[renormalised (Carl)]

Originally Posted by mswhin63

Although not to be taken as gospel http://en.wikipedia.org/wiki/Habitable_zone gives a brief explanation in current physics understanding of habital zone.

HZ's are only a general concept...based on one example only....us. There could be many exceptions to the rule.

We extrapolate on the basis of the conditions found on Earth, but even here there are exceptions to the rule.