Sinope (moon)

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Discovered by S. B. Nicholson
Discovery date July 21, 1914
Orbital characteristics
Periapsis 18,237,600 km
Apoapsis 30,191,200 km
Mean orbit radius
23,540,000 km[1]
Eccentricity 0.25[1]
724.1 d (1.95 a)[1]
2.252 km/s
Inclination 128.11° (to the ecliptic)
153.12° (to Jupiter's equator)[1]
Satellite of Jupiter
Physical characteristics
Mean radius
~19 km[2][3]
Volume ~28,700 km3
Mass 7.5×1016 kg
Mean density
2.6 g/cm3 (assumed)[2]
0.014 m/s2 (0.001 g)
~0.023 km/s
Albedo 0.04 (assumed)[2][3]
Temperature ~124 K

Sinope (/sɪˈnpi/ si-NOH-pee;[4] Greek: Σινώπη) is a retrograde irregular satellite of Jupiter discovered by Seth Barnes Nicholson at Lick Observatory in 1914,[5] and is named after Sinope of Greek mythology.

Sinope did not receive its present name until 1975;[6][7] before then, it was simply known as Jupiter IX. It was sometimes called "Hades"[8] between 1955 and 1975.

Sinope was the outermost known moon of Jupiter until the discovery of Megaclite in 2000. The most distant moon of Jupiter now known is S/2003 J 2.


Pasiphae group.

Sinope orbits Jupiter on a high-eccentricity and high-inclination retrograde orbit. The orbital elements are as of January 2000.[1] They are continuously changing due to solar and planetary perturbations. It is often believed to belong to the Pasiphae group.[3] 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.[9] 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.[10]

Physical characteristics[edit]

Sinope has an estimated diameter of 38 km (assuming an albedo of 0.04)[3] Sinope is red (colour indices B−V=0.84, R−V=0.46),[9] unlike Pasiphae, which is grey.

Sinope's infrared spectrum is similar to those of D-type asteroids but different from that of Pasiphae.[11] These dissimilarities of the physical parameters suggest a different origin from the core members of the group.

See also[edit]


  1. ^ a b c d e Jacobson, R. A. (2000). "The Orbits of the Outer Jovian Satellites". Astronomical Journal. 120 (5): 2679–2686. Bibcode:2000AJ....120.2679J. doi:10.1086/316817. 
  2. ^ a b c "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 2008-10-24. Retrieved 2008-12-12. 
  3. ^ a b c d Sheppard, S. S.; and Jewitt, D. C.; An Abundant Population of Small Irregular Satellites Around Jupiter, Nature, Vol. 423 (May 2003), pp. 261-263
  4. ^
  5. ^ Nicholson, S. B. (1914). "Discovery of the Ninth Satellite of Jupiter". Publications of the Astronomical Society of the Pacific. 26: 197–198. Bibcode:1914PASP...26..197N. doi:10.1086/122336. PMC 1090718Freely accessible. 
  6. ^ Nicholson, S. B. (April 1939). "The Satellites of Jupiter". Publications of the Astronomical Society of the Pacific. 51 (300): 85–94. Bibcode:1939PASP...51...85N. doi:10.1086/125010.  (in which he declines to name the recently discovered satellites (pp. 93–94))
  7. ^ IAUC 2846: Satellites of Jupiter 1974 October (naming the moon)
  8. ^ Payne-Gaposchkin, Cecilia; Katherine Haramundanis (1970). Introduction to Astronomy. Englewood Cliffs, N.J.: Prentice-Hall. ISBN 0-13-478107-4. 
  9. ^ a b Grav, T.; Holman, M. J.; Gladman, B. J.; and Aksnes, K.; Photometric Survey of the Irregular Satellites, Icarus, Vol. 166 (2003), pp. 33-45
  10. ^ Nesvorný, D.; Beaugé, C. & Dones, L. (2004). "Collisional Origin of Families of Irregular Satellites". The Astronomical Journal. 127 (3): 1768–1783. Bibcode:2004AJ....127.1768N. doi:10.1086/382099. 
  11. ^ Grav, T.; Holman, M. J. (2004). "Near-Infrared Photometry of the Irregular Satellites of Jupiter and Saturn". The Astrophysical Journal. 605 (2): L141–L144. arXiv:astro-ph/0312571Freely accessible. Bibcode:2004ApJ...605L.141G. doi:10.1086/420881. 

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