Unlocking Secrest of the Universe

John Farnum Professor of Astronomy Stephen Boughn credits his mother for laying the first bricks of his career path during his childhood. “For Christmas in 1953, she gave me the Golden Book of Natural History,” he explains, “with a whole section on astronomy.”

He began as an experimental physicist, receiving his bachelor’s degree in physics from Princeton in 1969 and his master’s and Ph.D. from Stanford in 1970 and 1975 respectively. But facets of astronomy always seasoned his work. As an undergraduate he worked with a microwave radiometer for his senior thesis project, measuring the isotropy (lumpiness) of the Cosmic Microwave Background (CMB) — leftover heat radiation waves from the Big Bang. (His advisor for this project was Bruce Partridge, current professor of astronomy at Haverford.) In graduate school he built a cryogenic gravitational wave detector. Later, as an assistant professor of physics at Princeton, he built microwave radiometers to measure the CMB, used optical telescopes to make observations, and helped build an infrared camera to be used with the telescopes at the Wyoming Infrared Observatory. Before coming to Haverford in 1986, he was officially a physicist, but his research kept reaching for the stars.

Today, Boughn’s projects have firm footholds in astronomy, specifically cosmology — the study of the large-scale structure and evolution of the universe. For years he has studied the existence of dark matter and dark energy, unseen sources of gravitational force thought to comprise 95 percent of the universe’s energy content. According to Boughn, the presence of dark energy causes the expansion of the universe to accelerate rather than decelerate, resulting in the correlation of the CMB with distant gravitationally collapsing structures. This is known as the Integrated Sachs-Wolfe (ISW) effect.

To the non-scientific, this all may sound like an indecipherable interplanetary language. Fortunately, Boughn has a knack for smoothing out the knottiest concepts.

It begins, appropriately enough, with Einstein. “When Einstein first wrote down the equations of general relativity in 1915, they didn’t allow for a static universe,” says Boughn. “It could be either expanding or contracting, but was always being accelerated inward because of gravity.” Einstein invented the cosmological constant, a negative gravity that would keep the universe at rest.

Later, in 1929, astronomer Edwin Hubble (for whom the telescope is named) discovered that the universe was not at rest but was, in fact, expanding. “Einstein dropped the cosmological constant and called it the greatest blunder of his life,” says Boughn.

But he may have been hasty in his misgivings. In the mid-’90s astrophysicists revisited the existence of a cosmological constant, as it became clear from the behavior of the large-scale structure of the universe that Einstein’s equations weren’t accounting for the details of the structure. Two Princeton scientists predicted that, if there were a cosmological constant, some of the fluctuations in the CMB would correlate with fluctuations in the cosmic X-ray background. Boughn, who was a member of Princeton’s Institute for Advanced Studies during the 1996-97 academic year, had already been cross-correlating these fluctuations, and joined his Princeton colleagues in trying to detect the cosmological constant and the ISW effect that would result from it.

“For four to five years we couldn’t find the correlation,” says Boughn. “We only set limits as to how big the cosmological constant could be.”

Then in February of 2003, NASA’s W-Map satellite produced a new full-sky map of the CMB. Boughn and his colleagues checked this new map against their X-ray and radio maps and found a correlation that implied the presence of a cosmological constant or some other form of dark energy. “This was a direct indication that not only is the universe expanding, but the expansion is accelerating,” he says. “In terms of cosmology, this is probably the most important accomplishment in my modest career.” These findings were reported by Boughn and his collaborator, professor Robert Crittenden, in an article for the Jan. 1 edition of the journal Nature.

Last year, Boughn was a visiting fellow at Princeton as he took a sabbatical from Haverford during the 2003-2004 academic year and continued studying the CMB and the ISW effect. Another aspect of his research involves searching for intergalactic diffuse light that exists in regions between galaxies. He looks at the formation and evolution of huge clusters of galaxies. “Galaxies in close contact occasionally smash into each other,” he says, “and gravity can strip these galaxies of their outer layers of stars. The light is so spread out and faint it’s hard to see.”

Boughn, who won a Christian and Mary Lindback Award for Teaching in 1989, often involves his Haverford students in his research projects, affording them the opportunity to work alongside him collecting and analyzing data. “Being involved in research is not the same as coursework, because there are no answers to the problems in the back of the book,” he says. “But it’s a wonderful experience to be confused about what you’re doing and then find your way out of that confusion.”

Christine Lamanna ’04 worked with Boughn during the summer of 2002, helping him cross-correlate the CMB with radio sources in an attempt to measure the acceleration of the universe’s expansion. “Working with Steve has been challenging and rewarding,” she says. “Because of him I intend to pursue a career in astrophysics, specifically in his own field of observational cosmology. I know this will be extremely challenging — especially because very few women are in this field — but with Steve’s preparation, I know I have the skills to tackle this task.”

Those not inclined toward astronomy might wonder: Why is research such as Boughn’s important, and how will it affect the human race in the grand scheme of things? Boughn admits that his wife Susan, a professor of nursing and women’s studies at the College of New Jersey, has posed this same question to him. “In one sense, understanding how the universe was created, what it was like some 13 billion years ago, how it evolved into the kind of universe we live in now and where it’s going, you don’t even have to ask if it’s an important question — how could studying the universe not be important?” he says. “But is it likely to do anything to alleviate human suffering? No.” However, Boughn believes that if the only kind of scientific research funded is the kind that will result in technological advances and applications to improve others’ lives, then science as a field may fade into obscurity. “It’s important to pursue science from a pure inquiry point of view,” he says.

“Besides,” he adds, “if I have to justify my existence as a human being and why I’m a useful member of society, I never say I’m a cosmologist. I say I’m a teacher.”

Steve Boughn has taught the following courses in astronomy and physics:

Freshman Seminar in Astrophysics
This half-credit course is intended for prospective physical science majors with an interest in recent developments in astrophysics. Topics in modern astrophysics will be viewed in the context of underlying physical principles. Topics include black holes, quasars, neutron stars, supernovae, dark matter, the Big Bang, and Einstein’s relativity theories.

Introduction to Astrophysics I
General introduction to astronomy including: the structure and evolution of stars; the structure and formation of the Milky Way; the interstellar medium; and observational projects using the Strawbridge Observatory telescopes.

Observational Optical Astronomy
Five observing projects that involve using the CCD camera on a 16-inch Schmidt-Cassegrain telescope. Projects include spectroscopy; variable star photometry; H-alpha imaging; imaging and photometry of galaxies and star cluster; instruction in the use of image processing software and CCD camera operation.

Stellar Structure and Evolution
The theory of the structure of stellar interiors and atmospheres and the theory of star formation and stellar evolution, including compact stellar remnants.

Research in Astrophysics
Intended for those students who choose to complete an independent research project in astrophysics under the supervision of a faculty member.

Advanced Electromagnetism
Boundary value problems, multipole fields, electromagnetic waves, optical properties of solids, radiating systems, diffraction, scattering, optical interferometry and Fourier optics.

General Relativity
Development and application of tensor calculus to the theories of special and general relativity; review of observational and experimental evidence; consideration of problems of astrophysics, particularly gravitation