NASA physicist realizes her dream by discovering two new stars with space-based observatory

June 08, 1999

As a child, NASA astrophysicist Dr. Colleen Wilson-Hodge and her father observed craters on the Moon with a small telescope. Now, using one of NASA's most powerful telescopes, she has been able to look at the outer reaches of the universe and has discovered two new, exotic stars called X-ray pulsars.

"I've always wanted to be an astronomer," said Wilson-Hodge, who has worked at NASA's Marshall Space Flight Center in Huntsville, Ala., for 10 years while earning undergraduate and doctorate degrees.

Wilson-Hodge's parents encouraged her to pursue her dreams.

"They always told me I could do anything and it didn't matter that there weren't many women in the career I dreamed of pursuing," she said.

Wilson-Hodge is a member of the instrument team for the Burst and Transient Source Experiment on NASA's orbiting Compton Gamma Ray Observatory. The 34-member team includes five women -- three with doctorate degrees and two with undergraduate degrees -- all working in the field of high-energy astrophysics. Other women work on the project as computer scientists, engineers, and in educational outreach.

The team's make-up reflects surveys by the American Astronomical Society that indicate more young women are becoming astronomers. The society's data show that approximately one in three young astronomers are women and about 20 percent of doctorate degrees in astronomy and physics are awarded to women.

Wilson-Hodge became intrigued by the world of high-energy astrophysics because of the example of Dr. Gerald Fishman, the principal investigator at the Marshall Center for the Burst and Transient Source Experiment. Fishman's excitement about the Gamma Ray Observatory and its ability to reveal a view of the universe never seen before proved contagious.

Like Fishman, Wilson-Hodge hopes to become a science team leader and design a new instrument capable of detecting even more of the invisible universe. "Gamma-ray astronomy is opening up a whole new frontier of research," she said. "I decided to become a gamma-ray astronomer because there was more potential for discovering something new. Pulsars were particularly fascinating because they were bizarre, mysterious stars and not much was known about them."

A pulsar is a rotating neutron star formed when a large, ordinary star explodes as a supernova and then collapses. A neutron star is very small and dense but has a tremendously strong magnetic and gravitational field. Wilson-Hodge discovered a particular type of pulsar called an X-ray pulsar. Unlike radio pulsars, which are powered by rotation and emit radio waves as they spin slower and slower, X-ray pulsars emit X-rays and gamma-rays and are powered by accretion -- gobbling up material from a companion star.

"Discovering a new pulsar is very exciting. When I was a kid, I imagined a job at NASA would be like this. For just a little while, the universe is putting on a show that only I -- and members of the gamma-ray team -- know about."

Both pulsars discovered by Wilson-Hodge do appear to be devouring material ejected by superhot, blue-white stars that emit visible light and are eight to 15 times more massive than our Sun. As these X-ray pulsars orbit another star, their strong gravity pulls the matter toward their surfaces.

"We get a giant outburst from matter being dumped onto the surface of the pulsar," said Wilson-Hodge. This outburst is accompanied by increases in X-ray and gamma-ray emissions that help astronomers discover new stars not visible to the naked eye.

"When I think there is a new source in the Burst and Transient Source Experiment data, I can't wait to get to work to see what the source will do next," she said. "I'm like a kid waiting to open a Christmas present."

Her most recent pulsar discovery came Sept. 7, 1998. It has two names -- XTE J1946+274 and GRO J1944+26 -- because both the Compton Gamma Ray Observatory and the Rossi X-Ray Timing Explorer captured its signal.

"My first pulsar discovery was the most exciting," conceded Wilson-Hodge of her 1995 discovery of GRO J2058+42. "At the time I found it, I knew we were the first to see it. It is thrilling to study something no one has ever seen before."

Wilson-Hodge has bachelor's degrees in physics and math from the University of Arkansas and a master's in physics from the University of Alabama in Huntsville, where she also recently completed her doctorate in physics. Her dissertation is on X-ray transient pulsars -- like the ones she located with this detector developed at the Marshall Center -- and a type of pulsar thought to be a magnetar, one of 1998's biggest astronomical discoveries.
Note to Editors: For more information, photographs or to arrange interviews, contact Steve Roy of the Marshall Media Relations Office at 256-544-6535 or 256-544-0034 or visit Marshall's News Center on the Web at:

For more information on Wilson-Hodge?s discoveries and other Compton Gamma Ray Observatory science highlights, visit the Marshall Space Sciences Laboratory Web site at:

NASA Photo #9900609: Colleen Wilson-Hodge, an astrophysicist at NASA's Marshall Space Flight Center in Huntsville, Ala., recently discovered two pulsars using the Burst and Transient Source Experiment. The prototype of the burst detector (left) is similar to the eight gamma-ray burst detectors orbiting Earth on NASA's Compton Gamma Ray Observatory.

View this photo at:

NASA/Marshall Space Flight Center News Center

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