 Hubble Space Telescope image of Ceto and Phorcys, taken in 2006 | |
| Discovery | |
|---|---|
| Discovered by | C. A. Trujillo andM. Brown |
| Discovery site | Palomar |
| Discovery date | 22 March 2003 |
| Designations | |
| (65489) Ceto | |
| Pronunciation | /ˈsiːtoʊ/ |
Named after | Ceto |
| 2003 FX128 | |
| TNO Centaur–extended[1] | |
| Adjectives | Cetoan/siːˈtoʊən/ or Cetoian/siːˈtoʊ.iən/ |
| Orbital characteristics[2] | |
| Epoch 13 January 2016 (JD 2457400.5) | |
| Uncertainty parameter 2 | |
| Observation arc | 9239 days (25.30 yr) |
| Aphelion | 187.74 AU (28.086 Tm) |
| Perihelion | 17.8498 AU (2.67029 Tm) |
| 102.79 AU (15.377 Tm) | |
| Eccentricity | 0.82635 |
| 1042.22yr (380669.7d) | |
| 9.1219° | |
| 0.00094570°/day | |
| Inclination | 22.266° |
| 171.85° | |
| 320.086° | |
| Knownsatellites | Phorcys/ˈfɔːrsɪs/ (171±10[3] ~132+6 −14 km[4] in diameter) |
| Earth MOID | 16.895 AU (2.5275 Tm) |
| Jupiter MOID | 12.7433 AU (1.90637 Tm) |
| Physical characteristics | |
| Dimensions | 223±10 km[3] 174+16 −18 km[4] |
| Mass | (5.4±0.4)×1018 kg (system)[4] |
Meandensity | 1.37 g/cm3 (system)[4] |
Equatorialsurface gravity | 3.3 cm/s2[4] |
| 4.43 h (0.185 d) | |
| 0.056±0.006[3] 0.084±0.02[4] | |
| 6.54±0.06,[3] 6.4[2] | |
65489 Ceto, as a binary also(65489) Ceto–Phorcys[4] (provisional designation2003 FX128), is abinarytrans-Neptunian object (TNO) discovered on March 22, 2003, byChad A. Trujillo andMichael Brown atPalomar. It is named after the sea goddessCeto from Greek mythology. It came toperihelion in 1989.[2]
Ceto is an example of a close binary TNO system in which the components are of similar size. Combined observations with the infraredSpitzer Space Telescope and theHubble Space Telescope allow the diameter of Ceto itself to be estimated at174+16
−18 km and the diameter of Phorcys at132+6
−14 km, assuming equalalbedo for both components.[4]
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 estimateddensity of Ceto is1.37+0.66
−0.32 g/cm3, significantly less than that of the large TNOs (Haumea:3.0 g/cm3,Eris: 2.26,Pluto: 2.03,Charon: 1.65) but significantly more than that of smaller TNOs (e.g.0.7 g/cm3 for(26308) 1998 SM165). Phorcys has a mass of about1.67×1018 kg.[4] Unless the bodies areporous, the density is consistent with rock–ice composition, with rock content around 50%.[4]
It has been suggested thattidal forces, together with other potential heat sources (e.g. collisions or26Aldecay) might have raised the temperature sufficiently to crystalliseamorphous 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.[4]
| Discovery | |
|---|---|
| Discovered by | Keith S. Nollet al. |
| Discovery date | 2006 April 11 |
| Designations | |
| Pronunciation | /ˈfɔːrsɪs/ |
Named after | Phorcys |
| (65489) Ceto I | |
| Adjectives | Phorcynian/fɔːrˈsɪniən/,[5] Phorcyan/ˈfɔːrsiən/[6][7] |
| Orbital characteristics | |
| Satellite of | Ceto |
| Physical characteristics[8] | |
| Dimensions | 171±10[3] 132+6 −14 km.[4] primary/secondary ratio0.76±0.01 |
| ΔM =0.56±0.03 | |
Ceto's satellite was identified as abinary on April 11, 2006, by K. Noll, H. Levison, W. Grundy and D. Stephens using the Hubble Space Telescope; the object was namedPhorcys afterthe Greek sea god, formally(65489) Ceto I. Using an extended definition of acentaur as an object on a non-resonant (unstable) orbit with its perihelion inside the orbit of Neptune,[9]the Ceto system can be considered the second known binary centaur.[4]
Phorcys's diameter has been estimated to be171±10[3] and132+6
−14 km.[4]
