2025ApJ...984L..39L

Among the ways that an outer giant planet can alter the architecture of an inner planetary system is by tilting the orbits of the inner planets and reducing their mutual transit probabilities. Here, we report on an example of this phenomenon: we show that the Kepler-139 system contains a nontransiting planet just exterior to three transiting planets and interior to a giant planet. This newly discovered planet, Kepler-139f, has an orbital period of 355 ± 2 days and a mass of 36 ± 10 M_⊕ based on transit-timing and radial-velocity data. Through dynamical simulations, we show that gravitational perturbations on planet f's orbit from the outer giant planet reduce the probability for a randomly located observer to see transits of all four inner planets. Thus, Kepler-139 illustrates the role that outer giant planets can play in the apparent truncation of compact systems of multiple transiting planets.