by including a small number of binaries formed by other processes and by considering the change of orbital elements of binaries after their formation. Trapezia were likely formed also by more than one mechanism.That several stars could be formed, from a single condensation requires the” existence oí pre-stellar nuclei which are briefly: discussed at the end of the paper.

scholarly journals Atmospheric thermal tides and planetary spin

2018 ◽  
Vol 609 ◽  
pp. A118 ◽  
Author(s):  
P. Auclair-Desrotour ◽  
S. Mathis ◽  
J. Laskar
Keyword(s):  
Rotation Frequency ◽  
Maxwell Model ◽  
Stable Stratification ◽  
Atmospheric Tides ◽  
Dissipated Energy ◽  
Tidal Dissipation ◽  
Tidal Torque ◽  
Tidal Waves ◽  
Tidally Driven ◽  
Thermal Tides

Context. Thermal atmospheric tides can torque telluric planets away from spin-orbit synchronous rotation, as observed in the case of Venus. They thus participate in determining the possible climates and general circulations of the atmospheres of these planets. Aims. The thermal tidal torque exerted on an atmosphere depends on its internal structure and rotation and on the tidal frequency. Particularly, it strongly varies with the convective stability of the entropy stratification. This dependence has to be characterized to constrain and predict the rotational properties of observed telluric exoplanets. Moreover, it is necessary to validate the approximations used in global modelings such as the traditional approximation, which is used to obtain separable solutions for tidal waves. Methods. We wrote the equations governing the dynamics of thermal tides in a local vertically stratified section of a rotating planetary atmosphere by taking into account the effects of the complete Coriolis acceleration on tidal waves. This allowed us to analytically derive the tidal torque and the tidally dissipated energy, which we used to discuss the possible regimes of tidal dissipation and to examine the key role played by stratification. Results. In agreement with early studies, we find that the frequency dependence of the thermal atmospheric tidal torque in the vicinity of synchronization can be approximated by a Maxwell model. This behavior corresponds to weakly stably stratified or convective fluid layers, as observed previously. A strong stable stratification allows gravity waves to propagate, and makes the tidal torque negligible. The transition is continuous between these two regimes. The traditional approximation appears to be valid in thin atmospheres and in regimes where the rotation frequency is dominated by the forcing or the buoyancy frequencies. Conclusions. Depending on the stability of their atmospheres with respect to convection, observed exoplanets can be tidally driven toward synchronous or asynchronous final rotation rates. The domain of applicability of the traditional approximation is rigorously constrained by calculations.

scholarly journals Architectures of exoplanetary systems – I. A clustered forward model for exoplanetary systems around Kepler’s FGK stars

2019 ◽  
Vol 490 (4) ◽  
pp. 4575-4605 ◽  
Author(s):  
Matthias Y He ◽  
Eric B Ford ◽  
Darin Ragozzine
Keyword(s):  
Point Process ◽  
Process Model ◽  
Planetary Systems ◽  
Forward Modelling ◽  
Marginal Distributions ◽  
Period Ratio ◽  
Modelling Framework ◽  
Exoplanetary Systems ◽  
Orbital Periods ◽  
Gaia Dr2

ABSTRACT Observations of exoplanetary systems provide clues about the intrinsic distribution of planetary systems, their architectures, and how they formed. We develop a forward modelling framework for generating populations of planetary systems and ‘observed’ catalogues by simulating the Kepler detection pipeline (SysSim). We compare our simulated catalogues to the Kepler DR25 catalogue of planet candidates, updated to include revised stellar radii from Gaia DR2. We constrain our models based on the observed 1D marginal distributions of orbital periods, period ratios, transit depths, transit depth ratios, transit durations, transit duration ratios, and transit multiplicities. Models assuming planets with independent periods and sizes do not adequately account for the properties of the multiplanet systems. Instead, a clustered point process model for exoplanet periods and sizes provides a significantly better description of the Kepler population, particularly the observed multiplicity and period ratio distributions. We find that $0.56^{+0.18}_{-0.15}$ of FGK stars have at least one planet larger than 0.5R⊕ between 3 and 300 d. Most of these planetary systems ($\sim 98{{\ \rm per\ cent}}$) consist of one or two clusters with a median of three planets per cluster. We find that the Kepler dichotomy is evidence for a population of highly inclined planetary systems and is unlikely to be solely due to a population of intrinsically single planet systems. We provide a large ensemble of simulated physical and observed catalogues of planetary systems from our models, as well as publicly available code for generating similar catalogues given user-defined parameters.

Asynchronous and chaotic rotation for compact planetary systems

2020 ◽  
Author(s):  
Alexandre C. M. Correia ◽  
Jean-Baptiste Delisle
Keyword(s):  
Orbital Period ◽  
Spin Dynamics ◽  
Rotation Period ◽  
Planetary Systems ◽  
Circular Orbits ◽  
Simple Method ◽  
Tidal Dissipation ◽  
Orbital Perturbations ◽  
Spin Evolution

&lt;p&gt;We study the spin evolution of close-in planets in compact multi-planetary systems. The rotation period of these planets is often assumed to be synchronous with the orbital period due to tidal dissipation. Here we show that planet-planet perturbations can drive the spin of these planets into non-synchronous or even chaotic states. These asynchronous configurations are possible even for nearly circular orbits and will impact the habitability of these planets. We also present a very simple method to probe the spin dynamics from the orbital perturbations.&lt;/p&gt;

scholarly journals Simulation of 3 Body Exo-Planetary System Orbits

2020 ◽  
Vol 12 (2) ◽  
pp. 25
Author(s):  
Zixin Li
Keyword(s):  
Computer Program ◽  
Planetary System ◽  
Planetary Systems ◽  
Motion Model ◽  
Body System ◽  
Planetary Orbits ◽  
Orbital Periods ◽  
General Motion ◽  
Over Time

To find out the general motion model of exo-planetary systems with one star and two planets, a computer program was used to carry out simulations and generate graphs showing the orbits of planets. When given the orbital periods and masses of the planets and stars, it is possible to predict the location of the planets over time and plot the shape of the orbit by considering the gravitational interactions between planets and the star, assuming that the planetary orbits are co-planar. I used the program to reproduce the result of transit timing variations (TTVs) of Kepler-46 system, I then investigated on the magnitude of transit timing variations on a 3-body system with various masses and periods. I also ran simulations to investigate the pattern of orbits for different periods of planets in order to get a systematic conclusion.

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