Life that should not be.

[corundscale]

Short version: Life around massive stars needs to go, life on planets with too thin atmospheres needs to go. Life around brown and white dwarfs might not be impossible.

Long version: Currently in Pioneer life is considered possible on planets with temperatures permitting liquid surface water. Except the assumption that there is a fixed temperature range allowing for liquid water is wrong. While water melting point generally stays around 0 for pretty much any reasonable pressure, boiling point heavily depends on atmospheric pressure.
Below 0.0060373 atmospheres you simply can't get any liquid water at any temperature. Above, the range first starts very narrow, but broadens with increasing pressure, at high pressures you can have liquid water way above 100 Celsius. Worlds with no significant atmosphere and complex ecosystems or even microbial life need to go.

Another thing is system's lifetime. If Earth is any indication life takes around 1Gy to arise, around 2.6 to get anything multicellular, more than 3.1 to start conquering the land. Since stellar lifetime is fortunately correlated with stellar mass, a system must contain no stars above around 1.5 solar masses if any planet in it is to boast a complex ecosystem, no stars above around 2.5 if any planet is to feature even microbial life. http://www.asc-csa.gc.ca/eng/educators/resources/astronomy/module2/calculator.asp

This doesn't account for red giants (which can maintain habitable zones for long enough if they aren't very massive), but I guess we can ballpark it along the lines of main sequence stars, especially if we are generous and assume that life might get kickstarted out of habitable zone before red giant stage if the body is highly volcanic, and than survive (probably barely) thawing its Europa-like planet or moon (we don't account for those at all at current stage - volcanicity as function of mass AND tides and then anything ice that's larger than asteroid and volcanic can get life?).

OTOH there doesn't seem to be anything prohibiting life around brown and white dwarfs. Sure, such life is fairly improbable - very small habitable zone, a lot of UV at the beginning, difficulty of even getting the planets close enough to WD, tidal forces, etc., but those aren't insurmountable problems, so maybe we should do away with checks for those stars and give life around them a fighting chance? http://www.astrobio.net/news-exclusive/white-or-brown-dwarf-planets-not-likely-to-host-life/

[impaktor]

I recommend going through this post on the dev forum.

write up the conclusions of what is discussed there into a bullet list, or psedu code.

[impaktor]

Further discussions on the dev forum. -> closing.

[corundscale]

Made a PR:

3015

Removed or downscaled life according to the most massive star in the system, enabled life around WDs and BDs.

Atmospheres, liquid water, volcanicity and tidally heated iceballs with watery filling still TBD.