(303775) 2005 QU182 is a large trans-Neptunian object in the scattered disc. It was discovered on 30 August 2005 by American astronomers Mike Brown, David Rabinowitz and Chad Trujillo at the Palomar Observatory in California, with precovery images going back to 1974. It was assigned its permanent number in 2014. Its diameter is approximately 584+155−144 km, which makes it among the top 34 largest known trans-Neptunian objects. Its surface shows medium reddening and a composition rich in carbon dioxide ice. 2005 QU182 completes one rotation every 9.61 hours. Simulations show that its orbit is unstable over a one-billion-year timeframe because of Neptune's gravity. The Hubble Space Telescope is scheduled to observe the object in 2026 to search for potential moons. If a moon is discovered, it could allow a direct measurement of its mass and density.
History
Discovery
2005 QU182 was discovered on 30 August 2005 by American astronomers Mike Brown, David Rabinowitz and Chad Trujillo at the Palomar Observatory in California, United States. At the time, they were searching for distant trans-Neptunian objects using the observatory's 1.2-meter Samuel Oschin telescope. As of 2026, it has been observed 626 times over 52 years, with precovery images back to 1974.
Further observations Following its discovery, 2005 QU182 was tracked by multiple stations, including the Cerro Tololo Observatory, Las Campanas Observatory, and Mauna Kea Observatory. As of 2026, the object has been observed 626 times over an observation arc of 52 years. 2005 QU182 is scheduled for observation with the Hubble Space Telescope in 2026, if those observations discover a moon, they could lead to a measurement of the mass and density of 2005 QU182.
Provisional designation and numbering The object was formally given the provisional designation 2005 QU182 by the Minor Planet Center on 1 September 2007. The provisional designation of 2005 QU182 indicates its discovery date, the first letter represents the second half of August and the second letter and numbers means that it is the 4571st object discovered during that half-month. 2005 QU182 was assigned its permanent number 303775 in 2014.
Orbit and classification
2005 QU182 is a trans-Neptunian object that orbits the Sun at a distance of 36.8–189.1 AU with an semi-major axis or average orbital distance of 113.0 AU once every 1201 years (for reference, Neptune's orbit is at 30 AU). Its orbit has a high eccentricity of 0.674 and an inclination of 14.05° with respect to the ecliptic. 2005 QU182 came to perihelion in 1971 and is currently 51.8 AU from the Sun. In April 2013, it moved beyond 50 AU from the Sun. 2005 QU182 belongs to the scattered disc, which is a population of TNOs that have distant, inclined, and eccentric orbits that come close to Neptune at perihelion. The scattered disc population, which includes the dwarf planets Eris and Gonggong, are strongly influenced by Neptune's gravitational perturbations and consequently experience gravitational scattering. Both the Minor Planet Center (MPC) and Buie classify that 2005 QU182 is a scattered disc object.
Orbital stability In a 2021 study, scientists analyzed the orbital stability of 2005 QU182 over a period of one billion years. At first, those models predicted that its orbit will be very stable, calculating a diffusion time of 68.272 billion years. However, a full 1 billion year simulation showed that the orbit is unstable, due to the object eventually entering the direct influence of Neptune's gravitational influence. In the simulations, none of its tracks managed to stay near its original orbit size. Even though its orbit size changes dramatically, none of the simulation tracks were completely lost or kicked out of the Solar System.
Physical characteristics
Size, mass and density
In 2012, the diameter of 2005 QU182 was initially estimated to be 416±73 km using data from the Herschel Space Telescope. Later in 2020, the data was reanalyzed, which yielded a notably larger nominal diameter and uncertainty of 584+155−144 km, making it approximately ³/4 the size of the possible dwarf planet Aya. 2005 QU182 is a relatively large trans-Neptunian object and is among the top 34 largest known TNOs. 2005 QU182 is not known to have any natural satellites or moons, which means there is currently no way to measure its mass and density. 2005 QU182's size is large enough that Mike Brown classify it as a possible dwarf planet, putting it in the 'probably' zone. However, based on its size of approximately 440–740 km, it belongs to the proposed class of "mid-sized" TNOs between 400 and 1,000 km (250 and 620 mi) in diameter, which are believed to represent the transition between small, low-density TNOs and large, high-density dwarf planets. Planetary scientists have hypothesized that mid-sized TNOs should have highly porous and unheated interiors, because TNOs in this size range (such as Uni and Gǃkúnǁʼhòmdímà) have been found to have low densities around 1 g/cm3.
Surface
Composition and spectrum
2005 QU182 shares its composition with the CO2-type (aka "double-dip") trans-Neptunian objects, which are commonly found on dynamically excited orbits such as those in the hot classical Kuiper belt. The CO2 type TNO exhibits two adjacent absorption minima in the 3 μm region, resulting in the “double dip” feature. Their spectra is dominated by carbon dioxide ices,carbon monoxide ices, and isotopologue ices, with other irradiation products like light hydrocarbons. The CO2-type TNOs like 2005 QU182 is the most common spectral type in the DiSco sample.
Color, albedo and surface temperature 2005 QU182 has color indices of: B–V 0.94 ± 0.03; V–R 0.54 ± 0.03; R–I 0.51 ± 0.03. It also has a known spectral slope of 16 ± 2%/100 nm, indicating a surface with medium reddening. Observations by the Herschel Space Telescope show that it has a geometric albedo of 0.129+0.115−0.046. The surface temperature of 2005 QU182 at perihelion (closest point to the Sun) is estimated to be approximately 45 Kelvin.
Brightness and visibility 2005 QU182 has a bright absolute magnitude of 3.74. According to the Minor Planet Center, it is the seventh intrinsically brightest scattered-disc object. However, due to its very far distance from Earth, it has a dim apparent magnitude of 20.9 when viewed from Earth.
Rotation According to a 2013 photometric survey, 2005 QU182 has a rotation period of 9.61 hours, with its brightness varying by 0.12 magnitudes during each rotation, indicating an approximate spherical shape.
Origin As a scattered-disc object, 2005 QU182 is believed to have formed from a primordial disk of icy planetesimals surrounding the young Sun. During the early evolution of the Solar System, gravitational interactions with Neptune scattered the object into its current highly eccentric orbit.
Exploration concepts 2005 QU182 has not been visited by any spacecraft. A 2019 study on flyby mission opportunities between 2025 and 2040 calculated hypothetical trajectories to 2005 QU182 using gravity assists from Jupiter, Saturn, and Neptune. These trajectories make launch windows between 2025 and 2033,with travel times ranging from 15.7 to 24.5 years. Two specific trajectories using swingbys of both Jupiter and Neptune have launch windows in April 2032, with arrival dates at 2005 QU182 in 2048 and 2050.
See also List of trans-Neptunian objects List of minor planets: 303001–304000 List of possible dwarf planets Scattered disc
Notes
References
External links (303775) 2005 QU182 at the JPL Small-Body Database