Space Forum / Astronomy / July 2008

Hello Androcles:

On Jul 31, 10:23 am, "Androcles" <Headmas...@Hogwarts.physics> wrote:

http://www.reuters.com/article/scienceNews/idUSN1749463620080718?feed...

It is darker than the portion of Africa (?) showing too.  I hear there
is dirt there too.

David A. Smith

You are looking at a contrast of the shadow side of the Moon
and sunlit Sahara.
Contrasts can be deceiving as this demo shows.
 http://www.michaelbach.de/ot/lum_adelsonCheckShadow/index.html

Luna's albedo is far less than Charon's.
 http://www.nineplanets.org/pluto.html#charon

"Though the sum of the masses of Pluto and Charon is known pretty well (it
can be determined from careful measurements of the period and radius of
Charon's orbit and basic physics) the individual masses of Pluto and Charon
are difficult to determine because that requires determining their mutual
motions around the center of mass of the system which requires much finer
measurements -- they're so small and far away that even HST has difficulty.
The ratio of their masses is probably somewhere between 0.084 and 0.157;
more observations are underway but we won't get really accurate data until a
spacecraft is sent.
Pluto is the second most contrasty body in the Solar System (after Iapetus).
"

 http://hubblesite.org/newscenter/archive/releases/1996/09

 http://hyperphysics.phy-astr.gsu.edu/Hbase/phyopt/albedo.html

Note that Earth's albedo is only slightly greater than Jupiter's, the Moon's

comparable to Mercury's.

Dear OG:

[snipped link broken by Google.Groups...]

Not composite, same story I linked, just you correctly identified the
name of the spacecraft.  Somewhere there is a "slideshow" too...

I'd go with a "dirty blackboard" that needs to be cleaned.  The
brightness of the Earth will cause the image to bloom if they left the
image exposing longer.

Funny how there are no stars in this image either... wonder what the
Apollo hoaxers make of that?

David A. Smith