"Finding Supports Theory that Single Collision Created Ninth Planet's Three Satellites" - OK...

Unless common debris has covered a more diverse set of bodies.

I think that conclusions like this based on such scant data are close to useless, especially because we are going to "know" in 2015.

I'm sure whatever details can be gleaned/guessed from this distance will be rapidly overturned in July 2015, and as usual the truth will be Much more surprising.

Just hold those theories untill we have been there.

Nick

"All three satellites have surfaces that reflect sunlight with equal efficiency at all wavelengths, which means they have the same color as the Sun or Earth's moon. In contrast, Pluto has more of a reddish hue."

Is this saying that they also have the same albedo? or are just a neutral Grey?
I which case they could be different shades of grey... and different compositions!

Hmmmm

Nick

I'm a geologist, not an astronomer, so I only know what I have to know about spectroscopy...but...does it seem premature to anyone else to call things "the same color" when you only have views through two filters? That's a two-point spectrum. I understand that the filters on Hubble have probably been carefully chosen to make the most of differences at particular points on the electromagnetic spectrum, but still, two points isn't much of a spectrum, is it? Am I missing something?

--Emily

"Am I missing something?"
don't think so...

although...a colour TV for instance has only 3 points in it's 'spectrum'
Depends how you define color I suppose. Does e.g. UV and IR count?

Well, with three we can tell the difference between roses, emeralds, and the blue sky of a summer day.

Not to trivialize the difference between two and three: there's a reason why tripods sell better than bipods.

I think the answer lies in looking at known spectra. Typically, you see either a flat line, a sloped line, or a "hump", with definite exceptions for absorption lines that send the spectrum potentially near to zero, before returning the the general trend. It's easy to avoid the likely absorption lines, since we know that these worlds might have CO2, CO, N2, CH4, and H2O ices on their surfaces and aren't likely to be beryllium-strontium-cobalt. Then the question is, how many samples do you need to distinguish a flat line from a slope or a hump? Two seems to do it if you can avoid the case where you sample two values on opposite sides of the hump.

Check out the visible spectrum of Pluto (left end of the top figure here)

http://ifp.uni-muenster.de/~sohl/images/pl...to_spectrum.jpg

It rises quite steeply through the visible. Two points could distinguish something like that from a flat line.

Of course, it's theoretically possible that something psychopathic happens to a spectrum between two samples, but when we can constrain the possible materials, we can virtually eliminate that possibility.

Astrophysics, abstract
astro-ph/0603214

From: Man Hoi Lee [view email]

Date: Wed, 8 Mar 2006 23:51:27 GMT (85kb)

On the Orbits and Masses of the Satellites of the Pluto-Charon System

Authors: Man Hoi Lee, S. J. Peale (UCSB)

Comments: 24 pages, including 11 figures; uses AASTeX; submitted to Icarus

(Abridged) The orbits of the recently discovered satellites of Pluto, S/2005 P2 and S/2005 P1, are significantly non-Keplerian, even if P2 and P1 have negligible masses, because the mass ratio of Charon-Pluto is ~0.1. We present an analytic theory with P2 and P1 treated as test particles. This analytic theory shows that the azimuthal periods of P2 and P1 are shorter than the Keplerian orbital periods and that the periapse and ascending node precess at nearly equal rates in opposite directions for P2 and P1. The deviation from Kepler's third law is already detected in the unperturbed Keplerian fit of Buie and coworkers. We also present direct numerical orbit integrations with different assumed masses for P2 and P1 within the ranges allowed by the albedo uncertainties. If the albedos are as high as that of Charon, the masses of P2 and P1 are sufficiently low that their orbits are well described by the analytic theory. There is at present no evidence that P2 has any significant epicyclic eccentricity. However, the orbit of P1 has a significant epicyclic eccentricity, and its prograde periapse precession with a period of 5300 days should be easily detectable. If the albedos are as low as that of comets, the large inferred masses induce significant variations in the epicyclic eccentricities and/or periapse longitudes on the 400-500-day timescales, due to the proximity of P2 and P1 to the 3:2 mean-motion commensurability. In fact, for the maximum inferred masses, P2 and P1 may be in the 3:2 mean-motion resonance, with the resonance variable involving the periapse longitude of P1 librating. Observations that sample the orbits of P2 and P1 well on the 400- 500-day timescales should provide strong constraints on the masses of P2 and P1 in the near future.

http://arxiv.org/abs/astro-ph/0603214

I don't think there's any way to accurately measure the albedo of the two smaller satellites. It's saying that each of them individually reflects blue light as well as it reflects green and red.

JR--

You are right, we have no way at present to measure the albedo. We have a color, which is
solar, meaning the bodies reflect sunlight equally across the B-V range (~4400-6500 A). But
we do not know if they are dark and neutral or bright and neutral.

I think the best chance for an albedo is going to come as a result of the Lee & Peale paper cited above.

Stan and Man Hoi sent it out to many of us last week. From their work they have shown we can get
masses for at least one, perhaps both, small sats. Masses mean we can get a good handle on the
radii by assuming a density-- say 1.5 g/cm^3-- that's got to be right to within a factor of two,
which means it only effects the radius by a factor or 2^0.333. Once we have a radius estimate
we can determine a good albedo estimate. I am confident we can determine if P1 and P2 are dark
like comets or more like Charon's 35% albedo this way, we might even do a little better
than that. So stay tuned, in a year or two we'll have enough positions (I hope) to solve for the
masses themselves. Of course, this does depend on the HST TAC giving time to at least one of the
two proposals they have to get more astrometry. That TAC meets in 10 days...

Well - it would have my vote not that it counts for much.

Just out of curiosity - did you suspect that pluto would have multiple satellites or has the discovery of these moons been a complete surprise?

I expected a multiple system. This is why we searched for 15 years and wrote a total of 9 observing
proposals. Of all the tools we used, only HST was capable of the task, and it found them in just 8 minutes flat.

Once again we're reminded of the usefulness of Hubble, and the need of one repair mission to keep it going.
And no I cant place any bets on being alive in 2016, facts speaks against that so I close the book on Pluto by going with the 'collision created theory' for Charon and the two new moons.

Now, now, one must remain an optimist. You never know what surprises lie in store in the near fututre. And if we don't figure it out with HST or some creative use of other instruments prior to NH, then there is always the possibility that Vulcans will land in Montana next year and take some of us on a tour of our solar system. Then you'll have your answers. (So be prepared to tell them how to pronounce "Quaoar" when you get there.)

Er... ...2063?

Did I miss an episode or ten?

Bob Shaw

Well thank you ElkGroveDan trying to cheer me up. Actually im not the slightest depressed over this fact. But rather pleased that the 'space buff' part of me have gotten answers to most of the things i've wondered about our moons. As for Pluto i view the things we know as half the answer.

Vulcans? Oh you got me there, its my pointy MrSpock ears that helps me to be all logical about all these facts.
Everything sounds logical when I put them on. Dunno if that was the manufacturers intention, or should I turn them in for a refund?

It was a post-series movie called First Contact

I remember reading somewhere online that they could build an upgraded Hubble and launch it for less than the cost of a servicing mission. Just getting the shuttle ready for launch is a huge expense. The major expense of designing the Hubble is paid for already - now they just would need to follow the existing plans to build another one.

Jeff7:

Perfectly true.

I still reckon that the James Webb Space Telescope is too mechanically complicated *not* to be man-tended, however!

Bob Shaw

Astrophysics, abstract
astro-ph/0511837

From: Andrew Steffl [view email]

Date (v1): Wed, 30 Nov 2005 19:37:52 GMT (124kb)
Date (revised v2): Wed, 12 Apr 2006 21:25:39 GMT (249kb)

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, J.R. Spencer

Comments: 17 pages including 4 figures

Observations of Pluto and its solar-tidal stability zone were made using the Advanced Camera for Surveys' (ACS) Wide Field Channel (WFC) on the Hubble Space Telescope 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, as discussed by Weaver et al. (2006) and Stern et al. (2006a). Confirming observations of the newly discovered moons were obtained using the ACS in the High Resolution Channel (HRC) mode on 2006 Feb 15 (Mutchler et al. 2006). Both sets of observations provide strong constraints on the existence of any additional satellites in the Pluto system. Based on the May 2005 observations using the ACS/WFC, we place a 90%-confidence lower limit of m_V = 26.8 (m_V = 27.4 for a 50%-confidence lower limit) on the magnitude of undiscovered satellites greater than 5" (1.1x10^5 km) from Pluto. Using the 2005 Feb 15 ACS/HRC observations we place 90%-confidence lower limits on the apparent magnitude of any additional satellites of m_V = 26.4 between 3"-5" (6.9x10^4-1.1x10^5 km) from Pluto, m_V = 25.7 between 1"-3" (2.3x10^4-6.9x10^4 km) from Pluto, and m_V = 24. between 0.3"-1" (6.9x10^3-2.3x10^4 km) from Pluto. The 90%-confidence magnitude limits translate into upper limits on the diameters of undiscovered satellites of 29 km outside of 5" from Pluto, 36 km between 3"-5" from Pluto, 49 km between 1"-3" from Pluto, and 115 km between 0.3"-1" for a comet-like albedo of p_V = 0.04. If potential satellites are assumed to have a Charon-like albedo of p_V = 0.38, the diameter limits are 9 km, 12 km, 16 km, and 37 km, respectively.

http://arxiv.org/abs/astro-ph/0511837

Yup. More to the point, NASA KNEW this to be true almost from the beginning, and (according to the former head of the National Academy of Sciences' Space Science Board) actually threatened the scientific advocates of Hubble into keeping their mouths shut on the subject by informing them that unless they publicly backed Shuttle repair missions instead of launching Hubble replacements (which could be done on unmanned boosters), NASA would make sure they never got ANY kind of Hubble. (They had wanted one at a somewhat higher altitude, which would allow better and longer-duration observations but make Shuttle repair flights impossible.) Charming.

There also already exists a detailed design for a more capable but cheaper replacement Hubble -- called "Hubble Origins Probe" (you can find data on it in several places on the Web) -- which, however, has been ruled out for the time being in favor of yet another Shuttle repair flight.

The Positions, Colors, and Photometric Variability of Pluto's Small Satellites from HST Observations 2005-2006

- http://arxiv.org/abs/astro-ph/0605014

HST related paper with all four observations (15.1 and 18.1 May 2005, 15.7 February 2006, and 2.8 March 2006).