Sinope (moon)

Sinope /səˈnoʊpiː/ also known as Jupiter IX, is a one of the outermost and larger of irregular satellite of Jupiter.

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]
Spectral type	D [7]
Apparent magnitude	18.3[9]
Absolute magnitude (H)	11.1[6]

Discovery and Naming

Sinope was discovered by Seth Barnes Nicholson at Lick Observatory in 1914. ^[1]

Its 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.

Orbit

The diagram illustrates Sinope's orbital elements in relation to other satellites of the Pasiphae group.

Sinope orbits Jupiter at an average distance of 24,371,650 km km in 777,29 days, at an inclination of about 159° to the ecliptic, in a retrograde direction and with an eccentricity of 0.337. Its orbit is continuously changing due to solar and planetary perturbations.

Sinope belongs to the Pasiphae group, a group of retrograde moons jupiters with semi-major axes spread over 22–25 million km, inclinations between 141° and 158°, and higher eccentricities between 0.22 and 0.44.

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.^[13]

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 about 35 kilometers (Albedo 4,2%). ^[7]

Sinope is pale red in color (colour indices B−V=0.84, R−V=0.46),^[14] 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.^[15] These dissimilarities of the physical parameters suggest a different origin from the core members of the group.

Furthermore, a measured low beam value of 0.82 ± 0.02 indicates that Sinope has considerable surface roughness.^[7]

The rotation period is approximately 13 hours and 9,6 minutes with a peak amplitude of about ∼0.2 magnitudes.^[8]

Origin

Sinope probably did not form near Jupiter but was captured by Jupiter later.Like the other members of the Pasiphae group, which have similar orbits, Sinope is probably the remnant of a broken, captured heliocentric asteroid.

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.^[14]

Aoede, a small irregular moon of Jupiter, has a similar orbit to Sinope and could be a remnant of the latter.^[7]

See also

• Sinope in fiction