Formation of exomoons: a solar system perspective

Barr, A. C.

doi:10.1080/21672857.2017.1279469

Cited by 17 publications

(10 citation statements)

References 140 publications

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“…We begin to tackle this by considering the "soft" constraint that, for all solar system giant planets, the ratio of the satellites' total mass to that of the host planet, is 0.024% (Canup & Ward 2006;Barr 2017). As Triton itself is already ∼ 0.02% of the mass of Neptune, it is rea- sonable to expect exactly one large, Triton-sized moon with the remaining mass of surviving moons (Other Surviving Small Moons or OSSMs) being small enough so that Triton survives the ensuing collisional evolution.…”

Section: Aftermath: Evolution Of Circumneptunian Materials Post-encou...mentioning

confidence: 99%

“…While the assumption that one Triton-sized moon exists seems sensible at least mass-wise (Barr 2017;Szulágyi et al 2018), the number of smaller moons, a few tens, is estimated from the expectation that one Nereid should be created during the best encounters (those featuring the highest occurrence rates of TriAs & NerAs). A few tens of such moons, under these encounters, give rise to a NerA at an efficiency close to unity and, fortuitously, provide just the right amount of impacting mass to shrink the orbit of the TriA (its creation still a small-likelihood event) quickly enough to protect the NerA without disrupting the TriA.…”

Section: The Primordial Satellite Populationmentioning

confidence: 99%

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The Origin of Neptune’s Unusual Satellites from a Planetary Encounter

Christou

2020

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The Neptunian satellite system is unusual, comprising Triton, a large (∼ 2700 km) moon on a close-in, circular, yet retrograde orbit, flanked by Nereid, the largest irregular satellite (∼300 km) on a highly eccentric orbit. Capture origins have been previously suggested for both moons. Here we explore an alternative in-situ formation model where the two satellites accreted in the circum-Neptunian disk and are imparted irregular and eccentric orbits by a deep planetary encounter with an ice giant (IG), like that predicted in the Nice scenario of early solar system development. We use N -body simulations of an IG approaching Neptune to 20 Neptunian radi (R Nep ), through a belt of circular prograde regular satellites at 10-30 R Nep . We find that half of these primordial satellites remain bound to Neptune and that 0.4-3% are scattered directly onto wide and eccentric orbits resembling that of Nereid. With better matches to the observed orbit, our model has a success rate comparable to or higher than capture of large Nereid-sized irregular satellites from heliocentric orbit. At the same time, the IG encounter injects a large primordial moon onto a retrograde orbit with specific angular momentum similar to Triton's in 0.3-3% of our runs. While less efficient than capture scenarios (Agnor & Hamilton 2006), our model does indicate that an in-situ origin for Triton is dynamically possible. We also simulate the post-encounter collisional and tidal orbital evolution of Triton analogue satellites and find they are decoupled from Nereid on timescales of ∼10 4 years, in agreement withĆuk & Gladman (2005).

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Section: Aftermath: Evolution Of Circumneptunian Materials Post-encou...mentioning

confidence: 99%

Section: The Primordial Satellite Populationmentioning

confidence: 99%

The Origin of Neptune’s Unusual Satellites from a Planetary Encounter

Christou

2020

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“…Most simulation studies of giant impacts have focused on the collisional phase space conductive to the formation of Solar system planets and satellites (Barr 2016). Despite an extensive collision simulation literature, there have only been a few studies that investigated hydrodynamical giant impact simulations relevant to exoplanets that are more massive than the Earth (Genda & Abe 2003;Marcus et al 2010a,b;Liu et al 2015;Inamdar & Schlichting 2015, 2016Barr & Bruck Syal 2017;Biersteker & Schlichting 2019). In particular, only Barr & Bruck Syal (2017) (hereafter BB17) focus on the formation of exosolar satellites (or rather the discs from which they accreted), while all the rest examine the effects on the exoplanets themselves.…”

Section: Collisional Formation Of Exomoonsmentioning

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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“…Moons can form similarly to planets, i.e. in the circumplanetary disk, or by collision (as it was probably the case for the Moon), or by binary-exchange which requires two bodies of comparable size that encounter a giant planet, which captures one of the binary bodies, while the other one is ejected (Barr 2016, Williams 2013).…”

Section: Formation Of Habitable Planetsmentioning

confidence: 99%

Geoscience for Understanding Habitability in the Solar System and Beyond

et al. 2019

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This paper reviews habitability conditions for a terrestrial planet from the point of view of geosciences. It addresses how interactions between the interior of a planet or a moon and its atmosphere and surface (including hydrosphere and biosphere) can affect habitability of the celestial body. It does not consider in detail the role of the central star but focusses more on surface conditions capable of sustaining life. We deal with fundamental issues of planetary habitability, i.e. the environmental conditions capable of sustaining life, and the above-mentioned interactions can affect the habitability of the celestial body.We address some hotly debated questions including:-How do core and mantle affect the evolution and habitability of planets? -What are the consequences of mantle overturn on the evolution of the interior and atmosphere? -What is the role of the global carbon and water cycles? -What influence do comet and asteroid impacts exert on the evolution of the planet? -How does life interact with the evolution of the Earth's geosphere and atmosphere?-How can knowledge of the solar system geophysics and habitability be applied to exoplanets?In addition, we address the identification of preserved life tracers in the context of the interaction of life with planetary evolution.

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Formation of exomoons: a solar system perspective

Cited by 17 publications

References 140 publications

The Origin of Neptune’s Unusual Satellites from a Planetary Encounter

The Origin of Neptune’s Unusual Satellites from a Planetary Encounter

Collisional formation of massive exomoons of superterrestrial exoplanets

Geoscience for Understanding Habitability in the Solar System and Beyond

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