is a classical, non-resonant trans-Neptunian object from the

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 ...

in the outermost region of the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

, also known as a

cubewano A classical Kuiper belt object, also called a cubewano ( "QB1-o"), is a low-eccentricity Kuiper belt object (KBO) that orbits beyond Neptune and is not controlled by an orbital resonance with Neptune. Cubewanos have orbits with semi-major axe ...

. With a likely diameter of at least , it is approximately tied with and (to within measurement uncertainties) as the largest unnamed object in the Solar System. It was discovered at

Palomar Observatory Palomar Observatory is an astronomical research observatory in San Diego County, California, United States, in the Palomar Mountain Range. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

in 2002. Its

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 ...

is 8.8 hours and it is a moderately red color. Tancredi notes that photometric observations suggest that it is a

spheroid A spheroid, also known as an ellipsoid of revolution or rotational ellipsoid, is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters. A spheroid has cir ...

with a high

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

and small albedo spots.Tancredi, G., & Favre, S. (2008
''Which are the dwarfs in the Solar System?''
Depto. Astronomía, Fac. Ciencias, Montevideo, Uruguay; Observatorio Astronómico Los Molinos, MEC, Uruguay. Retrieved 10-08-2011 However, its low albedo suggests it does not have planetary geology, as it should if it were a dwarf planet.

Description

Discovery

was discovered on 10 January 2002, by astronomers at the

in California. Astronomers involved in the discovery were Michael Brown, Chad Trujillo,

Eleanor Helin Eleanor Francis "Glo" Helin (née Francis, 19 November 1932 – 25 January 2009) was an American astronomer. She was principal investigator of the Near-Earth Asteroid Tracking (NEAT) program of NASA's Jet Propulsion Laboratory. (Some sources gi ...

, Michael Hicks, Kenneth Lawrence and Steven H. Pravdo. It is located near the

Kuiper cliff 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 ...

Orbit and classification

orbits the Sun at a distance of 40.9–53.2 AU once every 322.6 years (over 117,800 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 47 AU). Its orbit has an eccentricity of 0.13 and an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

of 24 ° with respect to the ecliptic. The body's

observation arc In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...

begins with a

precovery In astronomy, precovery (short for pre-discovery recovery) is the process of finding the image of an object in images or photographic plates predating its discovery, typically for the purpose of calculating a more accurate orbit. This happens mos ...

taken at Haleakala-NEAT/GEODSS in December 1997, more than 4 years prior to its official discovery observation at Palomar. At 45.4 AU from the Sun, it continues to slowly approach the Sun until its perihelion passage at 41.1 AU in May 2078.

Physical characteristics

Combined observations of thermal emissions by the

Herschel Space Observatory The Herschel Space Observatory was a space observatory built and operated by the European Space Agency (ESA). It was active from 2009 to 2013, and was the largest infrared telescope ever launched until the launch of the James Webb Space Telesc ...

and

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003. Operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, f ...

give a diameter of and a geometric albedo of .

Surface

ESO The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental research organisation made up of 16 member states for ground-based ast ...

analysis of spectra reveals a strong red slope and no presence of water ice (in contrast to

Quaoar Quaoar (50000 Quaoar), provisional designation , is a dwarf planet in the Kuiper belt, a region of icy planetesimals beyond Neptune. A non-resonant object (cubewano), it measures approximately in diameter, about half the diameter of Pluto. T ...

, also red) suggesting organic material (see comparison of

colours Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associa ...

and typical composition inferred from spectra of the TNOs).

References

External links

* Cruikshank, D., et al. ''High Albedo KBO (55565)2002 AW₁₉₇'', The Astronomical Journal Letters, 624,53 (May 2004)
Abstract

Physical and dynamical characteristics of icy "dwarf planets" (plutoids)
G. Tancredi, IAU Symposium No. 263 (2009)

Stephen C. Tegler, June 2018 * * * {{DEFAULTSORT:055565 Classical Kuiper belt objects Discoveries by the Palomar Observatory Possible dwarf planets 20020110