(690420) 2014 FC72

Lore & Background

2014 FC72 was first observed on 24 March 2014 by astronomers with the Pan-STARRS survey at Haleakala Observatory, Hawaii, United States. It orbits the Sun at a distance of 51.7–100.6 AU once every 664 years, with a semi-major axis of 76.11 AU, a moderate eccentricity of 0.32, and an inclination of 30° with respect to the ecliptic. The object belongs to the same orbital group as (612911) 2004 XR190 ("Buffy"), 2014 FZ71, 2015 FJ345, and 2015 KQ174, and may be a resonant trans-Neptunian object in a 1:4 resonance with Neptune, similar to 2003 LA7 and 2011 UP411 but with lower eccentricities and higher perihelia. Considered a scattered and detached object, 2014 FC72 is particularly unusual because it has an unusually circular orbit for a scattered-disc object. Traditional scattered-disc objects are thought to have been ejected into their current orbits by gravitational interactions with Neptune, but the low eccentricity of its orbit and the distance of its perihelion seem hard to reconcile with such celestial mechanics. This has led to some uncertainty in the current theoretical understanding of the outer Solar System. Proposed explanations include close stellar passages, unseen planet or rogue planets or planetary embryos in the early Kuiper belt, and resonance interaction with an outward-migrating Neptune. The Kozai mechanism is also capable of transferring orbital eccentricity to a higher inclination. Physical characteristics: 2014 FC72 has a diameter estimated at 400 to 500 kilometers, making it approximately 18% to 21% the size of the dwarf planet Pluto. Johnston's Archive estimates 431 kilometers, and Mike Brown estimates 506 kilometers, assuming albedos of 0.124 and 0.07 respectively. However, Mike Brown's estimate uses an outdated absolute magnitude of 5.0, not the newer 4.68 nor 4.70.

Reader's Guide

The significance of (690420) 2014 FC72 lies in its challenge to the standard model of scattered-disc object formation. Its unusually circular orbit and high perihelion distance are difficult to explain solely by gravitational interactions with Neptune, which typically produce highly eccentric orbits with perihelia less than 38 AU. This discrepancy has led to uncertainty in the theoretical understanding of the outer Solar System, prompting alternative theories such as close stellar passages, the presence of an unseen planet or rogue planets or planetary embryos in the early Kuiper belt, and resonance interaction with an outward-migrating Neptune. The Kozai mechanism is also considered as a possible explanation. As a member of a small group of objects with moderate eccentricities, 2014 FC72 contributes to the ongoing debate about the dynamical history and evolution of the trans-Neptunian region. Its estimated diameter of 400 to 500 kilometers places it among the larger known trans-Neptunian objects, though its exact size remains uncertain due to differing albedo assumptions and absolute magnitude values.

Did You Know?

• Its diameter is estimated at 400 to 500 kilometers, about 18% to 21% the size of Pluto.
• It may be in a 1:4 orbital resonance with Neptune, similar to 2003 LA7 and 2011 UP411.