Researchers discover non-transiting exoplanet orbiting KIC 9139163

An international research team led by the National Institute for Astrophysics (INAF) has identified a candidate exoplanet that does not transit its host star, KIC 9139163, in the Cygnus constellation. Unlike most exoplanets discovered via the transit method—which measures the dip in a star's brightness as a planet passes in front of it—this object was detected by analyzing phase curves, or the subtle variations in reflected and emitted light as the planet orbits.

The candidate is a sub-Neptune with a minimum mass approximately 7.3 times that of Earth and a radius about 2.4 times larger. It completes a full orbit in just 14 hours. Due to its extreme proximity to its star, researchers suggest it may be a ‘boiling water world’ with a composition potentially rich in water. The planet resides in the ‘Neptune desert,’ a region where planets of this size are rarely observed.

To confirm the discovery, researchers combined data from the Kepler and TESS space telescopes with observations from the HARPS-N spectrograph at the Telescopio Nazionale Galileo in the Canary Islands. The data suggests a dynamic atmosphere with evolving, highly reflective clouds. However, the intense tidal forces caused by its close orbit may eventually lead to the planet being consumed by its star.