, internally nicknamed Caju, is an extreme trans-Neptunian object from the scattered disc on a highly eccentric and inclined orbit in the outermost region of the Solar System. It has been described as an extended scattered disc object (ESDO), and fits into the group of extreme objects that led to the prediction of Planet Nine, and has the highest orbital inclination of any of these objects.
History Discovery and observations
was first observed on 17 January 2015, by astronomers with the Dark Energy Survey at Cerro Tololo Observatory in Chile. The body's observation arc begins with a precovery taken on 27 November 2014 by astronomers with the Dark Energy Survey using the DECam instrument of the Víctor M. Blanco Telescope at Cerro Tololo Inter-American Observatory in Chile. Its discovery was reported in a paper published by Dark Energy Survey astronomers in 2018.
Naming As of 2026, has not been named, but it is nicknamed Caju ("cashew") by the discovery team.
Orbit and classification
Orbital characteristics orbits the Sun at a distance of 35.2–821 AU once every 8856 years (3,234,488 days; semi-major axis of 428 AU). Its orbit has an exceptionally high eccentricity of 0.92 and an inclination of 54° with respect to the ecliptic. This makes it a probable outlier among the known extreme trans-Neptunian objects. It has been described as an extended scattered disc object (ESDO).
Planet Nine hypothesis fits into the group of extreme trans-Neptunian objects that originally led to the prediction of Planet Nine. The group consists of more than a dozen bodies with a perihelion greater than 30 AU and a semi-major axis greater than 250 AU, with having the highest orbital inclination of any of these objects. Subsequently, unrefereed work by de la Fuente Marcos (2018) found that current orbital orientation in space is not easily explained by the same mechanism that keeps other extreme trans-Neptunian objects together, suggesting that the clustering in its orbital angles cannot be attributed to Planet Nine's influence. However, regardless of the current direction of its orbit, its high orbital inclination appears to fit into the class of high-semi major axis, high-inclination objects predicted by Batygin & Morbedelli (2017) to be generated by Planet Nine.
Physical characteristics Size and albedo According to the original paper for the discovery of the object, its diameter is estimated to be 400 km to 700 km, using a albedo of 0.07 to 0.21. However, according to Michael Brown and Johnston's Archive, measures 524 and 516 kilometers in diameter based on an assumed albedo of 0.08 and 0.124, respectively.
Spectra and surface has color indices of: g-r 0.79 ± 0.17, r-i 0.19 ± 0.12, r-z 0.42 ± 0.15 and i-z 0.23 ± 0.15. The color of is moderately red.
Upcoming observations As of 2018, no rotational lightcurve of has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown. It has not yet been imaged by high-resolution telescopes, so it has no known moons. The Hubble Space Telescope is planned to image in 2026, which should determine if it has significantly sized moons.
See also Sedna
Notes
References
External links Discovery and Dynamical Analysis of an Extreme Trans-Neptunian Object with a High Orbital Inclination, 14 May 2018 A New World's Extraordinary Orbit Points to Planet Nine 15 May 2018