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Exploring the Origins of the Universe
By Jennifer Fisher Wilson
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Jacqueline N. Hewitt '80 |
When Jacqueline N. Hewitt '80 started graduate studies in astrophysics at the Massachusetts Institute of Technology, Cambridge, she launched into a field of research that was undergoing radical changes. Advances in digital signal processing were changing the way radio telescopes were built and giving them exciting new capabilities. And just a year earlier, scientists had discovered the first gravitational lens — a phenomenon that occurs when light from a distant, bright source like a quasar is "bent" by the gravitational field of a massive object, such as a galaxy, located between the source object and the observer. Gravitational lenses provided astrophysicists an important, new way to measure mass distribution.
"Measuring mass distribution was something that was previously very difficult to do. With gravitational lensing, you could measure things at very long distances to find out what's out there in the universe. You could actually probe the history of the universe and see how it behaved long ago," Hewitt says. "It was very exciting to be at the beginning of a very new field like that."
For her doctoral thesis, Hewitt traveled to a remote location 7,000 feet above ground level in the plains of St. Augustine, N.M, where she used the new Very Large Array radio telescope — a Y-shaped configuration of 27 radio dish antennas — to compile the first major systematic survey of gravitational lenses. "Up to that point, gravitational lenses had been discovered accidentally here and there, and the systematic approach helped us begin to understand them. You know better what you've got if you don't discover them by accident," Hewitt observes. "There I was with a whole new research instrument and a whole new research topic in the middle of nowhere, surrounded by scientists from all over the world. It was terrific fun."
Interdisciplinary Research
Hewitt's thesis was the beginning of a remarkable astrophysics career that has helped shape a more unified picture of the phases of the early universe. In 1986 she was hired as a postdoctoral associate in the Very Long Baseline Interferometry group at the MIT Haystack Observatory. She joined the MIT faculty in 1989 as an assistant professor of physics, where she continued to work on gravitational lenses, cosmology and surveys of transient astronomical radio emission. She also pioneered new astrophysical applications of radio astronomy, interferometry, and image and signal processing.
Since 2002, Hewitt has directed MIT's Kavli Center for Astrophysics and Space Research, formerly the Center for Space Research. The interdisciplinary center supports research in space science and engineering, astronomy and astrophysics. As Hewitt notes, the center provides an exciting marriage of science and technology. Its varied projects incorporate X-ray, optical, radio and planetary astronomy, theoretical astrophysics, space plasma physics, gravitational and cosmological physics, and theoretical plasma physics.
Looking Back in Time
Hewitt is currently working with the Kavli Institute's radio astronomy group and others to build a new low-frequency-array telescope at Mileura Station in remote Western Australia. The telescope will initially employ 500 antennas to detect very-low-frequency radio waves, and if it is successful it will be expanded to several thousand antennas. The location is important because of the need for "radio quiet" — that is, no interference from television stations, airplane communication, cell phones or other intrusive radio frequencies.
The new telescope will be able to detect primordial neutral hydrogen, the focus of Hewitt's current research. "Neutral hydrogen is very, very far away, and because the speed of light is constant, when you look at something so far away, you are seeing how it appeared in the distant past. We want to look at the universe before there were any stars — when it was just a cloud of hydrogen and dark matter and dark energy — to understand the process of star formation and even the origins of matter," she says. "We believe that the universe started out very hot and, as it cooled, various particles condensed out of the mix and produced the matter that exists today. The research is fundamental: we still don't know what 99 percent of the universe is. It is really remarkable."
Traveling Family
Hewitt has included her family in her work. She is married to Robert Redwine, Ph.D., a nuclear physicist who is currently dean of undergraduate education at MIT, and they have 11- and 16-year-old sons. Together they have traveled the world to visit new observatories. She hopes that once the Mileura telescope is completed, she can convince her family to travel there with her.
Looking back on her own early influences in science, Hewitt credits Bryn Mawr with introducing her to physics and astronomy. "I came to Bryn Mawr convinced that I did not want to do science. But a friend of mine had taken Astronomy 101 at Haverford and recommended it to me. I took the class, and it grabbed me in a way that chemistry and other sciences never had before," she recalls. It was too late to change her major, so she graduated with a degree in economics.
Twenty-five years later, Hewitt still finds astrophysics an amazing, stimulating challenge. "It's hard work and sometimes frustrating," she said. "But, on the whole, it's a privilege to do what I do."
Jennifer Fisher Wilson is the science writer for the Annals of Internal Medicine .
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