Close encounters in young stellar clusters: implications for planetary systems in the solar neighbourhood

Malmberg, Daniel; Angeli, F. De; Davies, Melvyn B.; Church, Ross P.; Mackey, A. D.; Wilkinson, M. I.

doi:10.1111/j.1365-2966.2007.11885.x

Cited by 156 publications

(140 citation statements)

References 39 publications

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“…Moreover, most stars form in embedded cluster environments (Lada & Lada 2003) where dynamical evolution can lead to the acquisition of transient companions (Malmberg et al 2007). Recently, Batygin (2012) showed that the presence of a companion to a young star can force the proto-planetary disk to precess around the binary's axis, so that the plane in which planets eventually form and the equatorial plane of the central star can differ.…”

Section: Disk Torquingmentioning

confidence: 99%

Spin-orbit angle distribution and the origin of (mis)aligned hot Jupiters

Crida

Batygin

2014

A&A

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Context. For 61 transiting hot Jupiters, the projection of the angle between the orbital plane and the stellar equator (called the spinorbit angle) has been measured. For about half of them, a significant misalignment is detected, and retrograde planets have been observed. This challenges scenarios of the formation of hot Jupiters. Aims. In order to better constrain formation models, we relate the distribution of the real spin-orbit angle Ψ to the projected one β. Then, a comparison with the observations is relevant. Methods. We analyse the geometry of the problem to link analytically the projected angle β to the real spin-orbit angle Ψ. The distribution of Ψ expected in various models is taken from the literature, or derived with a simplified model and Monte Carlo simulations in the case of the disk-torquing mechanism.Results. An easy formula to compute the probability density function (PDF) of β knowing the PDF of Ψ is provided. All models tested here look compatible with the observed distribution beyond 40 degrees, which is so far poorly constrained by only 18 observations. But only the disk-torquing mechanism can account for the excess of aligned hot Jupiters, provided that the torquing is not always efficient. This is the case if the exciting binaries have semi-major axes as large as ∼10 4 AU. Conclusions. Based on comparison with the set of observations available today, scattering models and the Kozai cycle with tidal friction models can not be solely responsible for the production of all hot Jupiters. Conversely, the presently observed distribution of the spin-orbit angles is compatible with most hot Jupiters having been transported by smooth migration inside a proto-planetary disk, itself possibly torqued by a companion.

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Section: Disk Torquingmentioning

confidence: 99%

Spin-orbit angle distribution and the origin of (mis)aligned hot Jupiters

Crida

Batygin

2014

A&A

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“…At the same time, the orbital elements of the planet are changed on a short timescale. A sudden jump occurs in both eccentricity and semimajor axis, as predicted by Malmberg et al (2011Malmberg et al ( , 2007, Davies (2009), andZakamska &Tremaine (2004).…”

Section: Case A: a Single Planet Orbiting At 18 Au From The Starmentioning

confidence: 84%

“…In effect, most numerical modeling of the effects of stellar encounters on planetary systems in clusters are based on pure N-body simulations where the effects of circumstellar disks are neglected (Malmberg et al 2011(Malmberg et al , 2007Malmberg & Davies 2009;Zakamska & Tremaine 2004). However, as suggested by the near coincidence between the cluster lifetime and that of circumstellar disks, this assumption may not be fully justified.…”

Section: Introductionmentioning

confidence: 99%

“…During the early stages of cluster evolution, stellar encounters are believed to significantly affect the formation and subsequent dynamical evolution of planetary systems around stars belonging to the structure. According to Malmberg et al (2011Malmberg et al ( , 2007, Malmberg & Davies (2009), and Zakamska & Tremaine (2004), scattering interactions with other stars in their birth cluster may excite the eccentricity of planets populating the outer parts of the system. This dynamical mechanism might contribute to explaining why eccentric orbits occur relatively commonly in extrasolar planetary systems.…”

Section: Introductionmentioning

confidence: 99%

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Circumstellar disks do erase the effects of stellar flybys on planetary systems

Marzari

Picogna

2013

A&A

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Context. Most stars form in embedded clusters. Stellar flybys may affect the orbital architecture of the systems by exciting the eccentricity and causing dynamical instability. Aims. Since, incidentally, the timescale on which a cluster loses it gaseous component and begins to disperse is comparable to the circumstellar disk's lifetime, we expect that closer and more perturbing stellar flybys occur when the planets are still embedded in their birth disk. We investigate the effects of the disk on the dynamics of planets after the stellar encounter to test whether it can damp the eccentricity and return the planetary system to a nonexcited state. Methods. We used the hydrodynamical code FARGO to study the disk+planet(s) system during and after the stellar encounter in the context of evolved disk models whose superficial density is 10 times lower than that of the minimum mass solar nebula.Results. The numerical simulations show that the planet's eccentricity, excited during a close stellar flyby, is damped on a short timescale (∼10 Kyr) in spite of the disk's low initial density and subsequent tidal truncation. This damping is also effective for a system of 3 giant planets, and the effects of the dynamical instability induced by the passing star are quickly absorbed. Conclusions. If the circumstellar disk is still present around the star during a stellar flyby, a planet (or a planetary system) is returned to a nonexcited state on a short timescale. This does not mean that stellar encounters do not affect the evolution of planets, but they do it in a subtle way with a short period of agitated dynamical evolution. At the end of it, the system resumes a quiet evolution and the planetary orbits are circularized by the interaction with the disk.

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“…Stellar flybys have been invoked to explain the high eccentricity orbits of some Kuiper belt objects such as Sedna (Kenyon & Bromley 2004), the dynamics of planetary systems (Malmberg et al 2007;Spurzem et al 2009), and the structures of debris disks (Larwood 1997;Mouillet et al 1997;Kalas et al 2000;Kobayashi & Ida 2001). Impacts of stellar flybys during A&A 532, A120 (2011) the first few million years have also been studied in the context of the evolution of protoplanetary disks and planet formation (Bonnell et al 2001;Olczack et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Stripping a debris disk by close stellar encounters in an open stellar cluster

Lestrade

Morey

Lassus

et al. 2011

A&A

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A debris disk is a constituent of any planetary system surrounding a main sequence star. We study whether close stellar encounters can disrupt and strip a debris disk of its planetesimals in the expanding open cluster of its birth with a decreasing star number density over 100 Myr. Such stripping would affect the dust production and hence detectability of the disk. We tabulated the fractions of planetesimals stripped off during stellar flybys of miss distances between 100 and 1000 AU and for several mass ratios of the central to passing stars. We then estimated the numbers of close stellar encounters over the lifetime of several expanding open clusters characterized by their initial star densities. We found that a standard disk, with inner and outer radii of 40 and 100 AU, suffers no loss of planetesimals over 100 Myr around a star born in a common embedded cluster with star density ≤1000 pc −3 . In contrast, we found that such a disk is severely depleted of its planetesimals around a star born in an Orion-type cluster where the star density is >20 000 pc −3 . In this environment, a disk loses >97% of its planetesimals around an M-dwarf, >63% around a solar-type star, and >42% around an A-dwarf, over 100 Myr. We roughly estimate that two-thirds of the stars may be born in such high star density clusters. This might explain in part why fewer debris disks are observed around lower mass stars.

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Close encounters in young stellar clusters: implications for planetary systems in the solar neighbourhood

Cited by 156 publications

References 39 publications

Spin-orbit angle distribution and the origin of (mis)aligned hot Jupiters

Spin-orbit angle distribution and the origin of (mis)aligned hot Jupiters

Circumstellar disks do erase the effects of stellar flybys on planetary systems

Stripping a debris disk by close stellar encounters in an open stellar cluster

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