(505478) 2013 UT15

(505478) 2013 UT₁₅ is an extreme trans-Neptunian object from the scattered disc, located in the outermost regions of the Solar System, approximately 260 kilometers (160 miles) in diameter. It was discovered on 2 August 2013, by astronomers of the Outer Solar System Origins Survey at Mauna Kea Observatory, Hawaii, United States.^[4]

(505478) 2013 UT₁₅

Discovery[1]
Discovered by	OSSOS
Discovery site	Mauna Kea Obs.
Discovery date	2 August 2013
Designations
MPC designation	(505478) 2013 UT15
Alternative designations	o3L83[2]
Minor planet category	TNO[1] · SDO[3] detached · distant[4]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 4
Observation arc	4.08 yr (1,489 days)
Aphelion	347.97 AU
Perihelion	43.853 AU
Semi-major axis	195.91 AU
Eccentricity	0.7762
Orbital period (sidereal)	2742.19 yr (1,001,586 days)
Mean anomaly	353.50°
Mean motion	0° 0m 1.44s / day
Inclination	10.682°
Longitude of ascending node	191.97°
Argument of perihelion	252.40°
Physical characteristics
Dimensions	243 km estimate)[3] 260 km (est. at 0.08)[5] 340 km estimate)[6]
Geometric albedo	0.04 (estimate)[6] 0.09 (assumed)[3]
Spectral type	BB (estimate)[6]
Absolute magnitude (H)	6.2951[1] · 6.4[6]

Orbit

With a semi-major axis of 196 AU, 2013 UT₁₅ orbits the Sun at a distance of 43.9–348 AU once every 2,742 years. Its orbit has an eccentricity of 0.78 and an inclination of 11° with respect to the ecliptic.^[1] It has a similar orbit to (148209) 2000 CR105, except for a smaller inclination.

2013 UT₁₅ belongs to a small number of detached objects with perihelion distances of 30 AU or more, and semi-major axes of 150 AU or more.^[7] Such objects can not reach such orbits without some perturbing object, which leads to the speculation of Planet Nine.

Physical characteristics

Spectral type

The object is estimated to have a bluish spectra (BB).^[6]

Diameter

2013 UT₁₅ has been estimated to measure 243 and 340 kilometers in diameter, based on an assumed albedo of 0.09 and 0.04, respectively.^[3][6] A generic magnitude-to-diameter conversion gives a mean-diameter of 260 kilometers,^[5] using with a typical albedo of 0.08 and a published absolute magnitude of 6.2951.^[1]

Numbering and naming

2013 UT₁₅ was numbered (505478) by the Minor Planet Center on 4 November 2017 (M.P.C. 107067).^[8] As of 2025, this minor planet has not received a name.^[4]