474640 Alicanto (provisional designation ) is a detached extreme trans-Neptunian object. It was discovered on 6 November 2004, by American astronomer Andrew C. Becker at Cerro Tololo Inter-American Observatory in Chile. It never gets closer than 47 AU from the Sun (near the outer edge of the main Kuiper belt) and averages more than 300 AU from the Sun. Its large eccentricity strongly suggests that it was gravitationally scattered onto its current orbit. Because it is, like all detached objects, outside the current gravitational influence of Neptune, how it came to have this orbit cannot yet be explained. It was named after Alicanto, a nocturnal bird in Chilean mythology.

History Discovery

Alicanto was discovered by American astronomer A. C. Becker with the ESSENCE supernova survey on 6 November 2004 observing with the 4-meter Blanco Telescope from Cerro Tololo Inter-American Observatory.Discovery MPEC Precovery images have been found back to 26 September 2000. Alicanto was observed by the Hubble Space Telescope in November 2008, and found not to have any detectable companions.

Naming On 14 May 2021, the object was named by the Working Group for Small Bodies Nomenclature (WGSBN) after Alicanto from Chilean mythology. The nocturnal bird of the Atacama Desert has wings that shine at night with beautiful, metallic colors.

Orbit

Alicanto reached perihelion (closest approach to the Sun) in 2009 and is currently 47.7 AU from the Sun. It was in the constellation of Cetus until 2019. It comes to opposition at the start of November.

With a perihelion greater than 40 AU, Alicanto is an extreme trans-Neptunian object which are practically detached from Neptune's gravitational influence. Its orbit is characterized by high eccentricity (0.850), moderate inclination (25.58°) and a semi-major axis of 316 AU. Upon discovery, it was classified as a trans-Neptunian object. Its orbit is well determined; as of 11 January 2017 its orbital solution is based on 34 observations spanning a data-arc of 5821 days. Alicanto's orbit is similar to that of , indicating that they may have both been thrown onto the 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.

A paper by Kathryn Volk and Renu Malhotra, shows that Alicanto overlaps with a 36:1 resonance with Neptune, and could be in a 36:1 resonance with the planet.

Physical characteristics

Diameter and albedo

Alicanto has an absolute magnitude of 6.46 which gives a characteristic diameter of for an assumed albedo in the range 0.25–0.05.

Michael Brown's website lists it with a diameter of based on an assumed albedo of 0.04. and because of that diameter, he ranks it to be a "possibly" a dwarf planet. However, Mike Brown uses an outdated absolute magnitude of 6.7, not the newer 6.46. The albedo is expected to be low because the object has a blue (neutral) color. However, if the albedo is higher, the object could easily be half that size.

Johnston's archive estimates a diameter of assuming an albedo of 0.124.

MinorPlanet.info estimates a diameter of , assuming an albedo of 0.057.

Color and spectra

Alicanto's visible spectrum is very different from that of 90377 Sedna. With a mean spectral slope of %/0.1 μm. The value of its spectral slope suggests that the surface of this object can have pure methane ices (like in the case of Pluto) and highly processed carbons, including some amorphous silicates. Its spectral slope is similar to that of . A paper published slightly after in 2019 shows that Alicanto has a spectral slope of %/Å.

A paper by Hainaut and colleagues measured color indices of; B-V of 0.900; V-R of 0.520; R-I of 0.450; and V-I of 0.970. with V-J, J-H, and H-K having no measured value. A earlier paper by Scott S. Sheppard measured color indices of: B-R of ; V-R of ; R-I of ; and B-I of .

Alicanto has no measured albedo as of 2026, however there have been estimates for its albedo. Michael Brown's estimate uses an albedo of 0.04, Johnston's archive uses an albedo of 0.124. and MinorPlanet.info uses an albedo of 0.057.

A paper by Holler and colleagues using NIRSpec IFU on the James Webb Space Telescope reported that Alicanto has a "double-dip" spectrum, showing that it has an absorption feature that indicates carbon dioxide is on its surface, with a reflectance peak at around 4.26 μm indicating small grains. Comparison

See also List of Solar System objects by greatest aphelion Planet Nine

Notes 1.It has also been measured to be %/0.1 μm, and %/0.1 μm, however the mean as said in the paper is %/0.1 μm.

References (Bulletin #1)

(Ephemeris Type:Elements and Center:@0)

External links New data about two distant asteroids give a clue to the possible "Planet Nine" Dos asteroides lejanos apoyan la hipótesis del Planeta Nueve