Orbital elements of the material surrounding comet 67P/Churyumov-Gerasimenko

¹ Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
e-mail: bjorn.davidsson@physics.uu.se
² Instituto de Astrofísica de Andalucía (CSIC), c/ Glorieta de la Astronomía s/n, 18008 Granada, Spain
³ Max–Planck–Institut für Sonnensystemforschung, Justus–von–Liebig–Weg, 3, 37077 Göttingen, Germany
⁴ University of Padova, Department of Physics and Astronomy, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
⁵ Laboratoire d’Astrophysique de Marseille, UMR 7326, CNRS & Aix Marseille Université, 38 rue Frédéric Joliot–Curie, 13388 Marseille Cedex 13, France
⁶ Centro de Astrobiologia, CSIC–INTA, 28850 Torrejon de Ardoz, Madrid, Spain
⁷ International Space Science Institute, Hallerstraße 6, 3012 Bern, Switzerland
⁸ Scientific Support Office, European Space Research and Technology Centre/ESA, Keplerlaan 1, Postbus 299, 2201 AZ Noordwijk ZH, The Netherlands
⁹ PAN Space Research Center, Bartycka 18A, 00716 Warszawa, Poland
¹⁰ Institut für Geophysik und extraterrestrische Physik (IGEP), Technische Universität Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany
¹¹ University of Maryland, Department of Astronomy, College Park, MD 20742-2421, USA
¹² Gauss Professor, Akademie der Wissenschaften zu Göttingen and Max–Planck–Institut für Sonnensystemforschung, Justus–von–Liebig–Weg 3, 37077 Göttingen, Germany
¹³ LESIA–Observatoire de Paris, CNRS, Université Pierre et Marie Curie, Université Paris Diderot, 5 place J. Janssen, 92195 Meudon, France
¹⁴ LATMOS, CNRS/UVSQ/IPSL, 11 boulevard d’Alembert, 78280 Guyancourt, France
¹⁵ Centro di Ateneo di Studi ed Attivitá Spaziali “Giuseppe Colombo” (CISAS), University of Padova, via Venezia 15, 35131 Padova, Italy
¹⁶ INAF, Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹⁷ CNR–IFN UOS Padova LUXOR, via Trasea, 7, 35131 Padova, Italy
¹⁸ University of Trento, via Mesiano 77, 38100 Trento, Italy
¹⁹ Department of Industrial Engineering – University of Padova, via Venezia 1, 35131 Padova, Italy
²⁰ INAF–Osservatorio Astronomico, via Tiepolo 11, 34014 Trieste, Italy
²¹ Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
²² Deutsches Zentrum für Luft– und Raumfahrt (DLR), Institut für Planetenforschung, Rutherfordstraße 2, 12489 Berlin, Germany
²³ National Central University, Graduate Institute of Astronomy, 300 Chung–Da Rd, 32054 Chung–Li, Taiwan
²⁴ Operations Department, European Space Astronomy Centre/ESA, PO Box 78, 28691 Villanueva de la Canada, Madrid, Spain
²⁵ Centre for Astrophysics and Planetary Science, School of PhysicalSciences, The University of Kent, Canterbury, CT2 7NH, UK
²⁶ University of Padova, Department of Physics and Astronomy, via Marzolo 8, 35131 Padova, Italy
²⁷ Institut für Datentechnik und Kommunikationsnetze der TU Braunschweig, Hans–Sommer–Str. 66, 38106 Braunschweig, Germany
²⁸ University of Padova, Department of Information Engineering, via Gradenigo 6/B, 35131 Padova, Italy
²⁹ Planetary and Space Sciences, Department of Physical Sciences, The Open University, Milton Keynes, MK7 6AA, UK
³⁰ Physikalisches Institut der Universität Bern, Sidlerstr. 5, 3012 Bern, Switzerland

Received: 7 February 2015
Accepted: 9 April 2015

Abstract

Context. We investigate the dust coma within the Hill sphere of comet 67P/Churyumov-Gerasimenko.

Aims. We aim to determine osculating orbital elements for individual distinguishable but unresolved slow-moving grains in the vicinity of the nucleus. In addition, we perform photometry and constrain grain sizes.

Methods. We performed astrometry and photometry using images acquired by the OSIRIS Wide Angle Camera on the European Space Agency spacecraft Rosetta. Based on these measurements, we employed standard orbit determination and orbit improvement techniques.

Results. Orbital elements and effective diameters of four grains were constrained, but we were unable to uniquely determine them. Two of the grains have light curves that indicate grain rotation.

Conclusions. The four grains have diameters nominally in the range 0.14–0.50 m. For three of the grains, we found elliptic orbits, which is consistent with a cloud of bound particles around the nucleus. However, hyperbolic escape trajectories cannot be excluded for any of the grains, and for one grain this is the only known option. One grain may have originated from the surface shortly before observation. These results have possible implications for the understanding of the dispersal of the cloud of bound debris around comet nuclei, as well as for understanding the ejection of large grains far from the Sun.