A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation

Bruno Sicardy (1, 2) , J. L. Ortiz (3) , M. Assafin (4) , E. Jehin (5) , A. Maury (6) , E. Lellouch (1) , R. Gil Hutton (7) , F. Braga-Ribas (1, 8) , Francois Colas (9) , Daniel Hestroffer (9) , J. Lecacheux (1) , F. Roques (1) , P. Santos-Sanz (1) , T. Widemann (1) , N. Morales (3) , R. Duffard (3) , A. Thirouin (3) , A. J. Castro-Tirado (3) , M. Jelínek (3) , P. Kubánek (3) , A. Sota (3) , R. Sánchez-Ramírez (3) , A. H. Andrei (8, 10) , J. I. B. Camargo (8, 10) , D. N. da Silva Neto (8, 11) , A. Ramos Gomes (10) , R. Vieira Martins (8, 9, 10) , M. Gillon (5) , J. Manfroid (5) , G. P. Tozzi (12) , C. Harlingten (13) , S. Saravia (6) , R. Behrend (14) , S. Mottola (15) , E. García Melendo (16, 17) , V. Peris (18) , J. Fabregat (18) , J. M. Madiedo (19) , L. Cuesta (20) , M. T. Eibe (20) , A. Ullán (20) , F. Organero (21) , S. Pastor (22) , J. A. de Los Reyes (22) , S. Pedraz (23) , A. Castro (24) , I. de La Cueva (25) , G. Muler (26) , I. A. Steele (27) , M. Cebrián (28) , P. Montañés-Rodríguez (28) , A. Oscoz (28) , D. Weaver (29) , C. Jacques (30) , W. J. B. Corradi (31) , F. P. Santos (31) , W. Reis (31) , A. Milone (32) , M. Emilio (33) , L. Gutiérrez (34) , R. Vázquez (34) , H. Hernández-Toledo (34)

1 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
2 IUF - Institut universitaire de France
3 IAA - Instituto de Astrofísica de Andalucía
4 Observatório do Valongo/UFRJ [Rio de Janeiro]
5 Institut d'Astrophysique et de Géophysique [Liège]
6 SPACE - San Pedro de Atacama Celestial Explorations
7 CASLEO - Complejo Astronómico El Leoncito [San Juan]
8 Observatório Nacional/MCT
9 IMCCE - Institut de Mécanique Céleste et de Calcul des Ephémérides
10 Observatório do Valongo
11 Universidade Estadual da Zona Oeste (UEZO)
12 OAA - INAF - Osservatorio Astrofisico di Arcetri
13 Caisey Harlingten Observatory
14 Geneva Observatory
15 DLR - German Aerospace Center
16 Fundació Privada Observatori Esteve Duran
17 ICE-CSIC - Institut de Ciencies de l'Espai [Barcelona]
18 Observatorio Astronomico de Valencia
19 Facultad de Ciencias Experimentales
20 CAB - Centro de Astrobiologia [Madrid]
21 Observatorio astronómico de La Hita
22 Observatorio de la Murta
23 CAHA - Centro Astronómico Hispano Alemán, Observatorio de Calar Alto
24 Sociedad Malagueña de Astronomía
25 Astroimagen
26 Observatorio Nazaret
27 Liverpool JMU
28 IAC - Instituto de Astrofisica de Canarias
29 Observatório Astronomico Christus
30 Observatório CEAMIG-REA
31 ICEx - Departamento de Física
32 INPE - Instituto Nacional de Pesquisas Espaciais
33 Universidade Estadual de Ponta Grossa
34 Instituto de Astronomía

The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 UT. The event is consistent with a spherical shape for Eris, with radius 1,163+/-6kilometres, density 2.52+/-0.05 grams per cm3 and a high visible geometric albedo, . No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ~1nanobar, about 10,000 times more tenuous than Pluto's present atmosphere. As Pluto's radius is estimated to be between 1,150 and 1,200 kilometres, Eris appears as a Pluto twin, with a bright surface possibly caused by a collapsed atmosphere, owing to its cold environment. We anticipate that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun.

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]; Planétologie et astrophysique de la terre [astro-ph.EP]

Bruno Sicardy, J. L. Ortiz, M. Assafin, E. Jehin, A. Maury, et al.. A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation. Nature, 2011, 478, pp.493-496. ⟨10.1038/NATURE10550⟩. ⟨hal-00637720⟩