(12) Let the foci of an ellipse be $F_{1}(-1,0)$ and $F_{2}(1,0)$ with eccentricity $e$. A parabola with vertex at $F_{1}$ and focus at $F_{2}$ intersects the ellipse at a point $P$. If $\frac{\left|P F_{1}\right|}{\left|P F_{2}\right|}=e$, then the value of $e$ is . $\qquad$
12 In the parabola, the directrix is $x=-3$, and $\left|P F_{2}\right|$ is the distance from $P$ to the directrix; in the ellipse, $\frac{\left|P F_{1}\right|}{\left|P F_{2}\right|}=e$, and $\left|P F_{2}\right|$ is also the distance from $P$ to the left directrix, so the directrix of the parabola coincides with the left directrix of the ellipse, hence $\frac{a^{2}}{c}=3$. Since $c=1$, it is easy to know that $e=\frac{\sqrt{3}}{3}$.