Margaret Geller

• Born: December 8, 1947
• Place of Birth: Ithaca, New York

• AMERICAN ASTROPHYSICIST
• American astrophysicist Margaret Geller’s research into the structure of galaxies yielded a new understanding of their shape and distribution. With colleague John Huchra, Geller discovered and named the Great Wall, a superstructure cluster of galaxies.
• BORN: December 8, 1947; Ithaca, New York
• PRIMARY FIELDS: Physics; astronomy
• SPECIALTIES: Astrophysics; cosmology

Early Life

Margaret Joan Geller was born in Ithaca, New York, on December 8, 1947. Her father, a chemist who specialized in crystallography, encouraged her early interest in science and mathematics. She also learned from his example that science could be a useful and rewarding field. Often bored with her curriculum at school, Geller became an ambitious autodidact. It was unusual in the 1950s for a girl to be interested in mathematics and science, but the reactions she drew prepared her for a future in a male-dominated field.

Geller’s family moved to Los Angeles during her high-school career. Geller began attending the University of California, Berkeley in 1966 and earned her undergraduate degree in physics four years later. While deciding on her field of study for graduate and doctoral work, she was advised by one of her physics professors to enter a field that would evolve over the next decades into a major discipline, and thus she chose astrophysics.

The physics department at Princeton University, New Jersey, in the 1970s was still male dominated, and Geller was only the second woman to earn a place in the program. She obtained her master’s degree in 1972 and her PhD in 1974. Her doctoral thesis, entitled “Bright Galaxies in Rich Clusters: A Statistical Model for Magnitude Distributions,” employed statistics to discern the patterns of brightness and motion given off by galaxy clusters, with the ultimate goal of mapping the structure of the universe.

Life’s Work

Between 1974 and 1980, Geller undertook two fellowships, one as a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and the other as a senior visiting fellow at the Institute of Astronomy at Cambridge University in England. She also worked as a research associate and lecturer at Harvard University, which led to an offer in the 1980s to join the faculty as an untenured assistant professor. She became a full professor of astronomy at Harvard in 1988.

At Harvard, Geller began collaborating with fellow American astrophysicist John Huchra. Over the course of the 1980s, they performed major research and published results that detailed newly found structures of the universe. In 1983, Geller began working as an astronomer in the Smithsonian Astrophysical Observatory at the Harvard-Smithsonian Center. She was promoted to senior astronomer in 1991.

Before Geller began her astrophysics research, portions of the universe had been two-dimensionally mapped. Geller wanted to map the circumference of the space around Earth, extending five hundred million light-years away in three dimensions. Thus, not only the galaxies’ positions would be understood, but so would their large-scale structures and distance from Earth.

The American astronomer Edwin Hubble posited in 1929 that the distance of galaxies can be inferred from the speed with which they move away from Earth; those moving the fastest are farthest away. Using what was later named Hubble’s law, a scientist can estimate the age and size of the universe, and thus calculate its expansion rate. Geller and Huchra were not the first astrophysicists to apply Hubble’s law to create maps of the universe, but they went further than anyone had before.

Geller and Huchra began mapping their proposed five-hundred-million-light-year space around Earth in large wedges, until they had completed the circumference; one of the wedges was later named after them. To do this, they used the 1.5-meter telescope of the Smithsonian Observatory located in Arizona, and later a 6.5-meter telescope, to obtain spectrographic images in what are called redshift surveys. Redshift indicates the speed at which a galaxy is moving away from Earth because of the universe’s expansion; when this movement occurs, light waves appear to lengthen and thus move toward the red end of the visible spectrum. Though redshift does not yield exact measurements of distance, it gives a close approximation: the faster a galaxy is moving away, the greater its redshift and thus the greater its distance from Earth. Redshift surveys allow astrophysicists to view the universe in its current state, adjusted for the amount of time it takes light to travel, and understand the form the universe took historically. The initial aim of Geller and Huchra’s project was to establish the specifics of fifteen thousand galaxies in this manner, with each galaxy measured individually.

In 1989, Geller and Huchra discovered an enormous cluster of galaxies that they deemed the “Great Wall.” Also called the Coma Wall, Coma Cluster, or CfA2 Great Wall, this superstructure measures more than five hundred million light years in length, three hundred million light years in width, and fifteen million light years in thickness. It was the largest known structure in the universe at the time.

Geller authored numerous academic articles in collaboration with other scientists, as well as articles written for general audiences. Her commitment to educating the public on astronomy made her a popular figure in lecture halls and on radio, television, and film. Geller popularized her discoveries and her working methods in educational films, including two made with the cinematographer Boyd Estus. The first of these, Where the Galaxies Are (1991), demonstrates the results of her redshift surveys; the second, So Many Galaxies . . . So Little Time (1992), shows a team of scientists collaborating on an astronomy project.

With only a small percentage of the observable universe mapped thus far, Geller continued her explorations. She studied distant parts of the universe with the aim of better understanding its history, evolution, and geometric structures. She also researched the distribution of dark matter and mapped the Milky Way Galaxy as a means of understanding its relation to other galaxies.

Geller resigned from Harvard in 2001. She remained at the Smithsonian Astrophysical Observatory, continuing her work as a senior astrophysicist there. During her career, she earned many awards and honorary degrees, including the Newcomb-Cleveland Prize from the American Association for the Advancement of Science in 1989 and a MacArthur Fellowship in 1990. She also received the Magellanic Premium award from the American Philosophical Society (APS) in 2008, the James Craig Watson Medal from the National Academy of Sciences in 2010, the Lilienfeld Prize from the American Physical Society in 2013, and the Schwarzschild Medal from the German Astronomical Society in 2014. Geller was granted an honorary degree from the University of Turin in 2017.

In 2022, she was interviewed for Research Features about her career and her HectoMAP Cluster Survey. The project enabled scientists to see how galaxies have been distributed over the last six billion years.

Impact

Geller’s redshift surveys and her discovery of the Great Wall created a new image of the universe, which led to a series of metaphors to explain its structure. One of the metaphors is that the universe resembles bubbles of soap in a sink, with each bubble representing a galaxy. Another is that the universe resembles a sponge, in which the pockets of the sponge are the walls of the universe surrounding large voids. The clusters that emerged from Geller’s maps form a pattern called a “stick man” for the form it appears to represent.

Before Geller’s groundbreaking research, scientists held a different perspective on the structure of the universe. Galaxies, it was thought, were uniformly distributed. Moreover, scientists believed that the size of galaxies was limited by gravity and that massive structures therefore could not exist. Geller and Huchra, among others, proved these assumptions wrong through their spectrographic maps. Contrary to expectation, they discovered the Great Wall superstructure, and their maps revealed that galaxies are not evenly distributed, but rather take on the form of clusters and exist among huge voids.

With the advances that have taken place in the field of astronomy, scientists have been able to further broaden their perspective of the universe as they examine galaxies at ever-more-distant reaches. In 2003, for example, evidence for an even larger structure emerged from the redshift surveys of another team of astrophysicists. Called the Sloan Great Wall (SGW), it is at least 80 percent larger than the Great Wall and is based on surveys of a million galaxies. Other giant superstructures have also since been identified, building on Geller's groundbreaking work.

Bibliography

"Discovering Patterns in the Universe." Research Features, 8 Sept. 2022, researchfeatures.com/discovering-patterns-universe/. Accessed 15 Oct. 2024.

Kanipe, Jeff. Chasing Hubble’s Shadows: The Search for Galaxies at the Edge of Time. Hill, 2007.

"Margaret Joan Geller." American Academy of Arts & Sciences, 2022, www.amacad.org/person/margaret-joan-geller. Accessed 15 Oct. 2024.

Rossiter, Margaret W. Women Scientists in America: Forging a New World Since 1972. Vol. 3. Johns Hopkins UP, 2012.

Weinberg, Steven. Cosmology. Oxford UP, 2008.