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Ganymede Enhanced (APOD 2009 September 20)
Posted: Sun Sep 20, 2009 4:16 am
by neufer
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. As You Like It > Act I, scene III
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CELIA: What shall I call thee when thou art a man?
ROSALIND: I'll have no worse a name than Jove's own page;
. And therefore look you call me Ganymede.
. But what will you be call'd?
CELIA: Something that hath a reference to my state
. No longer Celia, but Aliena.
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http://antwrp.gsfc.nasa.gov/apod/ap001218.html
http://antwrp.gsfc.nasa.gov/apod/ap090106.html
http://antwrp.gsfc.nasa.gov/apod/ap070824.html
http://antwrp.gsfc.nasa.gov/apod/ap070329.html
http://antwrp.gsfc.nasa.gov/apod/ap041209.html
http://antwrp.gsfc.nasa.gov/apod/ap041111.html
http://antwrp.gsfc.nasa.gov/apod/ap011215.html
Re: Ganymede Enhanced (APOD 2009 September 20)
Posted: Sun Sep 20, 2009 9:48 pm
by orin stepanek
I take it that the rayed craters are the younger ones.
Some of the craters look as though they be bulged upwards; rather than indented. Could this be a possibility?
Planet sized-- 8) Two moons in our solar system are larger than Mercury; Ganymede and Titan. How big does a moon have to be to be called planet sized?
Orin
Re: Ganymede Enhanced (APOD 2009 September 20)
Posted: Mon Sep 21, 2009 1:49 am
by neufer
orin stepanek wrote:I take it that the rayed craters are the younger ones.
That sounds about right.
orin stepanek wrote:Some of the craters look as though they be bulged upwards; rather than indented. Could this be a possibility?
Certainly not
the floor of a crater if that's what you mean.
(E.g., our own moon:)
orin stepanek wrote:Planet sized-- 8)
Two moons in our solar system are larger than Mercury; Ganymede and Titan.
How big does a moon have to be to be called planet sized?
Actually a planet is more defined by
its mass than its volume:
- A planet must have sufficient mass:
1) for self-gravity to overcome rigid body forces such that
it assumes a hydrostatic equilibrium (nearly round) shape, and
2) that it is able to clear the neighborhood around its orbit.
If it were my decision I would make the cutoff at
10^23 kilograms
such that
Ganymede, Titan & Callisto are "planet sized"
Code: Select all
Mass in
10^22 kilograms
33.022 Mercury
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14.82 Ganymede
13.45 Titan
10.76 Callisto
..................
8.932 Io
7.348 Moon
4.80 Europa
2.14 Triton
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1.67 Eris
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