An interesting fact can be noted down that is similar for absolute values and conjugates:
$$ |z| = a^2+b^2 $$
$$ z times z^* = a^2+b^2$$
This means that:
$$|z| =z times z^* $$.
Using simple algebra, we can rearrange these, and later be able to find an absolute value, given complex number and its conjugate, for example.