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Hailey and Mori's New Atomic Calculation Uncovers a Neutron Star's Strange Atmosphere

By Caroline Ladhani

Charles Hailey

Neutron stars, those dense, mysterious remnants of burned-out suns that haunt the universe, may be surrendering some of their secrets to a new computer program developed at Columbia. This program rapidly calculates atomic properties of matter near a highly magnetized neutron star.

The program has already revealed new findings on the composition of one neutron star, and its continued application to neutron star interiors could bring scientists one step closer to understanding what the universe was like just after the Big Bang.

Physics Professor Charles Hailey and graduate student Kaya Mori created the program to study data transmitted from powerful satellite telescopes deep in space. It enables them to analyze the emissions from neutron stars with great speed and accuracy.

"It's been a long-term goal of neutron star physics to know the composition of a neutron star, both its atmosphere and its interior core," Professor Hailey said. "By studying the emissions of neutron stars, we potentially can learn about the exotic states of matter in their interiors."

For several years scientists have been studying data transmitted to Earth from two giant satellite telescopes, the Chandra X-Ray and the XXM-Newton. Hailey and Mori's new program enables them to analyze the data using quantum mechanics equations, which it can analyze at lightning speeds.

Kaya Mori

Hailey and Mori are focusing their research on an unusual neutron star known as 1E1207.4-5209, which was discovered in 1984 by another Columbia professor, David Helfand. Unlike most other neutron stars, which are binary, that is, they have another celestial body orbiting them, 1E1207.4-5209 is a solitary star. Additionally, its atmosphere differs from other neutron stars in that it is not composed of hydrogen.

These characteristics make it a particularly intriguing subject of study. Hailey and Mori begin with a spectroscopic analysis of data, which breaks X-rays into their component colors. By analyzing the wavelengths of radiation from a star, astronomers produce a unique "fingerprint" from which they can infer various characteristics of the star.

"Through X-ray or visible light, you see features that can teach us about conditions on the star, such as its temperature, density and composition," Hailey said, adding that if a star has no fingerprint, it suggests an atmosphere of hydrogen. This has been the case with all neutron stars, with the exception of 1E1207.4-5209.

Recent data from this star, transmitted by the Chandra X-ray satellite and analyzed this summer at another institution, revealed a fingerprint for the first time on any neutron star. Hailey and Mori entered this data into their new computer program, which compared it to computer-generated fingerprints of all possible elements and magnetic fields, until they found the combination that matched what had been observed by the telescope. From this they were able to determine that this object had an oxygen or neon atmosphere. This is the first clear evidence that neutron star atmospheres are composed of something other than hydrogen.

Published: Dec 02, 2002
Last modified: Nov 29, 2002

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