, informally nicknamed Buffy, is a trans-Neptunian object, classified as both a

scattered disc object The scattered disc (or scattered disk) is a distant circumstellar disc in the Solar System that is sparsely populated by icy small solar system bodies, which are a subset of the broader family of trans-Neptunian objects. The scattered-disc objec ...

and a

detached object Detached objects are a dynamical class of minor planets in the outer reaches of the Solar System and belong to the broader family of trans-Neptunian objects (TNOs). These objects have orbits whose points of closest approach to the Sun (perihelion ...

, located in the outermost region of the Solar System. It was first observed on 11 December 2004, by astronomers with the Canada–France Ecliptic Plane Survey at the Mauna Kea Observatories, Hawaii, United States. It is the largest known highly inclined (> 45°) object. With a perihelion of 51 AU, it belongs to a small and poorly understood group of very distant objects with moderate eccentricities.

Discovery and naming

was discovered on 11 December 2004. It was discovered by astronomers led by (Rhiannon) Lynne Allen of the University of British Columbia as part of the Canada–France Ecliptic Plane Survey (CFEPS) using the Canada–France–Hawaii Telescope (CFHT) near the ecliptic. The team included

Brett Gladman Brett James Gladman (born April 19, 1966) is a Canadian astronomer and a full professor at the University of British Columbia's Department of Physics and Astronomy in Vancouver, British Columbia. He holds the Canada Research Chair in planetary a ...

, John Kavelaars,

Jean-Marc Petit This is a list of minor-planet discoverers credited by the Minor Planet Center with the discovery of one or several minor planets (such as near-Earth and main-belt asteroids, Jupiter trojans and distant objects). , the discovery of 612,011 numb ...

, Joel Parker and Phil Nicholson. In 2015, six precovery images from 2002 and 2003 were found in

Sloan Digital Sky Survey The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project began in 2000 a ...

data. The object was nicknamed "Buffy" by the discovery team, after the fictional vampire slayer Buffy Summers, and the team proposed several Inuit-based official names to the International Astronomical Union.

Orbit and classification

Extreme transneptunian object eccentricity vs perihelion

orbits the Sun at a distance of 51.1–63.4 AU once every 433 years and 3 months (158,242 days;

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the long ...

of 57.26 AU). Its orbit has a moderate eccentricity of 0.11 and a high inclination of 47 ° with respect to the ecliptic. It belongs to the same group as , , and ''(also see diagram)'', that are poorly understood for their large

perihelia An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ellip ...

combined with moderate eccentricities. Considered a

scattered Scattered may refer to: Music * ''Scattered'' (album), a 2010 album by The Handsome Family * "Scattered" (The Kinks song), 1993 * "Scattered", a song by Ace Young * "Scattered", a song by Lauren Jauregui * "Scattered", a song by Green Day from ' ...

and

, is particularly unusual as it has an unusually circular orbit for a

scattered-disc object The scattered disc (or scattered disk) is a distant circumstellar disc in the Solar System that is sparsely populated by icy small solar system bodies, which are a subset of the broader family of trans-Neptunian objects. The scattered-disc objec ...

(SDO). Although it is thought that traditional scattered-disc objects have been ejected into their current orbits by gravitational interactions with

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 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. The theories include close stellar passages, unseen planet/ rogue planets/ planetary embryos in the early

Kuiper belt The Kuiper belt () is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...

, and resonance interaction with an

outward ''Outward'' is an open world fantasy role-playing video game developed by Canadian studio Nine Dots and published by Deep Silver.

- migrating Neptune. The Kozai mechanism is capable of transferring orbital eccentricity to a higher inclination. The object is the largest object with an inclination larger than 45°, traveling further "up and down" than "left to right" around the Sun when viewed edge-on along the ecliptic.

Most distant objects

came to aphelion around 1901. Other than

long-period comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are ...

s, it is currently about the thirteenth-most-distant known ''large body'' (57.5 AU) in the Solar System with a well-known orbit, after and Dysnomia (96.3 AU),

Gonggong Gonggong () is a Chinese water god who is depicted in Chinese mythology and folktales as having a copper human head with an iron forehead, red hair, and the body of a serpent, or sometimes the head and torso are human, with the tail of a serpen ...

(87.4 AU), (85.9 AU), (84.0 AU), (83.3 AU), (83.3 AU), (80.3 AU), (70.5 AU), (60.3 AU), (59.8 AU), and (59.6 AU).

Physical characteristics

With assumed albedos between 0.04 and 0.25, and absolute magnitudes from 4.3 to 4.6, has an estimated diameter of 335 to 850 kilometers; the mean arrived at by considering the two single-figure estimates plus the centre points of the three ranges is 562 km, approximately a quarter the diameter of Pluto. As of 2018, no well-documented spectral type and

color indices In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. The lower the color index, the more blue (or hotter) the object is. Conversely, the large ...

, nor a rotational lightcurve have been obtained from spectroscopic and photometric observations; however, the ''Johnston's Archive'' lists a "taxonomic type" of "BR", and a "B-R magnitude" of 1.24. The

rotation period The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the ...

, pole and shape officially remain unknown.

Gallery

File:XR190orb_top.gif, Orbital diagram of ( Earth's orbit in the center is for scale) File:XR190orb_side.gif, Side view of orbit, showing its high inclination

Notes

References

External links

MPEC 2005-X72 : 2004 XR190
'' Minor Planet Electronic Circular'', detailing discovery
Discovery webpage by research team

Canada-France-Hawaii Telescope Legacy Survey

''Minor Planet Center'' * * {{DEFAULTSORT:2004 XR190 612911 612911 612911 20041211