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New Horizons Captures Two of Pluto's Smaller Moons

nh-nix-hydra-7-21.jpg

Pluto has five known moons. In order of distance from Pluto they are: Charon, Styx, Nix, Kerberos, and Hydra.
While Pluto's largest moon Charon has grabbed most of the lunar spotlight, two of Pluto's smaller and lesser-known satellites are starting to come into focus via new images from the New Horizons spacecraft. Nix and Hydra - the second and third moons to be discovered - are approximately the same size, but their similarity ends there.

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Title: On the existence of regular and irregular outer moons orbiting the Pluto-Charon system
Author: Erez Michaely, Hagai B. Perets, Evgeni Grishin

The dwarf planet Pluto is known to host an extended system of five co-planar satellites. Previous studies have explored the formation and evolution of the system in isolation, neglecting perturbative effects by the Sun. Here we show that secular evolution due to the Sun can strongly affect the evolution of outer satellites and rings in the system, if such exist. Although precession due to extended gravitational potential from the inner Pluto-Charon binary quench such secular evolution up to acrit~0.0035 AU (~0.09 RHill the Hill radius; including all of the currently known satellites), outer orbits can be significantly altered. In particular, we find that co-planar rings and satellites should not exist beyond acrit; rather, satellites and dust particles in these regions secularly evolve on timescales ranging between 104-106 yrs, and quasi-periodically change their inclinations and eccentricities through secular evolution (Lidov-Kozai oscillations). Such oscillations can lead to high inclinations and eccentricities, constraining the range where such satellites (and dust particles) can exist without crossing the orbits of the inner satellites, or crossing the outer Hill stability range. Outer satellites, if such exist are therefore likely to be irregular satellites, with orbits limited to be non-circular and/or highly inclined. These could be potentially detected and probed by the New-Horizon mission, possibly providing direct evidence for the secular evolution of the Pluto satellite system, and shedding new light on its origins.

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Hubble has revealed fascinating new details about Pluto's four smaller moons.
At a distance of five billion km, the telescope only sees the satellites as faint pinpricks of light, and yet it has been able to discern information on their size, colour, and rotational and orbital characteristics.
Hubble finds the little objects to be somewhat chaotic in their behaviour.

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NASA's Hubble Finds Pluto's Moons Tumbling in Absolute Chaos

If you lived on one of Pluto's moons, you might have a hard time determining when, or from which direction, the sun will rise each day. Comprehensive analysis of data from NASA's Hubble Space Telescope shows that two of Pluto's moons, Nix and Hydra, wobble unpredictably.
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Pluto Moons
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Hubble Finds Two Chaotically Tumbling Pluto Moons

Two of the most reliable changes in the sky are the daily rising of the sun in the east and setting of the sun in the west. But if you lived on a couple of Pluto's moons you wouldn't know when the day would begin, or even what direction the sun would rise. That's because, unlike Earth's moon, at least two of Pluto's small moons, Hydra and Nix, are tumbling chaotically through space.
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Title: Orbits of Potential Pluto Satellites and Rings Between Charon and Hydra
Author: Simon B. Porter, S. Alan Stern

Pluto and its five known satellites form a complex dynamic system. Here we explore where additional satellites could exist exterior to Charon (the innermost moon) but interior of Hydra (the outermost). We also provide dynamical constraints for the masses of the known satellites. We show that there are significant stable regions interior of Styx and between Nix and Kerberos. In addition, we show that coorbitals of the known small satellites are stable, even at high inclinations, and discuss mass constraints on undiscovered satellites in such orbits.

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Title: On the Origin of Pluto's Small Satellites by Resonant Transport
Author: W. H. Cheng (HKU), S. J. Peale (UCSB), Man Hoi Lee (HKU)

The orbits of Pluto's four small satellites (Styx, Nix, Kerberos, and Hydra) are nearly circular and coplanar with the orbit of the large satellite Charon, with orbital periods nearly in the ratios 3:1, 4:1, 5:1, and 6:1 with Charon's orbital period. These properties suggest that the small satellites were created during the same impact event that placed Charon in orbit and had been pushed to their current positions by being locked in mean-motion resonances with Charon as Charon's orbit was expanded by tidal interactions with Pluto. Using the Pluto-Charon tidal evolution models developed by Cheng et al. (2014), we show that stable capture and transport of a test particle in multiple resonances at the same mean-motion commensurability is possible at the 5:1, 6:1, and 7:1 commensurabilities, if Pluto's zonal harmonic J2P=0. However, the test particle has significant orbital eccentricity at the end of the tidal evolution of Pluto-Charon in almost all cases, and there are no stable captures and transports at the 3:1 and 4:1 commensurabilities. Furthermore, a non-zero hydrostatic value of J2P destroys the conditions necessary for multiple resonance migration. Simulations with finite but minimal masses of Nix and Hydra also fail to yield any survivors. We conclude that the placing of the small satellites at their current orbital positions by resonant transport is extremely unlikely.

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Pluto May Have 10 Undiscovered Moons

A flotilla of 10 or more tiny undiscovered moons might be in orbit around Pluto, complicating the New Horizon spacecraft's planned flyby of the distant dwarf planet in 2015, new simulations suggest.
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Hubble discovers new Pluto moon

The Hubble Space Telescope has discovered a fifth moon circling the dwarf planet Pluto.
The new moon, visible as a speck of light in Hubble images, is estimated to be irregular in shape and between 10km and 25km across.
Provisionally named S/2012 (134340) 1, or P5, the latest moon was detected in nine separate sets of images taken by Hubble's Wide Field Camera 3 taken during June and July.

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Pluto Has 5th Moon - Hubble Space Telescope Discovers

Astronomers have discovered an irregular shaped moon, between 6 and 15 miles across, circling the dwarf planet on an orbit 59,000 miles in diameter.



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