Listed below are my peer-reviewed publications, ordered in time. For each, all the publication details, including the abstract, the citations, the PDF of the article itself, and links to NASA/Ads and BibTeX entry are available. See the entire list in NASA/Ads.
P. Vernazza, J. Castillo-Rogez, P. Beck, J. Emery, R. Brunetto, M. Delbo, M. Marsset, F. Marchis, O. Groussin, B. Zanda, P. Lamy, L. Jorda, O. Mousis, A. Delsanti, Z. Djouadi, Z. Dionnet, F. Borondics & B. Carry
Anhydrous pyroxene-rich interplanetary dust particles (IDPs) have been proposed as surface analogs for about two-thirds of all C-complex asteroids. However, this suggestion appears to be inconsistent with the presence of hydrated silicates on the surfaces of some of these asteroids, including Ceres. Here, we report the presence of enstatite (pyroxene) on the surface of two C-type asteroids (Ceres and Eugenia) based on their spectral properties in the mid-infrared range. The presence of this component is particularly unexpected in the case of Ceres, because most thermal evolution models predict a surface consisting of hydrated compounds only. The most plausible scenario is that Ceres' surface has been partially contaminated by exogenous enstatite-rich material, possibly coming from the Beagle asteroid family. This scenario questions a similar origin for Ceres and the remaining C-types, and it possibly supports recent results obtained by the Dawn mission (NASA) that Ceres may have formed in the very outer solar system. Concerning the smaller D~200 km C-types such as Eugenia, both their derived surface composition (enstatite and amorphous silicates) and low density (<1.5 g.cm-3
Gaia collaboration, A. G. A. Brown, A. Vallenari, T. Prusti, J. H.J. de Bruijne, F. Mignard, R. Drimmel, C. Babusiaux, C. A.L. Bailer-Jones, U. Bastian, M. Biermann, D. W. Evans, L. Eyer, F. Jansen, C. Jordi, D. Katz, S. A. Klioner, U. Lammers, L. Lindegren, X. Luri, W. O'Mullane, C. Panem, D. Pourbaix, S. Randich, P. Sartoretti, H. I. Siddiqui, C. Soubiran, V. Valette, F. van Leeuwen, N. A. Walton, C. Aerts, F. Arenou, M. Cropper, E. Høg, M. G. Lattanzi, E. K. Grebel, A. D. Holland, C. Huc, X. Passot, M. Perryman, L. Bramante, C. Cacciari, J. Castañeda, L. Chaoul, N. Cheek, F. De Angeli, C. Fabricius, R. Guerra, J. Hernández, A. Jean-Antoine-Piccolo, E. Masana, R. Messineo, N. Mowlavi, K. Nienartowicz, D. Ordóñez-Blanco, P. Panuzzo, J. Portell, P. J. Richards, M. Riello, G. M. Seabroke, P. Tanga, F. Thévenin, J. Torra, S. G. Els, G. Gracia-Abril, G. Comoretto, M. Garcia-Reinaldos, T. Lock, E. Mercier, M. Altmann, R. Andrae, T. L. Astraatmadja, I. Bellas-Velidis, K. Benson, J. Berthier, R. Blomme, G. Busso, B. Carry, A. Cellino, G. Clementini, S. Cowell, O. Creevey, J. Cuypers, M. Davidson, J. De Ridder, A. de Torres, L. Delchambre, A. Dell'Oro, C. Ducourant, Y. Frémat, M. García-Torres, E. Gosset, J.-L. Halbwachs, N. C. Hambly, D. L. Harrison, M. Hauser, D. Hestroffer, S. T. Hodgkin, H. E. Huckle, A. Hutton, G. Jasniewicz, S. Jordan, M. Kontizas, A. J. Korn, A. C. Lanzafame, M. Manteiga, A. Moitinho, K. Muinonen, J. Osinde, E. Pancino, T. Pauwels, J.-M. Petit, A. Recio-Blanco, A. C. Robin, L. M. Sarro, C. Siopis, M. Smith, K. W. Smith, A. Sozzetti, W. Thuillot, W. van Reeven, Y. Viala, U. Abbas, A. Abreu Aramburu, S. Accart, J. J. Aguado, P. M. Allan, W. Allasia, G. Altavilla, M. A. Álvarez, J. Alves, R. I. Anderson, A. H. Andrei, E. Anglada Varela, E. Antiche, T. Antoja, S. Antón, B. Arcay, N. Bach, S. G. Baker, L. Balaguer-Núñez, C. Barache, C. Barata, A. Barbier, F. Barblan, D. Barrado y Navascués, M. Barros, M. A. Barstow, U. Becciani, M. Bellazzini, A. Bello García, V. Belokurov, P. Bendjoya, A. Berihuete, L. Bianchi, O. Bienaymé, F. Billebaud, N. Blagorodnova, S. Blanco-Cuaresma, T. Boch, A. Bombrun, R. Borrachero, S. Bouquillon, G. Bourda, H. Bouy, A. Bragaglia, M. A. Breddels, N. Brouillet, T. Brüsemeister, B. Bucciarelli, P. Burgess, R. Burgon, A. Burlacu, D. Busonero, R. Buzzi, E. Caffau, J. Cambras, H. Campbell, R. Cancelliere, T. Cantat-Gaudin, T. Carlucci, J. M. Carrasco, M. Castellani, P. Charlot, J. Charnas, A. Chiavassa, M. Clotet, G. Cocozza, R. S. Collins, G. Costigan, F. Crifo, N. J.G. Cross, M. Crosta, C. Crowley, C. Dafonte, Y. Damerdji, A. Dapergolas, P. David, M. David, P. De Cat, F. de Felice, P. de Laverny, F. De Luise, R. De March, D. de Martino, R. de Souza, J. Debosscher, E. del Pozo, M. Delbo, A. Delgado, H. E. Delgado, P. Di Matteo, S. Diakite, E. Distefano, C. Dolding, S. Dos Anjos, P. Drazinos, J. Duran, Y. Dzigan, B. Edvardsson, H. Enke, N. W. Evans, G. Eynard Bontemps, C. Fabre, M. Fabrizio, S. Faigler, A. J. Falcão, M. Farràs Casas, L. Federici, G. Fedorets, J. Fernández-Hernández, P. Fernique, A. Fienga, F. Figueras, F. Filippi, K. Findeisen, A. Fonti, M. Fouesneau, E. Fraile, M. Fraser, J. Fuchs, M. Gai, S. Galleti, L. Galluccio, D. Garabato, F. García-Sedano, A. Garofalo, N. Garralda, P. Gavras, J. Gerssen, R. Geyer, G. Gilmore, S. Girona, G. Giuffrida, M. Gomes, A. González-Marcos, J. González-Núñez, J. J. González-Vidal, M. Granvik, A. Guerrier, P. Guillout, J. Guiraud, A. Gúrpide, R. Gutiérrez-Sánchez, L. P. Guy, R. Haigron, D. Hatzidimitriou, M. Haywood, U. Heiter, A. Helmi, D. Hobbs, W. Hofmann, B. Holl, G. Holland, J. A.S. Hunt, A. Hypki, V. Icardi, M. Irwin, G. Jevardat de Fombelle, P. Jofré, P. G. Jonker, A. Jorissen, F. Julbe, A. Karampelas, A. Kochoska, R. Kohley, K. Kolenberg, E. Kontizas, S. E. Koposov, G. Kordopatis, P. Koubsky, A. Krone-Martins, M. Kudryashova, I. Kull, R. K. Bachchan, F. Lacoste-Seris, A. F. Lanza, J.-B. Lavigne, C. Le Poncin-Lafitte, Y. Lebreton, T. Lebzelter, S. Leccia, N. Leclerc, I. Lecoeur-Taibi, V. Lemaitre, H. Lenhardt, F. Leroux, S. Liao, E. Licata, H. E.P. Lindstrøm, T. A. Lister, E. Livanou, A. Lobel, W. Löffler, M. López, D. Lorenz, I. MacDonald, T. Magalhães Fernandes, S. Managau, R. G. Mann, G. Mantelet, O. Marchal, J. M. Marchant, M. Marconi, S. Marinoni, P. M. Marrese, G. Marschalkó, D. J. Marshall, J. M. Martín-Fleitas, M. Martino, N. Mary, G. Matijevi?c, T. Mazeh, P. J. McMillan, S. Messina, D. Michalik, N. R. Millar, B. M. H. Miranda, D. Molina, R. Molinaro, M. Molinaro, L. Molnár, M. Moniez, P. Montegriffo, R. Mor, A. Mora, R. Morbidelli, T. Morel, S. Morgenthaler, D. Morris, A. F. Mulone, T. Muraveva, I. Musella, J. Narbonne, G. Nelemans, L. Nicastro, L. Noval, C. Ordénovic, J. Ordieres-Meré, P. Osborne, C. Pagani, I. Pagano, F. Pailler, H. Palacin, L. Palaversa, P. Parsons, M. Pecoraro, R. Pedrosa, H. Pentikäinen, B. Pichon, A. M. Piersimoni, F.-X. Pineau, E. Plachy, G. Plum, E. Poujoulet, A. Prša, L. Pulone, S. Ragaini, S. Rago, N. Rambaux, M. Ramos-Lerate, P. Ranalli, G. Rauw, A. Read, S. Regibo, C. Reylé, R. A. Ribeiro, L. Rimoldini, V. Ripepi, A. Riva, G. Rixon, M. Roelens, M. Romero-Gómez, N. Rowell, F. Royer, L. Ruiz-Dern, G. Sadowski, T. Sagristà Sellés, J. Sahlmann, J. Salgado, E. Salguero, M. Sarasso, H. Savietto, M. Schultheis, E. Sciacca, M. Segol, J. C. Segovia, D. Segransan, I.-C. Shih, R. Smareglia, R. L. Smart, E. Solano, F. Solitro, R. Sordo, S. Soria Nieto, J. Souchay, A. Spagna, F. Spoto, U. Stampa, I. A. Steele, H. Steidelmüller, C. A. Stephenson, H. Stoev, F. F. Suess, M. Süveges, J. Surdej, L. Szabados, E. Szegedi-Elek, D. Tapiador, F. Taris, G. Tauran, M. B. Taylor, R. Teixeira, D. Terrett, B. Tingley, S. C. Trager, C. Turon, A. Ulla, E. Utrilla, G. Valentini, A. van Elteren, E. Van Hemelryck, M. van Leeuwen, M. Varadi, A. Vecchiato, J. Veljanoski, T. Via, D. Vicente, S. Vogt, H. Voss, V. Votruba, S. Voutsinas, G. Walmsley, M. Weiler, K. Weingrill, T. Wevers, L. Wyrzykowski, A. Yoldas, M. erjal, S. Zucker, C. Zurbach, T. Zwitter, A. Alecu, M. Allen, C. Allende Prieto, A. Amorim, G. Anglada-Escudé, V. Arsenijevic, S. Azaz, P. Balm, M. Beck, H.-H. Bernstein, L. Bigot, A. Bijaoui, C. Blasco, M. Bonfigli, G. Bono, S. Boudreault, A. Bressan, S. Brown, P.-M. Brunet, P. Bunclark, R. Buonanno, A. G. Butkevich, C. Carret, C. Carrion, L. Chemin, F. Chéreau, L. Corcione, E. Darmigny, K. S. de Boer, P. de Teodoro, P. T. de Zeeuw, C. Delle Luche, C. D. Domingues, P. Dubath, F. Fodor, B. Frézouls, A. Fries, D. Fustes, D. Fyfe, E. Gallardo, J. Gallegos, D. Gardiol, M. Gebran, A. Gomboc, A. Gómez, E. Grux, A. Gueguen, A. Heyrovsky, J. Hoar, G. Iannicola, Y. Isasi Parache, A.-M. Janotto, E. Joliet, A. Jonckheere, R. Keil, D.-W. Kim, P. Klagyivik, J. Klar, J. Knude, O. Kochukhov, I. Kolka, J. Kos, A. Kutka, V. Lainey, D. LeBouquin, C. Liu, D. Loreggia, V. V. Makarov, M. G. Marseille, C. Martayan, O. Martinez-Rubi, B. Massart, F. Meynadier, S. Mignot, U. Munari, A.-T. Nguyen, T. Nordlander, P. Ocvirk, K. S. O'Flaherty, A. Olias Sanz, P. Ortiz, J. Osorio, D. Oszkiewicz, A. Ouzounis, M. Palmer, P. Park, E. Pasquato, C. Peltzer, J. Peralta, F. Péturaud, T. Pieniluoma, E. Pigozzi, J. Poels, G. Prat, T. Prod'homme, F. Raison, J. M. Rebordao, D. Risquez, B. Rocca-Volmerange, S. Rosen, M. I. Ruiz-Fuertes, F. Russo, S. Sembay, I. Serraller Vizcaino, A. Short, A. Siebert, H. Silva, D. Sinachopoulos, E. Slezak, M. Soffel, D. Sosnowska, V. Straiys, M. ter Linden, D. Terrell, S. Theil, C. Tiede, L. Troisi, P. Tsalmantza, D. Tur, M. Vaccari, F. Vachier, P. Valles, W. Van Hamme, L. Veltz, J. Virtanen, J.-M. Wallut, R. Wichmann, M. I. Wilkinson, H. Ziaeepour & S. Zschocke
Context: At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7.
Aims: A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release.
Methods: The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue.
Results: Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the H ipparcos and Tycho-2 catalogues - a realisation of the Tycho-Gaia Astrometric Solution (TGAS) - and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ~3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr-1 for the proper motions. A systematic component of ~0.3 mas should be added to the parallax uncertainties. For the subset of ~94000 Hipparcos stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr-1 . For the secondary astrometric data set, the typical uncertainty of the positions is ~10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ~0.03 mag over the magnitude range 5 to 20.7.
Conclusions: Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data.
Gaia collaboration, T. Prusti, J. H. J. de Bruijne, A. G. A. Brown, A. Vallenari, C. Babusiaux, C. A. L. Bailer-Jones, U. Bastian, M. Biermann, D. W. Evans, L. Eyer, F. Jansen, C. Jordi, S. A. Klioner, U. Lammers, L. Lindegren, X. Luri, F. Mignard, D. J. Milligan, C. Panem, V. Poinsignon, D. Pourbaix, S. Randich, G. Sarri, P. Sartoretti, H. I. Siddiqui, C. Soubiran, V. Valette, F. van Leeuwen, N. A. Walton, C. Aerts, F. Arenou, M. Cropper, R. Drimmel, E. Høg, D. Katz, M. G. Lattanzi, W. O'Mullane, E. K. Grebel, A. D. Holland, C. Huc, X. Passot, L. Bramante, C. Cacciari, J. Castañeda, L. Chaoul, N. Cheek, F. De Angeli, C. Fabricius, R. Guerra, J. Hernández, A. Jean-Antoine-Piccolo, E. Masana, R. Messineo, N. Mowlavi, K. Nienartowicz, D. Ordóñez-Blanco, P. Panuzzo, J. Portell, P. J. Richards, M. Riello, G. M. Seabroke, P. Tanga, F. Thévenin, J. Torra, S. G. Els, G. Gracia-Abril, G. Comoretto, M. Garcia-Reinaldos, T. Lock, E. Mercier, M. Altmann, R. Andrae, T. L. Astraatmadja, I. Bellas-Velidis, K. Benson, J. Berthier, R. Blomme, G. Busso, B. Carry, A. Cellino, G. Clementini, S. Cowell, O. Creevey, J. Cuypers, M. Davidson, J. De Ridder, A. de Torres, L. Delchambre, A. Dell'Oro, C. Ducourant, Y. Frémat, M. García-Torres, E. Gosset, J.-L. Halbwachs, N. C. Hambly, D. L. Harrison, M. Hauser, D. Hestroffer, S. T. Hodgkin, H. E. Huckle, A. Hutton, G. Jasniewicz, S. Jordan, M. Kontizas, A. J. Korn, A. C. Lanzafame, M. Manteiga, A. Moitinho, K. Muinonen, J. Osinde, E. Pancino, T. Pauwels, J.-M. Petit, A. Recio-Blanco, A. C. Robin, L. M. Sarro, C. Siopis, M. Smith, K. W. Smith, A. Sozzetti, W. Thuillot, W. van Reeven, Y. Viala, U. Abbas, A. Abreu Aramburu, S. Accart, J. J. Aguado, P. M. Allan, W. Allasia, G. Altavilla, M. A. Álvarez, J. Alves, R. I. Anderson, A. H. Andrei, E. Anglada Varela, E. Antiche, T. Antoja, S. Antón, B. Arcay, A. Atzei, L. Ayache, N. Bach, S. G. Baker, L. Balaguer-Núñez, C. Barache, C. Barata, A. Barbier, F. Barblan, M. Baroni, D. Barrado y Navascués, M. Barros, M. A. Barstow, U. Becciani, M. Bellazzini, G. Bellei, A. Bello García, V. Belokurov, P. Bendjoya, A. Berihuete, L. Bianchi, O. Bienaymé, F. Billebaud, N. Blagorodnova, S. Blanco-Cuaresma, T. Boch, A. Bombrun, R. Borrachero, S. Bouquillon, G. Bourda, H. Bouy, A. Bragaglia, M. A. Breddels, N. Brouillet, T. Brüsemeister, B. Bucciarelli, F. Budnik, P. Burgess, R. Burgon, A. Burlacu, D. Busonero, R. Buzzi, E. Caffau, J. Cambras, H. Campbell, R. Cancelliere, T. Cantat-Gaudin, T. Carlucci, J. M. Carrasco, M. Castellani, P. Charlot, J. Charnas, P. Charvet, F. Chassat, A. Chiavassa, M. Clotet, G. Cocozza, R. S. Collins, P. Collins, G. Costigan, F. Crifo, N. J. G. Cross, M. Crosta, C. Crowley, C. Dafonte, Y. Damerdji, A. Dapergolas, P. David, M. David, P. De Cat, F. de Felice, P. de Laverny, F. De Luise, R. De March, D. de Martino, R. de Souza, J. Debosscher, E. del Pozo, M. Delbo, A. Delgado, H. E. Delgado, F. di Marco, P. Di Matteo, S. Diakite, E. Distefano, C. Dolding, S. Dos Anjos, P. Drazinos, J. Durán, Y. Dzigan, E. Ecale, B. Edvardsson, H. Enke, M. Erdmann, D. Escolar, M. Espina, N. W. Evans, G. Eynard Bontemps, C. Fabre, M. Fabrizio, S. Faigler, A. J. Falcão, M. Farràs Casas, F. Faye, L. Federici, G. Fedorets, J. Fernández-Hernández, P. Fernique, A. Fienga, F. Figueras, F. Filippi, K. Findeisen, A. Fonti, M. Fouesneau, E. Fraile, M. Fraser, J. Fuchs, R. Furnell, M. Gai, S. Galleti, L. Galluccio, D. Garabato, F. García-Sedano, P. Garé, A. Garofalo, N. Garralda, P. Gavras, J. Gerssen, R. Geyer, G. Gilmore, S. Girona, G. Giuffrida, M. Gomes, A. González-Marcos, J. González-Núñez, J. J. González-Vidal, M. Granvik, A. Guerrier, P. Guillout, J. Guiraud, A. Gúrpide, R. Gutiérrez-Sánchez, L. P. Guy, R. Haigron, D. Hatzidimitriou, M. Haywood, U. Heiter, A. Helmi, D. Hobbs, W. Hofmann, B. Holl, G. Holland, J. A. S. Hunt, A. Hypki, V. Icardi, M. Irwin, G. Jevardat de Fombelle, P. Jofré, P. G. Jonker, A. Jorissen, F. Julbe, A. Karampelas, A. Kochoska, R. Kohley, K. Kolenberg, E. Kontizas, S. E. Koposov, G. Kordopatis, P. Koubsky, A. Kowalczyk, A. Krone-Martins, M. Kudryashova, I. Kull, R. K. Bachchan, F. Lacoste-Seris, A. F. Lanza, J.-B. Lavigne, C. Le Poncin-Lafitte, Y. Lebreton, T. Lebzelter, S. Leccia, N. Leclerc, I. Lecoeur-Taibi, V. Lemaitre, H. Lenhardt, F. Leroux, S. Liao, E. Licata, H. E. P. Lindstrøm T. A. Lister, E. Livanou, A. Lobel W. Löffler, M. López, A. Lopez-Lozano, D. Lorenz, T. Loureiro, I. MacDonald, T. Magalhães Fernandes, S. Managau, R. G. Mann, G. Mantelet, O. Marchal, J. M. Marchant, M. Marconi, J. Marie, S. Marinoni, P. M. Marrese, G. Marschalkó, D. J. Marshall, J. M. Martín-Fleitas, M. Martino, N. Mary, G. Matijevic, T. Mazeh, P. J. McMillan, S. Messina, A. Mestre, D. Michalik, N. R. Millar, B. M. H. Miranda, D. Molina, R. Molinaro, M. Molinaro, L. Molnár, M. Moniez, P. Montegriffo, D. Monteiro, R. Mor, A. Mora, R. Morbidelli, T. Morel, S. Morgenthaler, T. Morley, D. Morris, A. F. Mulone, T. Muraveva, I. Musella, J. Narbonne, G. Nelemans, L. Nicastro, L. Noval, C. Ordénovic, J. Ordieres-Meré, P. Osborne, C. Pagani, I. Pagano, F. Pailler, H. Palacin, L. Palaversa, P. Parsons, T. Paulsen, M. Pecoraro, R. Pedrosa, H. Pentikäinen, J. Pereira, B. Pichon, A. M. Piersimoni, F.-X. Pineau, E. Plachy, G. Plum, E. Poujoulet, A. Prša, L. Pulone, S. Ragaini, S. Rago, N. Rambaux, M. Ramos-Lerate, P. Ranalli, G. Rauw, A. Read, S. Regibo, F. Renk, C. Reylé, R. A. Ribeiro, L. Rimoldini, V. Ripepi, A. Riva, G. Rixon, M. Roelens, M. Romero-Gómez, N. Rowell, F. Royer, A. Rudolph, L. Ruiz-Dern, G. Sadowski, T. Sagristà Sellés, J. Sahlmann, J. Salgado, E. Salguero, M. Sarasso, H. Savietto, A. Schnorhk, M. Schultheis, E. Sciacca, M. Segol, J. C. Segovia, D. Segransan, E. Serpell, I-C. Shih, R. Smareglia, R. L. Smart, C. Smith, E. Solano, F. Solitro, R. Sordo, S. Soria Nieto, J. Souchay, A. Spagna, F. Spoto, U. Stampa, I. A. Steele, H. Steidelmüller, C. A. Stephenson, H. Stoev, F. F. Suess, M. Süveges, J. Surdej, L. Szabados, E. Szegedi-Elek, D. Tapiador, F. Taris, G. Tauran, M. B. Taylor, R. Teixeira, D. Terrett, B. Tingley, S. C. Trager, C. Turon, A. Ulla, E. Utrilla, G. Valentini, A. van Elteren, E. Van Hemelryck, M. van Leeuwen, M. Varadi, A. Vecchiato, J. Veljanoski, T. Via, D. Vicente, S. Vogt, H. Voss, V. Votruba, S. Voutsinas, G. Walmsley, M. Weiler, K. Weingrill, D. Werner, T. Wevers, G. Whitehead, ?. Wyrzykowski, A. Yoldas, M. erjal, S. Zucker, C. Zurbach, T. Zwitter, A. Alecu, M. Allen, C. Allende Prieto, A. Amorim, G. Anglada-Escudé, V. Arsenijevic, S. Azaz, P. Balm, M. Beck, H.-H. Bernstein, L. Bigot, A. Bijaoui, C. Blasco, M. Bonfigli, G. Bono, S. Boudreault, A. Bressan, S. Brown, P.-M. Brunet, P. Bunclark, R. Buonanno, A. G. Butkevich, C. Carret, C. Carrion, L. Chemin, F. Chéreau, L. Corcione, E. Darmigny, K. S. de Boer, P. de Teodoro, P. T. de Zeeuw, C. Delle Luche, C. D. Domingues, P. Dubath, F. Fodor, B. Frézouls, A. Fries, D. Fustes, D. Fyfe, E. Gallardo, J. Gallegos, D. Gardiol, M. Gebran, A. Gomboc, A. Gómez, E. Grux, A. Gueguen, A. Heyrovsky, J. Hoar, G. Iannicola, Y. Isasi Parache, A.-M. Janotto, E. Joliet, A. Jonckheere, R. Keil, D.-W. Kim, P. Klagyivik, J. Klar, J. Knude, O. Kochukhov, I. Kolka, J. Kos, A. Kutka, V. Lainey, D. LeBouquin, C. Liu, D. Loreggia, V. V. Makarov, M. G. Marseille, C. Martayan, O. Martinez-Rubi, B. Massart, F. Meynadier, S. Mignot, U. Munari, A.-T. Nguyen, T. Nordlander, P. Ocvirk, K. S. O'Flaherty, A. Olias Sanz, P. Ortiz, J. Osorio, D. Oszkiewicz, A. Ouzounis, M. Palmer, P. Park, E. Pasquato, C. Peltzer, J. Peralta, F. Péturaud, T. Pieniluoma, E. Pigozzi, J. Poels, G. Prat, T. Prod'homme, F. Raison, J. M. Rebordao, D. Risquez, B. Rocca-Volmerange, S. Rosen, M. I. Ruiz-Fuertes, F. Russo, S. Sembay, I. Serraller Vizcaino, A. Short, A. Siebert, H. Silva, D. Sinachopoulos, E. Slezak, M. Soffel, D. Sosnowska, V. Straiys, M. ter Linden, D. Terrell, S. Theil, C. Tiede, L. Troisi, P. Tsalmantza, D. Tur, M. Vaccari, F. Vachier, P. Valles, W. Van Hamme, L. Veltz, J. Virtanen, J.-M. Wallut, R. Wichmann, M. I. Wilkinson, H. Ziaeepour & S. Zschocke
Gaia is a cornerstone mission in the science programme of the European Space Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach. Both the spacecraft and the payload were built by European industry. The involvement of the scientific community focusses on data processing for which the international Gaia Data Processing and Analysis Consortium (DPAC) was selected in 2007. Gaia was launched on 19 December 2013 and arrived at its operating point, the second Lagrange point of the Sun-Earth-Moon system, a few weeks later. The commissioning of the spacecraft and payload was completed on 19 July 2014. The nominal five-year mission started with four weeks of special, ecliptic-pole scanning and subsequently transferred into full-sky scanning mode. We recall the scientific goals of Gaia and give a description of the as-built spacecraft that is currently (mid-2016) being operated to achieve these goals. We pay special attention to the payload module, the performance of which is closely related to the scientific performance of the mission. We provide a summary of the commissioning activities and findings, followed by a description of the routine operational mode. We summarise scientific performance estimates on the basis of in-orbit operations. Several intermediate Gaia data releases are planned and the data can be retrieved from the Gaia Archive, which is available through the Gaia home page.
F. Gourgeot, B. Carry, C. Dumas, F. Vachier, F. Merlin, P. Lacerda, M. A. Barucci & J. Berthier
Context: The transneptunian region of the solar system is populated by a wide variety of icy bodies showing great diversity in orbital behavior, size, surface color, and composition.
Aims: The dwarf planet (136108) Haumea is among the largest transneptunian objects (TNOs) and is a very fast rotator (~3.9 h). This dwarf planet displays a highly elongated shape and hosts two small moons that are covered with crystalline water ice, similar to their central body. A particular region of interest is the Dark Red Spot (DRS) identified on the surface of Haumea from multiband light-curve analysis (Lacerda et al. 2008). Haumea is also known to be the largest member of the sole TNO family known to date, and an outcome of a catastrophic collision that is likely responsible for the unique characteristics of Haumea.
Methods: We report here on the analysis of a new set of near-infrared Laser Guide Star assisted observations of Haumea obtained with the Integral Field Unit (IFU) Spectrograph for INtegral Field Observations in the Near Infrared (SINFONI) at the European Southern Observatory (ESO) Very Large Telescope (VLT) Observatory. Combined with previous data published by Dumas et al. (2011), and using light-curve measurements in the optical and far infrared to associate each spectrum with its corresponding rotational phase, we were able to carry out a rotationally resolved spectroscopic study of the surface of Haumea.
Results: We describe the physical characteristics of the crystalline water ice present on the surface of Haumea for both regions, in and out of the DRS, and analyze the differences obtained for each individual spectrum. The presence of crystalline water ice is confirmed over more than half of the surface of Haumea. Our measurements of the average spectral slope (1.45 ± 0.82% by 100?nm) confirm the redder characteristic of the spot region. Detailed analysis of the crystalline water-ice absorption bands do not show significant differences between the DRS and the remaining part of the surface. We also present the results of applying Hapke modeling to our data set. The best spectral fit is obtained with a mixture of crystalline water ice (grain sizes smaller than 60 ?m) with a few percent of amorphous carbon. Improvements to the fit are obtained by adding ~10% of amorphous water ice. Additionally, we used the IFU-reconstructed images to measure the relative astrometric position of the largest satellite Hi`iaka and determine its orbital elements. An orbital solution was computed with our genetic-based algorithm GENOID and our results are in full agreement with recent results.
A. Santerne, G. H´brard, J. Lillo-Box, D. J. Armstrong, S. C. C Barros, O. Demangeon, D. Barrado, A. Debackere, M. Deleuil, E. Delgado Mena, M. Montalto, D. Pollacco, H. P. Osborn, S. .G Sousa, L. Abe, V. Adibekyan, J.-M. Almenara, P. Andr´, G.; Arlic, G. Barthe, P. Bendjoya, R. Behrend, I. Boisse, F.; Bouchy, H. Boussier, M. Bretton, D. J. A. Brown, B. Carry, A. Cailleau, E. Conseil, G. Coulon, B. Courcol, B. Dauchet, J.-C. Dalouzy, M. Deldem, O. Desormières, P. Dubreuil, J.-M. Fehrenbach, S. Ferratfiat, R. Girelli, J. Gregorio, S. Jaecques, F. Kugel, J. Kirk, O. Labrevoir, J.-C. Lachuri´, K. W. F. Lam, P. Le Guen, P. Martinez, L. P. Maurin, J. McCormac, J.-B. Pioppa, U. Quadri, A Rajpurohit, J. Rey, J.-P. Rivet, R. Roy, N. C. Santos, F. Signoret, L. Strabla, O. Suarez, D. Toublanc, M. Tsantaki, J.-M. Vienney, P. A. Wilson, M. Bachschmidt, F. Colas, O. Gerteis, P. Louis, J.-C. Mario, C. Marlot, J.; Montier, V. Perroud, V. Pic, D. Romeuf, S. Ubaud, D. Verilhac
In the present paper we report the discovery of a new hot Jupiter, K2-29 b, first detected by the Super-WASP observatory and then by the K2 space mission during its campaign 4. The planet has a period of 3.25 days, a mass of 0.73 ± 0.04 MJupiter, and a radius of 1.19 ± 0.02 RJupiter. The host star is a relatively bright (V = 12.5) G7 dwarf with a nearby K5V companion. Based on stellar rotation and the abundance of lithium, we find that the system might be as young as ~450 Myr. The observation of the Rossiter-McLaughlin effect shows that the planet is aligned with respect to the stellar spin. Given the deep transit (20 mmag), the magnitude of the star and the presence of a nearby stellar companion, the planet is a good target for both space- and ground-based transmission spectroscopy, in particular in the near-infrared where both stars are relatively bright.
J. Berthier, B. Carry, F. Vachier, S. Eggl & A. Santerne
All the fields of the extended space mission Kepler/K2 are located within the ecliptic. Many Solar system objects thus cross the K2 stellar masks on a regular basis. We aim at providing to the entire community a simple tool to search and identify Solar system objects serendipitously observed by Kepler. The sky body tracker (SkyBoT) service hosted at Institut de mécanique céleste et de calcul des éphémérides provides a Virtual Observatory compliant cone search that lists all Solar system objects present within a field of view at a given epoch. To generate such a list in a timely manner, ephemerides are pre-computed, updated weekly, and stored in a relational data base to ensure a fast access. The SkyBoT web service can now be used with Kepler. Solar system objects within a small (few arcminutes) field of view are identified and listed in less than 10 s. Generating object data for the entire K2 field of view (14°) takes about a minute. This extension of the SkyBoT service opens new possibilities with respect to mining K2 data for Solar system science, as well as removing Solar system objects from stellar photometric time series.
K. Muinonen, G. Fedorets, H. Pentikäinen, T. Pieniluoma, D. Oszkiewicz, M. Granvik, J. Virtanen, P. Tanga, F. Mignard, J. Berthier, A. Dell`Oro, B. Carry & W. Thuillot
We describe statistical inverse methods for the computation of initial asteroid orbits within the data processing and analysis pipeline of the ESA Gaia space mission. Given small numbers of astrometric observations across short time intervals, we put forward a random-walk ranging method, in which the orbital-element phase space is uniformly sampled, up to a limiting chi2-value, with the help of the Markov-chain Monte Carlo technique (MCMC). The sample orbits obtain weights from the a posteriori probability density value and the MCMC rejection rate. For the first time, we apply the method to Gaia astrometry of asteroids. The results are nominal in that the method provides realistic estimates for the orbital uncertainties and meets the efficiency requirements for the daily, short-term processing of unknown objects.
P. Tanga, F. Mignard, A. Dell`Oro, K. Muinonen, T. Pauwels, W. Thuillot, J. Berthier, A. Cellino, D. Hestroffer, J.-M. Petit, B. Carry, P. David, M. Delbo, G. Fedorets, L. Galluccio, M. Granvik, C. Ordenovic & H. Pentikäinen
The Gaia mission started its regular observing program in the summer of 2014, and since then it is regularly obtaining observations of asteroids. This paper draws the outline of the data processing for Solar System objects, and in particular on the daily "short-term" processing, from the on-board data acquisition to the ground-based processing. We illustrate the tools developed to compute predictions of asteroid observations, we discuss the procedures implemented by the daily processing, and we illustrate some tests and validations of the processing of the asteroid observations. Our findings are overall consistent with the expectations concerning the performances of Gaia and the effectiveness of the developed software for data reduction.
B. Carry, E. Solano, S. Eggl & F. E. DeMeo
The nature and origin of the asteroids orbiting in near-Earth space, including those on a potentially hazardous trajectory, is of both scientific interest and practical importance. We aim here at determining the taxonomy of a large sample of near-Earth and Mars-crosser asteroids and analyze the distribution of these classes with orbit. We use this distribution to identify the source regions of near-Earth objects and to study the strength of planetary encounters to refresh asteroid surfaces. We measure the photometry of these asteroids over four filters at visible wavelengths on images taken by the Sloan Digital Sky Survey (SDSS). These colors are used to classify the asteroids into a taxonomy consistent with the widely used Bus-DeMeo taxonomy (DeMeo et al. . Icarus 202, 160-180) based on visible and near-infrared spectroscopy. We report here on the taxonomic classification of 206 near-Earth and 776 Mars-crosser asteroids determined from SDSS photometry, representing an increase of 40% and 663% of known taxonomy classifications in these populations. Using the source region mapper by Greenstreet et al. (. Icarus, 217, 355-366), we compare for the first time the taxonomic distribution among near-Earth and main-belt asteroids of similar diameters. Both distributions agree at the few percent level for the inner part of the main belt and we confirm this region as a main source of near-Earth objects. The effect of planetary encounters on asteroid surfaces are also studied by developing a simple model of forces acting on a surface grain during planetary encounter, which provides the minimum distance at which a close approach should occur to trigger resurfacing events. By integrating numerically the orbit of the 519 S-type and 46 Q-type asteroids in our sample back in time for 500,000 years and monitoring their encounter distance with Venus, Earth, Mars, and Jupiter, we seek to understand the conditions for resurfacing events. The population of Q-type is found to present statistically more encounters with Venus and the Earth than S-types, although both S- and Q-types present the same amount of encounters with Mars.
B. Carry & J. Berthier
Observations of Solar System objects in Service Mode require a special procedure. Observers preparing Observing Blocks must submit a detailed ephemerides file for each target for the whole duration of the observability period, which can sometimes be the entire ESO Period. These ephemerides files are ASCII files and follow a strict format, compatible with the VLT parameter file format. We present a simple web service that is now available to replace the former two-step process.
J. Hanus, J. Durech, D. A. Oszkiewicz, R. Behrend, B. Carry, M. Delbo, O. Adam, V. Afonina, R. Anquetin, P. Antonini, L. Arnold, M. Audejean, P. Aurard, M. Bachschmidt, B.; Baduel, E. Barbotin, P. Barroy, P. Baudouin, L. Berard, N. Berger, L. Bernasconi, J.-G. Bosch, S. Bouley, I. Bozhinova, J. Brinsfield, L. Brunetto, G. Canaud, J. Caron, F. Carrier, G. Casalnuovo, S. Casulli, M. Cerda, L. Chalamet, S. Charbonnel, B. Chinaglia, A. Cikota, F. Colas, J.-F. Coliac, A. Collet, J. Coloma, M. Conjat, E. Conseil, R. Costa, R. Crippa, M. Cristofanelli, Y. Damerdji, A. Debackere, A. Decock, Q. Dehais, T. Deleage, S. Delmelle, C. Demeautis, M. Drozdz, G. Dubos, T. Dulcamara, M. Dumont, R. Durkee,R. Dymock, A. Escalante del Valle, N. Esseiva, R. Esseiva, M. Esteban, T. Fauchez, M. Fauerbach, M. Fauvaud, S. Fauvaud, E. Forne, C. Fournel, D. Fradet, J. Garlitz, O. Gerteis, C. Gillier, M. Gillon, R. Giraud, J.-P. Godard, R. Goncalves,H. Hamanowa, H. Hamanowa, K. Hay, S. Hellmich, S. Heterier, D. Higgins, R. Hirsch, G. Hodosan, M. Hren, A. Hygate, N. Innocent, H. Jacquinot, S. Jawahar, E. Jehin, L. Jerosimic, A. Klotz, W. Koff, P. Korlevic, E. Kosturkiewicz,P. Krafft, Y. Krugly, F. Kugel, O. Labrevoir, J. Lecacheux, M. Lehky, A. Leroy, B. Lesquerbault, M. Lopez-Gonzales, M. Lutz, B. Mallecot, J. Manfroid, F. Manzini, A. Marciniak, A. Martin, B. Modave, R. Montaigut, J. Montier, E. Morelle, B. Morton, S. Mottola, R. Naves, J. Nomen, J. Oey, W. Og?oza, M. Paiella, H. Pallares, A. Peyrot, F. Pilcher, J.-F. Pirenne, P. Piron, M. Poli?ska, M. Polotto, R. Poncy, J. P. Previt, F. Reignier, D. Renauld, D. Ricci, F. Richard, C. Rinner, V. Risoldi, D. Robilliard, D. Romeuf, G. Rousseau, R. Roy, J. Ruthroff, P. A. Salom, L. Salvador, S. Sanchez, T. Santana-Ros, A. Scholz,G. Sene, B. Skiff, K. Sobkowiak, P. Sogorb, F. Soldan, A. Spiridakis, E. Splanska, S. Sposetti, D. Starkey, R. Stephens, A. Stiepen, R. Stoss, J. Strajnic, J.-P. Teng, G. Tumolo, A. Vagnozzi, B. Vanoutryve, J. M. Vugnon, B. D. Warner, M. Waucomont, O. Wertz, M. Winiarski, M. Wolf
Context: Asteroid modeling efforts in the last decade resulted in a comprehensive dataset of almost 400 convex shape models and their rotation states. These efforts already provided deep insight into physical properties of main-belt asteroids or large collisional families. Going into finer detail (e.g., smaller collisional families, asteroids with sizes <20 km) requires knowledge of physical parameters of more objects.
Aims: We aim to increase the number of asteroid shape models and rotation states. Such results provide important input for further studies, such as analysis of asteroid physical properties in different populations, including smaller collisional families, thermophysical modeling, and scaling shape models by disk-resolved images, or stellar occultation data. This provides bulk density estimates in combination with known masses, but also constrains theoretical collisional and evolutional models of the solar system.
Methods: We use all available disk-integrated optical data (i.e., classical dense-in-time photometry obtained from public databases and through a large collaboration network as well as sparse-in-time individual measurements from a few sky surveys) as input for the convex inversion method, and derive 3D shape models of asteroids together with their rotation periods and orientations of rotation axes. The key ingredient is the support of more that 100 observers who submit their optical data to publicly available databases.
Results: We present updated shape models for 36 asteroids, for which mass estimates are currently available in the literature, or for which masses will most likely be determined from their gravitational influence on smaller bodies whose orbital deflections will be observed by the ESA Gaia astrometric mission. Moreover, we also present new shape model determinations for 250 asteroids, including 13 Hungarias and three near-Earth asteroids. The shape model revisions and determinations were enabled by using additional optical data from recent apparitions for shape optimization.
D. Scheeres, D. Britt, B. Carry & K. Holsapple
The geophysical study of asteroids has moved from the realm of speculation and constraint to a more data rich environment where observations can be directly used to understand and probe the physical nature of these bodies. While many broad questions were posed in the Asteroids III chapter on asteroid interiors, in the current setting we are now able to probe more deeply into these questions, taking advantage of many different observations of asteroids across their entire size scale. The current chapter will take a very broad survey of what constraints currently exist in this area, what progress has been made in understanding these bodies analytically and through simulations, and what current theories can inform and guide future observations and tests of our understanding. The following topics are covered in this chapter: the strength of asteroid materials as inferred from meteors and meteorites, the density and porosity of asteroids as inferred from remote observations, global constraints on asteroid strength and morphology based on ground- and spacebased observations, analytical theories of asteroid strength and evolution, and the current state of numerical simulation techniques of asteroid interiors and morphology.
J.-L. Margot, P. Pravec, P. Taylor, B. Carry & S. Jacobson
In the past decade, the number of known binary near-Earth asteroids has more than quadrupled and the number of known large main-belt asteroids with satellites has doubled. Half a dozen triple asteroids have been discovered, and the previously unrecognized populations of asteroid pairs and small main-belt binaries have been identified. The current observational evidence confirms that small (≤20 km) binaries form by rotational fission and establishes that the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect powers the spin-up process. A unifying paradigm based on rotational fission and post-fission dynamics can explain the formation of small binaries, triples, and pairs. Large (≥20 km) binaries with small satellites are most likely created during large collisions.
J. Durech, B. Carry, M. Delbo, M. Kaasalainen & M. Viikinkoski
In the past decade, hundreds of asteroid shape models have been derived using the lightcurve inversion method. At the same time, a new framework of three-dimensional shape modeling based on the combined analysis of widely different data sources -- such as optical lightcurves, disk-resolved images, stellar occultation timings, mid-infrared thermal radiometry, optical interferometry, and radar delay-Doppler data -- has been developed. This multi-data approach allows the determination of most of the physical and surface properties of asteroids in a single, coherent inversion, with spectacular results. We review the main results of asteroid lightcurve inversion and also recent advances in multi-data modeling. We show that models based on remote sensing data were confirmed by spacecraft encounters with asteroids, and we discuss how the multiplication of highly detailed three-dimensional models will help to refine our general knowledge of the asteroid population. The physical and surface properties of asteroids, i.e., their spin, three-dimensional shape, density, thermal inertia, and surface roughness, are among the least known of all asteroid properties. Apart from the albedo and diameter, we have access to the whole picture for only a few hundreds of asteroids. These quantities are nevertheless very important to understand, as they affect the nongravitational Yarkovsky effect responsible for meteorite delivery to Earth, as well as the bulk composition and internal structure of asteroids.
W. Thuillot, D. Bancelin, A. Ivantsov, J. Desmars, M. Assafin, S. Eggl, D. Hestroffer, P. Rocher, B. Carry, P. David, L. Abe, M. Andreev, J.-E. Arlot, A. Asami, V. Ayvasian, A. Baransky, M. Belcheva, Ph. Bendjoya, I. Bikmaev, O. A. Burkhonov, U. Camci, A. Carbognani, F. Colas, A. V. Devyatkin, Sh. A. Ehgamberdiev, P. Enikova, L. Eyer, A. Galeev, E. Gerlach, V. Godunova, A. V. Golubaev, D. L. Gorshanov, R. Gumerov, N. Hashimoto, M. Helvaci,S. Ibryamov, R. Ya. Inasaridze, I. Khamitov, A. Kostov, A. M. Kozhukhov, Y. Kozyryev, Yu N. Krugly, V. Kryuchkovskiy, N. Kulichenko, N.; Maigurova, A. Manilla-Robles, A. A. Martyusheva, I. E. Molotov, G. Nikolov, P. Nikolov, K. Nishiyama, S. Okumura, L. Palaversa, O. Parmonov, Q. Y. Peng, S. N. Petrova, G. I. Pinigin, A. Pomazan, J.-P. Rivet, T. Sakamoto, N. Sakhibullin, O. Sergeev, A. V. Sergeyev, O. V. Shulga, O. Suarez, Y. Sybiryakova, N. Takahashi, V. Tarady, M. Todd, S. Urakawa, O. Uysal, O. Vaduvescu, V. Vovk & X.-L. Zhang
Aims: Astrometric observations performed by the Gaia Follow-Up Network for Solar System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects first detected by ESA's Gaia mission remain recoverable after their discovery. An observation campaign on the potentially hazardous asteroid (99 942) Apophis was conducted during the asteroid's latest period of visibility, from 12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall performance of the Gaia-FUN-SSO.
Methods: The 2732 high quality astrometric observations acquired during the Gaia-FUN-SSO campaign were reduced with the Platform for Reduction of Astronomical Images Automatically (PRAIA), using the USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric reduction process and the precision of the newly obtained measurements are discussed. We compare the residuals of astrometric observations that we obtained using this reduction process to data sets that were individually reduced by observers and accepted by the Minor Planet Center.
Results: We obtained 2103 previously unpublished astrometric positions and provide these to the scientific community. Using these data we show that our reduction of this astrometric campaign with a reliable stellar catalog substantially improves the quality of the astrometric results. We present evidence that the new data will help to reduce the orbit uncertainty of Apophis during its close approach in 2029. We show that uncertainties due to geolocations of observing stations, as well as rounding of astrometric data can introduce an unnecessary degradation in the quality of the resulting astrometric positions. Finally, we discuss the impact of our campaign reduction on the recovery process of newly discovered asteroids.
M. Viikinkoski, M. Kaasalainen, J. Durech, B. Carry, M. Marsset, T. Fusco, C. Dumas, W. J. Merline, B. Yang, J. Berthier, P. Kervella, & P. Vernazza
We use the recently released Atacama Large Millimeter Array (ALMA) and VLT/SPHERE science verification data, together with earlier adaptive-optics images, stellar occultation, and lightcurve data to model the 3D shape and spin of the large asteroid (3) Juno with the all-data asteroid modelling (ADAM) procedure. These data set limits on the plausible range of shape models, yielding reconstructions suggesting that, despite its large size, Juno has sizable unrounded features moulded by non-gravitational processes such as impacts.
P. Tanga, B. Carry, F. Colas, M. Delbo, A. Matter, J. Hanus, V. Ali Lagoa, A. H. Andrei, M. Assafin, M. Audejean, R. Behrend, J. Camargo, A. Carbognani, M. Cedres Reyes, M. Conjat, N. Cornero, D. Coward, R. Crippa, E. de Ferra Fantin, M. Devogele, G. Dubos, E. Frappa, M. Gillon, H. Hamanowa, E. Jehin, A. Klotz, A Kryszczynska, J. Lecacheux, A. Leroy, J. Manfroid, F. Manzini, L. Maquet, E. Morelle, S. Mottola, M. Polinska, R. Roy, M. Todd, F. Vachier, C. Vera Hernandez & P. Wiggins
Asteroid (234) Barbara is the prototype of a category of asteroids that has been shown to be extremely rich in refractory inclusions, the oldest material ever found in the Solar system. It exhibits several peculiar features, most notably its polarimetric behaviour. In recent years other objects sharing the same property (collectively known as `Barbarians') have been discovered. Interferometric observations in the mid-infrared with the ESO VLTI (Very Large Telescope Interferometer) suggested that (234) Barbara might have a bi-lobated shape or even a large companion satellite. We use a large set of 57 optical light curves acquired between 1979 and 2014, together with the timings of two stellar occultations in 2009, to determine the rotation period, spin-vector coordinates, and 3-D shape of (234) Barbara, using two different shape reconstruction algorithms. By using the light curves combined to the results obtained from stellar occultations, we are able to show that the shape of (234) Barbara exhibits large concave areas. Possible links of the shape to the polarimetric properties and the object evolution are discussed. We also show that VLTI data can be modelled without the presence of a satellite.
B. Carry, A. Matter, P. Scheirich, P. Pravec, L. Molnar, S. Mottola, A. Carbognagni, E. Jehin, A. Marcinial, R. P. Binzel, F. E. DeMeo, M. Birlan, M. Delbo, E. Barbotin, R. Behrend, M. Bonnardeau, F. Colas, P. Farissier, M. Fauvaud, S. Fauvaud, C. Gillier, M. Gillon, S. Hellmich, R. Hirsch, A. Leroy, J. Mangroid, J. Montier, E. Morelle, F. Richard, K. Sobkowiak, J. Strajnic & F. Vachier
In understanding the composition and internal structure of asteroids, their density is perhaps the most diagnostic quantity. We aim here to characterize the surface composition, mutual orbit, size, mass, and density of the small main-belt binary asteroid (939) Isberga. For that, we conduct a suite of multi-technique observations, including optical lightcurves over many epochs, near-infrared spectroscopy, and interferometry in the thermal infrared. We develop a simple geometric model of binary systems to analyze the interferometric data in combination with the results of the lightcurve modeling. From spectroscopy, we classify Ibserga as a Sq-type asteroid, consistent with the albedo of 0.14+0.09-0.06 (all uncertainties are reported as 3-sigma range) we determine (average albedo of S-types is 0.197 ± 0.153, Pravec et al., 2012, Icarus 221, 365-387). Lightcurve analysis reveals that the mutual orbit has a period of 26.6304 ± 0.0001 h, is close to circular, and has pole coordinates within 7 deg. of (225°, +86°) in ECJ2000, implying a low obliquity of 1.5°. The combined analysis of lightcurves and interferometric data allows us to determine the dimension of the system and we find volume-equivalent diameters of 12.4+2.5-1.2 km and 3.6+0.7-0.3 km for Isberga and its satellite, circling each other on a 33 km wide orbit. Their density is assumed equal and found to be 2.91+1.72-2.01 g.cm-3, lower than that of the associated ordinary chondrite meteorites, suggesting the presence of some macroporosity, but typical of S-types of the same size range (Carry, 2012, P&SS 73, 98-118). The present study is the first direct measurement of the size of a small main-belt binary. Although the interferometric observations of Isberga are at the edge of MIDI capabilities, the method described here is applicable to others suites of instruments (e.g, LBT, ALMA).
F. E. DeMeo, C. Dumas, J. C. Cook, B. Carry, F. Merlin, A. J. Verbiscer, & R. P. Binzel
The clear angular separation of Pluto and Charon from ground-based telescopes has been enabled by improved technology, particularly adaptive optics systems. Near-infrared spectral data have revealed Charon's surface to be rich in crystalline water ice and ammonia hydrates. In this work, we search for spectral differences across Charon's surface with new near-infrared spectral data taken in the K-band (2.0-2.4 μm) with SINFONI on the VLT and NIRI on Gemini North as well as with previously published spectral data. The strength of the absorption band of ammonia hydrate is dependent on the state of the ice, concentration in H2O, grain size, temperature and exposure to radiation. We find variability of the band center and band depth among spectra. This could indicate variability of the distribution of ammonia hydrate across Charon's surface. If the spectral variation is due to physical properties of Charon, the New Horizons flyby could find the concentration of ammonia hydrate heterogeneously distributed across the surface. Comparison between this work and New Horizons results will test the limits of ground-based reconnaissance.
O. Mousis, R. Hueso, J.-P. Beaulieu, S. Bouley, B. Carry, F. Colas, A. Klotz, C. Pellier, J.-M. Petit, P. Rousselot, M. Ali Dib, W. Beisker, M. Birlan, C. Buil, A. Delsanti, E. Frappa, H. B. Hammel, A.-C. Levasseur-Regourd, G. S. Orton, A. Sanchez-Lavega, A. Santerne, P. Tanga, J. Vaubaillon, B. Zanda, D. Baratoux, T. Boehm, V. Boudon, A. Bouquet, L. Buzzi, J.-L. Dauvergne, A. Decock, M. Delcroix, P. Drossart, N. Esseiva, G. Fischer, L. N. Fletcher, S. Foglia, J. M. Gomez-Forrellad, J. Guarro-Flo, D. Herald, F. Kugel, J.-P. Lebreton, J. Lecacheux, A. Leroy, L. Maquet, G. Masi, A. Maury, F. Meyer, S. Pérez-Hoyos, A. S. Rajpurohit, C. Rinner, J. H. Rogers, F. Roques, R. W. Schmude, Jr., B. Sicardy, B. Tregon, M. Vanhuysse, A. Wesley & T. Widemann
Amateur contributions to professional publications have increased exponentially over the last decades in the field of planetary astronomy. Here we review the different domains of the field in which collaborations between professional and amateur astronomers are effective and regularly lead to scientific publications.We discuss the instruments, detectors, software and methodologies typically used by amateur astronomers to collect the scientific data in the different domains of interest. Amateur contributions to the monitoring of planets and interplanetary matter, characterization of asteroids and comets, as well as the determination of the physical properties of Kuiper Belt Objects and exoplanets are discussed.
J. Berthier, F. Vachier, F. Marchis, J. Durech & B. Carry
We present the analysis of high angular resolution observations of the triple Asteroid (87) Sylvia collected with three 8-10 m class telescopes (Keck, VLT, Gemini North) and the Hubble Space Telescope. The moons' mutual orbits were derived individually using a purely Keplerian model. We computed the position of Romulus, the outer moon of the system, at the epoch of a recent stellar occultation which was successfully observed at less than 15 km from our predicted position, within the uncertainty of our model. The occultation data revealed that the Moon, with a surface-area equivalent diameter DS=23.1±0.7 km, is strongly elongated (axes ratio of 2.7±0.3), significantly more than single asteroids of similar size in the main-belt. We concluded that its shape is probably affected by the tides from the primary. A new shape model of the primary was calculated combining adaptive-optics observations with this occultation and 40 archived light-curves recorded since 1978. The difference between the J2=0.024-0.009+0.016 derived from the 3-D shape model assuming an homogeneous distribution of mass for the volume equivalent diameter DV=273±10 km primary and the null J2 implied by the Keplerian orbits suggests a non-homogeneous mass distribution in the asteroid's interior.
J. D. Drummond, B. Carry, W. J. Merline, C. Dumas, H. Hammel, S. Erard, A. Conrad, P. Tamblyn & C. Chapman
The dwarf planet (1) Ceres, the largest object between Mars and Jupiter, is the target of the NASA Dawn mission, and we seek a comprehensive description of the spin-axis orientation and dimensions of Ceres in order to support the early science operations at the rendezvous in 2015. We have obtained high-angular resolution images using adaptive optics cameras at the W.M. Keck Observatory and the ESO VLT over ten dates between 2001 and 2010, confirming that the shape of Ceres is well described by an oblate spheroid. We derive equatorial and polar diameters of 967 ± 10 km and 892 ± 10 km, respectively, for a model that includes fading of brightness towards the terminator, presumably linked to limb darkening. These dimensions lie between values derived from a previous analysis of a subset of these images obtained at Keck by Carry et al. (Astron. Astrophys. 478 (4), 235-244) and a study of Hubble Space Telescope observations (Thomas et al. . Nature 437, 224-226). Although the dimensions are 1-2 percent smaller than those found from the HST, the oblateness is similar.
We find the spin-vector coordinates of Ceres to lie at (287°, +64°) in equatorial EQJ2000 reference frame (346°, +82° in ecliptic ECJ2000 coordinates), yielding a small obliquity of 3°. While this is in agreement with the aforementioned studies, we have improved the accuracy of the pole determination, which we set at a 3° radius.
S. Renner, B. Sicardy, D. Souami, B. Carry & C. Dumas
Context. Neptune's incomplete ring arcs have been stable since their discovery in 1984 although these structures should be destroyed in a few months through differential Keplerian motion. Regular imaging data are needed to address the question of the arc stability.
Aims We present the first NACO observations of Neptune's ring arcs taken at 2.2 mum (Ks band) with the Very Large Telescope in August 2007, and propose a model for the arc stability based on co-orbital motion.
Methods The images were aligned using the ephemerides of the satellites Proteus and Triton and were suitably co-added to enhance ring or satellite signals. Resonance theory and N-body simulations were used to model the arcs' confinement.
Results We derive accurate mean motion values for the arcs and Galatea and confirm the mismatch between the arcs' position and the location of the 42:43 corotation inclination resonance. We propose a new confinement mechanism where small co-orbital satellites in equilibrium trap ring arc material. We constrain the masses and locations of these hypothetical co-orbital bodies.
F. E. DeMeo, R. P. Binzel, B. Carry, D. Polishook & N. A. Moskvitz
Very red featureless asteroids (spectroscopic D-types) are expected to have formed in the outer solar system far from the sun. They comprise the majority of asteroids in the Jupiter Trojan population, and are also commonly found in the outer main belt and among Hildas. The first evidence for D-types in the inner and middle parts of the main belt was seen in the Sloan Digital Sky Survey (SDSS). Here we report follow-up observations of SDSS D-type candidates in the near-infrared. Based on follow up observations of 13 SDSS D-type candidates, we find a ~20% positive confirmation rate. Known inner belt D-types range in diameter from roughly 7 to 30 kilometers. Based on these detections we estimate there are ~100 inner belt D-types with diameters between 2.5 and 20km. The lower and upper limits for total mass of inner belt D-types is 2x1016kg to 2x1017kg which represents 0.01% to 0.1% of the mass of the inner belt. The inner belt D-types have albedos at or above the upper end typical for D-types which raises the question as to whether these inner belt bodies represent only a subset of D-types, they have been altered by external factors such as weathering processes, or if they are compositionally distinct from other D-types. All D-types and candidates have diameters less than 30km, yet there is no obvious parent body in the inner belt. Dynamical models have yet to show how D-types originating from the outer solar system could penetrate into the inner reaches of the Main Belt under current scenarios of planet formation and subsequent Yarkovsky drift.
E. Solano, C. Rodrigo, R. Pulido & B. Carry
This article describes a citizen-science project conducted by the Spanish Virtual Observatory (SVO) to improve the orbits of near-Earth asteroids (NEAs) using data from astronomical archives. The list of NEAs maintained at the Minor Planet Center (MPC) is checked daily to identify new objects or changes in the orbital parameters of already catalogued objects. Using NEODyS we compute the position and magnitude of these objects at the observing epochs of the 938 046 images comprising the Eigth Data Release of the Sloan Digitised Sky Survey (SDSS). If the object lies within the image boundaries and the magnitude is brighter than the limiting magnitude, then the associated image is visually inspected by the project's collaborators (the citizens) to confirm or discard the presence of the NEA. If confirmed, accurate coordinates and, sometimes, magnitudes are submitted to the MPC. Using this methodology, 3,226 registered users have made during the first fifteen months of the project more than 167,000 measurements which have improved the orbital elements of 551 NEAs (6% of the total number of this type of asteroids). Even more remarkable is the fact that these results have been obtained at zero cost to telescope time as NEAs were serendipitously observed while the survey was being carried out. This demonstrates the enormous scientific potential hidden in astronomical archives. The great reception of the project as well as the results obtained makes it a valuable and reliable tool for improving the orbital parameters of near-Earth asteroids.
F. E. DeMeo & B. Carry
Advances in the discovery and characterization of asteroids over the past decade have revealed an unanticipated underlying structure that points to a dramatic early history of the inner Solar System. The asteroids in the main asteroid belt have been discovered to be more compositionally diverse with size and distance from the Sun than had previously been known. This implies substantial mixing through processes such as planetary migration and the subsequent dynamical processes.
M. Küppers, L. O'Rourke, D. Bocklee-Morvan, V. Zakharov, S. Lee, P. von allmen, B. Carry, D. Teyssier, A. Marston, T. Muller, J. Crovisier, M. A. Barucci & R. Moreno
The "snowline" conventionally divides Solar System objects into dry bodies, ranging out to the main asteroid belt, and icy bodies beyond the belt. Models suggest that some of the icy bodies may have migrated into the asteroid belt. Recent observations indicate the presence of water ice on the surface of some asteroids, with sublimation a potential reason for the dust activity observed on others. Hydrated minerals have been found on the surface of the largest object in the asteroid belt, the dwarf planet (1) Ceres, which is thought to be differentiated into a silicate core with an icy mantle. The presence of water vapour around Ceres was suggested by a marginal detection of the photodissociation product of water, hydroxyl (A'Hearn & Feldman, 1992), but could not be confirmed by later, more sensitive observations. Here we report the detection of water vapour around Ceres, with at least 1026 molecules being produced per second, originating from localized sources that seem to be linked to mid-latitude regions on the surface. The water evaporation could be due to comet-like sublimation or to cryo-volcanism, in which volcanoes erupt volatiles such as water instead of molten rocks.
F. E. DeMeo & B. Carry
The distribution of asteroids across the Main Belt has been studied for decades to understand the compositional distribution and what that tells us about the formation and evolution of our solar system. All-sky surveys now provide orders of magnitude more data than targeted surveys. We present a method to bias-correct the asteroid population observed in the Sloan Digital Sky Survey (SDSS) according to size, distance, and albedo. We taxonomically classify this dataset consistent with the Bus and Bus-DeMeo systems and present the resulting taxonomic distribution. The dataset includes asteroids as small as 5 km, a factor of three in diameter smaller than in previous works. Because of the wide range of sizes in our sample, we present the distribution by number, surface area, volume, and mass whereas previous work was exclusively by number. While the distribution by number is a useful quantity and has been used for decades, these additional quantities provide new insights into the distribution of total material. We find evidence for D-types in the inner main belt where they are unexpected according to dynamical models of implantation of bodies from the outer solar system into the inner solar system during planetary migration (Levison et al. 2009). We find no evidence of S-types or other unexpected classes among Trojans and Hildas, albeit a bias favoring such a detection. Finally, we estimate for the first time the total amount of material of each class in the inner solar system. The main belt's most massive classes are C, B, P, V and S in decreasing order. Excluding the four most massive asteroids, Ceres, Pallas, Vesta and Hygiea that heavily skew the values, primitive material (C-, P-types) account for more than half main-belt and Trojan asteroids by mass, most of the remaining mass being in the S-types. All the other classes are minor contributors to the material between Mars and Jupiter.
A. Matter, M. Delbo, B. Carry & S. Ligori
We describe the first determination of thermal properties and size of the M-type asteroid (16) Psyche from interferometric observations obtained with the Mid-Infrared Interferometric Instrument (MIDI) of the Very Large Telescope Interferometer. We used a thermophysical model to interpret our interferometric data. Our analysis shows that Psyche has a low macroscopic surface roughness. Using a convex 3-D shape model obtained by Kaasalainen et al. (2002, Icarus 159, 369-395), we derived a volume-equivalent diameter for (16) Psyche of 247 ± 25 km or 238 ± 24 km, depending on the possible values of surface roughness. Our corresponding thermal inertia estimates are 133 or 114 J.m-2.s-0.5.K-1, with a total uncertainty estimated to 40 J.m-2.s-0.5.K-1. They are among the highest thermal inertia values ever measured for an asteroid of this size. We consider this as a new evidence of a metal-rich surface for the asteroid (16) Psyche.
W. J. Merline, J. D. Drummond, B. Carry, A. Conrad, P. M. Tamblyn, C. Dumas, M. Kaasalainen, A. Erikson, S. Mottola, J. Durech, G. Rousseau, R. Behrend, G. B. Casalnuovo, B. Chinaglia, J. C. Christou, C. R. Chapman & C. Neyman
With the adaptive optics (AO) system on the 10 m Keck-II telescope, we acquired a high quality set of 84 images at 14 epochs of asteroid (52) Europa on 2005 January 20, when it was near opposition. The epochs covered its 5.63 h rotation period and, by following its changing shape and orientation on the plane of sky, we obtained its triaxial ellipsoid dimensions and spin pole location. An independent determination from images at three epochs obtained in 2007 is in good agreement with these results. By combining these two data sets, along with a single epoch data set obtained in 2003, we have derived a global fit for (52) Europa of diameters a x b x c = (379 x 330 x 249) ± (16 x 8 x 10) km, yielding a volume-equivalent spherical-diameter of 315 ± 7 km, and a prograde rotational pole within 7° of [RA; Dec] = [257°, +12° ] in an Equatorial J2000 reference frame (Ecliptic: 255°, +35° ). Using the average of all mass determinations available for (52) Europa, we derive a density of 1.5 ± 0.4 g cm-3 , typical of C-type asteroids. Comparing our images with the shape model of Michalowski et al. (Astron. and Astrophys. 416, p 353, 2004), derived from optical lightcurves, illustrates excellent agreement, although several edge features visible in the images are not rendered by the model. We therefore derived a complete 3-D description of (52) Europa's shape using the KOALA algorithm by combining our 18 AO imaging epochs with 4 stellar occultations and 49 lightcurves. We use this 3-D shape model to assess these departures from ellipsoidal shape. Flat facets (possible giant craters) appear to be less distinct on (52) Europa than on other C-types that have been imaged in detail, (253) Mathilde and (511) Davida. We show that fewer giant craters, or smaller craters, is consistent with its expected impact history. Overall, asteroid (52) Europa is still well modeled as a smooth triaxial ellipsoid with dimensions constrained by observations obtained over several apparitions.
C. Snodgrass & B. Carry
EFOSC, in common with many instruments with older CCDs, shows a fringe pattern in images taken at red wavelengths. These fringes are difficult to remove without significant manual adjustment for each individual frame, which is a time-consuming exercise, but necessary for reliable photometry of faint objects across the whole field of view. We present a simple technique to automatically remove fringes from CCD images, and provide scripts (available on the ESO website) to apply this to EFOSC data, or to any other images.
J. Hanus, J. Durech, M. Broz, A. Marciniak, B. D. Warner, F. Pilcher, R. Stephnes, R. Behrend, B. Carry, D. Capek, P. Antonini, M. Audejean, K. Augustesen, E. Barbotin, P. Baudouin, A. Bayol, L. Bernasconi, W. Borczyk, J.-G. Bosch, E. Brochard, L. Brunetto, S. Casulli, A. Cazenave, S. Charbonnel, B. Christophe, F. Colas, J. Coloma, M. Conjat, W. Cooney, H. Correira, V. Cotrez, A. Coupier, R. Crippa, M. Cristofanelli, Ch. Dalmas, C. Danavaro, C. Demeautis, T. Droege, R. Durkee, N. Esseiva, M. Esteban, M. Fagas, G. Farroni, M. Fauvaud, S. Fauvaud, F. Del Freo, L. Garcia, S. Geier, C. Godon, K. Grangeon, H. Hamanowa, H. Hamanowa, N. Heck, S. Hellmich, D. Higgins, R. Hirsch, M. Husarik, T. Itkonen, O. Jade, K. Kaminski, P. Kankiewicz, A. Klotz, R. A. Koff, A. Kryszczynska, T. Kwiatkowski, A. Laffont, A. Leroy, J. Lecacheux, Y. Leonie, C. Leyrat, F. Manzini, A. Martin, G. Masi, D. Matter, J. Micha?owski, M. J. Micha?owski, T. Micha?owski, J. Michelet, R. Michelsen, E. Morelle, S. Mottola, R. Naves, J. Nomen, J. Oey, W. Og?oza, A. Oksanen, D. Oszkiewicz, P. Paakkonen, M. Paiella, H. Pallares, J. Paulo, M. Pavic, B. Payet, M. Polinska, D. Polishook, R. Poncy , Y. Revaz , C. Rinner , M. Rocca , A. Roche , D. Romeuf , R. Roy , H. Saguin, P. A. Salom, S. Sanchez, G. Santacana, T. Santana-Ros, J.-P. Sareyan, K. Sobkowiak, S. Sposetti, D. Starkey, R. Stoss, J. Strajnic, J.-P. Teng, B. Tregon, A. Vagnozzi, F. P. Velichko, N. Waelchli, K. Wagrez & H. Wucher
Context. The larger number of models of asteroid shapes and their rotational states derived by the lightcurve inversion give us better insight into both the nature of individual objects and the whole asteroid population. With a larger statistical sample we can study the physical properties of asteroid populations, such as main-belt asteroids or individual asteroid families, in more detail. Shape models can also be used in combination with other types of observational data (IR, adaptive optics images, stellar occultations), e.g., to determine sizes and thermal properties.
Aims. We use all available photometric data of asteroids to derive their physical models by the lightcurve inversion method and compare the observed pole latitude distributions of all asteroids with known convex shape models with the simulated pole latitude distributions.
Methods. We used classical dense photometric lightcurves from several sources (Uppsala Asteroid Photometric Catalogue, Palomar Transient Factory survey, and from individual observers) and sparse-in-time photometry from the U.S. Naval Observatory in Flagstaff, Catalina Sky Survey, and La Palma surveys (IAU codes 689, 703, 950) in the lightcurve inversion method to determine asteroid convex models and their rotational states. We also extended a simple dynamical model for the spin evolution of asteroids used in our previous paper.
Results. We present 119 new asteroid models derived from combined dense and sparse-in-time photometry. We discuss the reliability of asteroid shape models derived only from Catalina Sky Survey data (IAU code 703) and present 20 such models. By using different values for a scaling parameter cYORP (corresponds to the magnitude of the YORP momentum) in the dynamical model for the spin evolution and by comparing synthetics and observed pole-latitude distributions, we were able to constrain the typical values of the cYORP parameter as between 0.05 and 0.6.
The small bodies of our solar system are the remnants of the early stages of planetary formation. A considerable amount of information regarding the processes that occurred during the accretion of the early planetesimals is still present among this population. A review of our current knowledge of the density of small bodies is presented here. Density is indeed a fundamental property for the understanding of their composition and internal structure. Intrinsic physical properties of small bodies are sought by searching for relationships between the dynamical and taxonomic classes, size, and density. Mass and volume estimates for 287 small bodies (asteroids, comets, and transneptunian objects) are collected from the literature. The accuracy and biases affecting the methods used to estimate these quantities are discussed and best-estimates are strictly selected. Bulk densities are subsequently computed and compared with meteorite density, allowing to estimate the macroporosity (i.e., amount of voids) within these bodies. Dwarf-planets apparently have no macroporosity, while smaller bodies (<400 km) can have large voids. This trend is apparently correlated with size: C and S-complex asteroids tends to have larger density with increasing diameter. The average density of each Bus-DeMeo taxonomic classes is computed (DeMeo et al., 2009, Icarus 202). S-complex asteroids are more dense on average than those in the C-complex that in turn have a larger macroporosity, although both complexes partly overlap. Within the C-complex asteroids, B-types stand out in albedo, reflectance spectra, and density, indicating a unique composition and structure. Asteroids in the X-complex span a wide range of densities, suggesting that many compositions are included in the complex. Comets and TNOs have high macroporosity and low density, supporting the current models of internal structures made of icy aggregates. Although the number of density estimates sky-rocketed during last decade from a handful to 287, only a third of the estimates are more precise than 20%. Several lines of investigation to refine this statistic are contemplated, including observations of multiple systems, 3-D shape modeling, and orbital analysis from Gaia astrometry.
B. Carry, C. Snodgrass, P. Lacerda, O. Hainaut & C. Dumas
Context. From a dynamical analysis of the orbital elements of transneptunian objects (TNOs), Ragozzine & Brown reported a list of candidate members of the first collisional family found among this population, associated with (136 108) Haumea (a.k.a. 2003 EL61).
Aims. We aim to distinguish the true members of the Haumea collisional family from interlopers. We search for water ice on their surfaces, which is a common characteristic of the known family members. The properties of the confirmed family are used to constrain the formation mechanism of Haumea, its satellites, and its family.
Methods. Optical and near-infrared photometry is used to identify water ice. We use in particular the CH4 filter of the Hawk-I instrument at the European Southern Observatory Very Large Telescope as a short H-band (Hs), the (J?Hs) colour being a sensitive measure of the water ice absorption band at 1.6 μm.
Results. Continuing our previous study headed by Snodgrass, we report colours for 8 candidate family members, including near-infrared colours for 5. We confirm one object as a genuine member of the collisional family (2003 UZ117), and reject 5 others. The lack of infrared data for the two remaining objects prevent any conclusion from being drawn. The total number of rejected members is therefore 17. The 11 confirmed members represent only a third of the 36 candidates.
Conclusion. The origin of Haumea's family is likely to be related to an impact event. However, a scenario explaining all the peculiarities of Haumea itself and its family remains elusive.
B. Carry, M. Kaasalainen, W. J. Merline, T. G. Müller, L. Jorda, J. D. Drummond, J. Berthier, L. O'Rourke, J. Durech, M. Küppers, A. Conrad, P. Tamblyn, C. Dumas, H. Sierks & the OSIRIS team
We present here a comparison of our results from ground-based observations of asteroid (21) Lutetia with imaging data acquired during the flyby of the asteroid by the ESA Rosetta mission. This flyby provided a unique opportunity to evaluate and calibrate our method of determination of size, 3-D shape, and spin of an asteroid from ground-based observations. Knowledge of certain observable physical properties of small bodies (e.g., size, spin, 3-D shape, and density) have far-reaching implications in furthering our understanding of these objects, such as composition, internal structure, and the effects of non-gravitational forces. We review the different observing techniques used to determine the above physical properties of asteroids and present our 3-D shape-modeling technique KOALA - Knitted Occultation, Adaptive-optics, and Lightcurve Analysis - which is based on multi-dataset inversion.
We compare the results we obtained with KOALA, prior to the flyby, on asteroid (21) Lutetia with the high-spatial resolution images of the asteroid taken with the OSIRIS camera on-board the ESA Rosetta spacecraft, during its encounter with Lutetia on 2010 July 10. The spin axis determined with KOALA was found to be accurate to within two degrees, while the KOALA diameter determinations were within 2% of the Rosetta-derived values. The 3-D shape of the KOALA model is also confirmed by the spectacular visual agreement between both 3-D shape models (KOALA pre- and OSIRIS post-flyby). We found a typical deviation of only 2 km at local scales between the profiles from KOALA predictions and OSIRIS images, resulting in a volume uncertainty provided by KOALA better than 10%. Radiometric techniques for the interpretation of thermal infrared data also benefit greatly from the KOALA shape model: the absolute size and geometric albedo can be derived with high accuracy, and thermal properties, for example the thermal inertia, can be determined unambiguously. The corresponding Lutetia analysis leads to a geometric albedo of 0.19±0.01 and a thermal inertia below 40 J m-2 s-0.5 K-1, both in excellent agreement with the Rosetta findings. We consider this to be a validation of the KOALA method. Because space exploration will remain limited to only a few objects, KOALA stands as a powerful technique to study a much larger set of small bodies using Earth-based observations.
L. O'Rourke, T. Müller, I. Valtchanov, B. Altieri, B. Gonzalez-Garcia, B. Bhattacharya, L. Jorda, B. Carry, M. Küppers, O. Groussin, K. Altwegg, M. A. Barucci, D. Bockelee-Morvan, J. Crovisier, E. Dotto, P. Garcia-Lario, M. Kidger, A. Llorente, R. Lorente, A. P. Marston, M. Sanchez Portal, R. Schulz, M. Sierra, D. Teyssier & R. Vavrek
Prior to and around the Rosetta flyby of (21) Lutetia, the Herschel Space Observatory performed a collaborative observation campaign with its two photometers observing the asteroid in the far infrared, at wavelengths not covered by Rosetta's instruments. The Herschel observations, fed into a thermophysical model (TPM) using as input a shape model based on in-situ images, were also further correlated with ~ 70 multi-wavelength observations of Lutetia. We confirm the geometric albedo measured by Rosetta, derive a H-mag value based upon the effective diameter of the asteroid and point to (21) Lutetia having an extremely low thermal inertia (5 J m-2 s-0.5 K-1). This thermal inertia is only possible through the existence of a significant amount of small scale roughness which is not directly observable by the OSIRIS (Optical, Spectroscopic, and Infrared Imaging System) instrument on-board Rosetta. In addition, our results point to the existence of a hill/crater surface feature located on the asteroids southern region not observed by Rosetta. From our results, we conclude that only through the merging of in situ and remote sensing observations can a true global picture be obtained of this asteroid.
M. Küppers, R. Moissl, J.-B. Vincent, S. Besse, S. F. Hvvid, B. Carry, B. Grieger, H. Sierks, H. .U. Keller, S. Marchi & the OSIRIS team
More than 200 boulders are among the many prominent geological features seen on Lutetia by the OSIRIS cameras onboard Rosetta. Most are concentrated around the central crater in Baetica regio with a few more apparently associated with Patavium crater. The size range of boulders visible to OSIRIS is about 60-300 m. We model the trajectories of boulders ejected from the central crater and show that their distribution is consistent with most of them being created from that crater, similar to the situation on asteroid Eros where most of the boulders are believed to originate from Shoemaker crater. We evaluate various destruction mechanisms for ejecta blocks and conclude that, using current estimates of the number of small asteroids in the main belt, destruction by impacts of small (several meters diameter) projectiles limits the lifetime of the boulders (and the age of the central crater) to a maximum of 300 million years. Since several analyses of crater ages and size distributions also come up with surprisingly young ages, the size-frequency distribution of small main-belt asteroids (below the size currently reached by surveys) may warrant to be revisited.
B. Carry, P. Vernazza, C. Dumas, W. J. Merline, O. Mousis, P. Rousselot, E. Jehin, J. Manfroid, M. Fulchignoni & J.-M. Zucconi
Dwarf-planet (1) Ceres is one of the two targets, along with (4) Vesta, that will be studied by the NASA Dawn spacecraft via imaging, visible and near-infrared spectroscopy, and gamma-ray and neutron spectroscopy. While Ceres' visible and near-infrared disk-integrated spectra have been well characterized, little has been done about quantifying spectral variations over the surface. Any spectral variation would give us insights on the geographical variation of the composition and/or the surface age. The only work so far was that of Rivkin & Volquardsen (2010, Icarus 206, 327) who reported rotationally-resolved spectroscopic (disk-integrated) observations in the 2.2-4.0 μm range; their observations showed evidence for a relatively uniform surface.
Here, we report disk-resolved observations of Ceres with SINFONI (ESO VLT) in the 1.17-1.32 μm and 1.45-2.35 μm wavelength ranges. The observations were made under excellent seing conditions (0.6"), allowing us to reach a spatial resolution of ?75 km on Ceres' surface. We do not find any spectral variation above a 3% level, suggesting a homogeneous surface at our spatial resolution. Slight variations (about 2%) of the spectral slope are detected, geographically correlated with the albedo markings reported from the analysis of the HST and Keck disk-resolved images of Ceres (Li et al., 2006, Icarus 182, 143; Carry et al., 2008, A&A 478, 235). Given the lack of constraints on the surface composition of Ceres, however, we cannot assert the causes of these variations.
H. Sierks, P. Lamy, C. Barbieri, D. Koschny, H. Rickman, R. Rodrigo, M. F. A'Hearn, F. Angrilli, M. A. Barucci, J.-L. Bertaux, I. Bertini, S. Besse, B. Carry, G. Cremonese, V. Da Deppo, B. Davidsson, S. Debei, M. De Cecco, J. De Leon, F. Ferri, S. Fornasier, M. Fulle, S. F. Hviid, R. W. Gaskell, O. Groussin, P. Gutierrez, W. Ip, L. Jorda, M. Kaasalainen, H. U. Keller, J. Knollenberg, R. Kramm, E. Kührt, M. Küppers, L. Lara, M. Lazzarin, C. Leyrat, J. J. Lopez Moreno, S. Magrin, S. Marchi, F. Marzari, M. Massironi, H. Michalik, R. Moissl, G. Naletto, F. Preusker, L. Sabau, W. Sabolo, F. Scholten, C. Snodgrass, N. Thomas, C. Tubiana, P. Vernazza, J.-B. Vincent, K.-P. Wenzel, T. Andert, M. Patzold & B. P. Weiss
Images obtained by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras onboard the Rosetta spacecraft reveal that asteroid 21 Lutetia has a complex geology and one of the highest asteroid densities measured so far, 3.4 ± 0.3 grams per cubic centimeter. The north pole region is covered by a thick layer of regolith, which is seen to flow in major landslides associated with albedo variation. Its geologically complex surface, ancient surface age, and high density suggest that Lutetia is most likely a primordial planetesimal. This contrasts with smaller asteroids visited by previous spacecraft, which are probably shattered bodies, fragments of larger parents, or reaccumulated rubble piles.
P. Rousselot, E. Jehin, J. Manfroid, O. Mousis, C. Dumas, B. Carry, U. Marboeuf & J.-M. Zucconi
There are hints that the dwarf planet (1) Ceres may contain a large amount of water ice. Some models and previous observations suggest that ice could be close enough to the surface to create a flux of water outward through the regolith. This work aims to confirm a previous detection of OH emission off the northern limb of Ceres with the International Ultraviolet Explorer (IUE). Such emission would be evidence of water molecules escaping from the dwarf planet. We used the Ultraviolet and Visual Echelle Spectrograph of the Very Large Telescope to obtain spectra off the northern and southern limbs of Ceres at several epochs. These spectra cover the 307-312 nm wavelength range corresponding to the OH (0,0) emission band, which is the brightest band of this radical, well known in the cometary spectra. These new observations, five times more sensitive than those from IUE, did not permit detection of OH around Ceres. We derive an upper limit for the water production of about ~7 x 1025 molecule/s and estimate the minimum thickness of the dust surface layer above the water ice layer (if present) to be about 20 m.
B. Carry, D. Hestroffer, F. DeMeo, A. Thirouin, J. Berthier, P. Lacerda, B. Sicardy, A. Doressoundiram, C. Dumas, D. Farrelly, & T. G. Müller
Aims. We seek to constrain the surface composition of the Trans-Neptunian Object (90482) Orcus and its small satellite Vanth, as well as their mass and density.
Methods. We acquired near-infrared spectra (1.4-2.4 μm) of (90482) Orcus and its companion Vanth using the adaptive-optics-fed integral-field spectrograph SINFONI mounted on Yepun/UT4 at the European Southern Observatory Very Large Telescope. We took advantage of a very favorable appulse (separation of only 4") between Orcus and the UCAC2 29643541 star (R = 11.6) to use the adaptive optics mode of SINFONI, allowing both components to be spatially resolved and Vanth colors to be extracted independently from Orcus.
Results. The spectrum of Orcus we obtain has the highest signal-to-noise ratio to date, and we confirm the presence of H2O ice in crystalline form, together with the presence of an absorption band at 2.2 μm. We set an upper limit of about 2% for the presence of methane, and 5% for ethane. Because the methane alone cannot account for the 2.2 μm band, the presence of ammonia is suggested to the level of a couple of percent. The colors of Vanth are found slightly redder than those of Orcus, but the large measurement uncertainties forbid us from drawing conclusions on the origin of the pair (capture or co-formation). Finally, we reset the orbital phase of Vanth around Orcus, and confirm the orbital parameters derived by Brown et al. (2010, AJ 139).
F. DeMeo, B. Carry, F. Marchis, M. Birlan, R. P. Binzel, S. J. Bus, P. Descamps, A. Nedelcu, M. Busch & H. Bouy
We present near-infrared spectral measurements of Themis family asteroid (379) Huenna (D?98 km) and its 6 km satellite using SpeX on the NASA IRTF. The companion was farther than 1.5" from the primary at the time of observations and was approximately 5 magnitudes dimmer. We describe a method for separating and extracting the signal of a companion asteroid when the signal is not entirely resolved from the primary. The spectrum of (379) Huenna has a broad, shallow feature near 1 μm and a low slope, characteristic of C-type asteroids. The secondary's spectrum is consistent with the taxonomic classification of C-complex or X-complex. The quality of the data was not sufficient to identify any subtle feature in the secondary's spectrum.
C. Dumas, B. Carry, D. Hestroffer & F. Merlin
Context. The trans-Neptunian region of the Solar System is populated by a wide variety of icy bodies showing great diversity in orbital behavior, size, surface color, and composition. One can also see there are dynamical families and binary systems. One surprising feature detected in the spectra of some of the largest trans-Neptunians is the presence of crystalline water-ice. This is the case for the large TNO (136108) Haumea (2003 EL61).
Aims. We seek to constrain the state of the water ice of Haumea and its satellites and to investigate possible energy sources that maintain the water ice in its crystalline form.
Methods. Spectro-imaging observations in the near infrared were performed with the integral field spectrograph SINFONI mounted on UT4 at the ESO Very Large Telescope. The spectra of both Haumea and its larger satellite Hi'iaka were analyzed. Relative astrometry of the components was also measured, providing a check of the orbital solutions and equinox seasons.
Results. We describe the physical characteristics of the crystalline water-ice present on the surface of Haumea and its largest satellite Hi'iaka and analyze possible sources of heating to maintain water in a crystalline state: tidal dissipation in the system components vs radiogenic source. The surface of Hi'iaka appears to be covered by large grains of water ice, almost entirely in its crystalline form. Under some restricted conditions, both radiogenic heating and tidal forces between Haumea and Hi'iaka could provide the energy needed to maintain the ice in its crystalline state.
B. Carry, M. Kaasalainen, C. Leyrat, W. J. Merline, J. D. Drummond, A. Conrad, H. A. Weaver, P. M. Tamblyn, C. R. Chapman, C. Dumas, F. Colas, J. C. Christou, E. Dotto, D. Perna, S. Fornasier, L. Bernasconi, R. Behrend, F. Vachier, A. Kryszczynska, M. Polinska, M. Fulchignoni, R. Roy, R. Naves, R. Poncy & P. Wiggins
Aims. We determine the physical properties (spin state and shape) of asteroid (21) Lutetia, target of the ESA Rosetta mission, to help in preparing for observations during the flyby on 2010 July 10 by predicting the orientation of Lutetia as seen from Rosetta.
Methods. We use our novel KOALA inversion algorithm to determine the physical properties of asteroids from a combination of optical lightcurves, disk-resolved images, and stellar occultations, although the latter are not available for (21) Lutetia.
Results. We find the spin axis of (21) Lutetia to lie within 5° of (λ = 52°, β = -6°) in Ecliptic J2000 reference frame (equatorial α = 52°, δ = +12°), and determine an improved sidereal period of 8.168 270 ± 0.000 001 h. This pole solution implies the southern hemisphere of Lutetia will be in "seasonal" shadow at the time of the flyby. The apparent cross-section of Lutetia is triangular as seen "pole-on" and more rectangular as seen "equator-on". The best-fit model suggests the presence of several concavities. The largest of these is close to the north pole and may be associated with large impacts.
J. D. Drummond, A. Conrad, W. J. Merline, B. Carry, C. R. Chapman, H. A. Weaver, P. M. Tamblyn, J. C. Christou & C. Dumas
Context. Asteroid (21) Lutetia is the target of the ESA Rosetta mission flyby in 2010 July.
Aims. We seek the best size estimates of the asteroid, the direction of its spin axis, and its bulk density, assuming its shape is well described by a smooth featureless triaxial ellipsoid, and to evaluate the deviations from this assumption.
Methods. We derive these quantities from the outlines of the asteroid in 307 images of its resolved apparent disk obtained with adaptive optics (AO) at Keck II and VLT, and combine these with recent mass determinations to estimate a bulk density.
Results. Our best triaxial ellipsoid diameters for Lutetia, based on our AO images alone, are a x b x c = 132 x 101 x 93 km, with uncertainties of 4 x 3 x 13 km including estimated systematics, with a rotational pole within 5° of ECJ2000 [λ, β] = [45°, -7°], or EQJ2000 [RA, DEC] = [44°, +9°]. The AO model fit itself has internal precisions of 1 x 1 x 8 km, but it is evident, both from this model derived from limited viewing aspects and the radius vector model given in a companion paper, that Lutetia has significant departures from an idealized ellipsoid. In particular, the long axis may be overestimated from the AO images alone by about 10 km. Therefore, we combine the best aspects of the radius vector and ellipsoid model into a hybrid ellipsoid model, as our final result, of 124 ± 5 x 101 ± 4 x 93 ± 13 km that can be used to estimate volumes, sizes, and projected areas. The adopted pole position is within 5° of [λ, β] = [52°, -6°] or [RA, DEC] = [52°, +12°].
Conclusions. Using two separately determined masses and the volume of our hybrid model, we estimate a density of 3.5 ± 1.1 or 4e.3 ± 0.8 g. cm-3. From the density evidence alone, we argue that this favors an enstatite-chondrite composition, although other compositions are formally allowed at the extremes (low-porosity CV/CO carbonaceous chondrite or high-porosity metallic). We discuss this in the context of other evidence.
C. Snodgrass, C. Tubiana, J.-B. Vincent, H. Sierks, S. Hviid, R. Moissl, H. Boehnhardt, C. Barbieri, D. Koschny, P. Lamy, H. Rickman, R. Rodrigo, B. Carry, S. C. Lowry, R. J. M. Laird, P. R. Weissman, A. Fitzsimmons, S. Marchi & the OSIRIS Team
The peculiar object P/2010 A2 was discovered by the LINEAR near-Earth asteroid survey in January 2010 and given a cometary designation due to the presence of a trail of material, although there was no central condensation or coma. The appearance of this object, in an asteroidal orbit (small eccentricity and inclination) in the inner main asteroid belt attracted attention as a potential new member of the recently recognized class of 'Main Belt Comets' (MBCs). If confirmed, this new object would greatly expand the range in heliocentric distance over which MBCs are found. Here we present observations taken from the unique viewing geometry provided by ESA's Rosetta spacecraft, far from the Earth, that demonstrate that the trail is due to a single event rather than a period of cometary activity, in agreement with independent results from the Hubble Space Telescope (HST). The trail is made up of relatively large particles of millimetre to centimetre size that remain close to the parent asteroid. The shape of the trail can be explained by an initial impact ejecting large clumps of debris that disintegrated and dispersed almost immediately. We determine that this was an asteroid collision that occurred around February 10, 2009.
P. Vernazza, B. Carry, J. Emery, J. L. Hora, D. Cruikshank, R. P. Binzel, J. Jackson, J. Helbert & A. Maturilli
We report an unexpected variability among mid-infrared spectra of asteroids for which all other remote sensing interpretations (e.g. VNIR spectroscopy, albedo) yield similar compositions. Following the laboratory work of Ramsey & Christensen (1998), we interpret this variability to be physically caused by differences in surface particle size. Mid-IR measurements of surfaces having particle sizes that are large compared to the 8-13 μm wavelength range yield compositional interpretations that remain compatible with other types of remote sensing. Surfaces having grain sizes near or below the 8-13 μm wavelength scale of mid-IR measurements yield divergent compositional interpretations. Thus for asteroids, we find mid-infrared measurements are a powerful tool for inter-comparison of surface properties for objects of known compositions. Those yielding compatible mid-IR compositional interpretations likely have large particle sizes on their surfaces. Divergent compositional interpretations are more likely indicative of surfaces dominated by particles at or below the 8-13 μm scale of mid-IR radiation. Thus for mid-IR measurements of objects whose surface properties are not known, a reliable compositional interpretation based solely on linear deconvolution of mid-IR measurements with existing spectral libraries is problematic.
A. Moullet, M. Gurwell & B. Carry
Context. Previously published measurements of the millimeter-wave thermal rotational lightcurve of dwarf-planet (1) Ceres show incompatible results, proposing peak-to-peak lightcurve amplitudes during the ~9 h rotation period of either 4% or 50%, the latter being difficult to explain physically.
Aims: Better calibrated measurements are necessary to firmly assess the behavior of Ceres' thermal lightcurve, and to relate possible brightness temperature variations to the distribution of local surface properties such as bolometric albedo and emissivity.
Methods: One partial lightcurve of 6.5 h was obtained with the Submillimeter Array (Hawaii) in subcompact configuration at 235 GHz in January 2009, providing better absolute and relative calibration than the previously used single-dish facilities.
Results: The observed disk-averaged lightcurve is compatible with no variation over the measurement window, and has an upper limit of 3% on its amplitude.
Conclusions: The results obtained rule out the possibility of extreme brightness temperature variations, and the upper limit on the lightcurve amplitude could be physically realized by a combination of albedo distribution and realistic ground emissivity variations.
C. Snodgrass, B. Carry, C. Dumas & O. Hainaut
Ragozzine & Brown  presented a list of candidate members of the first collisional family to be found among the trans-Neptunian Objects (TNOs), the one associated with (136108) Haumea (2003 EL61). We aim to identify which of the candidate members of the Haumea collisional family are true members, by searching for water ice on their surfaces. We also attempt to test the theory that the family members are made of almost pure water ice by using optical light-curves to constrain their densities. We use optical and near-infrared photometry to identify water ice, in particular using the (J - HS) colour as a sensitive measure of the absorption feature at 1.6 micron. We use the CH4 filter of the new Hawk-I instrument at the VLT as a short H-band (HS) for this as it is more sensitive to the water ice feature than the usual H filter. We report colours for 22 candidate family members, including NIR colours for 15. We confirm that 2003 SQ317 and 2005 CB79 are family members, bringing the total number of confirmed family members to 10. We reject 8 candidates as having no water ice absorption based on our Hawk-I measurements, and 5 more based on their optical colours. The combination of the large proportion of rejected candidates and time lost to weather prevent us from putting strong constraints on the density of the family members based on the light-curves obtained so far; we can still say that none of the family members (except Haumea) require a large density to explain their light-curve.
B. Carry, P. Vernazza, C. Dumas & M. Fulchignoni
Vesta, the second largest Main Belt asteroid, will be the first to be explored in 2011 by NASA Dawn mission. It is a dry, likely differentiated body with spectrum suggesting that is has been resurfaced by basaltic lava flows, not too different from the lunar maria. Here we present the first disk-resolved spectroscopic observations of an asteroid from the ground. We observed (4) Vesta with the ESO-VLT adaptive optics equipped integral-field near-infrared spectrograph SINFONI, as part of its science verification campaign. The highest spatial resolution of 90 km on Vesta's surface was obtained during excellent seeing conditions (0.5") in October 2004. We observe spectral variations across Vesta surface that can be interpreted as variations of either the pyroxene composition, or the effect of surface aging. We compare Vesta 2 micron absorption band to that of howardite-eucrite-diogenite (HED) meteorites that are thought to originate from Vesta, and establish particular links between specific regions and HED subclasses. The overall composition is found to be mostly compatible with howardite meteorites, although a small area around 180° East longitude could be attributed to a diogenite-rich spot. We finally focus our spectral analysis on the characteristics of Vesta bright and dark regions as seen from Hubble Space Telescope visible and Keck-II near-infrared images.
B. Carry, C. Dumas, M. Kaasalainen, J. Berthier, W. J. Merline, S. Erard, A. Conrad, J. D. Drummond, D. Hestroffer, M. Fulchignoni & T. Fusco
Ground-based high angular-resolution images of asteroid (2) Pallas at near-infrared wavelengths have been used to determine its physical properties (shape, dimensions, spatial orientation and albedo distribution). We acquired and analyzed adaptive-optics (AO) J/H/K-band observations from Keck II and the Very Large Telescope taken during four Pallas oppositions between 2003 and 2007, with spatial resolution spanning 32-88 km (image scales 13-20 km/ We improve our determination of the size, shape, and by a novel method that combines our AO data with 51 visual light-curves spanning 34 years of as well as archived occultation The shape model of Pallas derived here reproduces well both the projected shape of Pallas on the sky (average deviation of edge profile of 0.4 pixel) and light-curve (average deviation of 0.019 mag) at the epochs We resolved the pole ambiguity and found the spin-vector coordinates to be within 5° of [long, lat] = [30°, -16°] in the Ecliptic J2000.0 reference frame, indicating high obliquity of about 84°, leading to high seasonal contrast. The best triaxial-ellipsoid fit returns ellipsoidal radii a=275 km, b= 258 km, and c= 238 From the mass of Pallas determined by gravitational perturbation on other minor bodies [(1.2 ± 0.3) x 10-10 MSun, Michalak 2000, A&, 360], we derive a density of 3.4 ± 0.9 g.cm-3$ significantly different from the density of C-type (1) Ceres of 2.2 ± 0.1 g.cm-3 [Carry et al., 2008, A&A 478, 235]. Considering the spectral similarities of Pallas and Ceres at visible and near-infrared wavelengths, this may point to fundamental differences in the interior composition or structure of these two bodies. We define a planetocentric longitude system for Pallas, following IAU guidelines. We also present the first albedo maps of Pallas covering ~80% of the surface in K-band. These maps reveal features with diameters in the 70-180 km range and an albedo contrast of about 6% with respect to the mean surface albedo.
A. Conrad, R. W. Goodrich, R. D. Campbell, W. J. Merline, J. D. Drummond, C. Dumas & B. Carry
From differential tracking techniques, required for appulse observations of KBOs with Laser Guide Star Adaptive Optics (LGSAO), to developing methods collecting spectra at the precise moment of a predicted impact, each Solar System observation conducted on a large telescope presents a unique of challenges. We present operational details and some key science results from our science program, adaptive optics observations of main belt asteroids and near earth objects; as well as the technical and operational details of several Keck Solar System observations conducted by other teams: the impact of Shoemaker-Levy 9 on Jupiter, volcanoes on Io, the Deep Impact mission to Comet 9P/Tempel 1, and recent observations of Pluto's moons Nix and Hydra. For each of these observations, we draw from our Keck experience to predict what challenges may lie ahead when sixsmilar observations are conducted on next generation telescopes.
B. Carry, C. Dumas, M. Fulchignoni, W. J. Merline, J. Berthier, D. Hestroffer, T. Fusco & P. Tamblyn
Aims: We study the physical characteristics (shape, dimensions, spin axis direction, albedo maps, mineralogy) of the dwarf-planet Ceres based on high angular-resolution near-infrared observations.
Methods: We analyze adaptive optics J/H/K imaging observations of Ceres performed at Keck II Observatory in September 2002 with an equivalent spatial resolution of ~50 km. The spectral behavior of the main geological features present on Ceres is compared with laboratory samples.
Results: Ceres' shape can be described by an oblate spheroid (a = b = 479.7 ± 2.3 km, c =444.4 ± 2.1 km) with EQJ2000.0 spin vector coordinates α0 = 288° ± 5° and δ0 = +66° ± 5°. Ceres sidereal period is measured to be 9.07410-0.000 14+0.000 10 h. We image surface features with diameters in the 50-180 km range and an albedo contrast of ~6% with respect to the average Ceres albedo. The spectral behavior of the brightest regions on Ceres is consistent with phyllosilicates and carbonate compounds. Darker isolated regions could be related to the presence of frost.
O. Mousis, Y. Alibert, D. Hestroffer, U. Marboeuf, C. Dumas, B. Carry, J. Horner & F. Selsis
We propose a scenario for the formation of the main belt in which asteroids incorporated icy particles formed in the outer solar nebula. We calculate the composition of icy planetesimals formed beyond a heliocentric distance of 5au in the nebula by assuming that the abundances of all elements, in particular that of oxygen, are solar. As a result, we show that ices formed in the outer solar nebula are composed of a mix of clathrate hydrates, hydrates formed above 50K and pure condensates produced at lower temperatures. We then consider the inward migration of solids initially produced in the outer solar nebula and show that a significant fraction may have drifted to the current position of the main belt without encountering temperature and pressure conditions high enough to vaporize the ices they contain. We propose that, through the detection and identification of initially buried ices revealed by recent impacts on the surfaces of asteroids, it could be possible to infer the thermodynamic conditions that were present within the solar nebula during the accretion of these bodies, and during the inward migration of icy planetesimals. We also investigate the potential influence that the incorporation of ices in asteroids may have on their porosities and densities. In particular, we show how the presence of ices reduces the value of the bulk density of a given body, and consequently modifies its macroporosity from that which would be expected from a given taxonomic type.
M. Gualteri, T. Tokieda, L. Advis-Gaiete, B. Carry, E. Reffet & C. Guthmann
A ball rolling on a vertical cylinder exhibits a bizarre quasi-periodic motion. We explain this behavior in terms of Coriolis torque and study the phenomenon experimentally. The data confirm the predicted motion and the surprising invariance of the ratio between the horizontal and vertical frequencies. This result might account for the frustrating sight of a golf ball escaping from the hole an instant after it is putted in.