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Sunday, June 14, 2015

GSE2 - A Field of Gas Giants

I'm back in the saddle. It turns out I was correct about the throttle assembly and Thursday I received a replacement. I spent Friday night reprogramming the X52 Pro HOTAS back to its original settings, but I didn't get a chance to fly. Yesterday I was able to invest about two hours towards my first goal, but I progressed less than 50 light years.

It's interesting how you can drop out of hyperspace and find a system that has nothing but a star in it, and the very next jump you land in a system with 64 celestial bodies other than the main star. It takes a long time to survey a system like that. That system is PRU EUQ QO-G C24-0. The system has two K type stars and an M type star orbiting in an Evan's hierarchy 2c arrangement. The primary K type and the M type dwarf comprise the binary pair which the second K type orbits approximately 50,000 light seconds out.

Around those three stars orbit a multitude of huge asteroid belts, three high metal content planets and five ringed gas giants as well as the average assortment of ice balls and Kuiper objects. Here's are the catalog stills from my survey.

[gallery columns="2" size="medium" type="rectangular" ids="5213,5212,5211,5210,5209,5208,5207,5206"]

PRU EUQ QO-G C24-0 C 2 is a water-based life-bearing world thus defying traditional classification and making this an inhabited system. Of the other four gas giants in this system, AB 1 and AB 4 are Class III gas giants while AB 2 and C 3 are Class I gas giants.

But that sort of begs a question. The detailed surface scanner returns these classification results but what do they really mean? I did a little research and it turns out they refer to Sudarsky's gas giant classification system proposed by David Sudarsky and colleagues Adam Burrows and Philip Pinto in the early years of the 21st century. It is an attempt to predict a gas giant's appearance based on its atmospheric composition. Here is an excerpt of their first paper on the subject.

We generate theoretical albedo and reflection spectra for a full range of extrasolar giant planet (EGP) models, from Jovian to 51 Pegasi class objects. Our albedo modeling utilizes the latest atomic and molecular cross sections, Mie theory treatment of scattering and absorption by condensates, a variety of particle size distributions, and an extension of the Feautrier technique, which allows for a general treatment of the scattering phase function. We find that, because of qualitative similarities in the compositions and spectra of objects within each of five broad effective temperature ranges, it is natural to establish five representative EGP albedo classes.

This was all done long before we had direct observation of gas giants beyond the Sol system, so it isn't 100% accurate when it comes to predicting what individual planets look like 1 .

However, it is a solid classification system for atmospheric composition and thus Cartographics continues to use it. Here are the five categories by atmosphere:

  • Class I - Ammonia Clouds

  • Class II - Water Clouds

  • Class III - Cloudless

  • Class IV - Alkali Metals

  • Class V - Silicate Clouds

In the Sol system, both Jupiter and Saturn are Class I gas giants. They both have ammonia based atmospheres. Uranus and Neptune are too small for classification as gas giants and are thus considered ice worlds. Therefore, beyond Class I gas giants people of the 21st century really didn't know what these planets would look like - with one recent exception.

Early in the second decade of the 21st century, scientists determined the color of an exoplanet for the first time. By measuring HD 189733b's (HD 189733 A 2 in our terms) visible light using polarimetry, and subsequently measuring the planet's albedo, they saw a predominance of blue spectrum wavelengths. They attributed this shift toward the blue end of the spectrum to Rayleigh scattering, the same phenomena that gives Earth's sky its blue color. Further observations confirmed this result and thus HD 189733 A 2 became the first extra-solar gas giant with a known color.

Nevertheless, this still did not tell them how the atmosphere looked. The didn't know if there was banding, or storms, or if it was a uniform color like Uranus. Since it orbits HD 189733 A closer than Mercury orbits Sol, they imagined it could also be a roiling cauldron of 1100 kelvin gas, for such is the temperature of HD 189733 A 2. Such knowledge would not come for centuries, and is still being fleshed out today by explorers like me.

Damn. Now this entire log entry seems to be one long self-congratulatory pat on the back. That's not my intent. It's just that we've been investigating these worlds through observation and visitation for a millennium, and we still have billions (trillions?) of worlds left to investigate - many more than we already have in fact. It's seems like it's a job with no end. Well, at least I know what I'll be doing the rest of my life. I suppose there's comfort in that. Fly careful.

  1. Or Elite: Dangerous has deviated from the classification system when it comes to planet rendering. If you want to see what certain extra-solar gas giants are predicted to look like according to Sudarsky's system, you can download the NASA sponsored program Celestia for Windows, Linux or OS X at You can also see the five representative types at's_gas_giant_classification

1 comment:

  1. Make Arthur C. Clarke proud by finding a way to ignite one of those Class I gas giants in the Sol system!


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