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More Moons Around Pluto?
post Dec 1 2005, 03:36 PM
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Paper: astro-ph/0511837

Date: Wed, 30 Nov 2005 19:37:52 GMT (124kb)

Title: New Constraints on Additional Satellites of the Pluto System

Authors: A.J. Steffl, M.J. Mutchler, H.A. Weaver, S.A.Stern, D.D. Durda, D.
Terrell, W.J. Merline, L.A. Young, E.F. Young, M.W. Buie, and J.R. Spencer

Comments: 18 pages including 4 figures
Observations of Pluto and its solar-tidal stability zone were made using the
Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST) on UT
2005 May 15 and UT 2005 May 18. Two small satellites of Pluto, provisionally
designated S/2005 P 1 and S/2005 P 2, were discovered and are reported by
(Weaver et al. 2005). These observations also provide strong constraints on the
existence of any additional satellites of Pluto. We place a 90%-confidence
lower limit of V=26.2 (V=27.1 for a 50%-confidence lower limit) on the
magnitude of undiscovered satellites >5" from Pluto. Assuming an albedo of
p_v=0.04 (similar to cometary nucleii and a reasonable lower limit), this
corresponds to a limiting diameter of 37 km at 90%-confidence (25 km at
50-confidence). For an assumed albedo similar to Charon, i.e p_v=0.38, the
magnitude limit corresponds to a limiting diameter of 12 km at 90%-confidence
(8 km at 50%-confidence). At distances <5" from Pluto, scattered light from
both Pluto and Charon degrades the sensitivity of our search, such that at 1.7"
from Pluto the 50%-confidence magnitude limit is V=25.3, corresponding to a
limiting diameter of 57 km for an object with p_v=0.04.

\\ ( http://arXiv.org/abs/astro-ph/0511837 , 124kb)

"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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Rob Pinnegar
post Dec 7 2005, 02:42 AM
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It's good to see that some abstracts are starting to come out of the two new Plutonian moons.

Not to harp on this too much, but I'm still *really* interested to see how much Charon perturbs their orbits. A few weeks back (in this thread) I tried to figure out a rough estimate of this effect, but my attempt was ridiculously oversimplified as it didn't take into account the rotating frame of reference (as seen from 2005 P1 and P2). It'll be neat to see the real solution.
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post Dec 17 2005, 09:50 PM
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QUOTE (Rob Pinnegar @ Dec 6 2005, 08:42 PM)
Not to harp on this too much, but I'm still *really* interested to see how much Charon perturbs their orbits.

The article in the link and the original one both indicate that the new moons are in resonant orbits with Pluto-Charon and their 6.3 day rotation. They may be in the fourth and sixth harmonic orbits. (I don't have the original article to repeat the calculation.) Whether you can say that Charon "perturbs" the orbit or "regulates" them is semantics, but the system isn't chaotic. As for your simple model, determining how large the libration swings can be would require some real sophistication.
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