I'm trying to figure out some details to a world that I'm developing.
I'm not a mathematician, nor an astrophysicist.
I'd like some help to make the solar system of this place "realistic" and figure out various details.
Here's the detail:
It's a gas giant orbiting a solar class star. The gas giant has 5 large moons. The Gravity (compared to earth) of the moons is as follows:
1) .17G
2) .38G
3) 1.01G
4) .90G
5) .40G
Things I want to include:
1) Lotsa small moons.
2) A ring system.
3) A magnetic field from the gas giant that surrounds the entire small system of major moons.
I need to know things like:
1) Reasonable rotational periods for the moons.
2) Should any of them be tidally locked?
3) How long does it take to rotate around the gas giant parent?
4) What the calendar would be like for one of the moons, consider they may experience a "day" when the gas giant is between them and the sun and a "night" when the reflective light from the gas giant eliminates all shadows...
Anyone willing to help out with this? :)
Disclaimer: I'm not an astrophysicist and don't know anything (I do have a B.Sc. but in biological sciences).
Well, just to start with Jupiters larger moons have (according to wikipedia) orbital period 1.77 days (Io), 3.55 (Europa), 7.15 (Ganymede) and 16.69 (Callisto). If you want a bigger gas giant orbital times will increase, of course.
All of those are tidally locked. Whether yours would all be probably mostly depend on how old the system is - tidal forces gradually brake the rotation speed (I've heard it said that Earth initially had a 5-hour day, and eventually it'll have one side facing the sun permanently as well).
Not sure about the magnetic fields or how long they're likely to spend in 'eclipse' each period, sorry.
Quote from: Vellorian;400029It's a gas giant orbiting a solar class star. The gas giant has 5 large moons. The Gravity (compared to earth) of the moons is as follows:
1) .17G
2) .38G
3) 1.01G
4) .90G
5) .40G
Your first problem is that you'll have two moons that are roughly as massive as Earth, and two more that are more massive than any other moon in our solar system and orbiting bodies that massive can interfere with each other substantially. If you want to fake it, spread them out quite a bit.
Quote from: Vellorian;400029Things I want to include:
1) Lotsa small moons.
2) A ring system.
3) A magnetic field from the gas giant that surrounds the entire small system of major moons.
Those large orbiting moons are going to sweep up a lot of the debris around the planet so the only way you'll get (significant) rings and a lot of small moons is if a moon as recently been ripped apart and the material forming the rings and small moons is relatively recent. But at least some of it would wind up bombarding your large moons with catastrophic results (think dinosaur extinction). As for orbiting inside of the magnetic field, you may want to look at what Jupiter's magnetic field does to its moons, particularly Io. Jupiter has huge Van Allen radiation belts to contend with, too. Tides may also be a significant problem, both in terms of shifting the oceans around and in terms of heating up the planet.
Quote from: Vellorian;400029I need to know things like:
1) Reasonable rotational periods for the moons.
2) Should any of them be tidally locked?
3) How long does it take to rotate around the gas giant parent?
4) What the calendar would be like for one of the moons, consider they may experience a "day" when the gas giant is between them and the sun and a "night" when the reflective light from the gas giant eliminates all shadows...
As Bloody Stupid Johnson points out, tidal locking is likely for all of them (Saturn's large moon Titan is also tidally locked).
Since your moons are essentially planets, I suggesting fudging the orbital distances using the Titius–Bode law (aka Bode's Law) (http://en.wikipedia.org/wiki/Titius-Bode_Law), treating your gas giant like the star. Jupiter's magnetic field extends something like 3-7 million km out. Since you are dealing with such large moons and want rings, I suggest starting out around 7 to 10 million km from your fictional gas giant and use the Titius–Bode law to fit your moons inside of that. Fudge the tidal issues (make them stronger closer to the gas giant), fudge the tidal locking problem (which could give your moons days that are many Earth days long), and fudge the radiation issues (give your planets strong magnetic fields and spectacular aurora displays if you want to acknowledge the problem). Here (http://en.wikipedia.org/wiki/Orbital_period) is the math for calculating orbital periods. Pick planets like Earth and Jupiter to get the masses needed for the calculation.
You might also find this page (http://www.extrasolar.net/speculations.html) and this (http://www.astro.virginia.edu/~pla7y/Homepage/Home_files/ms.pdf) useful.
(Disclaimer: I'm not an astrophysicist, either, but have read papers by real astrophysicists on things like moon formation and what happened when moon formation models produced two large moons for Earth instead of one.)