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Re: Speculation on a gas giant's habitable moon in a binary system

Subject: Re: Speculation on a gas giant's habitable moon in a binary system
From: Steve Willner
Date: 3 Mar 2006 18:47:35 -0500
Newsgroups: sci.astro, alt.astronomy
In article <1140722770.192757.112640@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
 news@xxxxxxxxxxxxxx writes:
> It takes place on a moon of a gas giant which orbits a binary system.
> Possibly semi-detatched if possible.

You've already gotten some good comments.  Here are a few more, and
I'll also be following up some of the other articles.

I don't think you can use semi-detached. One of the components would
have to be an evolved star, and the system lifetime would be very
short with stellar luminosity (hence planetary climates) changing
quickly.

> A little ancient terraforming was done to make Earth-like flora and
> fauna possible.
> I'm thinking of having the rotation of the moon as long as about two
> Earch days, and the revolution of the moon and its planet around the
> stars around 456 Earth days.
> I see Titan and Ganamyde are like our moon and have rotations that
> match the revolution, causing the same hemisphere to always face the
> planet. Is that nearly necessary, or can I have a slight difference so
> that it would appear on the moon that the planet travels around every 1
> to 5 Earth years (haven't decided which yet.)

How long ago was that "ancient terraforming?"  A moon in a two-day
orbit around a gas giant is going to tidally lock pretty quickly.
However, if the terraforming involved (say) dumping comets onto the
moon, and the comets all came in at an angle, you might be left with
a tiny bit of rotation.  It would take some calculating to say how
much, but I think you could get away with a 1-5 year period for your
story.  The period would have been shorter when the terraforming was
done and will gradually lengthen with time.

Have you thought about radiation belts from the gas giant?  Jupiter's
are pretty fierce, but I don't know about the other gas giants in our
solar system.  You might have to do some hand-waving there; maybe
have a character mention how lucky it was for the terraformers to
find a gas giant without a strong magnetic field and thus no
radiation belts.

-- 
Steve Willner            Phone 617-495-7123     swillner@xxxxxxxxxxxxxxx
Cambridge, MA 02138 USA                 
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