474640 Alicanto, provisionally designated , is a detached

extreme trans-Neptunian object An extreme trans-Neptunian object (ETNO) is a trans-Neptunian object orbiting the Sun well beyond Neptune (30 AU) in the outermost region of the Solar System. An ETNO has a large semi-major axis of at least 150–250 AU. Its orbit is m ...

. It was discovered on 6 November 2004, by American astronomer

Andrew C. Becker This is a list of minor-planet discoverers credited by the Minor Planet Center with the discovery of one or several minor planets (such as near-Earth and main-belt asteroids, Jupiter trojans and distant objects). , the discovery of 612,011 numb ...

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 The Kuiper belt () is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...

) 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 Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...

, how it came to have this orbit cannot yet be explained. It was named after

Alicanto The Alicanto is a mythological nocturnal bird of the desert of Atacama, pertaining to Chilean mythology. Legend says that the alicanto's wings shine at night with beautiful, metallic colors, and their eyes emit strange lights. The color of the wi ...

, a nocturnal bird in Chilean mythology.

Discovery and orbit

''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 Blanco (''white'' or ''blank'' in Spanish) or Los Blancos may refer to: People *Blanco (surname) Fictional characters *Blanco, a hobbit in J. R. R. Tolkien's Middle-earth *Blanco Webb, character in the BBC sitcom ''Porridge'' * El Blanco, albino ...

from Cerro Tololo Inter-American Observatory.Discovery MPEC
/ref> Precovery images have been found back to September 26, 2000. ''Alicanto'' was observed by the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

in November 2008, and found not to have any detectable companions. It reached perihelion (closest approach to the Sun) in 2009 and is currently 47.7 AU from the Sun. It will be in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

of Cetus until 2019. It comes to

opposition Opposition may refer to: Arts and media * ''Opposition'' (Altars EP), 2011 EP by Christian metalcore band Altars * The Opposition (band), a London post-punk band * ''The Opposition with Jordan Klepper'', a late-night television series on Comed ...

at the start of November. With an perihelion greater than 40 AU, ''Alicanto'' is an

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'' 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.

Naming

On 14 May 2021, the object was named by the Working Group Small Body Nomenclature (WGSBN) after

from Chilean mythology. The nocturnal bird of the Atacama Desert has wings that shine at night with beautiful, metallic colors.

Physical characteristics

''Alicanto'' has an absolute magnitude of 6.5 which gives a characteristic diameter of 130 to 300 km for an assumed albedo in the range 0.25–0.05. Michael Brown's website lists it as a possible dwarf planet with a diameter of based on an assumed

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

of 0.04. The albedo is expected to be low because the object has a

blue Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between violet and cyan on the spectrum of visible light. The eye perceives blue when obs ...

(neutral) color. However, if the albedo is higher, the object could easily be half that size. ''Alicanto'' visible spectrum is very different from that of

90377 Sedna Sedna (minor-planet designation 90377 Sedna) is a dwarf planet in the outer reaches of the Solar System that is in the innermost part of its orbit; it is 84 astronomical units (AU), or 1.26×1010 km, from the Sun, almost three times farther ...

. The value of its spectral slope suggests that the surface of this object can have pure methane ices (like in the case of

Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the S ...

) and highly processed carbons, including some amorphous silicates. Its spectral slope is similar to that of .

Relevance to the Planet Nine Hypothesis

This minor planet is one of a number of objects discovered in the Solar System to have a

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the long ...

> 150 AU, a perihelion beyond Neptune, and an argument of perihelion of 340 ± 55°. Of these, only eight, including ''Alicanto'', have perihelia beyond Neptune's current influence.

Comparison

References

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
* * {{DEFAULTSORT:Alicanto 474640 474640 Discoveries by Andrew C. Becker Named minor planets 20041106