(143707) 2003 UY117

(143707) 2003 UY₁₁₇ is a trans-Neptunian object located in the outermost regions of the Solar System. It measures approximately 228 kilometers in diameter. Discovered on 21 October 2003, by astronomer Marc W. Buie during the Deep Ecliptic Survey at the Kitt Peak National Observatory, it orbits the Sun in a 2:5 orbital resonance with Neptune.

Orbit and classification

2003 UY₁₁₇ orbits the Sun at a distance of 32.6–68.8 AU once every 360 years and 9 months (131,750 days). Its orbit has a relatively high eccentricity of 0.36 and an inclination of 12.2° relative to the ecliptic.

It is classified as a resonant trans-Neptunian object, maintaining a 2:5 orbital resonance with the planet Neptune. For every two orbits Neptune completes around the Sun, 2003 UY₁₁₇ completes exactly five. This stable resonance prevents gravitational disruptions from Neptune despite a perihelion that brings it close to Neptune's orbit.

Physical characteristics

Prior to 2024, knowledge of 2003 UY₁₁₇ was limited to absolute magnitude estimates. A stellar occultation campaign tracked the shadow cast by the object against a magnitude 14.6 background star. Four positive chords captured across multi-station observatories allowed astronomers to map its profile.

The occultation data derived an instantaneous projected elliptical profile with dimensions of 282 ± 18 km by 184 ± 32 km, establishing an area-equivalent diameter of 228 ± 21 km. Photometric follow-ups revealed a double-peaked rotational light curve with a period of 12.376 ± 0.0033 hours and a peak-to-valley amplitude variation of 0.36 ± 0.13 mag.