| Minorplanet: | yes |
| (55638) | |
| Background: |
|
| Discovered: | 14 November 2002 |
| Earliest Precovery Date: | 12 October 1990 |
| Mpc Name: | (55638) |
| Epoch: | 1 July 2021 (JD 2459396.5) |
| Uncertainty: | 20 |
| Observation Arc: | 27.27 yr (9,960 d) |
| Perihelion: | 27.910 AU |
| Semimajor: | 39.176 AU |
| Eccentricity: | 0.2876 |
| Period: | 245.21 yr (89,562 d) |
| Mean Motion: | / day |
| Inclination: | 16.327° |
| Asc Node: | 199.72° |
| Time Periastron: | 29 June 2001 |
| Arg Peri: | 206.35° |
| Spectral Type: | |
| Magnitude: | 20.64 |
| Abs Magnitude: | 5.3 |
(provisional designation ) is a trans-Neptunian object from the outermost region of the Solar System. It was discovered on 14 November 2002, by astronomers with the Near-Earth Asteroid Tracking program at the Palomar Observatory in California, United States. This resonant trans-Neptunian object is a member of the plutino population, locked in a 2:3 resonance with Neptune. The object is likely of primordial origin with a heterogeneous surface and a notably reddish color (RR) attributed to the presence of methanol and tholins. It has a poorly defined rotation period of 6.8 hours and measures approximately 250km (160miles) in diameter, too small to be a dwarf planet candidate., it has not yet been named.
belongs to the plutino population, named after its largest member, Pluto. Plutinos are resonant trans-Neptunian objects, that are locked in a stable 2:3 mean-motion resonance with Neptune, orbiting the Sun twice for every three orbits Neptune does. They form a significantly large part of the inner Kuiper belt, as hundreds of these objects have already been discovered.
This minor planet orbits the Sun at a distance of 27.9–50.4 AU once every 245 years and 3 months (89,562 days; semi-major axis of 39.18 AU). Its orbit has an eccentricity of 0.29 and an inclination of 16° with respect to the ecliptic. On 29 June 2001, it came to perihelion and has since been moving away from the Sun. Due to precovery images recovered from the Digitized Sky Survey, the body's observation arc begins already in October 1990, or 12 years prior to its official discovery observation by astronomers with the Near-Earth Asteroid Tracking at Palomar.
was numbered (55638) by the Minor Planet Center on 16 February 2003 ., it has not been named. According to the established naming conventions for plutinos, it will be named after a mythological figure from the underworld.
The rotation period of is poorly defined and has ambiguous results with multiple alternative period solutions between 4.90 and 10 hours. In December 2002, a rotational lightcurve of this object was obtained from photometric observations by astronomers from the Sierra Nevada Observatory in Spain. Lightcurve analysis gave a poorly defined period of hours with a brightness variation of magnitude . Two years later in December 2004, it was revisited by the same astronomers, obtaining another poorly defined period of hours with an amplitude of magnitude . Other observations by Sheppard only determined an amplitude of less than 0.06 magnitude .
In 2010, observations with the Herschel Space Telescope, using its PACS instrument to measure the object's thermal radiation, gave a mean diameter of with a relatively high albedo of for an absolute magnitude of . In addition, an asteroid occultations on 3 December 2015, gave a best-fit ellipse dimension of with an poor quality rating of 1. These timed observations are taken when the asteroid passes in front of a distant star. The Collaborative Asteroid Lightcurve Link assumes a more regular albedo for a distant object of 0.10 and hence estimates a larger diameter of 297 kilometers.
In the visible light, has a featureless reflectance spectrum. It is very red in color (RR), with a color index of 1.080 and 0.71, in the B–V and V−R passband filters, respectively.
The near-infrared spectrum of is flat with two distinct absorption bands of water ice at 1.5 and 2.0 μm. There is the third feature near 2.3 μm of unclear origin. The spectral behavior of this object is similar to 5145 Pholus, a centaur. Observations with the Very Large Telescope revealed that has a heterogeneous surface—the amount of different ices and non-ice components depends on the observed area. Among the probable surface materials are water ice (4–19%), methanol ice (10–12%), and various tholins, photochemically altered organic compounds, also found on Triton and Titan. The redder areas are generally associated with the presence of methanol ice. The surface of appears to be primordial in origin.