TITLE: Does there exist a curve defined over a number field $K$ such that every map to $\mathbb{P}^1_K$ is ramified over at least 4 points?
QUESTION [5 upvotes]: Belyi's theorem says that if $X$ is a curve defined over a number field $K$ then $X_{\overline{K}}$ admits a map to $\mathbb{P}^1_{\overline{K}}$ which at most 3 branch points. Must there also exist a map to $\mathbb{P}^1_K$ defined over $K$?
This may be a slightly lazy question, but I figure it's probably got a quick answer.

REPLY [2 votes]: To record nfdc23's answer:
The following is true:
If $X$ is a curve over a number field $K$, then it admits a map to $\mathbb{P}^1_K$ defined over $K$ branched over at most 3 points.
This follows from Theorem 2.5 in Mochizuki's 2004 paper here.