Colossal exomoon candidate could redefine the meaning of 'moon'

Astronomers using the GRAVITY instrument on the VLT detected a small but measurable wobble in the gas giant HD 206893 B’s orbit, implying a massive unseen companion — an exomoon potentially about 40% of Jupiter’s mass (roughly nine Neptune masses) orbiting at ~0.2 AU with a ~9‑month period and a ~60° inclination. If confirmed, it would be among the most massive moons known and could force a reevaluation of what defines a moon, while guiding future exomoon searches via astrometry.