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Prospects of Rogue Planets around Supermassive Black Holes at the Heart of Galaxies

Presentation #403.01 in the session Planet Formation (and Destruction) Theory.

Published onApr 03, 2024
Prospects of Rogue Planets around Supermassive Black Holes at the Heart of Galaxies

Accreting supermassive black holes in Active Galactic Nuclei (AGNs) provide the most powerful beacons of light in the Universe. Gaseous disks swirling around them are not only the sources of intense radiation but also the sites of ongoing star formation and prolific production of heavy elements. In addition to the super-solar metallicity inferred from their emission lines, they are surrounded by geometrically-thick dusty tori which obscure our view of the central regions of some AGN disks. Partial retention of this rich reservoir of building-block materials could lead to various potential formation and disruption channels for planetesimals, protoplanetary embryos, and protoplanets under the extreme environments of global AGN disks as well as protostellar disks around stars formed and embedded in them. We assess the prospect of prolific planet formation in these scaled-up analogues of protostellar disks. We analyze the likely implications of their dynamical evolution due to stochastic migration, dynamical relaxation, and secular perturbations by supermassive or intermediate-mass companions to the supermassive black holes in both active and dormant galactic nuclei. We highlight some potentially observable consequences of planetary photo-evaporation, tidal downsizing and disruption in the proximity of supermassive black holes, including Sgr A* at the Galactic center. Some possible diverse outcomes include G clouds, Miller planets near supermassive black holes’ gravitational radius, hyper-velocity interstellar and intergalactic freely-floating asteroids and planets with distinctly observable signatures. Comparative studies of planet formation processes under these two vastly different but scalable environments not only brings hitherto overlooked synergy but also enriches the context and implication in two closely related fields.

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