ROANOKE TIMES
                         Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: THURSDAY, July 12, 1990                   TAG: 9007120166
SECTION: NATIONAL/INTERNATIONAL                    PAGE: A8   EDITION: METRO 
SOURCE: Associated Press
DATELINE: NEW YORK                                LENGTH: Medium


STUDY: 'DARK MATTER' OF GALAXIES IS STARS, DUST

Part of the universe's mysterious, elusive "dark matter" may be just ordinary stars hidden by dust, a study suggests.

The study concludes that spiral-shaped galaxies contain far more light-blocking dust than scientists had thought.

If that is true, it weakens one line of evidence for the existence of unseen mass called dark matter. But it does not address other arguments for the matter's existence, scientists said.

Dark matter is thought to exist because visible objects can account for only about 10 percent of the mass detected in the universe.

One line of evidence is that the rotation of spiral galaxies appears to reflect the gravitational tug of unseen objects. The new study suggests that at least part of this gravitational pull actually may come from undetected stars hidden by dust in the galaxies.

The work is presented in today's issue of the British journal Nature by Edwin Valentijn of the European Southern Observatory and the Kapteyn Astronomical Institute in The Netherlands.

He analyzed the brightness of 9,381 galaxies, and concluded that major parts of many spiral galaxies are opaque. "In many cases, perhaps only the outer layer of stars is observable," he wrote.

The work "looks like a careful analysis using new data," commented astrophysicist Jeremiah Ostriker of Princeton University. If it is true, he said, it would reduce the need to invoke dark matter to explain behavior of galaxies.

Susan Simkin, a Michigan State University professor of physics and astronomy who studies brightness of galaxies, said the result must be checked in further studies. But it fits previous evidence from satellite observations, she said.

The study did not address two major arguments for the existence of dark matter, said David Latham of the Harvard-Smithsonian Center for Astrophysics.

One is a theoretical belief that the universe must contain more mass than is observed, so that its expansion will be halted. The other is that immense clusters of galaxies must contain unseen mass to explain the orbits of their individual galaxies, he said.



 by CNB