Astronomers have recently discovered a giant exoplanet, Kepler-139f, which is approximately 35 times more massive than Earth and roughly twice the mass of Neptune. This colossal world was found "hiding" in the Kepler-139 star system, which was already known to host other planets. The discovery was reported in a study published on May 2 in The Astrophysical Journal Letters.
Despite its immense size, Kepler-139f had previously evaded detection. The Kepler-139 system initially had three known rocky "super-Earths" and a fourth gas giant that was discovered later. Astronomers were able to infer the presence of this new, hidden planet by analyzing gaps and discrepancies in the orbits of the known planets within the system.
Researchers used a combination of techniques, including radial velocity (RV) measurements (which detect the wobble in a star caused by a planet's gravitational tug) and transit timing variations (TTVs), to confirm the existence of Kepler-139f. The revised TTVs, particularly those based on the 2023 discovery of Kepler-139e, provided crucial indirect evidence for the newfound planet. This discovery also helped resolve a previously observed anomaly in the density of Kepler-139c, the outermost super-Earth, as some of Kepler-139f's gravitational pull had been incorrectly attributed to it.
The finding highlights that even in well-studied star systems, there may be other unseen planets waiting to be discovered, emphasizing the complexity and dynamic nature of planetary systems beyond our own.