385571 Otrera

385571 Otrera, provisional designation 2004 UP₁₀, is a Neptune trojan leading Neptune's orbit in the outer Solar System. It was discovered by American astronomers Scott Sheppard and Chad Trujillo at Las Campanas Observatory on 16 October 2004.^[2] It measures approximately 100 kilometers in diameter and was the second such body to be discovered after 2001 QR322.^[3]

385571 Otrera

Discovery[1][2]
Discovered by	S. S. Sheppard C. Trujillo
Discovery site	Las Campanas Obs.
Discovery date	16 October 2004
Designations
MPC designation	(385571) Otrera
Named after	Otrera (Greek mythology)[2]
Alternative designations	2004 UP10
Minor planet category	Neptune trojan · L4[3] centaur[1] · distant[2]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 4
Observation arc	8.97 yr (3,277 days)
Aphelion	30.727 AU
Perihelion	29.327 AU
Semi-major axis	30.027 AU
Eccentricity	0.0233
Orbital period (sidereal)	164.54 yr (60,099 days)
Mean anomaly	355.52°
Mean motion	0° 0m 21.6s / day
Inclination	1.4334°
Longitude of ascending node	34.761°
Argument of perihelion	3.5334°
Physical characteristics
Dimensions	74 km (est. at 0.10)[4] 100 km[5]
Apparent magnitude	23.3[5]
Absolute magnitude (H)	8.8[1]

Orbit and classification

Neptune trojans are resonant trans-Neptunian objects in a 1:1 mean-motion orbital resonance with Neptune. These Trojans have a semi-major axis and an orbital period very similar to Neptune's (30.10 AU; 164.8 years).

Otrera belongs to the L₄ group, which leads 60° ahead Neptune's orbit. It orbits the Sun with a semi-major axis of 30.027 AU at a distance of 29.3–30.7 AU once every 164 years and 6 months (60,099 days). Its orbit has an eccentricity of 0.02 and an inclination of 1° with respect to the ecliptic.^[1]

Physical characteristics

The discoverers estimate that the body has a mean-diameter of 100 kilometers based on a magnitude of 23.3.^[5] Based on a generic magnitude-to-diameter conversion, it measures approximately 74 kilometers in diameter using an absolute magnitude of 8.8 and an assumed albedo of 0.10.^[4]

Naming

This minor planet was the first Neptune trojan to be named in November 2015. It was named after Otrera, the first Amazonian queen in Greek mythology.^[2] The naming scheme is to name these objects after figures related to the Amazons, which was an all-female warrior tribe that fought in the Trojan War on the side of the Trojans against the Greeks.^[6]