Creating the Manticore-A system in StarGen

I'll add one note just to make sure no one puts more faith in the model than is justified. Stargen and most other planetary modelling software are all based on the Accrete program. That program is based on the model produced by Dole, as part of the project that resulted in the book Habitable Planets for Man. The model is almost fifty years old. Stargen does seem to have incorporated some more modern research. But I don't know of any amateur planetary system model that really follows the current theory and produces systems like we are detecting now (i.e. with migrating planets).

But that's all right for casual purposes, because authors haven't been writing about systems like that, either. It looks like Stargen produces systems that feel right, which is pretty good. I certainly don't want to discourage people playing with it--it sounds nice.

61Cygni wrote: This also means that a realy high-g world like San Martin is complete fiction. That high a gravity would most likely hold onto a substantial hydrogen and helium atmosphere; not a gas giant, but a "gas dwarf". In fact, this is the highest-gravity world with a breathable atmosphere that the program created. I know David has a fondness for high-g worlds, but realistically, 1.3 g seems to be the upper limit.

I don't know if it's that simple. Temperature is also a factor in what gases a planet retains. What temperature is that assuming for the planet's early history? IIRC some models give the early Earth a massively greenhouse atmosphere & very high temperature with water remaining liquid only due to a higher atmospheric pressure at the time.

Also, Kepler found a Neptune-mass rocky world, at about 3 g, whose density doesn't allow for a gas/ice giant type mega-atmosphere.

cralkhi wrote:

61Cygni wrote: This also means that a realy high-g world like San Martin is complete fiction. That high a gravity would most likely hold onto a substantial hydrogen and helium atmosphere; not a gas giant, but a "gas dwarf". In fact, this is the highest-gravity world with a breathable atmosphere that the program created. I know David has a fondness for high-g worlds, but realistically, 1.3 g seems to be the upper limit.

I don't know if it's that simple. Temperature is also a factor in what gases a planet retains. What temperature is that assuming for the planet's early history? IIRC some models give the early Earth a massively greenhouse atmosphere & very high temperature with water remaining liquid only due to a higher atmospheric pressure at the time.

Also, Kepler found a Neptune-mass rocky world, at about 3 g, whose density doesn't allow for a gas/ice giant type mega-atmosphere.

See previous post. Stargen is based on a 50 year old model, and doesn't begin to account for recent discoveries.