2013 SK100

2013 SK₁₀₀ is a trans-Neptunian object, both considered a scattered and detached object, located in the outermost region of the Solar System. The object with a moderately inclined and eccentric orbit measures approximately 135 kilometers (84 miles) in diameter. It was first observed on 29 September 2013, by astronomers at the Mauna Kea Observatories in Hawaii, United States.

2013 SK₁₀₀

Discovery[1]
Discovered by	Mauna Kea Obs.
Discovery site	Mauna Kea Obs. (first observed only)
Discovery date	29 September 2013
Designations
MPC designation	2013 SK100
Minor planet category	TNO[2] detached[3][4] SDO[5] distant[1]
Orbital characteristics[2]
Epoch 27 April 2019 (JD 2458600.5)
Uncertainty parameter 4
Observation arc	4.07 yr (1,487 d)
Aphelion	78.109 AU
Perihelion	45.477 AU
Semi-major axis	61.793 AU
Eccentricity	0.2640
Orbital period (sidereal)	485.75 yr (177,421 d)
Mean anomaly	355.07°
Mean motion	0° 0m 7.2s / day
Inclination	26.312°
Longitude of ascending node	17.104°
Argument of perihelion	11.163°
Physical characteristics
Mean diameter	134 km[5] 135 km[6]
Geometric albedo	0.08 (assumed)[6] 0.09 (assumed)[5]
Apparent magnitude	24.1[7]
Absolute magnitude (H)	7.6[1][2]

Orbit and classification

2013 SK₁₀₀ orbits the Sun at a distance of 45.5–78.1 AU once every 485 years and 9 months (177,421 days; semi-major axis of 61.79 AU). Its orbit has an eccentricity of 0.26 and an inclination of 26° with respect to the ecliptic.^[2]

Considered both a scattered and detached object,^[3][4][5] 2013 SK₁₀₀ is particularly unusual as it has an unusually circular orbit for a scattered-disc object (SDO). Although 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, unseen planet/rogue planets/planetary embryos in the early Kuiper belt, and resonance interaction with an outward-migrating Neptune. The Kozai mechanism is capable of transferring orbital eccentricity to a higher inclination.^[8] It is in a 3:1 resonance to Neptune. It seems to belong to the same group as (145480) 2005 TB190.

Physical characteristics

Johnston's Archive estimates a diameter of 134 kilometers based on an assumed albedo of 0.09, while American astronomer Michael Brown, calculates a diameter of 135 kilometers, using an estimated albedo of 0.08 and an absolute magnitude of 7.8.^[5][6]