5. Given that $F_{1}$ and $F_{2}$ are the left and right foci of the ellipse $C: \frac{x^{2}}{19}+\frac{y^{2}}{3}=1$, and point $P$ is on the ellipse $C$. If $S_{\triangle P F_{1} F_{2}}=\sqrt{3}$, then $\angle F_{1} P F_{2}=$ $\qquad$