Stellar clustering shapes the architecture of planetary systems

Abstract

Planet formation is generally described in terms of a system containing the host star and a protoplanetary disk 1 – 3 , of which the internal properties (for example, mass and metallicity) determine the properties of the resulting planetary system 4 . However, (proto)planetary systems are predicted 5 , 6 and observed 7 , 8 to be affected by the spatially clustered stellar formation environment, through either dynamical star–star interactions or external photoevaporation by nearby massive stars 9 . It is challenging to quantify how the architecture of planetary sysems is affected by these environmental processes, because stellar groups spatially disperse within less than a billion years 10 , well below the ages of most known exoplanets. Here we identify old, co-moving stellar groups around exoplanet host stars in the astrometric data from the Gaia satellite 11 , 12 and demonstrate that the architecture of planetary systems exhibits a strong dependence on local stellar clustering in position-velocity phase space. After controlling for host stellar age, mass, metallicity and distance from the star, we obtain highly significant differences (with p values of 10 −5 to 10 −2 ) in planetary system properties between phase space overdensities (composed of a greater number of co-moving stars than unstructured space) and the field. The median semi-major axis and orbital period of planets in phase space overdensities are 0.087 astronomical units and 9.6 days, respectively, compared to 0.81 astronomical units and 154 days, respectively, for planets around field stars. ‘Hot Jupiters’ (massive, short-period exoplanets) predominantly exist in stellar phase space overdensities, strongly suggesting that their extreme orbits originate from environmental perturbations rather than internal migration 13 , 14 or planet–planet scattering 15 , 16 . Our findings reveal that stellar clustering is a key factor setting the architectures of planetary systems.

Determining dispersal mechanisms of protoplanetary disks using accretion and wind mass loss rates

“…Another important implication is that measuring the mass loss rate in different UV environments allows one to explore when external photoevaporation plays a defining role in disk evolution and planet formation. This will provide new insights about how sensitive planet formation is to the surrounding environments, and shed light on the origin of the diversity of observed exoplanetary systems (e.g., Concha-Ramírez et al 2019;Winter et al 2020).…”

Hot Jupiters: Origins, Structure, Atmospheres

“…The Gaia Mission will enable astrometry of hot Jupiters' companions to measure the mutual inclination and further investigations of connections between hot Jupiter occurrence and host star properties. For example, Winter et al (2020) recently found a correlation between hot Jupiters and present-day stellar clustering. If this present-day clustering reflects the early environment, the correlation suggests that dense stellar cluster environments facilitate processes that lead to hot Jupiters.…”

“…For example, Winter et al. (2020) recently found a correlation between hot Jupiters and present‐day stellar clustering. If this present‐day clustering reflects the early environment, the correlation suggests that dense stellar cluster environments facilitate processes that lead to hot Jupiters.…”

Exploring the link between star and planet formation with Ariel

“…Major efforts are currently being undertaken to link the properties of planetary systems to their large-scale stellar environment, with promising results (e.g. [112][113][114][115]). These studies show that planetary system architectures and planetary properties (e.g.…”