EK Cha b: Multi-tracer detection of a protoplanet candidate in a gas-rich environment

Despite sustained community efforts and advances in instrumentation and high-contrast imaging, the search for protoplanets remains difficult, with only two widely accepted systems to date in Class II systems (PDS 70 and WISPIT 2). Here we present the detection of EK Cha b, a new protoplanet candidate, identified through CO emission, millimeter continuum, and 0.82 μm broadband photometry, linked to EK Cha, a young late-type M star. The detection of a new protoplanet candidate offers an additional opportunity to advance our understanding of planet formation. By exploiting the wealth of archival data available for nearby star-forming regions, we aim to place EK Cha b in context, characterize its properties, and motivate future campaigns targeting similar systems. We analyzed high-spatial-resolution archival observations of EK Cha from HST, VLT/NACO, VLT/MUSE, and ALMA. We searched for EK Cha b in broadband continuum and gas tracers, reporting the measured flux with uncertainties, and upper limits for non-detections. EK Cha b shows a spectrally resolved footprint that matches the CO J=2--1 emission, together with 0.82 μm and millimeter continuum emission. EK Cha b is spectrally resolved in CO J=2--1 emission, kinematically consistent with a circumplanetary disk. Best fits from evolutionary models place EK Cha b as a planetary-mass companion, although deeper observations are required to fully confirm its nature. Although giant planets are uncommon around M dwarfs, these stars host the highest planet occurrence rate while remaining severely underrepresented in protoplanet searches. EK Cha b demonstrates that such systems are now within reach, and the advent of extremely large telescopes and improved high-contrast imaging — where the lower host luminosity relaxes the required contrast — will open this overlooked regime to systematic exploration.