Wednesday, April 10, 2002


Evidence Found for New Form of Ultra-Dense Matter





By Robert Roy Britt
Senior Science Writer
posted: 10:45 am ET
10 April 2002

Story first posted at 10:03 a.m., April 10, 2002
Astronomers announced Wednesday the discovery of evidence for a new state of matter heavier than any previously known, equivalent in density to stuffing all of Earth into an auditorium.
The apparent discovery, made with NASA's orbiting Chandra X-Ray Observatory, provides support for a two-decade-old theory suggesting the existence of so-called "strange quark stars." The findings were discussed at a press conference at NASA headquarters in Washington D.C.
The research involved two stars expected to be neutron stars, remnants of exploded stars that are composed primarily of neutrons and would be very dense. One of the stars, however, was found to be much smaller than expected.
"It is too small to be explained by the theory that governs neutron stars," said Jeremy Drake, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics.
Drake and his colleagues examined a star called RXJ-1856. It was found to be about 1.2 million degrees Fahrenheit (700,000 degrees Celsius) and has a diameter of roughly 7 miles (11.3 kilometers). Drake said it's possible they measured a hot spot, but he thinks it's more likely that the observations are correct and the theory of neutron stars needs revision.
A paper on the work will appear in the June2

The other object, called 3C-58, became a new star in the sky in the year 1181, when it exploded. According to neutron star theory, some of the material collapsed into a dense core, while the rest was cast off into space.

Now, more than eight centuries later, researchers observed the remaining core with certain expectations about how much it should have cooled off. The star' temperature is less than a million degrees Celsius, far below what was expected.

"Our observations suggest that the core of this star is made of a new kind of exotic material," said David Helfand, professor of astronomy and astrophysics at Columbia University in New York. "It appears that neutron stars are not made of pure neutrons after all."

Instead, each of the stars in the two new studies may contain exotic particles called quarks.

Michael Turner, a widely respected cosmologist at the University of Chicago, said both studies appear to show that Nature is able to produce forms of matter that scientists have been unable to create in laboratories.

Quarks are thought to be fundamental building blocks of matter. But they have never been observed alone, instead always existing together as the components of other matter. If they were liberated inside a star, they could theoretically be compressed into a smaller sphere, researchers said.

The results "suggest the existence of a new state of matter that's made of undifferentiated quarks," Turner said. "If this is indeed the case, then astronomers have provided us with a stunning insight on quarks."

Turner said powerful telescopes like Chandra are making it more and more possible to use the universe as a laboratory to study Nature's tiniest phenomena.

Norman Glendenning is one of those researchers who has been unable to isolate quarks in a lab. The senior scientist emeritus at the Lawrence Berkeley National Laboratory said that if the observations are correct, then RXJ-1856 appears to be made only of quarks, and as so it would have a sharp edge, not the gradual fuzzy outer surface typical of neutron stars and other stars.

"If all that is so, this star is in a class quite by itself and will be an astonishing discovery of fundamental significance," Glendenning said.

And there may be deeper implications to the two discoveries.

If the work is correct, "it will tells us that there were two paths that the universe might have taken" at inception, Glendenning said. The other universe, had it developed instead, might have been limited in the sorts of matter that were created.

"It made all the difference in the world that the universe evolved along one path and not the other, or else we would not be here to contemplate its wonders," Glendenning said.

Anne Kinney, director of the Astronomy and Physics Division at NASA's Office of Space Science, cautioned, "I'd like to emphasize that this is evidence for, not proof of, a new form of matter."

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