Motivation: the traditional belief is that there are enough planets out there in the universe for Earth-like planets to be common, but recent evidence has contradicted this by showing unique characteristics about our Earth/Sun/Galaxy/etc that aren't individually shared by as many exoplanets as previously believed. These rarities add up such that even the huge number of existing planets isn't enough to overcome the total rarity of our Earth.

So let's list every "rarity" of our Earth in one place. I'll start:

>The Sun appears to be unique in that it's very quiet, magnetically, compared to other stars in its reference class. The average magnetic noise of Sun-like stars is 150% of our Sun's. This is important because too much magnetic activity will sterilize a star's surrounding planets. On the other hand, expulsion of charged stellar material slows the star's rotation down due to conservation of angular momentum so if this "stellar magnetic breaking" is too LOW, then the mass of the star doesn't decline over time and thus the orbiting planets experience orbital decay. Ideally, a potentially life bearing planet's orbital decay will be perfectly counterbalanced by the decline in its parent star's mass to keep the orbit stable. This relationship is so rare that there are less than a thousand such cases in the entire Milky Way.

Any others?