Dolores Beasley

Headquarters, Washington                   April 10, 2002

(Phone: 202/358-1753)

Steve Roy

Marshall Space Flight Center, Huntsville, Ala.

(Phone: 256/544-6535)

Megan Watzke

Chandra X-ray Observatory Center, Cambridge, Mass.

(Phone: 617/496-7998)

RELEASE: 02-65

COSMIC X-RAYS REVEAL EVIDENCE FOR NEW FORM OF MATTER

     NASA's Chandra X-ray Observatory has found two stars -- 

one too small, one too cold -- that reveal cracks in our 

understanding of the structure of matter. These discoveries 

open a new window on nuclear physics, offering a link between 

the vast cosmos and its tiniest constituents.

Chandra's observations of RXJ1856.5-3754 and 3C58 suggest 

that the matter in these stars is even denser than nuclear 

matter found on Earth. This raises the possibility these 

stars are composed of pure quarks or contain crystals of sub-

nuclear particles that normally have only a fleeting 

existence following high-energy collisions. 

By combining Chandra and Hubble Space Telescope data, 

astronomers found that RXJ 1856 radiates like a solid body 

with a temperature of 1.2 million degrees Fahrenheit (700,000 

degrees Celsius) and has a diameter of about seven miles 

(11.3 kilometers). This size is too small to reconcile with 

standard models for neutron stars -- until now the most 

extreme form of matter known.

"Taken at face value, the combined observational evidence 

points to a star composed not of neutrons, but of quarks in a 

form known as strange quark matter," said Jeremy Drake of the 

Harvard-Smithsonian Center for Astrophysics (CfA) in 

Cambridge, Mass., and lead author of a paper on RXJ1856 to 

appear in the June 20, 2002, issue of The Astrophysical 

Journal. "Quarks, thought to be the fundamental constituents 

of nuclear particles, have never been seen outside a nucleus 

in Earth-bound laboratories."

Observations by Chandra of 3C58 also yielded startling 

results. A team composed of Patrick Slane and Steven Murray, 

also of CfA, and David Helfand of Columbia University, New 

York, failed to detect the expected X-radiation from the hot 

surface of 3C58, a neutron star believed to have been created 

in an explosion witnessed by Chinese and Japanese astronomers 

in A.D. 1181. The team concluded that the star has a 

temperature of less than one million degrees Celsius, which 

is far below the predicted value.  

"Our observations of 3C58 offer the first compelling test of 

models for how neutron stars cool, and the standard theory 

fails," said Helfand. "It appears that neutron stars aren't 

pure neutrons after all -- new forms of matter are required."

A teaspoonful of neutron-star material weighs a billion tons, 

as much as all the cars, trucks and buses on Earth. Its 

extraordinary density is equivalent to that of the nucleus of 

an atom with all the typical space between the atoms and 

their nuclei removed. An atom's nucleus is composed of 

positively charged protons and neutral neutrons, particles so 

small that 100 billion trillion of them would fit on the head 

of a pin.

Protons and neutrons are composed of even smaller particles 

called quarks, the basic building blocks of matter. Enormous 

atom-smashers are designed to probe the forces between quarks 

and the structure of the nucleus by smashing high-energy 

beams of nuclei into each other and observing the violent 

aftermath for a fraction of a second.

Drake cautioned that the observations of RXJ1856 could be 

interpreted as a more normal neutron star with a hot spot. 

Such a model is under consideration by Fred Walter of the 

State University of New York, Stony Brook, one of the 

discoverers of RXJ1856, which was originally found in 1996 by 

the German Roetgen satellite. However, the hot-spot model 

requires a very special orientation of the star with respect 

to the Earth to explain the absence of pulsations, which 

would be expected from the hot spot. The probability of such 

an orientation is quite small.

"Regardless of how these mysteries are resolved, these 

precise observations are highly significant," said Michael 

Turner of the University of Chicago. "They demonstrate our 

ability to use the universe as a laboratory where we can 

study some of the most fundamental questions in physics."

NASA's Marshall Space Flight Center in Huntsville, Ala., 

manages the Chandra program, and TRW, Inc., Redondo Beach, 

Calif., is the prime contractor. The Smithsonian's Chandra X-

ray Center controls science and flight operations from 

Cambridge, Mass.

Images and additional information about this result are 

available at:

http://chandra.harvard.edu 

and

http://chandra.nasa.gov

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