Contributors: Astronomical Institute of Charles University; Univerzita Karlova Praha, Česká republika = Charles University Prague, Czech Republic (UK); Laboratoire d'Astrophysique de Marseille (LAM); Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS); Tampere University of Technology Tampere (TUT); Space Sciences, Technologies and Astrophysics Research Institute (STAR); Université de Liège; Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE); Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris; Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Lille-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS); Astronomical Observatory Poznan; Uniwersytet im. Adama Mickiewicza w Poznaniu = Adam Mickiewicz University in Poznań (UAM); Joseph Louis LAGRANGE (LAGRANGE); Université Nice Sophia Antipolis (1965 - 2019) (UNS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur; Université Côte d'Azur (UniCA)-Université Côte d'Azur (UniCA)-Centre National de la Recherche Scientifique (CNRS); Department of Earth, Atmospheric and Planetary Sciences MIT, Cambridge (EAPS); Massachusetts Institute of Technology (MIT); SETI Institute; Center for Solar System Studies (CS3); Observatoire Astronomique de l'Université de Genève (ObsGE); Université de Genève = University of Geneva (UNIGE); Asociación Astronómica Astro Henares; Centro de Recursos Asociativos El Cerro; Institute of Geology Poznan; Observatoire de Durtal; Observatorio Astronómico de Córdoba (OAC); Universidad Nacional de Córdoba Argentina; Instituto de Astrofísica de Andalucía (IAA); Consejo Superior de Investigaciones Cientificas España = Spanish National Research Council Spain (CSIC); L'Uranoscope de l'Ile de France; Observatoire de Gretz-Armainvilliers; Anunaki Observatory; Departamento de Astrofísica La laguna; Universidad de La Laguna Tenerife - SP (ULL); Geneva Observatory; Institute for Astronomy Honolulu; University of Hawai‘i Mānoa (UHM); Observatorio Amanecer de Arrakis; Konkoly Observatory; Research Centre for Astronomy and Earth Sciences Budapest; Hungarian Academy of Sciences (MTA)-Hungarian Academy of Sciences (MTA); Thirty Meter Telescope Observatory; Jet Propulsion Laboratory (JPL); NASA-California Institute of Technology (CALTECH); European Space Research and Technology Centre (ESTEC); Agence Spatiale Européenne = European Space Agency (ESA); Observatoire de la Côte d'Azur (OCA); Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS); Department of Mathematics Tampere; PLANETO - LATMOS; Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS); Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS); Observatoire de la Côte d'Azur; Université Côte d'Azur (UniCA); Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Señal Alicante (DFESTS); Universidad de Alicante; Institut de Ciencies del Cosmos (ICCUB); Universitat de Barcelona (UB); European Southern Observatory Santiago (ESO); European Southern Observatory (ESO)
نبذة مختصرة : International audience ; Context. With an estimated diameter in the 320–350 km range, (704) Interamnia is the fifth largest main belt asteroid and one of the few bodies that fills the gap in size between the four largest bodies with D > 400 km (Ceres, Vesta, Pallas and Hygiea) and the numerous smaller bodies with diameter ≤200 km. However, despite its large size, little is known about the shape and spin state of Interamnia and, therefore, about its bulk composition and past collisional evolution.Aims. We aimed to test at what size and mass the shape of a small body departs from a nearly ellipsoidal equilibrium shape (as observed in the case of the four largest asteroids) to an irregular shape as routinely observed in the case of smaller (D ≤ 200 km) bodies.Methods. We observed Interamnia as part of our ESO VLT/SPHERE large program (ID: 199.C-0074) at thirteen different epochs. In addition, several new optical lightcurves were recorded. These data, along with stellar occultation data from the literature, were fed to the All-Data Asteroid Modeling algorithm to reconstruct the 3D-shape model of Interamnia and to determine its spin state.Results. Interamnia’s volume-equivalent diameter of 332 ± 6 km implies a bulk density of ρ = 1.98 ± 0.68 g cm −3 , which suggests that Interamnia – like Ceres and Hygiea – contains a high fraction of water ice, consistent with the paucity of apparent craters. Our observations reveal a shape that can be well approximated by an ellipsoid, and that is compatible with a fluid hydrostatic equilibrium at the 2σ level.Conclusions. The rather regular shape of Interamnia implies that the size and mass limit, under which the shapes of minor bodies with a high amount of water ice in the subsurface become irregular, has to be searched among smaller (D ≤ 300 km) less massive (m ≤ 3 × 10 19 kg) bodies.
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