2004 XR190
Encyclopedia
is a dwarf-planet candidate located in the scattered disc
. Astronomer
s 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
.
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 planet
s/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.
around 1901. Other than long-period comets and space probe
s, it is currently the eleventh-most-distant known large body (57.9 AU) in the Solar System
after Eris
and Dysnomia
(both 96.6 AU),
Sedna
(87.2 AU),
(86.3 AU),
(82.4 AU), (63.9 AU), (61.1 AU), (59.4 AU), (59.3 AU), and (59.2 AU).
, and orbits between 51 and 64 AU
(7.7 and 9.5 billion km) from the Sun
.
Scattered disc
The scattered disc is a distant region of the Solar System that is sparsely populated by icy minor planets, a subset of the broader family of trans-Neptunian objects. The scattered-disc objects have orbital eccentricities ranging as high as 0.8, inclinations as high as 40°, and perihelia greater...
. Astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
s led by Lynne Jones of the University of British Columbia
University of British Columbia
The University of British Columbia is a public research university. UBC’s two main campuses are situated in Vancouver and in Kelowna in the Okanagan Valley...
made the discovery as part of the Canada-France Ecliptic Plane Survey (CFEPS) using the Canada-France-Hawaii Telescope
Canada-France-Hawaii Telescope
The Canada–France–Hawaii Telescope is located near the summit of Mauna Kea mountain on Hawaii's Big Island at an altitude of 4,204 meters , and is one of the observatories that comprise the Mauna Kea Observatory...
(CFHT). The discovery team has temporarily nicknamed the object "Buffy", after the fictional vampire slayer
Buffy Summers
Buffy Summers is a fictional character from Joss Whedon's Buffy the Vampire Slayer franchise. She first appeared in the 1992 film Buffy the Vampire Slayer before going on to appear in the television series and subsequent comic book of the same name...
, and proposed a different official name to the IAU
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
.
Orbit
Considered a detached object, is particularly unusual for two reasons. With an inclinationInclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
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
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...
. Second, it has an unusually circular orbit for a scattered-disc object
Scattered disc
The scattered disc is a distant region of the Solar System that is sparsely populated by icy minor planets, a subset of the broader family of trans-Neptunian objects. The scattered-disc objects have orbital eccentricities ranging as high as 0.8, inclinations as high as 40°, and perihelia greater...
(SDO). While it is thought that traditional scattered-disc objects have been ejected into their current orbits by gravitational interactions with Neptune
Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...
, 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
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
. The theories include close stellar passages, rogue planet
Rogue Planet
- Literature :* "Rogue Planet" , a Dan Dare story that ran in the original Eagle comic from Volume 6, Issue 48 to Volume 8, Issue 7* Rogue Planet , a 2000 novel set in the Star Wars galaxy- Other :...
s/planetary embryos
Protoplanet
Protoplanets are large planetary embryos that originate within protoplanetary discs and have undergone internal melting to produce differentiated interiors. They are believed to form out of kilometer-sized planetesimals that attract each other gravitationally and collide...
in the early Kuiper belt, and resonance
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
interaction with an outward-migrating Neptune
Planetary migration
Planetary migration occurs when a planet or other stellar satellite interacts with a disk of gas or planetesimals, resulting in the alteration of the satellite's orbital parameters, especially its semi-major axis...
. The Kozai mechanism
Kozai mechanism
In celestial mechanics, the Kozai mechanism, or the Lidov-Kozai mechanism, causes a periodic exchange between the inclination and eccentricity of an orbit...
is capable of transferring the orbital eccentricity into an elevated inclination.
Eleventh-most-distant body
came to aphelionApsis
An apsis , plural apsides , is the point of greatest or least distance of a body from one of the foci of its elliptical orbit. In modern celestial mechanics this focus is also the center of attraction, which is usually the center of mass of the system...
around 1901. Other than long-period comets and space probe
Space probe
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...
s, it is currently the eleventh-most-distant known large body (57.9 AU) in the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
after Eris
Eris (dwarf planet)
Eris, formal designation 136199 Eris, is the most massive known dwarf planet in the Solar System and the ninth most massive body known to orbit the Sun directly...
and Dysnomia
Dysnomia (moon)
- References :...
(both 96.6 AU),
Sedna
90377 Sedna
90377 Sedna is a trans-Neptunian object discovered in 2003, which was about three times as far from the Sun as Neptune. For most of its orbit it is even further from the Sun, with its aphelion estimated at 960 astronomical units , making it one of the most distant known objects in the Solar System...
(87.2 AU),
(86.3 AU),
(82.4 AU), (63.9 AU), (61.1 AU), (59.4 AU), (59.3 AU), and (59.2 AU).
Size
The object has a diameter estimated at around 500 kilometres, roughly a quarter the size of PlutoPluto
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...
, and orbits between 51 and 64 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
(7.7 and 9.5 billion km) from the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
.