Matt Wilson wrote:
2) Wondering about current star data vs. what's still undiscovered. If I look at a display of all the stars near earth, there are some big empty gaps, such as between Earth and 61 Cygni. How likely is it that there are a few undiscovered M dwarfs in that direction? I assume we'll keep discovering new brown dwarfs by the truckload, but how many red dwarfs might be lurking still within say 20 ly?
That depends how dim an object you're prepared to consider. The Tycho-2 catalogue, based on Hipparcos data, is 99% complete to magnitude 11 and 90% complete to magnitude 11.5, but for an M9 with luminosity of 0.00015 L☉
I reckon that that is only 2 pc — 6.5 light-years or so. GAIA data will be a lot more complete. I think, though I am not confident that I am calculating the right things because the magnitude scale confuses me, that it ought to be 99% complete for M9 and brighter out to 126 parsecs, and published next year.
3) wikipedia keeps a list of nearby stars. Is there a good place to go with more current data that's easily accessible?
I don't know how easily accessible the GAIA data published so far is. There's an overwhelming amount of it and I think it is lacking any identifiers that would allow you to identify its data points with entries in any other catalogue. Also, the data published so far (last September) are preliminary and I don't know what they are missing.