 Stellar mass black holes can't get as close as neutron stars because their Schwarzschild radius is larger than the radius of a neutron star, but their mass alone can create larger gravitational wave amplitudes. Here we see a black hole merger simulation. If each black hole has a mass of seven suns, the Schwarzschild radius is 20 kilometers, twice the radius of the neutron stars. As the orbital radius shrinks to twice the Schwarzschild radius, and the black holes are approaching each other's photosphere, their velocities approach 70 percent of the speed of light. This produces a shorter gravitational wavelength and a larger amplitude, putting this kind of event well into the theoretically detectable area. A number of other major cosmological events can also create gravitational waves. Here is a chart of some of the events and their expected wavelengths and amplitudes. Supernova, binary mergers like the ones we've been analyzing, supermassive black hole mergers, and remnants from the Big Bang.