65489 Ceto, as a binary also (65489) Ceto/Phorcys, is a

binary Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two values (0 and 1) for each digit * Binary function, a function that takes two arguments * Binary operation, a mathematical op ...

trans-Neptunian object A trans-Neptunian object (TNO), also written transneptunian object, is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has an orbital semi-major axis of 30.1 astronomical units (AU). ...

(TNO) discovered on March 22, 2003, by Chad A. Trujillo and Michael Brown at Palomar. It is named after the sea goddess

Ceto Ceto (; ) is a primordial sea goddess in Greek mythology, the daughter of Pontus and his mother, Gaia. As a mythological figure, she is considered to be one of the most ancient deities, and bore a host of monstrous children fathered by Pho ...

from Greek mythology. It came to

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

in 1989.

Physical characteristics

65489 Ceto is an example of a close binary TNO system in which the components are of similar size. Combined observations with the infrared

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003, that was deactivated when operations ended on 30 January 2020. Spitzer was the third space telescope dedicate ...

and the

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

allow the diameter of Ceto itself to be estimated at and the diameter of Phorcys at , assuming equal

albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

for both components. The binary nature of Ceto enables direct calculation of the system mass, allowing estimation of the masses of the components and providing additional constraints on their composition. The estimated

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

of Ceto is , significantly less than that of the large TNOs (

Haumea Haumea ( minor-planet designation: 136108 Haumea) is a dwarf planet located beyond Neptune's orbit. It was discovered in 2004 by a team headed by Mike Brown of Caltech at the Palomar Observatory, and formally announced in 2005 by a team heade ...

: , Eris: 2.26,

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 Su ...

: 2.03,

Charon In Greek mythology, Charon or Kharon ( ; ) is a psychopomp, the ferryman of the Greek underworld. He carries the souls of those who have been given funeral rites across the rivers Acheron and Styx, which separate the worlds of the living and ...

: 1.65) but significantly more than that of smaller TNOs (e.g. for ). Phorcys has a mass of about . Unless the bodies are

porous Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

, the density is consistent with rock–ice composition, with rock content around 50%. It has been suggested that

tidal forces The tidal force or tide-generating force is the difference in gravitational attraction between different points in a gravitational field, causing bodies to be pulled unevenly and as a result are being stretched towards the attraction. It is the d ...

, together with other potential heat sources (e.g. collisions or ²⁶ Al

decay Decay may refer to: Science and technology * Bit decay, in computing * Decay time (fall time), in electronics * Distance decay, in geography * Software decay, in computing Biology * Decomposition of organic matter * Mitochondrial decay, in g ...

) might have raised the temperature sufficiently to crystallise

amorphous In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid) is a solid that lacks the long-range order that is a characteristic of a crystal. The terms "glass" and "glassy solid" are sometimes used synonymousl ...

ice and reduce the void space inside the object. The same tidal forces could be responsible for the quasi-circular orbits of the components of Ceto. Ceto is listed on Michael Brown's website as possibly a dwarf planet.

Satellite

Ceto's satellite was identified as a

on April 11, 2006, by K. Noll, H. Levison, W. Grundy and D. Stephens using the Hubble Space Telescope; the object was named Phorcys after the Greek sea god, formally (65489) Ceto I. Using an extended definition of a

centaur A centaur ( ; ; ), occasionally hippocentaur, also called Ixionidae (), is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse that was said to live in the mountains of Thessaly. In one version o ...

as an object on a non-resonant (unstable) orbit with its perihelion inside the orbit of Neptune, the Ceto system can be considered the second known binary centaur. Phorcys's diameter has been estimated to be and .

References

External links

* Binary asteroids a
johnstonsarchive
* {{DEFAULTSORT:Ceto 065489 Centaurs (small Solar System bodies) Discoveries by Chad Trujillo Discoveries by Michael E. Brown Named minor planets Binary trans-Neptunian objects 20030322

Physical characteristics

Satellite

See also

References

External links