[X] My Assistant

[SigurRosFan]

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=

[Ames]

"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

[JRehling]

"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 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.

[Alan Stern]

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...