Scientists think they've seen hint of dark matter Extra brilliance of stars is cited

September 21, 1993|By Los Angeles Times

Sudden, stunning flashes of brilliance by three nearby stars have led scientists to conclude they have seen the first direct evidence of one form of dark matter, the mysterious and until now unseen phenomenon that is believed to account for 90 percent or more of all mass in the universe.

Two teams of scientists, one American and Australian and the other French, reported yesterday at conferences in Italy that three stars in the Large Magellanic Cloud briefly grew brighter than usual, almost certainly because gravity from dark matter bent the star's light rays into focus on Earth.

Scientists said this particular type of dark matter most likely is in the form of a "brown dwarf," a blob of cold, listless gas the size of Jupiter. The example they detected is one of what is thought to be an ocean of billions of brown dwarfs engulfing the Milky Way galaxy.

The American and Australian researchers, led by Charles Alcock of the Lawrence Livermore National Laboratory near San Francisco, said they used a computerized, automated telescope find a star that grew seven times as bright as usual before returning to normal.

"This is an exciting result from a very elegant experiment," said P.J.E. "Jim" Peebles, a Princeton University astrophysicist.

The unusually intense increased brightness has led some scientists to wonder if the star was simply some unusual type of "variable" star, a class of stellar objects whose luminations wax and wane because of internal instabilities or other factors.

"Extraordinary results require extraordinary proofs," said University of Chicago astrophysicist Michael S. Turner. "They're

going to have to prove to their colleagues that this is not some weird sort of variable."

But the independent French findings seem to strengthen the American and Australian results.

According to what is known about the universe, ordinary visible matter -- stars, gas, dust and planets -- simply do not have sufficient mass by themselves to cause gas to condense into stars, stars to clump into galaxies and galaxies to gather into clusters.

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