TOI-5624 e

Lore & Background

TOI-5624 e was discovered by an international team led by Andrea Bonfant, announced in late April 2026 using the transit method. Its mass was determined via radial velocity, and its radius was measured with the European CHEOPS telescope to an uncertainty of less than 1.7%. The planet's average density suggests a significant gaseous envelope or an icy component. Its equilibrium temperature is 613.8 K (about 341 °C).

The planet orbits its parent star with an orbital inclination that ensures it passes almost through the center of the stellar disk. However, its orbit exhibits pronounced short-term dynamical instability, revealed by transit timing variations with an amplitude of about 80 minutes. These variations are caused by gravitational interaction with the non-transiting outer planet TOI-5624 f.

Data analysis indicates that planets e and f are in a configuration close to a 2:1 mean orbital resonance. The outer planet's orbital period is 45.37 days, producing regular gravitational perturbations that periodically accelerate and decelerate TOI-5624 e along its orbit.

Reader's Guide

TOI-5624 e is significant as a clear example of dynamical interactions between planets in a near-resonant configuration. The 80-minute transit timing variations provide direct evidence of gravitational perturbations from the non-transiting planet TOI-5624 f, which itself cannot be observed via transits. This makes the system a valuable laboratory for studying orbital resonances and their effects on planetary motion. The 2:1 mean orbital resonance between the two planets is a common but important configuration that can reveal details about planetary formation and migration. The high precision of the radius measurement (uncertainty less than 1.7%) from CHEOPS, combined with mass data from radial velocity, allows for robust density estimates. The density indicates a substantial gaseous envelope or icy component, typical of sub-Neptunes. The system's location in Ursa Major and its discovery in 2026 add to the growing catalog of multi-planet systems with measurable transit timing variations, which help refine models of planetary system architecture and long-term stability.

Did You Know?

• TOI-5624 e is the fourth and second largest exoplanet discovered in the TOI-5624 system.
• Its transit timing variations have an amplitude of about 80 minutes.
• The planet is in a configuration close to a 2:1 mean orbital resonance with the non-transiting planet TOI-5624 f.