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Sinope photographed by the Haute-Provence Observatory on 14 August 1998 | |
| Discovery[1] | |
|---|---|
| Discovered by | Seth B. Nicholson |
| Discovery site | Lick Observatory |
| Discovery date | 21 July 1914 |
| Designations | |
Designation | Jupiter IX |
| Pronunciation | /səˈnoʊpiː/[2][3] |
Named after | Σινώπη Sinōpē |
| Adjectives | Sinopean[4] /saɪnəˈpiːən/[5] |
| Orbital characteristics[6] | |
| Epoch 23 March 2018 (JD 2458200.5) | |
| Observation arc | 103.87 yr (37,938 days) |
| 0.1629144 AU (24,371,650 km) | |
| Eccentricity | 0.3366550 |
| –777.29 d (2.13 years) | |
| 71.53524° | |
| 0° 27m 47.33s / day | |
| Inclination | 158.63840° (to ecliptic) |
| 8.61437° | |
| 60.30205° | |
| Satellite of | Jupiter |
| Group | Pasiphae group |
| Physical characteristics | |
| 35.0±0.6 km[7] | |
| 13.16±0.10 h[8] | |
| Albedo | 0.042±0.006[7] |
| 18.3[9] | |
| 11.1[6] | |
Sinope /səˈnoʊpiː/ is a retrograde irregular satellite of Jupiter discovered by Seth Barnes Nicholson at Lick Observatory in 1914,[1] and is named after Sinope of Greek mythology.
Sinope did not receive its present name until 1975;[10][11] before then, it was simply known as Jupiter IX. It was sometimes called "Hades"[12] between 1955 and 1975.

Sinope orbits Jupiter on a high-eccentricity and high-inclination retrograde orbit. Its orbit is continuously changing due to solar and planetary perturbations.[13] Sinope is believed to belong to the Pasiphae group of retrograde irregular moons.[14] However, given its mean inclination and different colour, Sinope could be also an independent object, captured independently, unrelated to the collision and break-up at the origin of the group.[15] The diagram illustrates Sinope's orbital elements in relation to other satellites of the group.
Sinope is also known to be in a secular resonance with Jupiter, similar to Pasiphae. However, Sinope can drop out of this resonance and has periods of both resonant and non-resonant behaviour in time scales of 107 years.[16]

From measurements of its thermal emission, Sinope has an estimated diameter of 35 km (22 mi).[7] Sinope is pale red in color (colour indices V=18.63 B−V=0.84, R−V=0.46),[15] and it falls under the light red color-class, comparable to P-type asteroids and D-type asteroids. This sets it apart from Pasiphae, which is closer to C-type asteroids.
Sinope's infrared spectrum is similar to those of D-type asteroids but different from that of Pasiphae.[17] These dissimilarities of the physical parameters suggest a different origin from the core members of the group.