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More Moons Around Pluto?
Rob Pinnegar
post Nov 4 2005, 07:33 PM
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QUOTE (tty @ Nov 4 2005, 12:59 PM)
Hmm... I didn't know that and so apparently didn't Robert Heinlein. The big quake in "Farmer in the sky" happened when all 4 galileans lined up.

Callisto can line up with two of the other three, but the last one will always be out of place.
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JRehling
post Nov 4 2005, 07:36 PM
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QUOTE (Rob Pinnegar @ Nov 4 2005, 12:33 PM)
Callisto can line up with two of the other three, but the last one will always be out of place.
*


I don't know the details of the Heinlein story, but of course the Galileans can also all line up... but with one of them on the other side of Jupiter. We can also presume that the Galileans were capable of aligning on the same side of Jupiter in the past, before the synchrony was established. Finally, it is possible for all four Galileans to be within 180 degrees of each other, and have it be that from Earth they would appear to be on the same side of Jupiter.
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dvandorn
post Nov 4 2005, 07:39 PM
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Interesting. I always knew, at some level, that the image from "2001" showing all of Jupiter's moons aligned in a string with the planet itself wasn't possible...

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mike
post Nov 4 2005, 08:23 PM
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Yeah, but aligned spheres in space are part of what made 2001 such a great movie. smile.gif Movies like that are very rarely made, sadly..
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tasp
post Nov 4 2005, 10:42 PM
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QUOTE (mike @ Nov 4 2005, 08:23 PM)
Yeah, but aligned spheres in space are part of what made 2001 such a great movie.  smile.gif  Movies like that are very rarely made, sadly..
*



Would a hpothetical observer on Pluto become bored with a too clock like moon parade? Funny to look at it that way, but 'forbidden' configurations of resonant satellites kinda takes some of the pizzaz out of it.

Even if it simplifies NH mission design.
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JRehling
post Nov 4 2005, 11:52 PM
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QUOTE (tasp @ Nov 4 2005, 03:42 PM)
Would a hpothetical observer on Pluto become bored with a too clock like moon parade?  Funny to look at it that way, but 'forbidden' configurations of resonant satellites kinda takes some of the pizzaz out of it.

Even if it simplifies NH mission design.
*


Of course, because Pluto's rotation is locked on Charon, that means there is no apparent motion of Charon, although if these outer moons tug at Charon a bit, there may be slight motion of Charon WRT Pluto. In fact, note that there was, years ago, some evidence that Charon's orbit was somewhat elliptical, which had prompted the hypothesis that a recent impact may have caused it. It remains to be seen if the smaller moons may have tugged Charon into a slightly elliptical orbit.
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Gsnorgathon
post Nov 5 2005, 02:00 AM
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All this talk of resonance and opposition surges makes me wonder - are the masses of the two moons enough to result in any geological activity on any of the four bodies in the Pluto system?

I'm also wondering - I know the new moons were imaged in 2002; is there any chance that they show up in any of the data from the 1985 - 1990 Pluto/Charon mutual occulatations? My first guess is they'd be buried in the noise, but hope springs eternal.
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tasp
post Nov 5 2005, 03:29 AM
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QUOTE (Gsnorgathon @ Nov 5 2005, 02:00 AM)
All this talk of resonance and opposition surges makes me wonder - are the masses of the two moons enough to result in any geological activity on any of the four bodies in the Pluto system?

I'm also wondering - I know the new moons were imaged in 2002; is there any chance that they show up in any of the data from the 1985 - 1990 Pluto/Charon mutual occulatations? My first guess is they'd be buried in the noise, but hope springs eternal.
*



Yes, excellent point, the mutual occultation data may show something IF the observations, sync-ed to Charon, happened to sync up with the 2 'outies'.

Now, how everything was 'phased' out in that time period is a big???

Any data though would reveal diameter and oblateness, help pin down i and e, and perhaps mutual perturbations (if they occur in resonant relationships, if they are resonant) that might help derive masses for the two little guys. If you get diameter, you can figure albedo too. Color data during a mutual event would be great for narrowing down surface composition.

I believe data was taken as Pluto eclipsed Charon, and vice versa. How much data was recorded in between, I dunno.

Stellar occultation data from that time may show something too, if we get lucky, and the more data to go through, the better the chances get.
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Rob Pinnegar
post Nov 6 2005, 03:24 PM
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QUOTE (tasp @ Nov 4 2005, 09:29 PM)
Yes, excellent point, the mutual occultation data may show something IF the observations, sync-ed to Charon, happened to sync up with the 2 'outies'...

Ummm... I could be wrong about this, but doesn't that occultation data consist of measurements of the Pluto-Charon system's apparent magnitude, rather than images?
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tasp
post Nov 6 2005, 06:19 PM
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QUOTE (Rob Pinnegar @ Nov 6 2005, 03:24 PM)
Ummm... I could be wrong about this, but doesn't that occultation data consist of measurements of the Pluto-Charon system's apparent magnitude, rather than images?
*



Yes, and if one of the two new guys pops into or out of either Pluto or Charon's shadow, or if either transits Pluto or Charon, the brightness of the whole system changes.

Amazing if we have such data on hand waiting to be analyzed.
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Rob Pinnegar
post Nov 6 2005, 07:23 PM
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QUOTE (Gsnorgathon @ Nov 4 2005, 08:00 PM)
All this talk of resonance and opposition surges makes me wonder - are the masses of the two moons enough to result in any geological activity on any of the four bodies in the Pluto system?

Well, maybe. After a bit of looking, I found an equation that gives an estimate of the total rate of tidal energy dissipation in a satellite in an elliptical orbit about a planet (Murray and Dermott's book, page 173). Using e=0.0076 and assuming that Pluto and Charon's bulk physical characteristics are similar to Triton's, I get dE/dt~7*10^7 watts for Charon.

Comparing this with the predicted wattage for a few other moons, given in the same reference (keep in mind that this is total power over the whole satellite, not power pound-for-pound):

3e12: Io
1e11: Europa
4e10: Titan
3e08: The Moon, Mimas
7e07: Charon
2e07: Ariel
1e07: Enceladus
3e06: Miranda

It's fairly evident that this equation isn't infallible, since it predicts that Mimas should be more active than Enceladus; of course, that's ignoring secular changes in eccentricity (and probably a lot of other things too).
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tasp
post Nov 7 2005, 04:21 AM
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QUOTE (tasp @ Nov 6 2005, 06:19 PM)
Yes, and if one of the two new guys pops into or out of  either Pluto or Charon's shadow, or if either transits Pluto or Charon, the brightness of the whole system changes.

Amazing if we have such data on hand waiting to be analyzed.
*



Left out something:

It may be possible for either or both new objects to cast a shadow on Pluto or Charon, at various times during the Plutonian year. An observer on Pluto in the shadow would be experiencing a total solar eclipse. (I worked this out in my head, think both satellites should be large enough to eclipse sun). From earth's vantage point, the object casting the shadow upon Pluto (or Charon) would not necessarily simultaneously transit the disk of Pluto (or Charon).

But at some point it could. (I'm getting dizzy watching this happen in my head, yoiks)
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Rob Pinnegar
post Nov 7 2005, 05:36 PM
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QUOTE (tasp @ Nov 6 2005, 10:21 PM)
It may be possible for either or both new objects to cast a shadow on Pluto or Charon, at various times during the Plutonian year.

Yup... and if their orbits are coplanar with Charon's, the next set of eclipses of this type should start in about a hundred and ten years.
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ljk4-1
post Nov 7 2005, 10:19 PM
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QUOTE (Rob Pinnegar @ Nov 7 2005, 12:36 PM)
Yup... and if their orbits are coplanar with Charon's, the next set of eclipses of this type should start in about a hundred and ten years.
*


Has anyone gone back in the astronomical records to see if Pluto's two "new" moons were imaged before this year?

I know that was the case with Charon going back to 1965 at least and for Pluto going back to 1915 or so.

While I am wondering, if there are other KBOs out there bigger than Pluto, and assuming they are not ridiculously far away, how did they escape detection before 1992? Or do some of them also exist on older astrophotos hidden away in some dusty file cabinet of some university observatory?


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alan
post Nov 7 2005, 11:15 PM
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The last three large KBO's found were later found (precovered is the term used) on plates from the 50's taken as part of the Deep Sky Survey.
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