Discovery of five irregular moons of Neptune

Holman, Matthew J.; Kavelaars, J. J.; Grav, T.; Gladman, Brett; Fraser, Wesley C.; Milisavljevic, Dan; Nicholson, P. D.; Burns, Joseph A.; Carruba, V.; Petit, Jean-Marc; Rousselot, P.; Mousis, O.; Marsden, B. G.; Jacobson, R. A.

doi:10.1038/nature02832

Cited by 80 publications

(59 citation statements)

References 27 publications

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“…More than 90 irregular moons of the Jovian planets have recently been discovered (Gladman et al 1998(Gladman et al , 2000(Gladman et al , 2001bSheppard & Jewitt 2002Holman et al 2004;Kavelaars et al 2004;Sheppard et al , 2005Sheppard et al , 2006. Unlike regular satellites, the irregular moons revolve around planets at large distances in inclined and eccentric orbits.…”

Section: Introductionmentioning

confidence: 99%

Capture of Irregular Satellites during Planetary Encounters

2007

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More than 90 irregular moons of the Jovian planets have recently been discovered. These moons are an enigmatic part of the solar system inventory. Their origin, which is intimately linked with the origin of the planets themselves, has yet to be adequately explained. Here we investigate the possibility that the irregular moons were captured from the circumsolar planetesimal disk by three-body gravitational reactions. These reactions may have been a frequent occurrence during the time when the outer planets migrated within the planetesimal disk. We propose a new model for the origin of irregular satellites in which these objects are captured from the planetesimal disk during encounters between the outer planets themselves in the model for outer planet migration advocated by Tsiganis and collaborators. Through a series of numerical simulations we show that nearby planetesimals can be deflected into planet-bound orbits during close encounters between planets, and that the overall efficiency of this capture process is large enough to produce populations of observed irregular satellites at Saturn, Uranus, and Neptune. The orbits of captured objects are broadly similar to those of known distant satellites. Jupiter, which typically does not have close encounters with other planets in the model of Tsiganis and coworkers, must have acquired its irregular satellites by a different mechanism. Alternatively, the migration model should be modified to accommodate Jupiter's encounters. Moreover, we find that the original size-frequency distribution of the irregular moons must have significantly evolved by collisions to produce their present populations. Our new model may also provide a plausible explanation for the origin of Neptune's large moon Triton.

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Section: Introductionmentioning

confidence: 99%

Capture of Irregular Satellites during Planetary Encounters

2007

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“…2001; Holman et al 2004;Kavelaars et al 2004;Sheppard & Jewitt 2003;Sheppard et al 2005Sheppard et al , 2006. By 2007, 106 irregular satellites of the giant planets had been discovered, compared with 53 regular satellites.…”

Section: Introductionmentioning

confidence: 99%

Stability of the Distant Satellites of the Giant Planets in the Solar System

Shen¹,

Tremaine²

2008

The Astronomical Journal

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We conduct a systematic survey of the regions in which distant satellites can orbit stably around the four giant planets in the solar system, using orbital integrations of up to 10 9 yr. In contrast to previous investigations, we use a grid of initial conditions on a surface of section to explore phase space uniformly inside and outside the planet's Hill sphere (radius r H ; satellites outside the Hill sphere sometimes are also known as quasi-satellites). Our confirmations and extensions of old results and new findings include the following: (1) many prograde and retrograde satellites can survive out to radii ∼0.5r H and ∼0.7r H , respectively, while some coplanar retrograde satellites of Jupiter and Neptune can survive out to ∼r H ; (2) stable orbits do not exist within the Hill sphere at high ecliptic inclinations when the semimajor axis is large enough that the solar tide is the dominant non-Keplerian perturbation; (3) there is a gap between ∼r H and 2r H in which no stable orbits exist; (4) at distances 2r H stable satellite orbits exist around Jupiter, Uranus, and Neptune (but not Saturn). For Uranus and Neptune, in particular, stable orbits are found at distances as large as ∼10r H ; (5) the differences in the stable zones beyond the Hill sphere arise mainly from differences in the planet/Sun mass ratio and perturbations from other planets; in particular, the absence of stable satellites around Saturn is mainly due to perturbations from Jupiter. It is, therefore, likely that satellites at distances 2r H could survive for the lifetime of the solar system around Uranus, Neptune, and, perhaps, Jupiter.

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“…Triton is one of these irregular satellites, and is the subject of Section 3 due its scientific importance. In addition, Neptune has the 340-km satellite Nereid, and at least six other irregular satellites larger than about 40 km in size (Holman et al, 2004). These captured primitive bodies are thought to originate from the Kuiper Belt, and could provide us with important information about Neptune's history, the collisional processing of captured satellites, and the provenance and evolution of Kuiper Belt Objects (KBOs).…”

Section: Rings and Small Icy Satellitesmentioning

confidence: 99%