The effect of close-in giant planets’ evolution on tidal-induced migration of exomoons

Alvarado-Montes, Jaime A.; Zuluaga, Jorge I.; Sucerquia, Mario

doi:10.1093/mnras/stx1745

Cited by 55 publications

(33 citation statements)

References 34 publications

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“…This coupled evolution has proven to be important in star-planet systems too, as shown by Alvarado-Montes & García-Carmona (2019). According to the model by Alvarado-Montes et al (2017), which we also apply here, the most likely fate for exomoons whose orbit is modified as the result of a tidally-induced interchange of angular momentum with its planet, is to evolve towards even further circumplanetary orbits. Time-scales and hence the probability for this to occur during the age of the planetary system, strongly depend on the moon and host-planet initial orbits and other physical parameters, such as the planet and satellite masses and radii, the initial semi-major axes and the planet core-mass fraction.…”

Section: Time-scales Of Tidal 'Ejection'mentioning

confidence: 58%

“…Barnes & O'Brien 2002). Recently, Alvarado-Montes et al (2017) proposed a more realistic model for the interaction of planet-moon systems, including but not restricted to the evolution of the planetary radius and the variable mechanical response of the planetary interior to the tides raised by its moons and the host star. This coupled evolution has proven to be important in star-planet systems too, as shown by Alvarado-Montes & García-Carmona (2019).…”

Section: Time-scales Of Tidal 'Ejection'mentioning

confidence: 99%

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Ploonets: formation, evolution, and detectability of tidally detached exomoons

Sucerquia

Alvarado-Montes

Zuluaga

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Close-in giant planets represent the most significant evidence of planetary migration. If large exomoons form around migrating giant planets which are more stable (e.g. those in the Solar System), what happens to these moons after migration is still under intense research. This paper explores the scenario where large regular exomoons escape after tidal-interchange of angular momentum with its parent planet, becoming small planets by themselves. We name this hypothetical type of object a ploonet. By performing semi-analytical simulations of tidal interactions between a large moon with a close-in giant, and integrating numerically their orbits for several Myr, we found that in ∼50 per cent of the cases a young ploonet may survive ejection from the planetary system, or collision with its parent planet and host star, being in principle detectable. Volatile-rich ploonets are dramatically affected by stellar radiation during both planetocentric and siderocentric orbital evolution, and their radius and mass change significantly due to the sublimation of most of their material during time-scales of hundred of Myr. We estimate the photometric signatures that ploonets may produce if they transit the star during the phase of evaporation, and compare them with noisy lightcurves of known objects (Kronian stars and non-periodical dips in dusty lightcurves). Additionally, the typical transit timing variations (TTV) induced by the interaction of a ploonet with its planet are computed. We find that present and future photometric surveys' capabilities can detect these effects and distinguish them from those produced by other nearby planetary encounters.

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Section: Time-scales Of Tidal 'Ejection'mentioning

confidence: 58%

Section: Time-scales Of Tidal 'Ejection'mentioning

confidence: 99%

Ploonets: formation, evolution, and detectability of tidally detached exomoons

Sucerquia

Alvarado-Montes

Zuluaga

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…the secondary Hill radius 0.48 R Hill ), and dashed lines denote the position of the synchronous radius (a synch ) where Ω p = n m . Right-hand panel: same as before but using the model of Alvarado-Montes et al (2017). Due to differences in time-scales, we show for illustration purposes the orbital evolution of an exomoon around a planet located at 0.5 and 1.0 au.…”

Section: Tidally-driven Orbital Evolutionmentioning

confidence: 99%

“…are similar to that of Saturn and an ice-free Titan. 2 Although initial planetary rotation seems to be rather arbitrary, we use this value for two main reasons: (1) it is similar to the rotational period of Jupiter (∼10 hours), Saturn (∼11 hours), Uranus (∼17 hours) and Neptune (∼16 hours); and (2) the corresponding break-up period P break ∼ 2π GM p /R 3 p ; and the planetary interior structure parameters are similar to those of Saturn (see Alvarado-Montes et al 2017) with α = R c /R p = 0.219, and β = M c /M p = 0.196, where R c and M c are the radius and mass of the planet's core, respectively. In all cases we assume that the planetary and moon orbits are coplanar and circular.…”

Section: Synthetic Population Of Exomoonsmentioning

confidence: 99%

Can close-in giant exoplanets preserve detectable moons?

Sucerquia

Ramírez

Alvarado-Montes

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Exoplanet discoveries have motivated numerous efforts to find unseen populations of exomoons, yet they have been unsuccessful. A plausible explanation is that most discovered planets are located on close-in orbits, which would make their moons prone to tidal evolution and orbital detachment. In recent models of tidally-driven migration of exomoons, evolving planets might prevent what was considered their most plausible fate (i.e. colliding against their host planet), favouring scenarios where moons are pushed away and reach what we define as the satellite tidal orbital parking distance (a stop ), which is often within the critical limit for unstable orbits and depends mainly on the system's initial conditions: mass-ratio, semi-major axes, and rotational rates. By using semi-analytical calculations and numerical simulations, we calculate a stop for different initial system parameters and constrain the transit detectability of exomoons around close-in planets. We found that systems with M m /M p ≥ 10 −4 , which are less likely to form, are also stable and detectable with present facilities (e.g. Kepler and TESS ) through their direct and secondary effects in planet+moon transit, as they are massive, oversized, and migrate slowly. In contrast, systems with lower moon-to-planet mass ratios are ephemeral and hardly detectable. Moreover, any detection, confirmation, and full characterisation would require both the short cadence capabilities of TESS and high photometric sensitivity of ground-based observatories. Finally, despite the shortage of discovered long-period planets in currently available databases, the tidal migration model adopted in this work supports the idea that they are more likely to host the first detectable exomoon.

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“…Moreover, exomoon environments are im-portant due to their potential of hosting liquid water, thereby creating more opportunities for harbouring life (Williams et al 1997), and extending the normal boundaries of what is considered habitable environments. Such a possibility is intricately contingent upon multiple factors, including the amount of insolation, tidal heating, and other heat sources available to exomoons (Heller & Barnes 2013;Dobos et al 2017), as well as their orbital stability (Gong et al 2013;Hong et al 2015;Spalding et al 2016;Alvarado-Montes et al 2017;Zollinger et al 2017;Grishin et al 2018;Hong et al 2018;? ), atmosphere (Lammer et al 2014;Heller & Barnes 2015) and the magnetic field of either satellite or planet (Heller & Zuluaga 2013).…”

Section: Introductionmentioning

confidence: 99%

Collisional formation of massive exomoons of superterrestrial exoplanets

Malamud

Perets

Schäfer

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Exomoons orbiting terrestrial or super-terrestrial exoplanets have not yet been discovered; their possible existence and properties are therefore still an unresolved question. Here we explore the collisional formation of exomoons through giant planetary impacts. We make use of smooth particle hydrodynamical (SPH) collision simulations and survey a large phase-space of terrestrial/superterrestrial planetary collisions. We characterize the properties of such collisions, finding one rare case in which an exomoon forms through a graze & capture scenario, in addition to a few graze & merge or hit & run scenarios. Typically however, our collisions form massive circumplanetary discs, for which we use followup N-body simulations in order to derive lower-limit mass estimates for the ensuing exomoons. We investigate the mass, long-term tidal-stability, composition and origin of material in both the discs and the exomoons. Our giant-impact models often generate relatively iron-rich moons, that form beyond the synchronous radius of the planet, and would thus tidally evolve outward with stable orbits, rather than be destroyed. Our results suggest that it is extremely difficult to collisionally form currently-detectable exomoons orbiting super-terrestrial planets, through single giant impacts. It might be possible to form massive, detectable exomoons through several mergers of smaller exomoons, formed by multiple impacts, however more studies are required in order to reach a conclusion. Given the current observational initiatives, the search should focus primarily on more massive planet categories. However, about a quarter of the exomoons predicted by our models are approximately Mercury-mass or more, and are much more likely to be detectable given a factor 2 improvement in the detection capability of future instruments, providing further motivation for their development.

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The effect of close-in giant planets’ evolution on tidal-induced migration of exomoons

Cited by 55 publications

References 34 publications

Ploonets: formation, evolution, and detectability of tidally detached exomoons

Ploonets: formation, evolution, and detectability of tidally detached exomoons

Can close-in giant exoplanets preserve detectable moons?

Collisional formation of massive exomoons of superterrestrial exoplanets

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