I think the proper term is circumstellar habitable zone. If there is other life out there, why are we assuming that it’ll have the same basic needs as our animals? The universe is seemingly infinite, and there’s endless possibilities of what’s out there, so why do we only consider planets that are the ‘perfect’ distance away from their star?
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The main assumption about life we are making is that it many chemical reactions work best at specific temperature; and so having a material that is thermally stable (it doesn’t change temperature easily) that can also allow things to move is useful.
If that assumption holds, there’s only two options: water and ammonia. Both have remarkably high “specific heats” (measure of how much energy it takes to warm/cool them) and dissolve a wide range of other chemicals when liquid. Therefore, if that assumption holds, life can only exist in areas where you can find liquid water or liquid ammonia.
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Could life exist somewhere else? Yes. But we have no idea how they would look or what to look for. We know exactly what to look for for water-based life; and can make reasonable guesses for ammonia-based life.
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