We get a lot of questions about planetary habitability (just to name a few). This search will give you these and many, many more. I enjoy answering these, as Astronomy is one of my passions and I've learned quite a lot about it. As such, I answer quite a lot of these questions. If I don't answer one, it's generally because there was at least one superb answer before me - often more than one, actually - which I then read, upvote, comment on, and move on.
On the answers I write to some of them, I find myself repeating a few key points:
- Calculating the habitable zone's inner and outer radii
- The lifetime of the central star and whether or not it could support life
- Calculating planetary temperature
- Investigating whether such a planet could form (if applicable)
. . . and so on.
Most cases have something unique about them - whether it be that the planet is shaped like something other than a sphere or whether it is entirely covered by snow - but most ask about whether or not the planet would be habitable, which can be analyzed by the points I listed above, as well as a number of other things.
This question led me to write a loooong answer that addressed a bunch of these, but there's still a lot that's left out.
The point of all this is that I'd prefer to write much shorter answers in the future and not have to rehash all of this stuff. All of it is necessary framework to consider, but I think that sometimes people see some of it in my answer, say "Bleah, math and too many words" and skip it to move on to greener pastures.
I'd like to create a canonical "general habitability" question and answer that can be referenced in the future, so I don't have to keep bringing up these points time and time again. It would mean I (and others) could be much more concise and focus on the essential aspects of future questions, allowing me (and them) to go into more detail on the minute aspects of each scenario.
I was going to cover all of the points I described above and more in an answer, with mathematics in the relevant sections and links aplenty. If it was needed, I could add in some points about moons and other objects, which would be helpful.
Is this question and answer acceptable, or should I not post it?
If so, I'll post it either today or tomorrow (most likely tomorrow).
By the way, we appear to have a habitation tag, which has been unfortunately only used on three questions (as of this posting). It should probably be used more!
There was an issue previously with this question. I only came across it now. I realized that there's a chance that this question will suffer the same fate, in which case I totally understand if mine is closed. Still, I think that it should be kept open because, unlike CAgrppa's question, the material covered in mine has been reiterated time and time again, and will certainly prove useful in the future.
Again, though, I understand if the community wants to close it.
The question has been split up into two questions: one about the star, the other about the planet. Others may be added if necessary.
There are now multiple answers on the planet question dealing with different aspects of the planet.