Clockwise from top left: 1) Numerical simulation of gravitational waves generated by a black hole, 2) supernova 1987A, 3) Tarantula Nebula, 4) Whirlpool Galaxy M51, 5) Hourglass Planetary Nebula, 6) Cat's Eye Nebula, 7) supernova remnant M1, 8) supernova remnant Cas A.