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(704) Interamnia: a transitional object between a dwarf planet and a typical irregular-shaped minor body

Hanuš, J. and Vernazza, P. and Viikinkoski, M. and Ferrais, M. and Rambaux, N. and Podlewska-Gaca, E. and Drouard, A. and Jorda, L. and Jehin, E. and Carry, B. and Marsset, M. and Marchis, F. and Warner, B. and Behrend, R. and Asenjo, V. and Berger, N. and Bronikowska, M. and Brothers, T. and Charbonnel, S. and Colazo, C. and Coliac, J.-F. and Duffard, R. and Jones, A. and Leroy, A. and Marciniak, A. and Melia, R. and Molina, D. and Nadolny, J. and Person, M. and Pejcha, O. and Riemis, H. and Shappee, B. and Sobkowiak, K. and Soldán, F. and Suys, D. and Szakats, R. and Vantomme, J. and Birlan, M. and Berthier, J. and Bartczak, P. and Dumas, C. and Dudziński, G. and Ďurech, J. and Castillo-Rogez, J. and Cipriani, F. and Fetick, R. and Fusco, T. and Grice, J. and Kaasalainen, M. and Kryszczynska, A. and Lamy, P. and Michalowski, T. and Michel, P. and Santana-Ros, T. and Tanga, P. and Vachier, F. and Vigan, A. and Witasse, O. and Yang, B. (2020) (704) Interamnia: a transitional object between a dwarf planet and a typical irregular-shaped minor body. Astronomy and Astrophysics, 633 . Art. No. A65. ISSN 0004-6361.

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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 × 10¹⁹ kg) bodies.

Item Type:Article
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URLURL TypeDescription Paper
Hanuš, J.0000-0002-2934-3723
Additional Information:© 2020 ESO. Received 5 September 2019; Accepted 21 November 2019; Published online 13 January 2020. This work has been supported by the Czech Science Foundation through grant 18-09470S (J.H., J.D.) and by the Charles University Research program No. UNCE/SCI/023. This research was supported by INTER-EXCELLENCE grant LTAUSA18093 from the Czech Ministry of Education, Youth, and Sports (J.H. and O.P.). The research of O.P. is additionally supported by Horizon 2020 ERC Starting Grant “Cat-In-hAT” (grant agreement #803158) and award PRIMUS/SCI/17 from Charles University. P.V., A.D., and B.C. were supported by CNRS/INSU/PNP. M.M. was supported by the National Aeronautics and Space Administration under Grant No. 80NSSC18K0849 issued through the Planetary Astronomy Program. This work was supported by the National Science Centre, Poland, through grant no. 2014/13/D/ST9/01818 (A.M.). The research leading to these results has received funding from the European Union’s Horizon 2020 Research and Innovation Programme, under Grant Agreement no 687 378 (SBNAF). This project has been supported by the GINOP-2.3.2-15-2016-00003 and NKFIH K125015 grants of the Hungarian National Research, Development and Innovation Office (NKFIH) and by the Lendület grant LP2012-31 of the Hungarian Academy of Sciences. TRAPPIST-North is a project funded by the University of Liège, in collaboration with Cadi Ayyad University of Marrakech (Morocco). TRAPPIST-South is a project funded by the Belgian FNRS under grant FRFC 2.5.594.09. F.E.J. is a FNRS Senior Research Associate. ASAS-SN thanks the Las Cumbres Observatory and its staff for its continuing support of the ASAS-SN project. ASAS-SN is supported by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University and NSF grant AST-1515927. Development of ASAS-SN has been supported by NSF grant AST-0908816, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics at the Ohio State University, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), the Villum Foundation, and George Skestos.
Group:Thirty Meter Telescope
Funding AgencyGrant Number
Czech Science Foundation18-09470S
Charles UniversityUNCE/SCI/023
Ministry of Education, Youth, and Sports (Czech Republic)LTAUSA18093
European Research Council (ERC)803158
Charles UniversityPRIMUS/SCI/17
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Institut National des Sciences de l'Univers (INSU)UNSPECIFIED
National Science Centre (Poland)2014/13/D/ST9/01818
European Research Council (ERC)687378
National Research, Development and Innovation Office (Hungary)GINOP-2.3.2-15-2016-00003
National Research, Development and Innovation Office (Hungary)NKFIH K125015
Hungarian Academy of SciencesLP2012-31
University of LiègeUNSPECIFIED
Fond National de la Recherche Scientifique (FNRS)FRFC 2.5.594.09
Gordon and Betty Moore FoundationGBMF5490
Mt. Cuba Astronomical FoundationUNSPECIFIED
Ohio State UniversityUNSPECIFIED
Chinese Academy of Sciences South America Center for Astronomy (CASSACA)UNSPECIFIED
Villum FoundationUNSPECIFIED
Subject Keywords:minor planets, asteroids: individual: (704) Interamnia – methods: observational – techniques: high angular resolution – techniques: photometric
Record Number:CaltechAUTHORS:20200309-094655486
Persistent URL:
Official Citation:(704) Interamnia: a transitional object between a dwarf planet and a typical irregular-shaped minor body. J. Hanuš, P. Vernazza, M. Viikinkoski, M. Ferrais, N. Rambaux, E. Podlewska-Gaca, A. Drouard, L. Jorda, E. Jehin, B. Carry, M. Marsset, F. Marchis, B. Warner, R. Behrend, V. Asenjo, N. Berger, M. Bronikowska, T. Brothers, S. Charbonnel, C. Colazo, J.-F. Coliac, R. Duffard, A. Jones, A. Leroy, A. Marciniak, R. Melia, D. Molina, J. Nadolny, M. Person, O. Pejcha, H. Riemis, B. Shappee, K. Sobkowiak, F. Soldán, D. Suys, R. Szakats, J. Vantomme, M. Birlan, J. Berthier, P. Bartczak, C. Dumas, G. Dudziński, J. Ďurech, J. Castillo-Rogez, F. Cipriani, R. Fetick, T. Fusco, J. Grice, M. Kaasalainen, A. Kryszczynska, P. Lamy, T. Michalowski, P. Michel, T. Santana-Ros, P. Tanga, F. Vachier, A. Vigan, O. Witasse and B. Yang. A&A, 633 (2020) A65; DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101769
Deposited By: Tony Diaz
Deposited On:09 Mar 2020 17:04
Last Modified:09 Mar 2020 17:04

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