Gravity Waves Analysis Opens "Completely New Sense"

Wai-Mo Suen, Ph.D., professor of physics at Washington University in St. Louis is collaborating with researchers nationwide to develop waveform templates to comprehend the signals to be analyzed. In this manner, researchers will be able to determine what the data represent -- a neutron star collapsing, for instance, or black holes colliding.

"In the past, whenever we expanded our band width to a different wave length region of electromagnetic waves, we found a very different universe," said Suen. "But now we have a completely new kind of wave. It's like we have been used to experiencing the world with our eyes and ears and now we are opening up a completely new sense."

Suen discussed the observational and theoretical efforts behind this new branch of astronomy at the 40th annual New Horizons in Science Briefing, Oct. 27, 2002, at Washington University in St. Louis. The gathering of national and international science writers is a function of the Council for the Advancement of Science Writing.

Gravity waves will provide information about our universe that is either difficult or impossible to obtain by traditional means. Our present understanding of the cosmos is based on the observations of electromagnetic radiation, emitted by individual electrons, atoms, or molecules, and are easily absorbed, scattered, and dispersed. Gravitational waves are produced by the coherent bulk motion of matter, traveling nearly unscathed through space and time, and carrying the information of the strong field space-time regions where they were originally generated, be it the birth of a black hole or the universe as a whole.

This new branch of astronomy was born this year. The Laser Interferometer Gravitational Wave Observatory (LIGO) at Livingston, Louisiana, was on air for the first time last March. LIGO, together with its European counterparts, VIRGO and GEO600, and the outer-space gravitational wave observatories, LISA and LAGOS, will open in the next few years a completely new window to the universe.

Supercomputer runs Einstein equation to get templates

Suen and his collaborators are using supercomputing power from the National Center for Supercomputing Applications at the University of Illinois, Urbana-Champaign, to do numerical simulations of Einstein's equations to simulate what happens when, say, a neutron star plunges into a black hole. From these simulations, they get waveform templates. The templates can be superimposed on actual gravity wave signals to see if the signal has coincidences with the waveform.

"When we get a signal, we want to know what is generating that signal," Suen explained. "To determine that, we do a numerical simulation of a system, perhaps a neutron star collapsing, in a certain configuration, get the waveform and compare it to what we observe. If it's not a match, we change the configuration a little bit, do the comparison again and repeat the process until we can identify which configuration is responsible for the signal that we observe."

Suen said that intrigue about gravity waves is sky-high in the astronomy community.

"Think of it: Gravity waves come to us from the edge of the universe, from the beginning of time, unchanged," he said. "They carry completely different information than electromagnetic waves. Perhaps the most exciting thing about them is that we may well not know what it is we're going to observe. We think black holes, for sure. But who knows what else we might find?"