Complex sentence: Until recently, however, only about 11 Milky Way satellites were known (Pawlowski et al., 2015; Bechtol et al., 2015); and efforts have been underway to determine whether the predicted population of faint satellite galaxies could be observed.
Split into simpler sentences: Until recently, however, only about 11 Milky Way satellites were known (Pawlowski et al., 2015; Bechtol et al., 2015). Efforts have been underway to determine whether the predicted population of faint satellite galaxies could be observed.