(278361) 2007 JJ43 is a large trans-Neptunian object (TNO) orbiting the Sun near the outer edge of the Kuiper belt. Its discovery images were taken in 2007, and its absolute magnitude of 4.5 is one of the twenty brightest exhibited by unnamed TNOs. It has a diameter of roughly 610 km, making it a possible dwarf planet.
Observations
Observations by Mike Brown in 2012, using the W. M. Keck Observatory, suggest that 2007 JJ43 does not have a significantly sized companion. As of 2026, it is about 40.5 AU from the Sun.
Orbit and classification
Orbital characteristics 2007 JJ43 orbits the Sun at a distance of 40.3–55.4 AU with an semi-major axis or average orbital distance of 47.8 AU once every 331 years (for reference, Neptune's orbit is at 30 AU). Its orbit has a relatively high eccentricity of 0.158 and an inclination of 12.06° with respect to the ecliptic.
Classification
2007 JJ43 is classified as a Trans-Neptunian object.
Physical characteristics Assuming it has a typical albedo, this would make it roughly the same size as Ixion (about 530–620 km diameter). In a paper in the Astrophysical Journal Letters András Pál and colleagues estimate a geometric albedo of 0.13 with a diameter of 2007 JJ43 of 610+170−140 km. This size makes it a possible dwarf planet. However, 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. However, 2007 JJ43 is not known to have any natural satellites or moons, which means there is currently no way to measure its mass and density.
See also List of Solar System objects by size List of trans-Neptunian objects List of minor planets: 278001–279000
References
External links List of Transneptunian Objects, Minor Planet Center (278361) 2007 JJ43 at the JPL Small-Body Database