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More Moons Around Pluto?
David
post Nov 7 2005, 11:54 PM
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QUOTE (ljk4-1 @ Nov 7 2005, 10:19 PM)
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.
*


This sort of thing is apparently the rule for "newly-discovered" bodies, rather than the exception. Uranus, discovered in 1781 by Herschel, was first recorded in 1690 by Flamsteed. Neptune, discovered in 1846 by Galle, was first sighted as early as 1613 by Galileo! I don't know if Ceres appears on any astronomical charts before 1801, but I wouldn't be surprised.
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Rob Pinnegar
post Nov 8 2005, 01:20 AM
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QUOTE (David @ Nov 7 2005, 05:54 PM)
This sort of thing is apparently the rule for "newly-discovered" bodies, rather than the exception. 

Depends how bright they are, of course. It's not surprising that bodies like Uranus, being of the sixth magnitude, would show up in a few star charts (actually, one would think that Vesta should have made a few appearances, too). But once you get a few magnitudes below the limit of naked-eye visibility, there are so many stars that a practical limit to what can be catalogued by hand starts rearing its ugly head.

By the 1840's, astronomical photography started getting to be pretty decent in quality; this is the reason for the big spike in asteroid discoveries that happened at about the same time Neptune was found. For bodies like Pluto, "Xena" and most of the asteroids out there, this would be the farthest back we could reasonably expect to find records of their positions. (Galileo's recording of Neptune really is an amazing coincidence.)
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Guest_BruceMoomaw_*
post Nov 8 2005, 02:01 AM
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Well, Chiron (NOT Charon), after its 1977 discovery, turned up on photographic plates going all the way back to 1895!
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Comga
post Nov 8 2005, 04:14 AM
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QUOTE (David @ Nov 7 2005, 05:54 PM)
This sort of thing is apparently the rule for "newly-discovered" bodies, rather than the exception.  Uranus, discovered in 1781 by Herschel, was first recorded in 1690 by Flamsteed.  Neptune, discovered in 1846 by Galle, was first sighted as early as 1613 by Galileo!  I don't know if Ceres appears on any astronomical charts before 1801, but I wouldn't be surprised.
*


From
http://www.boulder.swri.edu/plutonews/

the new moons are 23rd magnitude and 23.5 or so, more than a factor of 100 less bright than Pluto, and lie less than three arc-second from Pluto. Perhaps only Hubble can resolve them. However, from the same web site

Marc Buie and Eliot Young located faint images of both satellites in HST ACS data taken for a Pluto mapping project they spearheaded in 2002.

So yes, they have been "precovered" but only from another dedicated Hubble search using the Advanced Camera for Surveys. It would seem unlikley that they will be found in any other archive.

As to finding old data on eclipses, Elliot Young may have been one of those involved with the Charon-Pluto mutual occultations some time ago or so, when the Earth passed through the plane of their mutual orbits. If there is data for the little moons there, there, he would be the one to find it. On the other hand the moons are about 5% the diameter of Pluto. Assuming similar albedos, the decrease in brightness would be a part in 400. It would be hard to believe that such a small change would have been resolvable, even if they had been watching between the mutual events, whose timing was well known.
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tasp
post Nov 9 2005, 01:25 AM
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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..... (sorry zorched the quote, T)
*



Wow! What a good question!

Pluto and Charon are known to have differing surface compositions, Pluto more methane, Charon more water ice.

Consider Io, depleted of light elements, presumably from tidal heating effects.

And now we are looking at Charon, seemingly depleted of a more volatile compound compared to nearby Pluto.

Seems reasonable that by what ever process created Charon, it was not in tide lock at inception. As Pluto and Charon tidally interacted, power dissapated in Charon 'boiled' off the methane. Also, I think Charon would have receded from Pluto while this was occuring (Pluto not tide locked to Charon at that time either, and it would have accelerated Charon in its orbit as earth is doing to our moon even now). While Charon is receding from Pluto, its' resonances will move outward with it and "snag" outer satellites as we now observe.

All this seems to fit together, resonant orbits, tide locking, tidal recession, and surface chemistry.

That was a really good question, Gsnorgathon.
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JRehling
post Nov 9 2005, 04:16 AM
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QUOTE (David @ Nov 7 2005, 04:54 PM)
This sort of thing is apparently the rule for "newly-discovered" bodies, rather than the exception.  Uranus, discovered in 1781 by Herschel, was first recorded in 1690 by Flamsteed.  Neptune, discovered in 1846 by Galle, was first sighted as early as 1613 by Galileo!  I don't know if Ceres appears on any astronomical charts before 1801, but I wouldn't be surprised.
*


Historians need not take note, but as an amateur, I spotted Vesta when it was very near Venus, and only much later realized that it was Vesta. Thank heavens for the ecliptic, making those coincidences likely.
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tasp
post Nov 9 2005, 05:09 AM
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Additional:

Perhaps the Io analogy needs to be pressed a little further. A tidal effect sufficient to 'demethanize' Charon should leave a lasting relic on the presumably now permanently frozen surface.

The phrase 'widespread and recurrent {methane} volcanism' in regards to Charon springs to mind. Once the tidal effects died down, Charon would have froze up and preserved the geological manifestations of this period.

Geysers or volcanoes? Tar pits or artesian springs?

What would such a modified object look like?
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edstrick
post Nov 9 2005, 07:39 AM
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Tasp: "The phrase 'widespread and recurrent {methane} volcanism' in regards to Charon springs to mind. Once the tidal effects died down, Charon would have froze up and preserved the geological manifestations of this period."

Before Cassen, Reynolds and Peale use dthe phrase "widespread and recurrent volcanism" to predict the result of tidal heating on Io in an abstract and then paper published shortly before Voyager 1 blew us away with "Plumes and Pizza", the most reasonable model of Io's strange colors and spectral properties and observed sodium torus was a model of early volcanic activity with significant water leaching salts to the surface, depositing them in vast salt-flats, followed by loss of the water and geologic "shut-down". It was perfectly reasonable till CR&P predicted just how bogglaceous the tidal heating might be.
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Gsnorgathon
post Nov 11 2005, 01:24 AM
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QUOTE (tasp @ Nov 9 2005, 01:25 AM)
[snip]

That was a really good question, Gsnorgathon.
*

Aww, shucks! Thanks, tasp. One of my main contributions to maintaining the site's high signal to noise ratio is not posting, but occasionally I can at least think of something interesting to ask!

Re: Vesta: A quick googling indicates that Vesta is only visible to the naked eye *sometimes*. Does anyone have an idea how much of the time that would be? And if there are any even dubious claims of pre-telescopic sightings?

Galileo's seeing Neptune in 1613 has made me wonder if there's a comprehensive listing somewhere of discoveries that includes an "earliest known observation" column along with the "discovery" column.
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odave
post Nov 11 2005, 03:46 AM
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QUOTE (Gsnorgathon @ Nov 10 2005, 08:24 PM)
Re: Vesta: A quick googling indicates that Vesta is only visible to the naked eye *sometimes*. Does anyone have an idea how much of the time that would be?
*


I did a quickie run through with my older version of "The Sky", considering magnitudes of less than 6 as naked eye:

Mag Date
----- ------------
5.40 14-Jul-2000
5.87 27-Mar-2003
5.44 01-Jun-2007
5.63 05-Aug-2011
5.74 15-Apr-2014
5.33 20-Jun-2018
5.85 23-Aug-2022

So it looks like Vesta could be reasonably "naked eye" every 3 to 4 years, given good eyes and a fairly dark site.


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ljk4-1
post Nov 12 2005, 04:00 AM
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Contact: Carolina Martinez (818) 354-9382

News Release: 2005-163

November 11, 2005

Free Lectures on Exploring Pluto

Two free public programs in Pasadena will offer an overview of the upcoming NASA mission to Pluto. Pluto is the only planet in our solar system not yet studied by a robotic explorer, but not for long.

Dr. Bonnie Buratti, a New Horizons science team co-investigator from NASA's Jet Propulsion Laboratory, Pasadena, Calif., will talk about the mission on Thursday evening, Nov. 17, at JPL and on Friday evening, Nov. 18, at Pasadena City College.

Now at the NASA Kennedy Space Center in Florida, the spacecraft is scheduled for launch on Jan. 11, 2006. JPL will provide the communications coverage for the mission via NASA’s Deep Space Network.

Buratti’s major interest is in whether there has been geologic activity on Pluto in the recent past and whether Pluto has seasons. She is also interested in the surface composition and texture of Pluto and the Kuiper Belt Objects, millions of asteroid-like bodies from outside the orbit of Pluto, which scientists hope to observe.

A native of Pennsylvania, she holds a bachelor's degree in earth and planetary sciences from the Massachusetts Institute of Technology, Cambridge, Mass., and a Ph.D. in astronomy and space sciences from Cornell University in Ithaca, N.Y. She is currently a science team member on the Cassini-Huygens mission to Saturn.

NASA's New Horizons mission will be the first to visit Pluto and its largest moon, Charon. The compact spacecraft carries seven science instruments for examining the geology, composition, surface, temperature and atmospheric structure of the planet and its main moon. The science team is studying whether New Horizons will be able to obtain data on the two recently discovered smaller moons of Pluto. The Johns Hopkins Applied Physics Laboratory in Laurel, Md., manages the mission and will operate the spacecraft for NASA.

Both lectures will begin at 7 p.m. Seating is first-come, first-served. The Thursday lecture will be in JPL's von Karman Auditorium. JPL is at 4800 Oak Grove Dr., off the Oak Grove Drive exit of the 210 (Foothill) Freeway. The Friday lecture will be in Pasadena City College's Vosloh Forum, 1570 E. Colorado Blvd. For more information, call (818) 354-0112.


Thursday's lecture will be webcast live at

http://www.jpl.nasa.gov/events/lectures/nov05.cfm


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JRehling
post Nov 12 2005, 06:05 AM
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QUOTE (Gsnorgathon @ Nov 10 2005, 06:24 PM)
Re: Vesta: A quick googling indicates that Vesta is only visible to the naked eye *sometimes*. Does anyone have an idea how much of the time that would be? And if there are any even dubious claims of pre-telescopic sightings?
*


Vesta would have been a better possibility than Uranus, most likely. It moves much faster in the sky. On the other hand, it also fades out, while Uranus is almost constant in its dim visibility, which I have seen just once without a telescope -- but I of course knew where to look.

Musings I did years ago on Uranus concluded that almost certainly no one discovered it before, and I would submit the same of Vesta. Essentially, someone would have had to compile a star map of stars down to the 6th magnitude with careful noting of the positions. They could have simply commited to memory a very small part of the sky, yes, and gotten lucky, but the rigor would still have been necessary. The sky is very crowded with 6th magnitude objects.

Of course, we'll never be able to prove that it didn't happen sans "publication", not once but thousands of times. Maybe some shepherd looked up and picked a random corner of the sky, memorized it, and noticed the next time that it had changed. In fact, perhaps an owl discovered Uranus/Vesta. We'll never know.
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tasp
post Nov 12 2005, 03:17 PM
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How conclusively do the occulatation derived studies of Pluto and Charon rule out rings around either object?

Discussion:

My thinking is, for the portion of the data derived when Pluto and Charon were directly aligned (center line of both bodies aligned with earth), the possible rings would have been exactly edge on to us and far below the resolving power of the occultation technique.

As the alignment of Pluto and Charon approach and recede from this condition, however, any rings would have been more open to our view, and would have affected the data being taken.

Noticeably?

Bright rings should have 'skewed' the light curves, but what about dark Uranian style rings?

Would the effect have been just a subtle darkening of the disk to either side of the center line? Would this have been noted?

The possible rings of either object would start ingress well ahead of the disk of the respective body, but this would have started as much as the length of time of the main occultation itself. Since the occultations occured every ~6 1/3 days, and this was known to high accuracy, would anyone have started data collection that far in advance?

Additional:

Would long term stability of rings around Pluto be more likely considering such rings would have resonances across their width from Charon? (and to a lesser extent from the new moons) Such 'curbs' may have restrained material from processes that tend to dissipate rings (such as dynamical ring spreading) and left them for us to discover.

Would dark tenuous rings be excluded by the existing stellar occultation data? I have no info on the geometry of those encounters, and I don't know if there were more than 2 or 3 recorded.

So do we have a 'toe in the door' to hope for rings in the Plutonian system?
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Comga
post Nov 12 2005, 09:52 PM
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QUOTE (tasp @ Nov 12 2005, 09:17 AM)
How conclusively do the occulatation derived studies of Pluto and Charon rule out rings around either object?

My thinking is, for the portion of the data derived when Pluto and Charon were directly aligned (center line of both bodies aligned with earth), the possible rings would have been exactly edge on to us and far below the resolving power of the occultation technique.

Would dark tenuous rings be excluded by the existing stellar occultation data?  I have no info on the geometry of those encounters, and I don't know if there were more than 2 or 3 recorded. 

So do we have a 'toe in the door' to hope for rings in the Plutonian system?
*


There are others who have read the papers by Young et al and know more about this than I do, but the basic geometry of the occultations is where the Earth passes through the plane of the oribit of Charon and Pluto about their mutual center of mass. Any rings would almost have to be in the same plane, and edge on during the occultation, just as you say. If so, they would appear as a constant offset of the signal in the occultations. These observations do not geometrically resolve the bodies. These are radiometric, power measurements so to speak. If so, they would not be seen.

(There must have been at least a dozen of these occultation events, judging soley from the resolution of the map of Pluto that was generated.)

The gravitational fields around Saturn and Neptune are fully dominated by the massive planets. We have recently seen in Cassini images the effects of even small bodies on the rings, as small moons leave wakes in the outer rings. Charon, on the other hand, is massive enough to have the center of mass of Pluto outside of it. Now we know of two more, which also seem to be coplanar and resonant. It would seem unlikely that rings could form in such an uneven gravitational field, with all the tidal forces that must exist. There must be some theoretical work on the impact of a relatively massive moon on the stability of rings. Does anyone know of any such work?
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tasp
post Nov 13 2005, 04:33 AM
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In re to Comga's post:

(I'm speculating here) For thin Uranian style rings would effects of a nearby mass (such as Charon) be mostly in bumping up the eccentricity of each ring? If that was the extent of the effect, not sure we see a big hit in ring longevity in this possibility. (I assume between each narrow ring would lie a strong resonance from Charon)

For broad Saturn style rings (with ring particles 'cheek by jowl') having the particles experiencing strong effects from Charon becomes, perhaps, more interesting. The dynamical ring spreading mechanism would seem to be enhanced in this scenario. Every orbit around the primary, all the ring particles bump more vigorously and transfer momentum across the ring plane. Would such effects 'overpower' the resonance 'curbs' in the ring system? Perhaps.

Then we are in a scenario where, due to the strong momentum transfer across the ring system, we see a large effect 'pushing' the lower edge of the ring downward and the upper edge outward.

This does not seem compatible with long ring retention, but, once the (possible) ring material thins out, you may approach the Uranian model, and perhaps get to see some skinny dark rings in 2014?

Are there other 'damaging' effects of a nearby Charon on rings of Pluto other than increased orbital eccentricity? Inclination changes seems unlikely.

Possible 'demethanization' of Charon from tidal heating would imply a slight degree of atmosphere interacting with the ring system when Charon passes between the sun and Pluto. Such an effect would not persist after tide lock, but atmosphereic drag and ring systems don't seem to go together.
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