  A mechanism of formation of gravitational waves in the Universe is considered
for a nonspherical collapse of matter. Nonspherical collapse results are
presented for a uniform spheroid of dust and a finite-entropy spheroid.
Numerical simulation results on core-collapse supernova explosions are
presented for the neutrino and magnetorotational models. These results are used
to estimate the dimensionless amplitude of the gravitational wave with a
frequency \nu ~1300 Hz, radiated during the collapse of the rotating core of a
pre-supernova with a mass of 1:2M(sun) (calculated by the authors in 2D). This
estimate agrees well with many other calculations (presented in this paper)
that have been done in 2D and 3D settings and which rely on more exact and
sophisticated calculations of the gravitational wave amplitude. The formation
of the large-scale structure of the Universe in the Zel'dovich pancake model
involves the emission of very long-wavelength gravitational waves. The average
amplitude of these waves is calculated from the simulation, in the uniform
spheroid approximation, of the nonspherical collapse of noncollisional dust
matter, which imitates dark matter. It is noted that a gravitational wave
radiated during a core-collapse supernova explosion in our Galaxy has a
sufficient amplitude to be detected by existing gravitational wave telescopes.
