It was discovered by American astronomers Scott Sheppard and Chad Trujillo at Las Campanas Observatory on 16 October 2004.
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.
[1] 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.