Gliese 581g

[Cairan]

It now has a chokingly thick atmospheric pressure of 27.1 earth atmos. The only reason there is even land showing is because alot of the ocean is locked in the polar ice caps. The lack of a global cloud cover is due to the friged tempuratures of this planet. It also rotates freely now with a rotation period of 96 hours.

Do you know if GI 581 d would be tidally locked? I haven't seen references to it in recent news... As for GI 581 f, I think the fact it is half the size of Uranus and the distance it is from the star would prevent it from being tidally locked. Or it could be like Venus, the solid part being (almost, actually retrograde) locked but the atmosphere in a state of superrotation.

I have seen your pictures of the sunward hemisphere of GI 581 g, and one note I must make is relative to the land configuration... I don't know if small, shallow lake or seas could endure near the sun facing point, as it would probably suffer heavy evaporation. In my opinion, it would tend either toward a solid land mass without much water surfaces within 30-something degrees of latitude and longitude away from the substellar point, maybe with deep bays connected to the open ocean, or an open ocean in itself.

Geez, this system really is fascinating... :hail:

 

[donatelo200]

There are only seas on the sunward side of GI 581 g because I have it with a thick atmosphere that carries away alot of the heat to the darkiside. Although the way i have GI 581 g the sunward side is still hot at 102 degrees celsius but the thickness of the atmosphere raises the boiling point of water enouph so that water would be stable. Surface pressure of GI 581 g is 77.6 psi giving water a boiling point of 154 dergrees celcius. GI 581 d is only rotating because it has a large moon that orbits in really close creating a tidal bulge mutch like on Earth but a bigger one just because the moon orbits really close. The moon though will eventually collide with GI 581 d for the same reason Phobose will collide with mars.

 

[Cairan]

GI 581 d is only rotating because it has a large moon that orbits in really close creating a tidal bulge mutch like on Earth but a bigger one just because the moon orbits really close. The moon though will eventually collide with GI 581 d for the same reason Phobose will collide with mars.

Don't forget [ame="http://en.wikipedia.org/wiki/Roche_limit"]Roche limits[/ame] if you want a plausible, albeit fictitious moon system around "d"... The ring system you placed around "d" really is a nice touch, because it hints that a moon recently suffered the outcome of getting closer than this limit. Depending on it's internal structure, Mars' Phobos will probably disintegrate in a ring system when it reaches this point, which is coming in a few million years. As for "GI 581 d I", it depends whether it is an icy body, a silicate or a metal-cored object.

Using data from your previous version, I get a mean density of 5351 kg/m3 ... Pluging that into the Roche limit equation, I get the following results:

A body of the exact same density would break the Roche limit at 17600 km of altitude above "GI 581 d" as it was in your latest release... A body of Earth's moon density would break up at 22700 km of altitude... An icy body, like a comet, would suffer the same fate at 53700 km above the surface.

Your existing "GI 581 d I" has a density of 4191 kg/m3 and would break up at 20134 km of altitude above the surface of "d". It currently orbits at about 62070 km above the surface, so there is a lot of spare space between it's position and the Roche limit below witch it would crumble.

As far as "falling" toward the parent planet, the rule of thumb is usually that if a tidally locked moon orbits faster around a planet than the rotational period, it will spiral down over time. If it's orbital period is greater than the rotational period, it will slowly move farther away while it's parent planet will very slowly loose rotational momentum, and spin slower on itself.

This is what is taking place with Earth's moon, which orbited a lot closer early in the Solar system's history, with the Earth spinning on itself in as little as 15 hours per solar day. Nowadays, the moon is moving about an inch a year away from the Earth, and both the Earth's rotational period and the Moon's orbital period slow down as an effect of this momentum transfer.

In the case of either your previous version or future version of GI 581 d and it's fictitious moons, the 21h orbital/rotational period of "d I" is much quicker than "d" either in tidal lock with the Gliese 581 star or with a sideral day of 96 hours.

So yeah, it would spiral down...

 

[donatelo200]

Yep right on the money. The only change to the moon will be it's inclination relative to the star otherwise it will reman the same.

 

[T.Neo]

Let's not forget the tidal effects of the parent star upon any moons...

 

[donatelo200]

The only major moon is completely under the influnce of GI 581 d. The third moon will eventually be pulled away from GI 581 d though. The second moon i'm not shure about it's on the borderline of being pulled in and being flung out.

---------- Post added at 04:00 PM ---------- Previous post was at 11:14 AM ----------

Screenes of my version of the Gliese 581 system are here.

---------- Post added at 08:33 PM ---------- Previous post was at 04:00 PM ----------

Here is Gliese 581 f witch was mentiend in the discovery of g.

It has a thick smoggy atmosphere that is 31 time the thicknes of Earth's.

 

[Rtyh-12]

As far as I can understand from the news article, scientists believe Zarmina is tidaly locked, right?

By the way, I'm trying to tidally lock a moon in a custom solar system, how can I do that?

Oh, and why do you like thick atmospheres? It will be difficult to land my XR-2 on Zarmina. compbash2

 

[JonnyBGoode]

As far as I can understand from the news article, scientists believe Zarmina is tidaly locked, right?

That's what I gathered. Which means it's probably arid and barren on one side, and a frozen iceball on the other, with just a narrow strip at the terminator that is "green."

And I'd imagine constant winds from the cold side (high pressure) to the hot side (low pressure).

 

[RisingFury]

The only major moon is completely under the influnce of GI 581 d. The third moon will eventually be pulled away from GI 581 d though. The second moon i'm not shure about it's on the borderline of being pulled in and being flung out.

I know it's your creative freedom and all and you're free to make your addon the way you want, but do you really *have* to toss out all the laws of physics?

 

[donatelo200]

No Gliese 581 d I is influenced by the parent star and the other lower massed moons, the effect just isn't enough to signifigantly change it's orbit. (it orbits in 20hrs in the new version)

This shows all of GI 581 d's moons orbits using Artlav's Videnie.

 

[T.Neo]

And I'd imagine constant winds from the cold side (high pressure) to the hot side (low pressure).

We also have to consider that air will be heated at the sunward point, as it is at Earth's equator. Essentially, the planet is one big hadley cell.

Warm, humid air travelling from evaporating ocean at the sunward point mixing with cold, dry air coming off the polar cap of the nightside, could cause storms and rain in that region.

I have a feeling that what is habitable will extend a good deal past the terminator, but things will obviously get warmer as you get nearer to the sunward point.

Of course, that is just my thumbsuck, but a real climate simulation would be interesting. I'm sure I've seen something of the sort, both with temperature and wind levels.

 

[JonnyBGoode]

Unlike Earth though, it would be a one-sided Hadley cell.

 

[RisingFury]

No Gliese 581 d I is influenced by the parent star and the other lower massed moons, the effect just isn't enough to signifigantly change it's orbit. (it orbits in 20hrs in the new version)

This shows all of GI 581 d's moons orbits using Artlav's Videnie.

What makes you think such a configuration would exist?

You have a system that is estimated to be at least 7 BILLION years old. You'd think that tidal evolution has played it's part and any situation you have now is pretty stable.

There's actually evidence of that if you just look at orbital times.
If you divide the orbital time of one planet with another and if the ratio is close to 2:1, 3:1, 4:1, 3:2, 5:2, 3:5, then you have what's called a resonance. A resonance is a powerful mechanism that reshapes the orbit over time. For this to work, the ratio of orbital periods has to be *very* close to a resonance. Within ~+/-1%. In this system, the inner most two planets are somewhat close to a 5:3, but not close enough. Other planets are not affected by resonance. Therefore their orbits will be stable (chaotic yes, but stable).

The same can be said with moons. Jupiter has a Laplace resonance with Io, Europa and Ganymede. 1:2:4 resonance. It's kept that way because of tidal interactions with Jupiter, same one that keeps Io and Europa warm.

In your example it seems to me that the ratio of radii of the two moons with circular orbits is about 5:3,5 which would give a ratio of orbital periods about 1.7, or close to 5/3 = 1.6666... Those two moons have a possibility to influence each other. The more massive would stay in a roughly circular orbit, the other one would get pushed into an elliptical one, until the resonance broke. Of course, one moon gains orbital energy at the expense of the other.

The third one, that you placed in an elliptical orbit I can't quite measure well, but the orbit does raise some questions. Again, how did the moon get there? Is there any resonance with another moon that did this? If not, what is the ratio of the moon's angular velocity at periapsis, relative to the planet's angular velocity? What is it's mass?

Also, why hasn't it collided or settled into a stable orbit after 7 billion years?

 

[donatelo200]

The largest moon formed with GI 581 d in a similar fashon to Earths and the two smaller ones were recently captured. GI 581 d I is 17.235e22 kg. GI 581 d II is 14.376e19 kg. GI 581 d III is 1.1536e19 kg.

 

[T.Neo]

Are they made of Platinum?

 

[tblaxland]

Are they made of Platinum?

Why? Their mass relative to their parent planet is not too extraordinary (Gliese 581 d is approx 6 Earth masses from what I can find). Also nothing is mentioned of their size.

RisingFury, I plugged the numbers for 581 d I & II into Tony's Gravity Simulator based on a 5:3 resonance. No kicked satellites yet, but I'll let it keep running for the rest of the afternoon and see what happens.

 

[RisingFury]

The largest moon formed with GI 581 d in a similar fashon to Earths and the two smaller ones were recently captured. GI 581 d I is 17.235e22 kg. GI 581 d II is 14.376e19 kg. GI 581 d III is 1.1536e19 kg.

Again you demonstrate a (not so surprising) lack of even basic laws of Physics. Unless you have some sort of drag or resistance or another way to lose angular momentum, it's gonna conserve. Spacecraft shed angular momentum by firing thrusters, but the sum of the space craft's angular momentum and ejected propellant remains the same.

If you now assume that you captured a moon, it's only fair to say it has no giant rocket engines on it. Therefore the only viable mechanism for capture is if another moon took away part of the angular momentum via a slingshot. The same way as for example MESSENGER spacecraft used multiple slings of various planets to lose angular momentum. The problem is that the angular momentum then gets transferred to the other object. In terms of a spacecraft and planet, the planet won't feel any huge increase in velocity, but when you have two moons of roughly similar mass, there will be a measurable effect. At the very least, both orbits would end up elliptical.

You can get the orbits back to circular, but it will take billions of years of tidal evolution if there is no resonance present, as explained in my last post.

Two out of three moon in your system have circular orbits and all of them have pretty low orbits to the planet, where the ratio of moon's orbital radius to the ratio of the planet's radius is around ~10. (~55 for Earth and Moon).

Now, I could start guessing what such a low orbit means, after 7 billion years of tidal evolution, but I'd prefer for you to give me the sidereal rotation period of the planet, all of the moons as well as orbital periods of all of the moons...

Are they made of Platinum?

Why? Their mass relative to their parent planet is not too extraordinary (Gliese 581 d is approx 6 Earth masses from what I can find). Also nothing is mentioned of their size.

donatelo200 released platinum density moons in his previous version of Gliese 581 system. Those densities were revised from original ones, ranging in like 100 000's kg/m^3 or something like that...

RisingFury, I plugged the numbers for 581 d I & II into Tony's Gravity Simulator based on a 5:3 resonance. No kicked satellites yet, but I'll let it keep running for the rest of the afternoon and see what happens.

Mmmm, I don't think this resonance will kick a satellite much. It seems pretty symmetrical. Might make for a wonko orbit though, where LAN circles around the planet and only slight changes in eccentricity...

 

[T.Neo]

donatelo200 released platinum density moons in his previous version of Gliese 581 system.

AFAIK donatelo200's platinum density moons were from his Upsilon Andromedae system.

 

[tblaxland]

Mmmm, I don't think this resonance will kick a satellite much. It seems pretty symmetrical. Might make for a wonko orbit though, where LAN circles around the planet and only slight changes in eccentricity...

That's what happened. Period changes in eccentricity and a steady precession of LAN and Arg Pe.

 

[donatelo200]

How long did the orbit take to become stable and what was it's eccentricy when it became stabile. I would like to know so i can ajust it's orbit to make things as realistic as possible.