Re: Double gas giants and a habitable world...
- From: Crown-Horned Snorkack <chornedsnorkack@xxxxxxx>
- Date: Fri, 8 Jan 2010 08:03:09 -0800 (PST)
On 7 jaan, 07:42, Johnny1a <shermanl...@xxxxxxxxxxx> wrote:
On Jan 6, 11:52 am, Crown-Horned Snorkack <chornedsnork...@xxxxxxx>
wrote:
On 4 jaan, 09:45, "Mike Dworetsky" <platinum...@xxxxxxxxxxxxxxxxxxxx>
wrote:> Johnny1a wrote:
I have a set of related questions about a specific orbital situation
or set of situations.
Hypothetically, assume two ~Jupiter mass gas giants, similar to
Jupiter in mass and volume to a very first approximation, in a double-
planet relationship. (For the moment, never mind whether there's any
easy way for that situation to arise.)
How far apart would they have to be to permit the equivalent of the
Galilean satellites to orbit them stably? Or would that even be
possible?
A simple rule of thumb was offered concerning a minimum of roughly 3
times separation. But there is an excellent counterexample in Solar
System. Pluto-Charon double with satellites Nix and Hydra. Nix is in
4/1 resonance, thus orbits at roughly 2,5 times the distance.
How close could they coorbit and still remain 'spherical' to the naked
human eye?
Assuming they orbit in the outer part of a star system, leaving rocky
bodies in the inner system, would it be plausible for an Earth-like
world to periodically come close enough to these bodies to show a
small disk in each case to the unaided human eye? Meaning the
habitable world and the double-gas giant both remain in the orbits
permitting this for geological time periods?
The human eye cannot resolve a disk of Jupiter in our solar system, so
unless the geometry puts the giants and inner habitable planet a lot closer
at opposition, it won't happen in your hypothetical either. You say the
star is F3; That would be more luminous than the Sun (G2), so you might be
able to have the habitable planet in an orbit like Mars or the asteroids in
terms of distance. Jupiter would still seem "point-like"as seen from the
asteroids except possibly for a very keen-sighted observer. However, I'm
not sure of the long term planetary system stability if the rocky planet and
jovian pair orbited that near to each other.
Also, if the above would not be viable, how about the habitable world
orbits close enough to at least permit the unaided eye to discern two
bodies?
If you had such a situation here and now at Jupiter, the double planet would
be easily visible from Earth.
--
If Jupiter orbited at Mars´ orbit, coming to within 0,4 AU of Earth,
Jupiter would be roughly one quarter the size of full Moon at great
opposition. Plainly an extended object. But I am not sure how easy it
is to see the small deviation from sphere.
Yeah, but could Earth still be habitable in that scenario? Would the
orbits of the inner planets be stable with Jupiter (to say nothing of
2 Jupiters) at Mars' distance from the Sun?
There are few Earth-like planets that are observable (understandably,
because small mass planets have small effects on radial velocity and
astrometry).
But there is Gliese 876.
Gliese 876b is 2,6 Jupiter masses, and orbits at 0,207 au from star.
And Gliese 876c at 0,8 Jupiter masses orbits at 0,130 au, at an
eccentric orbit. So, it approaches to 0,07...0,04 au of b (the orbits
are in 1:2 resonance, someone can check the relationship of apsides to
b). This orbit is stable.
How would Gliese 876 system look like from a large satellite of c? It
is right in habitable zone!
.
- References:
- Double gas giants and a habitable world...
- From: Johnny1a
- Re: Double gas giants and a habitable world...
- From: Mike Dworetsky
- Re: Double gas giants and a habitable world...
- From: Crown-Horned Snorkack
- Re: Double gas giants and a habitable world...
- From: Johnny1a
- Double gas giants and a habitable world...
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