Sinope (moon)

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

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)
Semi-major axis	0.1629144 AU (24,371,650 km)
Eccentricity	0.3366550
Orbital period (sidereal)	–777.29 d (2.13 years)
Mean anomaly	71.53524°
Mean motion	0° 27m 47.33s / day
Inclination	158.63840° (to ecliptic)
Longitude of ascending node	8.61437°
Argument of perihelion	60.30205°
Satellite of	Jupiter
Group	Pasiphae group
Physical characteristics
Mean diameter	35.0±0.6 km[7]
Synodic rotation period	13.16±0.10 h[8]
Albedo	0.042±0.006[7]
Apparent magnitude	18.3[9]
Absolute magnitude (H)	11.1[6]

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.

Orbit

Pasiphae group.

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]

Physical characteristics

Sinope observed by the Wide-field Infrared Survey Explorer (WISE) spacecraft in 2014

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.

See also

• Sinope in fiction