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Nest of stars spotted by X-ray telescope

May 18, 2001
Web posted at: 7:14 a.m. EDT (1114 GMT)

In a region of the sky equivalent to 1/15th the diameter of the full Moon, this Chandra image shows over 100 X-ray sources. The different colors represent the dominant X-ray energy range for different sources  

(CNN) -- Scientists using a combination of high-powered telescopes say they have found a bonanza of binary stars, a find that could help explain the evolution of globular clusters, some of the oldest structures in our galaxy.

The researchers used the Chandra X-ray telescope, the Hubble Space Telescope, and ground-based radio telescopes to study binary systems that dominate a globular cluster called 47 Tucanae. The system is about 12 billion years old and is located in our Milky Way galaxy.

Most of the binary stars in 47 Tucanae have normal, sun-like companions that orbit a collapsed star, either a white dwarf or a neutron star.

White dwarf stars are dense, burned-out remnants of stars such as the sun; neutron stars are even denser. When matter from a nearby star falls onto either a white dwarf or a neutron star, X-rays are produced.

"This Chandra image provides the first complete census of compact binaries in the core of a globular cluster," said Josh Grindlay of the Harvard-Smithsonian Center for Astrophysics (CfA). Grindlay is the lead author of the report that appears in the May 18 issue of Science.

"The relative number of neutron stars versus white dwarfs in these binaries tell us about the development of the first stars in the cluster, and the binaries themselves are key to the evolution of the entire cluster core," he said in a press release.

Many of the binaries in 47 Tucanae have never before been seen in such large quantities. They include "millisecond pulsars", which contain rapidly rotating neutron stars.

"The Chandra data, in conjunction with radio observations, indicate that there are many more millisecond pulsars than we would expect based on the number of their likely progenitors we found," said co-author Peter Edmonds, also of the CfA.

The Chandra observations of 47 Tucanae were conducted March 16-17, 2000.

• Chandra X-Ray Observatory Center
• Chandra's NASA link

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