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

SICARDY, B., ORTIZ, J. L., ASSAFIN, M., JEHIN, E., MAURY, A., LELLOUCH, E., GIL-HUTTON, R., BRAGA-RIBAS, Y OTROS

NATURE

NATURE PUBLISHING GROUP

Lugar: Londres; Año: 2011 vol. 478 p. 493 - 496

0028-0836

   The dwarf planet Eris is a Trans-Neptunian Object (TNO) with an elongated orbit (eccentricity 0.44), a large inclination (44 degrees) relative to the ecliptic plane, and a surface composition very similar to Pluto1 . It presently resides at 95.7 astronomical units (1 AUis 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 occultationby Eris on November 6, 2010 UT. The event is consistent with a spherical shape for Eris, with radius RE =1,163±6 km, density ρ=2.52±0.05 g cm−3 and a high visible geometricalbedo pV =0.96+0.09 . No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ∼1 nbar, about 10,000 times more tenuous than Pluto’s present atmosphere2−5 . As Pluto’s radius is estimated3−8 between 1,150 and 1,200 km, Eris appearsas 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 AU from the Sun.