Sinope , also known as , is a natural satellite or moon of Jupiter. Sinope is one of the outermost irregular satellites of Jupiter, which orbit far from the planet on highly inclined and eccentric orbits. Sinope was discovered by Seth Barnes Nicholson at Mount Wilson Observatory in 1914.

It orbits Jupiter in the retrograde direction—opposite to the direction of the planet's rotation—at an average distance of . Sinope shares similar orbital properties as Jupiter's larger irregular moon Pasipahe, which makes it a member of the Pasiphae group.The moons of the Pasiphae group are a group moons are believed to be fragments of an asteroid or trans-Neptunian object that was gravitationally captured by Jupiter and destroyed by a collision several billion years ago.

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.Grav, T.; Holman, M. J.; Gladman, B. J.; and Aksnes, K.; Photometric Survey of the Irregular Satellites, Icarus, Vol. 166 (2003), pp. 33-45 Most of Sinope 's physical properties are unknown, it to be about 35 km in diameter and its surface is be dark and red.

Discovery and Naming Sinope was discovered by Seth Barnes Nicholson at Lick Observatory in 1914.

It is named after Sinope of Greek mythology. Sinope did not receive its present name until 1975; (in which he declines to name the recently discovered satellites (pp. 93–94))IAUC 2846: Satellites of Jupiter 1974 October (naming the moon) before then, it was simply known as . It was sometimes called "Hades" between 1955 and 1975.

Orbit

The satellite orbits Jupiter at a mean distance of 23.679.300 km and completes one orbit in 741,8 days. Its orbit has an inclination of 159,3° relative to the ecliptic and an eccentricity of 0.269. The orbit is subject to continuous changes due to gravitational perturbation from the Sun and the other planets.

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.

Group membership and origin

Sinope belongs to the Pasiphae group, a group of irregular retrograde Jovian moons. Members of this group have orbits with semimajor axes ranging from approximately 22 to 25 million km, orbital inclinations between 141° and 158°, and relatively high eccentricities ranging from 0.22 to 0.44. The moons of the Pasiphae group are believed to be fragments of an asteroid or trans-Neptunian object that was gravitationally captured by Jupiter and destroyed by a collision several billion years ago.Sheppard, S. S.; Jewitt, D. C.; "An Abundant Population of Small Irregular Satellites Around Jupiter" , Nature, Volume 423 (May 2003), pages 261–263Nesvorný, D.; Alvarellos, J. L. A.; Dones, L.; and Levison, H. F.; "Orbital and Collisional Evolution of the Irregular Satellites", The Astronomical Journal, Volume 126 (2003), pages 398–429

Due to its large size and relatively distinct inclination, Sinope is sometimes considered to be of its own category and different from the other Pasiphae moons. Sinope also has dissimilar spectral features from Pasiphae, further supporting a different origin.

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

Physical characteristics

Measurements of its thermal emission yielded an estimated diameter of approximately 35 km and an albedo of 4.2% for Sinope.. Sinope is one of the larger irregular Jovian moons. The shape of the moon is currently unknown. However, given its small size, Sinope is likely to have an irregular shape, similar to other irregular moons.

In the visible spectrum, Sinope appears is red in color (colour indices B−V=0.84, R−V=0.46). Sinope's infrared spectrum is similar to those of D-type asteroids but different from that of Pasiphae.

Thermal modeling by WISE yielded a beaming parameter of 0.82 ± 0.02, which reflects the moon’s thermal properties and surface characteristics.

The rotation period was found to be approximately 13 hours and 9,6 minutes with a peak amplitude of about ~0.2 magnitudes. The rotation period was regarded by a later paper as uncertain due to the short observation periods.

Exploration Sinope has not been imaged up close by a space probe. All Jupiter irregular moons including Sinope are planned to be distant observation targets for the European Space Agency's Jupiter Icy Moons Explorer (Juice) mission, which will measure the Jupiter irregular moons' rotation periods and shapes by watching their brightness change over time.

See also Sinope in fiction Irregular satellites Other irregular Jovian moons discovered by Seth Barnes Nicholson: Ananke Lysithea Carme

References

External links Sinope Profile by NASA's Solar System Exploration David Jewitt pages Jupiter's Known Satellites (by Scott S. Sheppard) Ephemeris IAU-MPC NSES