(303775) 2005 QU182

Lore & Background

2005 QU182 was discovered during a search for distant trans-Neptunian objects using the 1.2-meter Samuel Oschin telescope. Precovery images date back to 1974, and as of 2026 it has been observed 626 times over 52 years. Its provisional designation was assigned on 1 September 2007, and its permanent number 303775 in 2014. The object orbits the Sun at a distance of 36.8–189.1 AU with a semi-major axis of 113.0 AU, taking about 1201 years to complete one orbit. Its orbit has a high eccentricity of 0.674 and an inclination of 14.05°. It belongs to the scattered disc, a population of trans-Neptunian objects strongly influenced by Neptune's gravitational perturbations. A 2021 study initially predicted a very stable orbit with a diffusion time of 68.272 billion years, but a full one-billion-year simulation showed the orbit is unstable due to Neptune's influence, though none of the simulation tracks were completely lost from the Solar System. Its surface shows medium reddening and a composition rich in carbon dioxide ice, with a geometric albedo of 0.129+0.115−0.046 and a surface temperature at perihelion of about 45 Kelvin. It completes one rotation every 9.61 hours, with brightness variations of 0.12 magnitudes, indicating an approximately spherical shape.

Reader's Guide

2005 QU182 is significant as one of the largest known trans-Neptunian objects, ranking among the top 34 in size. Its size of approximately 440–740 km places it in the proposed class of 'mid-sized' TNOs, which are believed to represent the transition between small, low-density objects and large, high-density dwarf planets. Mike Brown classifies it as a possible dwarf planet in the 'probably' zone. The object's composition, dominated by carbon dioxide ice and carbon monoxide ice, places it in the CO2-type spectral class, the most common type in the DiSco sample. Its orbit is dynamically interesting because, despite initial predictions of stability, simulations show it is unstable over a billion-year timescale due to Neptune's gravity. The scheduled Hubble Space Telescope observations in 2026 could discover a moon, which would allow direct measurement of its mass and density, currently unknown. A 2019 study identified hypothetical flyby mission opportunities between 2025 and 2040 using gravity assists from Jupiter, Saturn, and Neptune, with launch windows between 2025 and 2033 and travel times of 15.7 to 24.5 years.

Did You Know?

• Its orbit is unstable over a one-billion-year timeframe because of Neptune's gravity.
• The Hubble Space Telescope is scheduled to observe it in 2026 to search for potential moons.