eLISA/NGO will measure gravitational wave signals from a wide range of sources that are of strong interest for a deeper understanding of the cosmos.
In the same way that accelerated electric charges generate electromagnetic radiation, accelerated mass and energy generate gravitational radiation. The periodic motion of a system of mass M and size R at a (luminosity) distance D creates gravitational waves with a strain amplitude of about h ~ (GM/(Rc2 ))2 (R/D), with a frequency determined by the frequency of the motion. The shapes and strengths of the observed waves give us details about the structure and behaviour of the system that produced them.
eLISA/NGO data is expected to shed light on
- the astrophysics of black holes and galaxy formation,
- merging massive black holes in galaxies at all distances,
- massive black holes swallowing smaller compact objects like neutron stars,
- known binary compact stars and stellar remnants,
- members of known populations of more distant binaries,
- probably other sources, possibly including relics of the extremely early Big Bang, which are as yet unknown,
and it will provide exceptionally strong tests of the predictions of general relativity. These unique dynamical tests are based on mergers of two massive black holes with maximally warped vacuum spacetimes travelling nearly at the speed of light and interacting strongly with each other. This system will allow us to test the full nonlinear dynamics of gravitational theory.