What sets of stellar models are freely available for reference when worldbuilding?
Often, when I'm building a world, I want to start out by determining some of its key properties. Maybe I'm trying to calculate a habitable zone, or figure out how long a year would be on a particular planet, or determine what the sky would look like. To tackle any of these, I need to know a bit about the star - or stars - it's orbiting.
Some of the time that's easy. As someone brought up last week, for some stars we can do some approximations, and a couple minutes and a back-of-the-envelope calculation will get me the answer I need. But there are other cases where it's not so easy. Maybe I want my planet to be orbiting an aging red giant, or maybe a massive star in the early universe which would have been, in terms of metallicity, nothing like the stars we know today. The analytical approximations star tto break down a bit in these cases.
One workaround I like to do is find pre-tabulated grids of stellar models. Stellar astrophysicists spend a good deal of time simulating evolutionary tracks and generating populations of stars, and they do numerically - much, much, much more accurately than I could ever do. They often create grids of results, which list the properties of a particular range of stars. For instance, one group might be studying red dwarfs, and they might generate grids of M1V dwarfs, M1.5V dwarfs, M2V dwarfs, etc. This means I can be lazy and just look at a particular set of models, if they're posted online. I can take my pick of metallicities, rotation, masses, ages, etc. If a star of the mass and age I want isn't listed, I can crudely interpolate between grid points. It's much better than me crunching numbers to get results that will be off by a factor of 2 or 3.
I know of a couple sets of models I like to use, and I'm going to write an answer listing them, but I'd also like to find out about other grids, as a worldbuilding-resources question. What sets of grids of stellar models are freely available? To narrow things down a bit, here are my requirements - I'd like as many to be fulfilled as possible:
- They should include main sequence stars of masses $0.08M_{\odot}.
- They should contain some models of solar metallicity and some models of the metallicities of Population III stars.
- They should also have evolutionary tracks for stars in the above mass range through the asymptotic giant branch phase.
- Simulated spectra would be amazing, if possible.
- They should also be free to access - I can get some with my academic credentials, but ideally these should be available to everyone.
Taking into account rotation would be nice, but it certainly isn't required. I'd also appreciate grids with high-mass ($\geq10M_{\odot}$), low-metallicity Population III stars, but that's rather unrelated to the stars I've mentioned above, which won't end their lives as supernovae.
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