[en] In the 1980s, excess infrared emission was discovered around main- sequence stars; subsequent direct-imaging observations revealed orbiting disks of cold dust to be the source. These `debris disks' were thought to be by-products of planet formation because they often exhibited morphological and brightness asymmetries that may result from gravitational perturbation by planets. This was proved to be true for the β Pictoris system, in which the known planet generates an observable warp in the disk. The nearby, young, unusually active late-type star AU Microscopii hosts a well-studied edge-on debris disk; earlier observations in the visible and near-infrared found asymmetric localized structures in the form of intensity variations along the midplane of the disk beyond a distance of 20 astronomical units. Here we report high- contrast imaging that reveals a series of five large-scale features in the southeast side of the disk, at projected separations of 10-60 astronomical units, persisting over intervals of 1-4 years. All these features appear to move away from the star at projected speeds of 4-10 kilometres per second, suggesting highly eccentric or unbound trajectories if they are associated with physical entities. The origin, localization, morphology and rapid evolution of these features are difficult to reconcile with current theories.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Boccaletti, Anthony; LESIA, Observatoire de Paris, CNRS, Université Paris Diderot, Université Pierre et Marie Curie, 5 place Jules Janssen, 92190 Meudon, France
Thalmann, Christian; ETH Zürich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland
Lagrange, Anne-Marie; Université Grenoble Alpes, IPAG, F-38000 Grenoble, France ; CNRS, IPAG, F-38000 Grenoble, France
Janson, Markus; Department of Astronomy, Stockholm University, SE-106 91 Stockholm, Sweden ; Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
Augereau, Jean-Charles; Université Grenoble Alpes, IPAG, F-38000 Grenoble, France ; CNRS, IPAG, F-38000 Grenoble, France
Schneider, Glenn; Steward Observatory, 933 North Cherry Avenue, The University of Arizona, Tucson, Arizona 85721, USA
Milli, Julien; CNRS, IPAG, F-38000 Grenoble, France ; European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago, Chile
Grady, Carol; Eureka Scientific, 2452 Delmer, Suite 100, Oakland, California 96002, USA
Debes, John; Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA
Langlois, Maud; Centre de Recherche Astrophysique de Lyon, (CNRS/ENS-L/Université Lyon 1), 9 avenue Charles André, 69561 Saint-Genis-Laval, France ; Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
Mouillet, David; Université Grenoble Alpes, IPAG, F-38000 Grenoble, France ; CNRS, IPAG, F-38000 Grenoble, France
Henning, Thomas; Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
Dominik, Carsten; University of Amsterdam, Anton Pannekoek Institute for Astronomy, Science Park 904 1098 XH Amsterdam, The Netherlands
Beuzit, Jean-Luc; Université Grenoble Alpes, IPAG, F-38000 Grenoble, France ; CNRS, IPAG, F-38000 Grenoble, France
Carson, Joseph; Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany ; Department of Physics and Astronomy, College of Charleston, South Carolina, 29424, USA
Dohlen, Kjetil; Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
Engler, Natalia; ETH Zürich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland
Feldt, Markus; Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
Fusco, Thierry; Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France ; ONERA--The French Aerospace Laboratory, 92322 Châtillon, France
Ginski, Christian; Sterrewacht Leiden, PO Box 9513, Niels Bohrweg 2, NL-2300RA Leiden, The Netherlands
Girard, Julien H.; CNRS, IPAG, F-38000 Grenoble, France ; European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago, Chile
Hines, Dean; Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA
Kasper, Markus; CNRS, IPAG, F-38000 Grenoble, France ; European Southern Observatory (ESO), Karl Schwarzschild Strasse 2, 85748 Garching bei München, Germany
Mawet, Dimitri; Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, California 91125, USA
Ménard, François; UMI-FCA, CNRS/INSU France (UMI 3386), and Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Correo Central, Santiago, Chile
Meyer, Michael R.; ETH Zürich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland
Moutou, Claire; Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
Olofsson, Johan; Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
Rodigas, Timothy; Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington DC 20015, USA
Sauvage, Jean-Francois; Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France ; ONERA--The French Aerospace Laboratory, 92322 Châtillon, France
Schlieder, Joshua; Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany ; NASA Ames Research Center, Space Science and Astrobiology Division, MS 245-6, Moffett Field, California 94035, USA
Schmid, Hans Martin; ETH Zürich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland
Udry, Stephane; Observatoire de Genève, University of Geneva, 51 Chemin des Maillettes, 1290 Versoix, Switzerland
Vakili, Farrokh; Laboratoire J.-L. Lagrange, Observatoire de la Côte d'Azur (OCA), Université de Nice-Sophia Antipolis (UNS), CNRS, Campus Valrose, 06108 Nice Cedex 2, France
Vigan, Arthur; European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago, Chile ; Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
Wahhaj, Zahed; European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago, Chile ; Aix Marseille Université, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
Wisniewski, John; Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks Street, Norman, Oklahoma 73019, USA)
Smith, B. A. & Terrile, R. J. A circumstellar disk around b Pictoris. Science 226, 1421-1424 (1984).
Mouillet, D., Larwood, J. D., Papaloizou, J. C. B. & Lagrange, A. M. A planet on an inclined orbit as an explanation of the warp in the b Pictoris disc. Mon. Not. R. Astron. Soc. 292, 896-904 (1997).
Augereau, J. C., Nelson, R. P., Lagrange, A. M., Papaloizou, J. C. B. & Mouillet, D. Dynamicalmodeling of large scale asymmetries in the b Pictoris dust disk. Astron. Astrophys. 370, 447-455 (2001).
Lagrange, A.-M. et al. The position of b Pictoris b position relative to the debris disk. Astron. Astrophys. 542, A40 (2012).
Nesvold, E. R.& Kuchner,M. J.A SMACKmodel of colliding planetesimals and dust in the b Pictoris debris disk: thermal radiation and scattered light. Preprint at http://arxiv.org/abs/1506.07187 (2015).
Liu, M. C. Substructure in the circumstellar disk around the young star AU Microscopii. Science 305, 1442-1444 (2004).
Metchev, S. A., Eisner, J. A., Hillenbrand, L. A. & Wolf, S. Adaptive optics imaging of the AU Microscopii circumstellar disk: evidence for dynamical evolution. Astrophys. J. 622, 451-462 (2005).
Krist, J. E. et al. Hubble Space Telescope Advanced Camera for Surveys coronagraphic imaging of the AU Microscopii debris disk. Astron. J. 129, 1008-1017 (2005).
Fitzgerald, M. P., Kalas, P. G., Duchêne, G., Pinte, C. & Graham, J. R. The AU Microscopii debris disk: multiwavelength imaging and modeling. Astrophys. J. 670, 536-556 (2007).
Robinson, R. D., Linsky, J. L., Woodgate, B. E. & Timothy, J. G. Far-ultraviolet observations of flares on the dM0e star AU Microscopii. Astrophys. J. 554, 368-382 (2001).
Mamajek, E. E. & Bell, C. P.M. On the age of the b Pictorismoving group. Mon. Not. R. Astron. Soc. 445, 2169-2180 (2014).
Kalas, P., Liu, M. C. & Matthews, B. C. Discovery of a large dust disk around the nearby star AU Microscopii. Science 303, 1990-1992 (2004).
Augereau, J. C. & Beust, H. On the AU Microscopii debris disk. Astron. Astrophys. 455, 987-999 (2006).
Roberge, A., Weinberger, A. J., Redfield, S. & Feldman, P. D. Rapid dissipation of primordial gas fromthe AUMicroscopii debris disk. Astrophys. J. 626, L105-L108 (2005).
Schneider, G. et al. Probing for exoplanets hiding in dusty debris disks: disk imaging, characterization, and exploration with HST/STIS multi-roll coronagraphy. Astron. J. 148, 59 (2014).
Beuzit, J.-L. et al. SPHERE: a 'Planet Finder' instrument for the VLT. In Proc. SPIE Conf. Ser., 7014, 18 (Society of Photo-Optical Instrumentation Engineers, 2008).
Baudoz, P. et al. The differential tip-tilt sensor of SPHERE. In Proc. SPIE Conf. Ser, 7735, 5 (Society of Photo-Optical Instrumentation Engineers, 2010).
Lafrenière, D., Marois, C., Doyon, R., Nadeau, D. & Artigau, E. A new algorithm for point-spread function subtraction in high-contrast imaging: a demonstration with angular differential imaging. Astrophys. J. 660, 770-780 (2007).
Soummer, R., Pueyo, L. & Larkin, J. Detection and characterization of exoplanets and disks using projections on Karhunen-Loève eigenimages. Astrophys. J. 755, L28 (2012).
Milli, J. et al. Impact of angular differential imaging on circumstellar disk images. Astron. Astrophys. 545, A111 (2012).
Chabrier, G., Baraffe, I., Allard, F. & Hauschildt, P. Evolutionarymodels for very lowmass stars and browndwarfs with dusty atmospheres. Astrophys. J. 542, 464-472 (2000).
Baraffe, I., Chabrier, G., Barman, T. S., Allard, F. & Hauschildt, P. H. Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458. Astron. Astrophys. 402, 701-712 (2003).
Thalmann, C. et al. Imaging of a transitional disk gap in reflected light: indications of planet formation around the young solar analog LkCa 15. Astrophys. J. 718, L87-L91 (2010).
Moór, A. et al. ALMA continuum observations of a 30 Myr old gaseous debris disk around HD 21997. Astrophys. J. 777, L25 (2013).
Muto, T. The structure of a self-gravitating protoplanetary disk and its implications for direct imaging observations. Astrophys. J. 739, 10 (2011).
Weiss, J. W., Porco, C. C. & Tiscareno, M. S. Ring edge waves and the masses of nearby satellites. Astron. J. 138, 272-286 (2009).
Kral, Q., Thébault, P., Augereau, J. C., Boccaletti, A. & Charnoz, S. Signatures of massive collisions in debris discs. A self-consistent numerical model. Astron. Astrophys. 573, A39 (2015).
Kivelson, M. G. & Southwood, D. J. Dynamical consequences of two modes of centrifugal instability in Jupiter's outer magnetosphere. J. Geophys. Res. 110, A12209 (2005).
Fendt, C. Magnetically driven outflows from Jovian circum-planetary accretion disks. Astron. Astrophys. 411, 623-635 (2003).
