Wednesday, January 6, 1999

UH astronomer
offers ‘ghost
galaxy’ evidence

By Susan Kreifels


We may not see it as we scan the skies, but the dark stuff -- the "ghost galaxies" -- could determine the future of the universe.

That's why research presented in Texas today by John Kormendy, a professor of astronomy at the University of Hawaii, could have so much impact.

Kormendy's paper provides strong evidence that there could be many "ghost galaxies" of dark matter, a term he has coined. Although scientists cannot see dark matter, its gravitational force pulls on all other stuff of the universe.

"The future of the universe as we know it depends on how much dark matter there is," said colleague Gareth Wynn-Williams, also a UH astronomy professor. "If there's enough of it, it could stop the universe from expanding and make it collapse in a big crunch."

Astronomers have known for several years that most of the universe is made of dark matter, but they don't know what that matter is or how much is out there. They do know, however, that the dark matter exerts gravitational pull on the rest of the universe.

Kormendy has been searching out the dark matter by studying the movement of stars, which are pulled by this darkness. He has discovered that small galaxies, known to be much more numerous than large ones, are also more dominated by dark matter.

The Milky Way, a large galaxy, is about 50 percent dark. The smallest "dwarf galaxies," on the other hand, are almost completely dark. And there could be many that are invisible.

"Up till now we have found galaxies because they have stars and we see them shine," Kormendy said in a phone interview from Austin, Texas, where he presented his paper to the American Astronomical Society.

"We now have good reason to believe there could be an awful lot of these little (dark) guys. There may be whole galaxies out there that we haven't been able to find because they are dark."

Kormendy said the lack of information on dark matter became an "acute crisis" in the late 1970s among astronomers because of its implications for the evolution of the universe.

But because dark matter can't be seen, he said, it's difficult to study, and research has been slow.

Kormendy also found that the smaller the galaxy, the older it is, another important aspect of his study.

"They are relics of the earliest phase of galaxy formation," Kormendy said.

Just as significant, his observations make Earth, the Milky Way and other familiar parts of the universe less significant.

"You realize the place where you are is less special than you thought," Kormendy philosophized. "In the 1970s we began to realize the stuff the universe is made out of is not the ordinary stuff, not stars.

"That's like the frosting on the cake.

"The cake is the dark stuff."

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