I've come up with a couple of exoplanets for a story, and have reached the limits of my knowledge. I've googled around, and I had a space enthusiast friend look at them, but he freely admits that he's just guessing for most of this, especially the atmospheric makeup.
The other planet is here.
Based on suggestions and additional research, I now have two versions of the planet.
Hekaton (Version 1)
This chthonian planet orbits a BHB blue giant, with an orbital period of 510.8 earth days. Its mass is 14.5 earths, and its radius is 2.1 earths, with a surface gravity of 3.28g. Surface temperatures range from 110 - 180 C, with a mean of 138. Its thick atmosphere has a pressure of 1.85 atms, and is primarily composed of hydrogen,with moderate amounts of helium, and nitrogen, and trace amounts of arsenic, carbon monoxide, and sulfur. It has three moons, with respective radii of 0.13 earths, 0.19 earths, and 0.265 earths.
Its star emits high levels of UV radiation, and despite the thick atmosphere sunlight is very strong, capable of causing 3rd-degree burns in minutes. The combination of high volcanic activity combined with atmospheric turbulence caused by volcanism results in the air being filled with large quantities of rock. Most of this is just grit, but stone rain is not uncommon, ranging in size from gravel to boulders. High winds circle the equator, bringing rock and ash with them. When channeled through mountains or ravines, they become flensing storms that can reach speeds of over 200 kph, leaving huge plains of ash and debris behind them.
A few specific concerns for version 1:
- For a star capable of causing enough atmospheric loss in a pegasid like Hekaton to form a chthonian planet, is it possible for it to transition to a phase where the chthonian planet doesn't have a surface temperature of several hundred degrees?
- Can a chthonian planet be as small as this? I read that most potential chthonian planets are estimated to be at least 30 earth-masses, but could easily be smaller, and that hot Jupiters and the like often have unusually low densities.
- Would a blue giant be too hot to support this surface temperature? I chose a BHB blue giant because of its UV output, so that Hekaton can have deadly sunlight without being too hot, but if there's a better type of star for this, I'll happily switch.
- Can it have such strong UV (especially C-band) radiation while still having an atmosphere thick and turbulent enough to support the rock storms?
Hekaton (Version 2)
This chthonian planet orbits a blue giant in a tidally-locked orbit at a distance of .6 AU. Its mass is 14.5 earths, and its radius is 2.1 earths, with a surface gravity of 3.28g. Surface temperatures on the hot side range from 1500 - 1900 C, and on the cool side from 60 - 170 C. Its thick atmosphere has a pressure of 1.85 atms, and is primarily composed of hydrogen, with moderate amounts of helium, and trace amounts of sulfur, nitrogen, oxygen, and neon, with large quantities of metals. It is in the process of losing the remainder of its atmosphere. This temperature differential causes enormous atmospheric turbulence, carrying molten rock and metal from the hot side to the cool side to be deposited as rain. Volcanoes further this by pumping large quantities of ash and grit into the air, columns of which scour the surface in great storms. The portions of the cool side near the hot side also receive intense ultraviolet radiation reflected off the atmosphere.
A few specific concerns for version 2:
- I based this version off of Upsilon Andromedae b and picked a different type of atmosphere. Does the type of atmosphere I have still work?
- Can a planet become tidally locked at 0.6 AU, or should I dim the star and move the planet closer?
Its planetary system is relatively old. The inner system is two terrestrial planets (one of them less than 0.1 AU from the star), followed by Hekaton. Beyond Hekaton is an asteroid belt and a gas that has lost a large portion of its atmosphere. Beyond that is a super-Jupiter with over 65 Jupiter-masses that is near the threshold of becoming a brown dwarf. The final planet is an ice giant near the Oort cloud.
How plausible is it that this planet and system could have developed naturally? If it's implausible, what changes would make it more realistic?
My general goal is to create an interesting exoplanet planet that is thoroughly intimidating to biological life but could reasonably be permanently colonized by a robotic civilization with technology that functions best in the -200 - 200 C range, that has access to smart materials, self-repairing buildings, and nanofabrication. Their ideal gravity range is 0g - 2g, but they can function in up to 4g. Colonization would of course be underground.
The important unique aspects of this planet are that it is a chthonian planet with strong UV sunlight and rock storms that will be used for mining. Any suggestions for changes to any other aspects that would make the core aspects more plausible are greatly appreciated.