title: Accreting protoplanets in the LkCa 15 transition disk.
abstract: 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 confirmed, none are still in the process of formation. Transition disks, protoplanetary disks with inner clearings best explained by the influence of accreting planets, 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 asymmetries 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 unsuccessful. 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.
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: S
authors.initials: S
authors.lastname: Sallum
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.|Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, California 94305, USA.
authors.forename: K B
authors.initials: KB
authors.lastname: Follette
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Eisner
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Close
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: P
authors.initials: P
authors.lastname: Hinz
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: K
authors.initials: K
authors.lastname: Kratter
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: J
authors.initials: J
authors.lastname: Males
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: A
authors.initials: A
authors.lastname: Skemer
authors.affiliation: Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, California 94305, USA.
authors.forename: B
authors.initials: B
authors.lastname: Macintosh
authors.affiliation: School of Physics, University of Sydney, Sydney, New South Wales 2006, Australia.
authors.forename: P
authors.initials: P
authors.lastname: Tuthill
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: V
authors.initials: V
authors.lastname: Bailey
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: D
authors.initials: D
authors.lastname: Defrère
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: K
authors.initials: K
authors.lastname: Morzinski
authors.affiliation: Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Rd NW, Washington, Washington DC 20015, USA.
authors.forename: T
authors.initials: T
authors.lastname: Rodigas
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: E
authors.initials: E
authors.lastname: Spalding
authors.affiliation: Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: A
authors.initials: A
authors.lastname: Vaz
authors.affiliation: Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Rd NW, Washington, Washington DC 20015, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Weinberger