Plutos New Moons Part 2, News ... |
Plutos New Moons Part 2, News ... |
Dec 21 2005, 01:51 PM
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#1
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Member Group: Members Posts: 531 Joined: 24-August 05 Member No.: 471 |
Orbits and photometry of Pluto's satellites: Charon, S/2005 P1 and S/2005 P2
http://arxiv.org/abs/astro-ph/0512491 Orbital periods: Charon - 6.3872304 +/- 0.0000011 days S/2005 P2 - 24.8562 +/- 0.0013 days S/2005 P1 - 38.2065 +/- 0.0014 days Note: The old thread - http://www.unmannedspaceflight.com/index.p...wtopic=1622&hl= -------------------- - blue_scape / Nico -
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Dec 21 2005, 02:18 PM
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#2
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
OK, so I plugged these periods into my calculator and I get:
S/2005 P1 : Charon = 5.9817 : 1 S/2005 P2 : Charon = 3.8915 : 1 That first one is close to a resonant orbit (1:6), but I don't think that "close" counts with resonant orbits, does it? The second one seems pretty far off from 1:4. It seems like it shouldn't be stable to be so close but not quite at a resonant orbit. But then I never studied orbital dynamics so I don't know. --Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Dec 21 2005, 02:51 PM
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#3
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Member Group: Members Posts: 509 Joined: 2-July 05 From: Calgary, Alberta Member No.: 426 |
Yeah, the error bars on those periods are too far off to make resonance very likely.
Something I hadn't thought of before: Pluto-Charon is of course unique in that both bodies are tidally despun. Shouldn't this mean that Charon's orbit would have stopped evolving some time ago? Its semi-major axis should be exactly the same now as it was when Pluto's tidal despinning completed. The two newly discovered moons of course should still be evolving outwards from Pluto, but they may not have had time to reach the 4:1 and 6:1 resonances yet, just as Callisto won't hit the 2:1 with Ganymede for another billion years or so. Maybe they'll get there eventually. I wonder if the system will be stable when they do? (Mind you, the Sun may reach red giant stage before that, at which point all bets are off.) Does anyone know whether the small mass of the Pluto system would retard the outward evolution of moons? Intuitively one would think so, but I'd sooner trust the physics than my intuition. There's room here for a nice little Icarus paper. Wish I had the know-how to do it myself. |
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Dec 21 2005, 03:43 PM
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#4
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Member Group: Members Posts: 509 Joined: 2-July 05 From: Calgary, Alberta Member No.: 426 |
QUOTE (elakdawalla @ Dec 21 2005, 08:18 AM) That first one is close to a resonant orbit (1:6), but I don't think that "close" counts with resonant orbits, does it? Actually, unless I'm very wrong, "close" _can_ actually count, because resonances don't have to involve both bodies coming back to exactly the same locations after a set number of orbits. They can also involve things like the precession of periastron. I think this is called "resonance splitting"? Since the outer Plutonian satellite has a fairly big orbital eccentricity, and is quite close to the "formal" 6:1 resonance, I'm tempted to wonder whether that moon might be caught in one of these. (However, this would of course have been considered by the authors, and since it doesn't show up in the abstract, it's not likely to be true. It's worth mentioning, though.) |
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Dec 21 2005, 03:50 PM
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#5
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
And of course, the ratio doesnt have to be perfect, as whilst the moon orbits the planet, the planet wobbles a little to return the favour, that wobble may take a calculated measurement away from a perfect figure.
Doug |
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Dec 21 2005, 04:10 PM
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#6
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
Paper: astro-ph/0512491
Date: Tue, 20 Dec 2005 00:38:58 GMT (219kb) Title: Orbits and photometry of Pluto's satellites: Charon, S/2005 P1 and S/2005 P2 Authors: M. W. Buie (1), W. M. Grundy (1), E. F. Young (2), L. A. Young (2), and S. A. Stern (2) ((1) Lowell Observatory, (2) Southwest Research Institute) Comments: 21 pages, 5 figures, 4 tables \\ We present new astrometry of Pluto's three satellites from images taken of the Pluto system during 2002-3 with the High Resolution Camera (HRC) mode of the Advanced Camera for Surveys (ACS) instrument on the Hubble Space Telescope. The observations were designed to produce an albedo map of Pluto but they also contain images of Charon and the two recently discovered satellites, S/2005 P1 and S/2005 P2. Orbits fitted to all three satellites are co-planar and, for Charon and P2, have eccentricities consistent with zero. The orbit of the outermost satellite, P1, has a significant eccentricity of 0.0052 +/- 0.0011. Orbital periods of P1, P2, and Charon are 38.2065 +/- 0.0014, 24.8562 +/- 00013, and 6.3872304 +/- 0.0000011 days, respectively. The total system mass based on Charon's orbit is 1.4570 +/- 0.0009 x 10^22 kg. We confirm previous results that orbital periods are close to the ratio of 6:4:1 (P1:P2:Charon) indiciative of mean-motion resonances, but our results formally preclude precise integer period ratios. The orbits of P1 and P2, being about the barycenter rather than Pluto, enable us to measure the Charon/Pluto mass ratio as 0.1165 +/- 0.0055. This new mass ratio implies a density of 1.66 +/- 0.06 g cm^-3 for Charon and 2.03 +/- 0.06 g cm^-3 for Pluto thus adding confirmation that Charon is somewhat under-dense relative to Pluto. Finally, by stacking all images, we can extract globally averaged photometry. P1 has a mean opposition magnitude of V=24.39 +/- 0.02 and color of (B-V) = 0.644 +/- 0.028. P2 has a mean opposition magnitude of V=23.38 +/- 0.02 and color of (B-V) = 0.907 +/- 0.031. The colors indicate that P1 is spectrally neutral and P2 is slightly more red than Pluto. The variation in surface color with radial distance from Pluto is quite striking (red, neutral, red, neutral) and begs further study. \\ ( http://arXiv.org/abs/astro-ph/0512491 , 219kb) -------------------- "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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Dec 21 2005, 04:28 PM
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#7
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
I was about to blog this but realized I don't know how to refer to this paper because I don't quite understand what arXiv is archiving. The layout of the paper looks like it has been submitted to a journal. Which journal? Does its appearance on arXiv mean that it is in prep, in press, or what? Does anybody know?
--Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Dec 21 2005, 05:16 PM
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#8
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Member Group: Members Posts: 624 Joined: 10-August 05 Member No.: 460 |
QUOTE (elakdawalla @ Dec 21 2005, 09:28 AM) I was about to blog this but realized I don't know how to refer to this paper because I don't quite understand what arXiv is archiving. The layout of the paper looks like it has been submitted to a journal. Which journal? Does its appearance on arXiv mean that it is in prep, in press, or what? Does anybody know? --Emily Archives is for 'press ready' papers, allowing the author's to get 'first dibs' on the concept. Peer review is not required, but an author must either be established, or recommended by established authors. In general archive papers are not referenced, and you should contact the authors before extracting or publishing - very often they are awaiting peer review, and sometimes in the notes the authors will list where or when the paper will be published. They are fair game, though, for discussions such as this. I don't know where that puts your blog - right in the middle of gray |
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Dec 21 2005, 07:02 PM
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#9
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Member Group: Members Posts: 509 Joined: 2-July 05 From: Calgary, Alberta Member No.: 426 |
QUOTE (elakdawalla @ Dec 21 2005, 10:28 AM) I was about to blog this but realized I don't know how to refer to this paper because I don't quite understand what arXiv is archiving. Looks like Alan Stern is on the author list. He may be able to answer this for you next time he drops by. |
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Guest_AlexBlackwell_* |
Dec 22 2005, 08:28 PM
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#10
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Guests |
QUOTE (elakdawalla @ Dec 21 2005, 04:28 PM) I was about to blog this but realized I don't know how to refer to this paper because I don't quite understand what arXiv is archiving. The layout of the paper looks like it has been submitted to a journal. Which journal? I'm not sure but I think the paper has been submitted to and/or accepted by The Astrophysical Journal (ApJ), which isn't surprising given the subject matter and the apparent fact that the paper is not under embargo. And a close reading of page 11 of the preprint notes that the authors used a particular LaTeX macro that is typically used to prepare manuscripts for AAS journals.I wouldn't rule out other journals but ApJ or ApJL are safe bets. |
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Dec 23 2005, 05:09 AM
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#11
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
Thanks for the various replies. I decided that it seemed firm enough to blog it. What are blogs for but spreading rumors anyway?
--Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Dec 23 2005, 08:28 AM
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#12
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
At the risk of piquing the ire of some, does anybody think that these new moons will influence the IAU's decision about Pluto's planetary status (to say nothing of 2003UB313?)...
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Dec 23 2005, 12:50 PM
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#13
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Member Group: Members Posts: 529 Joined: 19-February 05 Member No.: 173 |
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Guest_AlexBlackwell_* |
Dec 23 2005, 03:57 PM
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#14
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Guests |
QUOTE (Alan Stern @ Dec 23 2005, 12:50 PM) One usually refers to the paper as submitted to the archival journal it will be published in. In this case, AJ, The Astronomical Journal. Yeah, that's the one I meant, Alan I always mix up the alphabet soup listing of astronomical and astrophysical journals (e.g., ApJ, ApJL, AJ, etc.).EDIT: Note the paper is listed as a submission on AJ's "Future Articles" webpage. This post has been edited by AlexBlackwell: Dec 23 2005, 06:54 PM |
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Dec 26 2005, 06:14 PM
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#15
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
Paper: astro-ph/0512599
Date: Fri, 23 Dec 2005 13:42:57 GMT (311kb) Title: Characteristics and Origin of the Quadruple System at Pluto Authors: S.A. Stern, H.A. Weaver, A.J. Steffl, M.J. Mutchler, W.J. Merline, M.W. Buie, E.F. Young, L.A. Young, & J.R. Spencer Comments: 15 pages, 1 figure \\ Our discovery of two new satellites of Pluto, designated S/2005 P 1 and S/2005 P 2 (henceforth, P1 and P2), combined with the constraints on the absence of more distant satellites of Pluto, reveal that Pluto and its moons comprise an unusual, highly compact, quadruple system. The two newly discovered satellites of Pluto have masses that are very small compared to both Pluto and Charon, creating a striking planet-satellite system architecture. These facts naturally raise the question of how this puzzling satellite system came to be. Here we show that P1 and P2's proximity to Pluto and Charon, along with their apparent locations in high-order mean-motion resonances, likely result from their being constructed from Plutonian collisional ejecta. We argue that variable optical depth dust-ice rings form sporadically in the Pluto system, and that rich satellite systems may be found, perhaps frequently, around other large Kuiper Belt objects. \\ ( http://arXiv.org/abs/astro-ph/0512599 , 311kb) -------------------- "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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