474640 Alicanto

Lore & Background

Alicanto was discovered by American astronomer A. C. Becker with the ESSENCE supernova survey on 6 November 2004 using the 4-meter Blanco Telescope from Cerro Tololo Inter-American Observatory. Precovery images have been found back to 26 September 2000. It was observed by the Hubble Space Telescope in November 2008 and found not to have any detectable companions. It reached perihelion in 2009 and is currently 47.7 AU from the Sun. Its orbit is well determined, based on 34 observations spanning a data-arc of 5821 days as of 11 January 2017.

Alicanto's orbit is similar to that of 2013 RF98, indicating they may have both been thrown onto their orbit by the same body, or that they may have been the same object (single or binary) at one point. Numerical simulations based on models of Solar System formation suggest this object, along with Sedna, may be part of the inner edge of the Oort cloud. On 14 May 2021, the object was named by the Working Group for Small Bodies Nomenclature after Alicanto, a nocturnal bird in Chilean mythology whose wings shine at night with beautiful, metallic colors.

Alicanto has an absolute magnitude of 6.46, giving a characteristic diameter of 140 to 300 km for an assumed albedo in the range 0.25–0.05. Michael Brown's website lists a diameter of 300 km based on an assumed albedo of 0.04, ranking it as a 'possibly' a dwarf planet, though using an outdated absolute magnitude of 6.7. Johnston's archive estimates a diameter of 193 km assuming an albedo of 0.124. Its visible spectrum is very different from that of Sedna, with a mean spectral slope of 12±2%/0.1 μm, suggesting the surface may have pure methane ices and highly processed carbons.

Reader's Guide

Alicanto is significant as a detached extreme trans-Neptunian object whose orbit cannot be explained by current gravitational influence of Neptune, pointing to an unknown scattering mechanism. Its orbit, with a perihelion greater than 40 AU, places it among objects practically detached from Neptune. The similarity of its orbit to that of 2013 RF98 suggests a possible common origin or past binary relationship, offering clues to dynamical processes in the outer Solar System. Numerical simulations link it to the inner Oort cloud, alongside Sedna, providing insight into the Solar System's early evolution. The object's naming after a Chilean mythological bird adds cultural context. Its physical characteristics remain uncertain, with diameter estimates ranging from 140 to 300 km depending on assumed albedo, and its blue (neutral) color suggests a low albedo. The spectral slope indicates possible surface ices and processed materials, though its spectrum differs markedly from Sedna's. Alicanto's well-determined orbit and Hubble observations showing no companions make it a key target for understanding the detached population and the potential existence of Planet Nine.

Did You Know?

• Its orbit is similar to that of 2013 RF98, suggesting they may have been thrown onto their orbit by the same body or were once the same object.
• The object was named after Alicanto, a nocturnal bird in Chilean mythology whose wings shine with metallic colors.

Discovery and Orbital Architecture

Alicanto entered the astronomical record on 6 November 2004, when American astronomer Andrew C. Becker, working with the ESSENCE supernova survey, spotted the distant object through the 4-meter Blanco Telescope at Cerro Tololo Inter-American Observatory in Chile. Though the formal discovery date falls in late 2004, precovery images later pushed the observational record back to 26 September 2000, revealing that the body had been quietly present in the sky for over four years before anyone recognized it. The object's orbit is striking: it swings to a perihelion beyond 47 AU—well past the outer reaches of the main Kuiper belt—while its semi-major axis stretches to roughly 316 AU. Its eccentricity of 0.850 and inclination of about 25.6 degrees paint a picture of a highly elongated, tilted path. By January 2017, its orbital solution rested on 34 observations spanning nearly 16 years of data. A November 2008 Hubble Space Telescope campaign confirmed that no companion objects orbit alongside it. The body reached its closest solar approach in 2009 and, as of recent measurements, sits at approximately 47.7 AU. Until 2019 it resided in the constellation Cetus, and it presents opposition to Earth observers at the beginning of November each year.

The Orbital Mystery and Oort Cloud Connection

One of the most compelling puzzles surrounding Alicanto is simply how it arrived at its present orbit. Its extreme eccentricity of 0.850 strongly implies that some gravitational encounter flung it onto this elongated trajectory, yet because the body's perihelion never dips below 47 AU, it sits well beyond Neptune's current gravitational reach. In other words, the planet that most naturally scatters Kuiper belt objects is not a plausible architect of Alicanto's path, leaving the mechanism behind its orbit genuinely unexplained. Numerical simulations rooted in models of early Solar System formation have suggested that Alicanto, together with the similarly distant 90377 Sedna, may represent the innermost fringe of the Oort cloud rather than a true Kuiper belt resident. Adding to the mystery, its orbital parameters closely resemble those of 2013 RF98, raising the possibility that both bodies were ejected by the same unknown mass, or that they were once a single object—perhaps even a binary system—that later split apart. These connections have made Alicanto a frequent subject in discussions about a hypothetical Planet Nine and the broader architecture of the outer Solar System.

Physical Profile and Surface Composition

Estimating Alicanto's true size remains challenging because of the wide range of plausible albedos. Its absolute magnitude of 6.46 yields a characteristic diameter between roughly 140 and 300 kilometres, depending on whether one assumes a surface reflectivity of 0.25 or 0.05. The astronomer Michael Brown has listed a 300-kilometre diameter based on a very low albedo of 0.04, a figure that leads him to rank the body as a possible dwarf planet, though he relies on an older magnitude value of 6.7. Johnston's archive, working with an albedo of 0.124, arrives at a more moderate 193 kilometres. The object's blue, neutral coloration points toward a genuinely low albedo, yet if the surface reflects more light than expected, the true diameter could be nearly half the upper estimate. Spectroscopically, Alicanto stands in sharp contrast to Sedna. Its mean spectral slope of 12 ± 2 percent per 0.1 micrometre hints at a surface that may host pure methane ices comparable to those on Pluto, alongside highly processed carbon compounds and traces of amorphous silicates. Notably, this spectral signature closely mirrors that of 2013 RF98, reinforcing the orbital link between the two bodies.

Naming and Mythological Roots

On 14 May 2021, the Working Group for Small Bodies Nomenclature officially bestowed the name Alicanto upon the distant body, drawing from a creature in Chilean mythology. In the folklore of the Atacama Desert, the Alicanto is a nocturnal bird whose wings glow with striking metallic colors in the darkness of night—a luminous, elusive presence in the sky. The naming carries a fitting resonance: the object was discovered from Cerro Tololo Inter-American Observatory in Chile, and like the mythical bird, it is a faint, distant light visible only under the right conditions to those who know where to look. The metallic sheen of the mythological wings finds a loose parallel in the object's blue, neutral coloration and its spectral signature, which suggests a surface rich in processed ices and carbon compounds that scatter light in distinctive ways. The connection between the arid, star-filled skies of the Atacama and the deep-space object observed from that very region gives the name a sense of place and story that goes well beyond a simple label, tying the object to a living cultural tradition of the land where it was first detected.