Circumbinary Chaos: Using pluto's newest moon to constrain the masses of nix and hydra

Andrew N. Youdin, Kaitlin Kratter, Scott J. Kenyon

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

The Pluto system provides a unique local laboratory for the study of binaries with multiple low-mass companions. In this paper, we study the orbital stability of P4, the most recently discovered moon in the Pluto system. This newfound companion orbits near the plane of the Pluto-Charon (PC) binary, roughly halfway between the two minor moons Nix and Hydra. We use a suite of few body integrations to constrain the masses of Nix and Hydra, and the orbital parameters of P4. For the system to remain stable over the age of the solar system, the masses of Nix and Hydra likely do not exceed 5 × 10 16kg and 9 × 1016kg, respectively. These upper limits assume a fixed mass ratio between Nix and Hydra at the value implied by their median optical brightness. Our study finds that stability is more sensitive to their total mass and that a downward revision of Charon's eccentricity (from our adopted value of 0.0035) is unlikely to significantly affect our conclusions. Our upper limits are an order of magnitude below existing astrometric limits on the masses of Nix and Hydra. For a density at least that of ice, the albedos of Nix and Hydra would exceed 0.3. This constraint implies they are icy, as predicted by giant impact models. Even with these low masses, P4 only remains stable if its eccentricity e ≲ 0.02. The 5:1 commensurability with Charon is particularly unstable, combining stability constraints with the observed mean motion places the preferred orbit for P4 just exterior to the 5:1 resonance. These predictions will be tested when the New Horizons satellite visits Pluto. Based on the results for the PC system, we expect that circumbinary, multi-planet systems will be more widely spaced than their singleton counterparts. Further, circumbinary exoplanets close to the three-body stability boundary, such as those found by Kepler, are less likely to have other companions nearby.

Original languageEnglish (US)
Article number17
JournalAstrophysical Journal
Volume755
Issue number1
DOIs
StatePublished - Aug 10 2012
Externally publishedYes

Fingerprint

Nix
Hydra
Pluto (planet)
Pluto
chaotic dynamics
natural satellites
Charon
Moon
chaos
eccentricity
Pluto satellites
orbits
orbitals
extrasolar planets
albedo
solar system
mass ratios
horizon
planets
brightness

Keywords

  • binaries: general
  • Kuiper Belt objects: individual (Pluto, Charon)
  • planets and satellites: dynamical evolution and stability
  • planets and satellites: formation
  • space vehicles

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Circumbinary Chaos : Using pluto's newest moon to constrain the masses of nix and hydra. / Youdin, Andrew N.; Kratter, Kaitlin; Kenyon, Scott J.

In: Astrophysical Journal, Vol. 755, No. 1, 17, 10.08.2012.

Research output: Contribution to journalArticle

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