The Milky Way contains approximately 150 observed globular clusters, such as M30, shown here, as imaged by the Hubble Space Telescope. Globular clusters are dense environments containing millions of stars packed tightly together. These clusters are efficient factories of gravitational wave sources that can be observed by detectors such as LIGO and the upcoming space-based observatory, LISA. A new Northwestern University study predicts approximately 50 binaries in the clusters will be detectable by LISA. These binary sources would contain all combinations of black hole, neutron star and white dwarf components.