Accreting protoplanets in the LkCa 15 transition disk
S. Sallum, K. B. Follette, J. A. Eisner, L. M. Close, P. Hinz + et al.
Nature 527, 342–344 (18 November 2015) | doi:10.1038/nature15761
“Exoplanet detections have revolutionized astronomy, offering new insights into solar system architecture and planet demographics. While nearly 1,900 exoplanets have now been discovered and confirmed1, none are still in the process of formation. Transition disks, protoplanetary disks with inner clearings2, 3, 4 best explained by the influence of accreting planets5, are natural laboratories for the study of planet formation. Some transition disks show evidence for the presence of young planets in the form of disk asymmetries6, 7 or infrared sources detected within their clearings, as in the case of LkCa 15 (refs 8, 9). Attempts to observe directly signatures of accretion onto protoplanets have hitherto proven unsuccessful10. Here we report adaptive optics observations of LkCa 15 that probe within the disk clearing. With accurate source positions over multiple epochs spanning 2009–2015, we infer the presence of multiple companions on Keplerian orbits. We directly detect Hα emission from the innermost companion, LkCa 15 b, evincing hot (about 10,000 kelvin) gas falling deep into the potential well of an accreting protoplanet.”