Mu Arae reimagined

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Mu Arae reimagined

Post by Winner on 11th January 2010, 10:09 am

I registered here because it looks like the right place to present my feeble attempts at picturing exoplanets Smile Specifically, I've been working on my vision of the Mu Area system, one of the most interesting in my opinion due to the fact that one of the planets is in the star's habitable zone. I tried to keep things plausible, at least to the extent my knowledge of astronomy allows WinkSo, here is my first draft of the system (the names in parentheses are taken from Slavic mythology; I just wanted "my" planets to have names Smile ), from the planet closest to its sun forwards:

HD 160691 c (Khors)
Class: Hot Super-Earth
Mass: 0.03321 M(Jup); ~ 10.55 M(Earth)
Semi-Major Axis: 0.09094 AU

Hot, hyper-volcanic, covered in thick hazy atmosphere full of greyish silicate vapours. The usual stuff you find on planets the journalists often call 'Earth-like' Smile




HD 160691 d (Stribog)
Class: III - Clarified Jovian
Mass: 0.5219 M(Jup)
Semi-Major Axis: 0.921 AU 

Not much to see here - essentially a huge dark blue ball in space. Only near the poles do the temperatures plunge low enough for some water clouds to form.




HD 160691 b (Perun)
Class: II - Water Cloud Jovian
Mass: 1.676 M(Jup)
Semi-Major Axis: 1.5 AU

The main planet of interest. Dynamic atmosphere with clouds made of water (and water ice); almost like Jupiter but in blue and white colours. I know the giant blue spot is a terrible cliché, but I couldn't resist Wink There is several smaller storms present, but in general the atmosphere looks less turbulent than Jupiter's, possibly due to slower rotation. The planet has many large rocky moons, two of them are 'habitable' (yet very different from each other).





HD 160691 e (Kupalo)
Class: I - Ammonia Cloud Jovian
Mass: 1.814 M(Jup)
Semi-Major Axis: 5.235 AU

Essentially a Jupiter-like planet with Saturn-like rings and Uranus-like axial tilt (though not as big).




-----------------------------------

So, that's it for now. It's work in progress, I am in the process of making textures for the (fictional, of course) moons. I've done it for Celestia, most of the textures are mine, some are heavily modified textures from other mods (sadly it's been sitting on my hard drive so long that I don't know where I taken them from Sad ). In any case, constructive criticism is welcome Smile
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Re: Mu Arae reimagined

Post by Edasich on 12th January 2010, 10:55 am

I know this addons is at Celestia, isn't it?

I find the "aurora" effects on the poles suggestive, but the shocking blue spot on the "water jovian" looks a bit odd.

The fourth planet at 0.92 UA (Mu Arae e) looks a bit too blue, alike a hot jovian in orbital zones spanning between 0.1-0.3 AUs. Maybe brighter, caerulean look could fit better.

About the super-earth, there should be some kind of hot clouds of methane, CO2 or something else. It looks a bit faded, while it should be stressed from star interactions and highly active.
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Re: Mu Arae reimagined

Post by Winner on 12th January 2010, 11:26 am

There is a veeery early version on CM, yes. I've completely redesigned the textures, orbits, added "e" and done other things. The blue spot is a cliché, I admit that. I tried to make it look more fuzzy, but the results looked even worse than this. I'll try to do something with it later.

About "e": afaik it's too hot for bands of bright water clouds to form in its atmosphere; Mu Arae is brighter than our Sun (it might even be at the end of its main sequence star existence) and the habitable zone is thus a bit farther away. Planets at ~1 AU should be pretty hot. I took the image I found on the old Extrasolar Visions site as a sort of model for "e", but I tried to make it look a bit more dynamic, so it isn't entirely featureless.

Finally, the hot super-earth: I was under impression that at these very high temperatures, alkali clouds do form high in the atmosphere, giving planets a greyish, faded look. At least that's what the old EV site says. This is the best I could do in Celestia without adding a cloudmap.
Of course it is possible that it applies only to gas giants, I don't know Neutral
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Re: Mu Arae reimagined

Post by Giangore on 12th January 2010, 12:42 pm

Excellent job! Especially the water jovian is very suggestive.
I hope they find out similar moons soon in this system

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Re: Mu Arae reimagined

Post by AVBursch on 12th January 2010, 2:45 pm

Some pointers here:

1 -- All three of the gas giants are far enough away from the parent star to have moons. The critical SMA for stars of the mass of the Sun is around 0.6 au. The innermost gas giant has an SMA of 0.921 au, so tidal locking and tidal interactions are not an issue. Planet-size moons are possible around all three of the gas giants.

2 -- The satellite scaling law should be kept in mind as well. For example, Saturn has a single planet-size moon of 10 Pluto masses, as well as a number of dwarf planet size moons. Jupiter has four planet-size moons which added together come to 30 Pluto masses. It is very likely that the scaling law applies to the gas giants in the Mu Arae system as well. If so, then the moons orbiting the innermost gas giant will add up to around 15 Pluto masses and the outer two gas giants, the moons will have a combined mass of around 55 - 60 Pluto masses. With that in mind, it is possible that Mu Arae b could have had an Earth-like moon early in its history (since such a moon could have been somewhat larger than Mars), which brings us to the next point:

3 -- Mu Arae is an "old dwarf" star on the verge of exhausting its core hydrogen, much like Gliese 777 A, as the star is around 6.5 billion years old. The star likely started its life as a G0V dwarf. Being older than the Sun, any moons orbiting the gas giant planets will already be geologically dead and would no longer have a magnetic field. Mars was an Earth-like planet early in its history, but lost its water after its core solidified and its magnetic field faded. Mu Arae c, on the other hand, would still have a high level of geological activity as it is far more massive than Earth, so internal heat would be lost very slowly.

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Re: Mu Arae reimagined

Post by Stalker on 14th January 2010, 4:28 am

I dislike the night side of Khros, it's Venus' texture.
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Re: Mu Arae reimagined

Post by Winner on 15th January 2010, 9:03 am

AVBursch wrote:Some pointers here:

1 -- All three of the gas giants are far enough away from the parent star to have moons. The critical SMA for stars of the mass of the Sun is around 0.6 au. The innermost gas giant has an SMA of 0.921 au, so tidal locking and tidal interactions are not an issue. Planet-size moons are possible around all three of the gas giants.

2 -- The satellite scaling law should be kept in mind as well. For example, Saturn has a single planet-size moon of 10 Pluto masses, as well as a number of dwarf planet size moons. Jupiter has four planet-size moons which added together come to 30 Pluto masses. It is very likely that the scaling law applies to the gas giants in the Mu Arae system as well. If so, then the moons orbiting the innermost gas giant will add up to around 15 Pluto masses and the outer two gas giants, the moons will have a combined mass of around 55 - 60 Pluto masses. With that in mind, it is possible that Mu Arae b could have had an Earth-like moon early in its history (since such a moon could have been somewhat larger than Mars), which brings us to the next point:

3 -- Mu Arae is an "old dwarf" star on the verge of exhausting its core hydrogen, much like Gliese 777 A, as the star is around 6.5 billion years old. The star likely started its life as a G0V dwarf. Being older than the Sun, any moons orbiting the gas giant planets will already be geologically dead and would no longer have a magnetic field. Mars was an Earth-like planet early in its history, but lost its water after its core solidified and its magnetic field faded. Mu Arae c, on the other hand, would still have a high level of geological activity as it is far more massive than Earth, so internal heat would be lost very slowly.

Few comments to this Smile

ad 2 - There are few other things to be considered, chiefly Mu Arae's high metallicity (2x Sol's). It means that there could have been more "rocky" material and heavy elements in the protoplanetary disc and thus the terrestrial planets/moons formed in it would have been correspondingly more massive/denser. This alone makes large terrestrial moons around "b" a real possibility, IMO. Then there is the fact that the gas giants "b" and "d" formed farther away from the star and subsequently travelled inwards (unless the accepted models of planetary formation are totally wrong). This means that "b", which orbits inside the star's habitable zone, could have captured terrestrial protoplanets forming in the region, or at least a lot of rocky material from which large moons could have formed.

ad 3 - Few more factors to consider:

- again, metallicity. I believe "b's" moons would be denser than planets of their size are in our Solar System, simply because there was more iron and other heavier elements at the time they were formed. Higher density + higher share of radioactive isotopes should mean higher innitial temperature and longer retention of internal heat.
- age of the system, it's "only" 1.5 billion years older than ours, which is IMO not enough time for the interior of earth- or venus-sized plantes to cool enough for geologic processes to stop. Mars is pretty small and light compared to Earth (0.1 Earth mass), so it isn't really a good example.
- most importantly, tidal stressing. It really needs to be appreciated, given the rather significant effects we observe on Jupiter's moons. It is powerful enough to keep Io's interior completely molten, on Europa it probably produce enough heat to maintain liquid subsurface ocean, and Ganymede even has its own magnetic field and partially molten mantle. "b" is more massive than Jupiter, its hypothetical moons are larger, so we can assume the tidal stressing does produce significant amount of internal heat for even smaller moons to remain geologically active. Earth- or Venus-sized moons would actually be more active than Earth. One of my hypothetical moon is an Earth-Mars hybrid with roughly 1/3 Earth mass, and even it should have enough primordial heat trapped inside PLUS heat produced by tidal stressing to maintain active volcanism and strong-enough magnetic field to protect its atmosphere (which is slightly thinner than Earth's; also the moon lost a lot of water which led to the end of plate tectonics, if it had ever been present).

Yes, I am speculation a lot, but I do believe it is plausible to model this system as one which harbours life.
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