(65489) Ceto

Asteroid (65489) Ceto
Properties of the orbit ( animation ) Epoch: 4th September 2017 ( JD 2,458,000.5)
Orbit type	TNO , centaur
Major semi-axis	102.65 AU
eccentricity	0.826
Perihelion - aphelion	17.9061 AU - 187.4 AU
Inclination of the orbit plane	22.3 °
Length of the ascending node	171.9 °
Argument of the periapsis	320.2 °
Time of passage of the perihelion	August 10, 1989
Sidereal period	1040 a 1 M.
Mean orbital velocity	2.299 km / s
Physical Properties
Medium diameter	223 ± 10 km
Dimensions	3.74  ·  10 ¹⁸ kg System 5.41 ± 0.42  ·  10 ¹⁸ kg
Albedo	0.058 ± 0.03
Medium density	1.37 ^+0.66_−0.32 g / cm³
Rotation period	4.43 ± 0.03 h
Absolute brightness	6.2 ± 0.5 mag
Spectral class	BV = 0.86 VR = 0.56
history
Explorer	Michael E. Brown Chadwick A. Trujillo
Date of discovery	March 22, 2003
Another name	2003 FX ₁₂₈
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . The affiliation to an asteroid family is automatically determined from the AstDyS-2 database . Please also note the note on asteroid items.

(65489) Ceto is a Trans-Neptunian object classified as an SDO and a centaur . Since Ceto has a great companion named Phorcys , this system can also be understood as a double asteroid system.

Discovery and naming

Ceto was discovered on March 22, 2003 by a team of astronomers from the California Institute of Technology in Pasadena, consisting of Mike Brown and Chad Trujillo, as part of the NEAT program at the Palomar Observatory . The asteroid was initially given the preliminary designation 2003 FX ₁₂₈ .

On November 23, 2006, together with the Typhon / Echidna and Logos / Zoe systems , Ceto and Phorcys were officially named by the International Astronomical Union (IAU) after the sea monster Keto from Greek mythology , who with her brother Phorkys the Gorgons who Graiai as well as Echidna and Ladon gave birth. She is mainly famous for her monstrous offspring.

After his discovery, Ceto could be dated back to the year 1987 on photos and thus the orbit calculated relatively precisely. Since then, the asteroid and its companion have been observed through various telescopes such as the Hubble , Herschel and Spitzer space telescopes, as well as earth-based telescopes. In January 2018, there were 190 observations on 17 oppositions over a period of 28 years.

properties

Orbit

Orbit of the Ceto-Phorcys system

Ceto and Phorcys orbit the sun on a prograde , highly elliptical orbit between 17.906 AU and 187.4 AU from its center. The orbit eccentricity is 0.826, the orbit is inclined 22.27 ° with respect to the ecliptic . Therefore, the strongly eccentric orbit of the system in its perihelion , which it reached in mid-1989, runs well within the orbit of Uranus , while in aphelion, after about 500 years of traversing the entire Kuiper belt, it is six times the distance of Neptune or 2.4- times Pluto's apheld distance from the sun. Currently, Ceto is about 38.4 AU from the Sun. The system should reach its next perihelion around the year 3029, the orbit period is around 1040 years.

rotation

Ceto rotates around its axis once every 4 hours and 25.8 minutes. From this it follows that it performs 1,993,320 self- rotations (“days”) in a ceto year .

Size / surface

Ceto has a diameter of 223 km, based on an assumed reflectivity of 5.8%. The surface is therefore extremely dark. Its diameter had previously been estimated at 174 km.

internal structure

The binary nature of the system has made it possible to calculate the mass of the system directly, with the mass fraction of ceto in the system being 69.1%. This also provided further information on the internal composition of both components. The density of the system was calculated to be relatively low at 1.37 g / cm³. If the system is not porous inside (→ Rubble Piles ), it consists of a mixture of water ice and rock , with a rock content of around 50%.

It has been hypothesized that tidal forces , along with other potential heat sources (for example, collisions or ²⁶Al - decay ) may have sufficiently raises the temperature, so amorphous ice crystallized and auffüllte the empty spaces in both bodies. The same tidal forces could be responsible for the quasi-circular orbits of the two components.

moon

On September 9, 2006, another team of astronomers headed by Keith S. Noll discovered the Hubble Space Telescope, a natural companion whose diameter is only 23.4% smaller. This system thus shows strong parallels in absolute and relative proportions to the Cubewano - double system Borasisi - Pabu , whose two components, on the other hand, circle around each other at a distance of about 2.5 times greater. Ceto-Phorcys is to be understood as a double asteroid system, comparable with the - officially as such - named system (79360) Sila - Nunam .

Web links

Will M. Grundy et al .: The orbit, mass, size, albedo, and density of (65489) Ceto / Phorcys study from 2007 on Ceto and Phorcys including recordings (PDF, English)
Wm. Robert Johnston: (65489) Ceto and Phorcys
Ceto in listing (Distant Minor Planets) of the Minor Planet Center
How many dwarf planets are there in the outer solar system? List of the largest TNOs by Mike Brown

Individual evidence

↑ Marc W. Buie: Orbit Fit and Astrometric record for 65489. SwRI (Space Science Department), accessed on January 25, 2018 (English).
^ Wm. Robert Johnston: List of Known Trans-Neptunian Objects. Johnston's Archives, December 30, 2017, accessed January 25, 2018 .
↑ v ≈ π * a / period (1 + sqrt (1-e²))
↑ ^a ^b P. Santos-Sanz, E. Lellouch, S. Fornasier, C. Kiss, A. Pal, TG Müller, E. Vilenius, J. Stansberry, M. Mommert, A. Delsanti, M. Mueller, N. Peixinho, F. Henry, JL Ortiz, A. Thirouin, S. Protopapa, R. Duffard, N. Szalai, T. Lim, C. Ejeta et al .: “TNOs are Cool”: A survey of the trans-Neptunian region . IV. Size / albedo characterization of 15 scattered disk and detached objects observed with Herschel-PACS . In: Astronomy and Astrophysics . 541, No. A92, May 2012, p. 18. arxiv : 1202.1481 . bibcode : 2012A & A ... 541A..92S . doi : 10.1051 / 0004-6361 / 201118541 .
↑ (65489) Ceto in the Small-Body Database of the Jet Propulsion Laboratory (English). Retrieved January 25, 2018.
↑ (65489) Ceto at the IAU Minor Planet Center (English). Accessed January 25, 2018.
↑ AstDyS-2. Universita di Pisa, accessed January 25, 2018 .

[Buie-1] Marc W. Buie: Orbit Fit and Astrometric record for 65489. SwRI (Space Science Department), accessed on January 25, 2018 (English).

[johnston-2] Wm. Robert Johnston: List of Known Trans-Neptunian Objects. Johnston's Archives, December 30, 2017, accessed January 25, 2018 .

[MittOrbGesch-3] v ≈ π * a / period (1 + sqrt (1-e²))

[TNOsCool4-4] P. Santos-Sanz, E. Lellouch, S. Fornasier, C. Kiss, A. Pal, TG Müller, E. Vilenius, J. Stansberry, M. Mommert, A. Delsanti, M. Mueller, N. Peixinho, F. Henry, JL Ortiz, A. Thirouin, S. Protopapa, R. Duffard, N. Szalai, T. Lim, C. Ejeta et al .: “TNOs are Cool”: A survey of the trans-Neptunian region . IV. Size / albedo characterization of 15 scattered disk and detached objects observed with Herschel-PACS . In: Astronomy and Astrophysics . 541, No. A92, May 2012, p. 18. arxiv : 1202.1481 . bibcode : 2012A & A ... 541A..92S . doi : 10.1051 / 0004-6361 / 201118541 .

[JPL-5] (65489) Ceto in the Small-Body Database of the Jet Propulsion Laboratory (English). Retrieved January 25, 2018.

[MPC-6] (65489) Ceto at the IAU Minor Planet Center (English). Accessed January 25, 2018.

[AstDyS-7] AstDyS-2. Universita di Pisa, accessed January 25, 2018 .