Pasiphaë group

The Pasiphaë group is a group of retrograde non-spherical moons of Jupiter that follow similar orbits to Pasiphaë and are thought of have a common origin.

Their semi-major axes (distances from Jupiter) range between 22,800,000 and 24,100,000 km (the same range as the Carme group), their inclinations between 144.5° and 158.3°, and their eccentricities between 0.25 and 0.43.

This diagram illustrates the biggest non-spherical moons of Jupiter. Among the Pasiphaë group, Sinope and Pasiphaë itself are labelled. An object's position on the horizontal axis indicates its distance from Jupiter. The vertical axis indicates its inclination. Eccentricity is indicated by yellow bars illustrating the object's maximum and minimum distances from Jupiter. Circles illustrate an object's size in comparison to the others.

Core members of the group include (from the biggest to the smallest):^[1]

• Pasiphae
• Sinope, two-thirds the size of Pasiphaë
• Callirrhoe
• Megaclite
• Autonoe
• Eurydome
• Sponde

The International Astronomical Union (IAU) reserves names ending in -e for all retrograde moons, including this group's members.

Origin

The Pasiphaë group is believed to have been formed when Jupiter captured an asteroid which broke up after a collision. The original asteroid was not disturbed heavily: the original body is calculated to have been 60 km in diameter, about the same size as Pasiphaë; Pasiphaë has 99% of the original body's mass. However, if Sinope belongs to the group, the amount is much smaller, 87%.^[2]

The differences of colour between the objects (grey for Pasiphaë, light red for Callirrhoe and Megaclite) also suggest that the group could have a more complex origin than a single collision.

This diagram compares the orbital elements and relative sizes of the core members of the Pasiphaë group. The horizontal axis illustrates their average distance from Jupiter, the vertical axis their orbital inclination, and the circles their relative sizes.

This diagram compares the wide dispersion of the Pasiphaë group (red) with the more compact Ananke (blue) and Carme (green) groups.

References

1. Scott S. Sheppard, David C. Jewitt, Carolyn Porco Jupiter's outer satellites and Trojans, In: Jupiter. The planet, satellites and magnetosphere. Edited by Fran Bagenal, Timothy E. Dowling, William B. McKinnon. Cambridge planetary science, Vol. 1, Cambridge, UK: Cambridge University Press, ISBN 0-521-81808-7, 2004, p. 263 - 280 Full text(pdf).
2. Sheppard, Scott S.; Jewitt, David C. (May 5, 2003). "An abundant population of small irregular satellites around Jupiter". Nature. 423 (6937): 261–263. Bibcode:2003Natur.423..261S. doi:10.1038/nature01584. PMID 12748634. S2CID 4424447. However, Nesvorny 2003, while concurring on the Ananke and Carme groups, lists only Megaclithe for Pasiphaë's group