Gravitational Wave Sources: From Quadrupole Moment to Compact Objects

This article explores the sources of gravitational waves. According to general relativity, the generation of gravitational waves is related to the time-varying quadrupole moment of the matter distribution in spacetime. Unlike electromagnetic waves, the lowest-order source term for gravitational waves is the quadrupole moment, meaning only non-spherical, accelerating objects can produce significant gravitational waves. Compact objects like white dwarfs, neutron stars, and black holes, and their binary systems are major sources of gravitational waves. Their non-spherical shapes and orbital motion cause changes in the quadrupole moment, generating detectable gravitational waves.