Eris (astronomy)

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Eris in astronomy, dwarf planet that is the most distant body known to be in orbit around the sun. Eris, whose highly eccentric elliptical orbit ranges from 38 AU to 97 AU and is inclined more than 44°, is the largest known object of the Kuiper belt (see comet ), with a diameter (c.1,500 mi/2,400 km) somewhat larger than that of Pluto. Taking 560 earth years to circle the sun, Eris is believed to be composed of rock and ice. At aphelion (the most distant point from the sun in Eris's orbit), where the temperature is -405°F (-243°C), Eris's surface is covered with highly reflective frozen methane, which forms its atmosphere when it is closer to the sun and the surface temperature is warmer (-360°F/-218°C). Eris was discovered on Jan. 5, 2005, by astronomers Mike Brown, Chad Trujillo, and David Rabinowitz, using computer analysis of images taken two years earlier in a survey of the Kuiper belt. It was named for the Greek goddess of strife because its discovery was a catalyst for the reclassification of Pluto as a dwarf planet. Eris is known to have one natural satellite, Dysnomia, named for the daughter of the goddess Eris; the moon is estimated to have a diameter about an eighth that of Eris. Eris and its moon were nicknamed Xena and Gabrielle, respectively, before they were officially named.

Eris The first trans‐Neptunian object found with a diameter larger than that of Pluto; also known as minor planet (136199). It is the largest of the new class of >dwarf planets.Eris is about 2400 km in diameter and has a satellite, Dysnomia, about one‐eighth its size. It was discovered in 2005 by the American astronomers Michael Edwards Brown (1965– ), Chadwick Aaron Trujillo (1973– ), and David Lincoln Rabinowitz (1960– ). Its orbit has a perihelion of 37.8 AU, aphelion 97.5 AU, inclination 44°.2, and period 557 years, placing it among the scattered‐disk objects.