This is an image of the sky as viewed by gravitational waves.
The Milky Way galaxy forms the band in the middle of the image. LISA will see thousands of binary star systems in our galaxy. Most of these will be White Dwarf binaries with orbital periods of a few hours. Some will contain neutron stars or black holes. LISA will be able to determine the position (direction and distance) to each binary, as well as the periods of the orbits and the masses of the stars.
Type Ia supernovae may occur when white dwarf binaries, with total mass 1.4 times the mass of the sun, lose enough energy to gravitational waves for the stars to collide. LISA will determine the directions to, and time of collision, for the next 500 type Ia supernovae in our galaxy.
Outside our galaxy, binary stars will be too weak to be seen. Instead, LISA will see gravitational waves associated with the massive black holes in the centers of other galaxies (millions of times the mass of our sun). Massive black holes may have formed before most stars. They may have originated from the coalescence of smaller black holes. LISA will investigate this and other formation mechanisms for massive black holes.
When galaxies collide, the massive black holes at their centers will interact, producing prodigious amounts of gravitational radiation, the most energetic events in the Universe. LISA will see these anywhere they occur in the Universe, probably several per year.
When normal black holes (a few times the mass of our sun) fall into massive black holes in the centers of galaxies, they will undergo bizarre orbit changes and emit gravitational waves. LISA will see these waves, which will provide a high precision test of General Relativity in the region near massive black holes.
The early Universe was so hot that all particles were ionized, making it impossible for light to travel until the universe cooled enough for atoms to form. LISA may see gravitational waves from the early Universe as a background, analogous to the 3 degree radiation background imaged by COBE but much earlier in time. This will reveal new information on the origin of structure in the Universe and the physical processes of extreme states of matter.