The young exoplanetary system TOI-4562: Confirming the presence of a third body in the system

Context. Young planetary systems represent an opportunity to investigate the early stages of (exo)planetary formation because the gravitational interactions have not yet significantly changed the initial configuration of the system. Aims. TOI-4562 b is a highly eccentric temperate Jupiter analogue orbiting a young F7V-type star of < 700 Myr in age with an orbital period of P_orb ∼ 225 days and an eccentricity of e = 0.76, and is one of the largest known exoplanets to have formed in situ. Methods. We observed a new transit of TOI-4562 b using the 0.6-m Zeiss telescope at the Pico dos Dias Observatory (OPD/LNA) in Minas Gerais, Brazil, and combine our data with Transiting Exoplanet Survey Satellite (TESS) and archive data, with the aim being to improve the ephemerides of this interesting system. Results. The O ‑ C diagram for the new ephemeris is consistent with the presence of a giant planet in an outer orbit around TOI-4562. TOI-4562 c is a planet with a mass of M = 5.77 M_Jup, an orbital period of P_orb = 3990 days, and a semi-major axis of a = 5.219 AU. Conclusions. We report the discovery of TOI-4562 c, the exoplanet with the longest orbital period discovered to date via the transit timing variation (TTV) method. The TOI-4562 system is in the process of violent evolution with intense dynamical changes – judging by its young age and high eccentricity – and is therefore a prime target for studies of formation and evolution of planetary systems.