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

NATURE Volume: 478 Issue: 7370 Pages: 493-496 DOI:10.1038/nature10550 Published: OCT 27 2011

Authors:
Sicardy, B (Sicardy, B.)1,2,3; Ortiz, JL (Ortiz, J. L.)4; Assafin, M (Assafin, M.)5; Jehin, E (Jehin, E.)6; Maury, A (Maury, A.)7; Lellouch, E (Lellouch, E.)1; Hutton, RG (Gil Hutton, R.)8,9; Braga-Ribas, F (Braga-Ribas, F.)1,10; Colas, F (Colas, F.)11; Hestroffer, D (Hestroffer, D.)11; Lecacheux, J (Lecacheux, J.)1; Roques, F (Roques, F.)1; Santos-Sanz, P (Santos-Sanz, P.)1; Widemann, T (Widemann, T.)1; Morales, N (Morales, N.)4; Duffard, R (Duffard, R.)4; Thirouin, A (Thirouin, A.)4; Castro-Tirado, AJ (Castro-Tirado, A. J.)4; Jelinek, M (Jelinek, M.)4; Kubanek, P (Kubanek, P.)4; Sota, A (Sota, A.)4; Sanchez-Ramirez, R (Sanchez-Ramirez, R.)4; Andrei, AH (Andrei, A. H.)10,5; Camargo, JIB (Camargo, J. I. B.)10,5; Neto, DND (da Silva Neto, D. N.)10,12; Gomes, AR (Ramos Gomes, A., Jr.)5; Martins, RV (Vieira Martins, R.)10,11,5; Gillon, M (Gillon, M.)6; Manfroid, J (Manfroid, J.)6; Tozzi, GP (Tozzi, G. P.)13; Harlingten, C (Harlingten, C.)14; Saravia, S (Saravia, S.)7; Behrend, R (Behrend, R.)15; Mottola, S (Mottola, S.)16; Melendo, EG (Garcia Melendo, E.)17,18; Peris, V (Peris, V.)19; Fabregat, J (Fabregat, J.)19; Madiedo, JM (Madiedo, J. M.)20; Cuesta, L (Cuesta, L.)21; Eibe, MT (Eibe, M. T.)21; Ullan, A (Ullan, A.)21; Organero, F (Organero, F.)22; Pastor, S (Pastor, S.)23; de los Reyes, JA (de los Reyes, J. A.)23; Pedraz, S (Pedraz, S.)24; Castro, A (Castro, A.)25; de la Cueva, I (de la Cueva, I.)26; Muler, G (Muler, G.)27; Steele, IA (Steele, I. A.)28; Cebrian, M (Cebrian, M.)29; Montanes-Rodriguez, P (Montanes-Rodriguez, P.)29; Oscoz, A (Oscoz, A.)29; Weaver, D (Weaver, D.)30; Jacques, C (Jacques, C.)31; Corradi, WJB (Corradi, W. J. B.)32; Santos, FP (Santos, F. P.)32; Reis, W (Reis, W.)32; Milone, A (Milone, A.)33; Emilio, M (Emilio, M.)34; Gutierrez, L (Gutierrez, L.)35; Vazquez, R (Vazquez, R.)35; Hernandez-Toledo, H (Hernandez-Toledo, H.)36

Abstract:
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(1). It resides at present at 95.7 astronomical units (1 AU 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 +/- 6 kilometres, density 2.52 +/- 0.05 grams per cm(3) and a high visible geometric albedo, p(V) = 0.96(-0.04)(+0.09). No nitrogen, argon or methane atmospheres are detected with surface pressure larger than similar to 1 nanobar, about 10,000 times more tenuous than Pluto's present atmosphere(2-5). As Pluto's radius is estimated(3-8) 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.

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