  It was suggested by several authors that hypothetical primordial black holes
(PBHs) may contribute to the dark matter in our Galaxy. There are strong
constraints based on the Hawking evaporation that practically exclude PBHs with
masses m~1e15-1e16g and smaller as significant contributors to the Galactic
dark matter. Similarly, PBHs with masses greater than about 1e26g are
practically excluded by the gravitational lensing observation. The mass range
between 10e16g<m<10e26g is unconstrained. In this paper, we examine possible
observational signatures in the unexplored mass range, investigating
hypothetical collisions of PBHs with main sequence stars, red giants, white
dwarfs, and neutron stars in our Galaxy. This has previously been discussed as
possibly leading to an observable photon eruption due to shock production
during the encounter. We find that such collisions are either too rare to be
observed (if the PBH masses are typically larger than about 1e20g), or produce
too little power to be detected (if the masses are smaller than about 1e20g).
