Stability of multiplanetary systems in star clusters

Cai, Maxwell X.; Kouwenhoven, M. B. N.; Zwart, Simon Portegies; Spurzem, Rainer

doi:10.1093/mnras/stx1464

Cited by 66 publications

(20 citation statements)

References 89 publications

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“…Interactions that would alter the orbit of binary systems would also likely disrupt the orbits of fledgling planetary systems (e.g. Parker & Quanz 2012;Cai et al 2017), and planets orbiting binary stars would likely be most susceptible due to a higher cross section for collisions (Adams et al 2006). However, in our simulations the majority of the perturbative interactions occur in the first 1-2 Myr of the star-forming regions' evolution, which is shorter than the timescale for terrestrial planet formation.…”

Section: Discussionmentioning

confidence: 99%

Enlarging habitable zones around binary stars in hostile environments

Wootton

Parker

2019

Monthly Notices of the Royal Astronomical Society: Letters

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Habitable zones are regions around stars where large bodies of liquid water can be sustained on a planet or satellite. As many stars form in binary systems with nonzero eccentricity, the habitable zones around the component stars of the binary can overlap and be enlarged when the two stars are at periastron (and less often when the stars are at apastron). We perform N-body simulations of the evolution of dense star-forming regions and show that binary systems where the component stars originally have distinct habitable zones can undergo interactions that push the stars closer together, causing the habitable zones to merge and become enlarged. Occasionally, overlapping habitable zones can occur if the component stars move further apart, but the binary becomes more eccentric. Enlargement of habitable zones happens to 1-2 binaries from an average initial total of 352 in each simulated star-forming region, and demonstrates that dense star-forming regions are not always hostile environments for planet formation and evolution.

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Section: Discussionmentioning

confidence: 99%

Enlarging habitable zones around binary stars in hostile environments

Wootton

Parker

2019

Monthly Notices of the Royal Astronomical Society: Letters

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“…We expect the survival rates to be lower in among multi-planet systems where planetplanet interactions are important (cf. Cai et al 2017). In this sense, the exoplanets listed in Table 1, most of which being short-period planets, are not entirely due to observational biases, because long-period planets indeed have difficulties to survive in dense clusters.…”

Section: Surviving Orbital Architecturesmentioning

confidence: 97%

“…No planet is detected despite that the cluster has 33,000 stars (Gilliland et al 2000;Masuda & Winn 2017). It is certainly possible that observational biases are responsible, but various analysis on planets in star clusters (e.g., Adams et al 2006;Malmberg et al 2007;Proszkow & Adams 2009;Spurzem et al 2009;Malmberg et al 2011;Parker & Quanz 2012;Hao et al 2013;Li & Adams 2015;Cai et al 2017Cai et al , 2018van Elteren et al 2019) have demonstrated that the dense star cluster environments (in particular, globular clusters) have implications to the formation and evolution of planets.…”

Section: Introductionmentioning

confidence: 99%

“…One could roughly divide the entire formation and evolution history of planets in star clusters, as shown in Fig 2. Planetary systems may be influenced by their birth environments in the following ways: first, during the planet formation process (Phase 1), protoplanetary discs may be photoevaporated due to the possible presence of nearby OB stars (e.g., Störzer & Hollenbach 1999;Armitage 2000;Adams 2010;Anderson et al 2013;Facchini et al 2016) and/or truncated due to stellar encounters (e.g., Clarke & Pringle 1993;Ostriker 1994;Olczak et al 2006;Portegies Zwart 2016;Concha-Ramírez et al 2019), which in turn modifies the properties of the discs and ultimately causes different outcome of planet formation; second: after the planet formation process (Phase 2), planets are no longer protected by the damping of the gaseous discs, and their orbital inclinations and eccentricities can be excited or even ejected by stellar flybys. Planetary systems in the dense regions of the cluster have lower chances to survive (Spurzem et al 2009;Hao et al 2013;Li & Adams 2015;Cai et al 2017;van Elteren et al 2019;Flammini Dotti et al 2019). Moreover, surviving planets from high-density regions tend to have relatively high mean eccentricities and inclinations due to their stellar encounter histories .…”

Section: Introductionmentioning

confidence: 99%

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On the survivability of planets in young massive clusters and its implication of planet orbital architectures in globular clusters

Cai

Zwart

Kouwenhoven

et al. 2019

Monthly Notices of the Royal Astronomical Society

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As of August 2019, among the more than 4000 confirmed exoplanets, only one has been detected in a globular cluster (GC) M4. The scarce of exoplanet detections motivates us to employ direct N -body simulations to investigate the dynamical stability of planets in young massive clusters (YMCs), which are potentially the progenitors of GCs. In an N = 128k cluster of virial radius 1.7 pc (comparable to Westerlund-1), our simulations show that most wide-orbit planets (a ≥ 20 au) will be ejected within a timescale of 10 Myr. Interestingly, more than 70% of planets with a < 5 au survive in the 100 Myr simulations. Ignoring planet-planet scattering and tidal damping, the survivability at t Myr as a function of initial semi-major axis a 0 in au in such a YMC can be described as f surv (a 0 , t) = −0.33 log 10 (a 0 ) 1 − e −0.0482t + 1. Upon ejection, about 28.8% of free-floating planets (FFPs) have sufficient speeds to escape from the host cluster at a crossing timescale. The other FFPs will remain bound to the cluster potential, but the subsequent dynamical evolution of the stellar system can result in the delayed ejection of FFPs from the host cluster. Although a full investigation of planet population in GCs requires extending the simulations to multi-Gyr, our results suggest that wideorbit planets and free-floating planets are unlikely to be found in GCs.

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“…A number of studies (e.g. Heggie & Rasio 1996;Laughlin & Adams 1998;Davies & Sigurdsson 2001;Bonnell et al 2001;Thies et al 2005;Fregeau et al 2006;Olczak et al 2010;Chatterjee et al 2012;Portegies Zwart & Jílková 2015;Cai et al 2017Cai et al , 2018Rice et al 2018;Cai et al 2019;van Elteren et al 2019;Flammini Dotti et al 2019) have shown how the evolution of planetary systems in interacting environments may provide alternative formation paths for planet properties which are difficult to account for by current theories of planetary formation. For example, internal dynamical interactions in multi planet systems may have played a role in producing eccentric planetary orbits (e.g.…”

Section: Introductionmentioning

confidence: 99%

Giant Planet Swaps during Close Stellar Encounters

Wang

Perna

Leigh

2020

ApJL

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The discovery of planetary systems outside of the solar system has challenged some of the tenets of planetary formation. Among the difficult-to-explain observations, are systems with a giant planet orbiting a very-low mass star, such as the recently discovered GJ 3512b planetary system, where a Jupiter-like planet orbits an M-star in a tight and eccentric orbit. Systems such as this one are not predicted by the core accretion theory of planet formation. Here we suggest a novel mechanism, in which the giant planet is born around a more typical Sunlike star (M * ,1 ), but is subsequently exchanged during a dynamical interaction with a flyby low-mass star (M * ,2 ). We perform state-of-the-art N-body simulations with M * ,1 = 1M and M * ,2 = 0.1M to study the statistical outcomes of this interaction, and show that exchanges result in high eccentricities for the new orbit around the low-mass star, while about half of the outcomes result in tighter orbits than the planet had around its birth star. We numerically compute the cross section for planet exchange, and show that an upper limit for the probability per planetary system to have undergone such an event is Γ ∼ 4.4(M c /100M ) −2 (a p /AU)(σ/1 km s −1 ) 5 Gyr −1 , where a p is the planet semi-major axis around the birth star, σ the velocity dispersion of the star cluster, and M c the total mass of the star cluster. Hence these planet exchanges could be relatively common for stars born in open clusters and groups, should already be observed in the exoplanet database, and provide new avenues to create unexpected planetary architectures.

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Stability of multiplanetary systems in star clusters

Cited by 66 publications

References 89 publications

Enlarging habitable zones around binary stars in hostile environments

Enlarging habitable zones around binary stars in hostile environments

On the survivability of planets in young massive clusters and its implication of planet orbital architectures in globular clusters

Giant Planet Swaps during Close Stellar Encounters

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