(303775) 2005 QU182

Lore & Background

2005 QU182 was discovered on 30 August 2005 by American astronomers Mike Brown, David Rabinowitz, and Chad Trujillo at the Palomar Observatory in California, 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. It was assigned the permanent number 303775 in 2014.

The object orbits the Sun at a distance of 36.8–189.1 AU with an average orbital distance 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. Simulations show its orbit is unstable over one billion years due to Neptune's gravity.

Physical characteristics include a diameter of 584+155−144 km, a rotation period of 9.61 hours, and a geometric albedo of 0.129+0.115−0.046. Its surface has medium reddening and is rich in carbon dioxide ice, carbon monoxide ice, and isotopologue ices. The Hubble Space Telescope is scheduled to observe it in 2026 to search for potential moons, which could allow direct measurement of its mass and density.

Reader's Guide

2005 QU182 is significant as one of the largest known trans-Neptunian objects, ranking among the top 34 in size. Its classification as a possible dwarf planet by Mike Brown places it in a transitional size range (400–1,000 km) where interiors are thought to be highly porous and unheated, with low densities around 1 g/cm³. The object's carbon dioxide-rich surface places it in the CO2-type spectral class, the most common type in the DiSco sample, providing insights into the composition of dynamically excited populations in the outer Solar System.

Its orbital instability over billion-year timescales highlights the dynamical influence of Neptune on scattered-disc objects. The scheduled Hubble Space Telescope observations in 2026 could reveal a moon, enabling direct mass and density measurements—critical for understanding the internal structure of mid-sized trans-Neptunian objects. The object's high absolute magnitude (3.74) makes it the seventh intrinsically brightest scattered-disc object, though its great distance gives it a dim apparent magnitude of 20.9.

Hypothetical spacecraft missions have been studied, with potential launch windows between 2025 and 2033 using gravity assists from Jupiter and Neptune, with travel times of 15.7 to 24.5 years. As of 2026, no spacecraft has visited 2005 QU182.

Did You Know?

• 2005 QU182 has a rotation period of 9.61 hours, with brightness variations of 0.12 magnitudes indicating an approximately spherical shape.
• Its surface temperature at perihelion is estimated to be about 45 Kelvin.
• The object's provisional designation indicates it was the 4571st object discovered in the second half of August 2005.
• A 2021 study found its orbit is unstable over one billion years due to Neptune's gravitational influence.