The detection and characterization of still-forming planets is one of the major goals in the study of planet formation. Such detections would provide crucial constraints on the earliest stages of a planet's life, and would facilitate studies of how giant planets evolve during their formation stages. A direct way to identify forming protoplanets is to detect emission lines associated with accretion processes.
In this contribution, we present the direct detection of localized H-alpha emission in the outer disk of AS209 using MagAO-X, which we interpret as an accreting protoplanet candidate. The measured line luminosity can be used to estimate the mass accretion rate of the protoplanet candidate, while the disk morphology provides tight constraints on the possible mass range. The candidate orbit (semi-major axis ~140 au) coincides with a radial range where CO line broadening has been reported, possibly indicating planet-disk interaction.
If confirmed, this protoplanet will provide a unique opportunity to study how and where gas giant planets form, how young planets interact with their natal protoplanetary disk and how volatile delivery to their atmosphere takes place.