  The only way to detect planets around stars at distances of several kpc is by
(photometric or astrometric) microlensing observations. In this paper, we show
that the capability of photometric microlensing extends to the detection of
signals caused by planets around stars in nearby galaxies (e.g. M31) and that
there is no other method that can achieve this. Due to the large crowding,
microlensing experiments towards M31 can only observe the high-magnification
part of a lensing light curve. Therefore, the dominating channel for
microlensing signals by planets is in distortions near the peak of
high-magnification events as discussed by Griest and Safizadeh. We calculate
the probability to detect planetary anomalies for microlensing experiments
towards M31 and find that jupiter-like planets around stars in M31 can be
detected. Though the characterization of the planet(s) involved in this signal
will be difficult, the absence of such signals can yield strong constraints on
the abundance of jupiter-like planets.
