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(also written 2004 XR190) is a dwarf-planet candidate located in the scattered disc. Astronomers led by Lynne Jones of the University of British Columbia made the discovery as part of the Canada-France Ecliptic Plane Survey (CFEPS) using the Canada-France-Hawaii Telescope (CFHT). The discovery team has temporarily nicknamed the object "Buffy", after the fictional vampire slayer, and proposed a different official name to the IAU.
Orbit Considered a detached object,[1][2] is particularly unusual for two reasons. With an inclination of 47 degrees, it is the most "tilted" dwarf-planet candidate discovered thus far, traveling further "up and down" than "left to right" around the Sun when viewed edge-on along the ecliptic. Second, it has an unusually circular orbit for a scattered-disc object (SDO). While it is thought that traditional scattered-disc objects have been ejected into their current orbits by gravitational interactions with Neptune, the low eccentricity of its orbit and the distance of its perihelion (SDOs generally have highly eccentric orbits and perihelia less than 38 AU) seems hard to reconcile with such celestial mechanics. This has led to some uncertainty as to the current theoretical understanding of the outer Solar System. The theories include close stellar passages, rogue planets/planetary embryos in the early Kuiper belt, and resonance interaction with an outward-migrating Neptune. The Kozai mechanism is capable of transferring the orbital eccentricity into an elevated inclination.[3] Eleventh-most-distant body came to aphelion around 1901.[4] Other than long-period comets and space probes[5], it is currently the eleventh-most-distant known large body (57.9 AU)[6] in the Solar System after Eris and Dysnomia (both 96.6 AU)[7], Sedna (87.2 AU)[8], (86.3 AU)[9], (82.4 AU)[10], (63.9 AU), (61.1 AU), (59.4 AU), (59.3 AU)[11], and (59.2 AU).[12] <gallery> Image:XR190orb_top.gif|The orbit of . The ring in the center is Earth's orbit shown for scale. Units are in AUs. Image:XR190orb_side.gif|A side view of 's orbit, showing the object's high inclination. Units are AUs. </gallery> Size The object has a diameter estimated at around 500 kilometres, roughly a quarter the size of Pluto, and orbits between 51 and 64 AU (7.7 and 9.5 billion km) from the Sun. References External links bar:2004 XR190 ca:2004 XR190 de:2004 XR190 el:2004 XR190 es:2004 XR190 fr:2004 XR190 it:2004 XR190 pl:2004 XR190 ru:2004 XR190 sk:2004 XR190 fi:2004 XR190 zh:2004 XR190
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