Number 135 (Story #1), July 1, 1993 by Phillip F. Schewe and Ben Stein DURING THE LAST THREE MINUTES before two neutron stars or two black holes spiral in on each other and coalesce there should be a "chirp" in which the gravitational-wave emission from the system increases in frequency from 10 up to 1000 Hz. Since this sort of dying gasp is just what proposed gravitational wave detectors such as LIGO (in the US) and VIRGO (in Italy) would be looking for, scientists at Caltech and Northwestern have produced computer simulations of waveforms from such collapsing binary systems so that they'll be able to separate signal from noise when the time comes (Curt Cutler et al., Physical Review Letters, 17 May 1993). The shape of the signal may enfold more information than was previously thought. For example, in some cases it might be possible to calculate the neutron stars' mass, density, and composition. (Science News, 26 June 1993.)