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From Black Holes to Dark Matter, Theoretical Astrophysicist Priyamvada Natarajan Confronts Theoretical Ideas with Observations

Priyamvada Natarajan
Priyamvada Natarajan. Credit: Gabe Miller.

As a high school student, AAAS Member Priyamvada Natarajan was captivated by the night sky. Her father gifted her a Commodore 64 computer, which allowed her to generate a map of the night sky over New Delhi, where she grew up. “I was obsessed with maps and that is an obsession I still have – maps of all kinds, including maps of the sky, maps of the Earth…just different ways to visualize data,” she says.

This project was her first taste of scientific research. Her passion for research, specifically in astronomy, was also nurtured by her parents, who were professors in India. “As gifts, I got both a microscope and telescope when I was young, and it was very clear to me that it was the telescope.”

Throughout her career, Natarajan – who is currently an astronomy professor in the physics department at Yale University and also the director of the Franke Program in Science and the Humanities – has pursued research in astronomy and physics. She soon discovered that she “loved confronting observations with the theoretical ideas,” which lends itself well to studying phenomena in the universe, including black holes and dark matter – two topics in astrophysics that she has made seminal contributions to. Two key problems in cosmology, which is the study of the origin and evolution of the universe, that she has dedicated much of her time to is mapping dark matter and tracing the accretion history of black holes.

Additionally, she is interested in broader questions, such as how do sciences in which you cannot do a controlled experiment generate new knowledge and truths? For example, in cosmology, you cannot do controlled experiments. However, Natarajan explains that, in lieu of controlled experiments, you can perform simulations because “you can’t go out and make these comparisons with other universes or expect a supernova to re-explode at will.”

Many exciting developments that moved the needle in her field of astrophysics occurred during the late 1990s when she was at Cambridge University completing her Ph.D. “It was fortunate timing,” she says. “Supermassive black holes were found in the centers of most galaxies, so it was clear they were no longer marginal and obscure.” Black holes and dark matter were the exciting new fields that were opening up.

During this time, she came up with a way to conceptualize how to map dark matter in clusters of galaxies from their observed gravitational lensing, which is the bending of light. Her efforts provided the groundwork for making dark matter maps from data that permitted easy comparison with simulations. She says those techniques are now standard in the field.

She also began the work of integrating supermassive black holes into the larger context of the formation and evolution of structure in the universe – which has since evolved into a very active subfield that it is today. During her time completing her Ph.D. at Trinity College Cambridge, she became the first woman in astrophysics to ever be elected to the fellowship there.

During her career, Natarajan has worked and interacted with some “amazing minds” she says, including physicist Alan Guth, astrophysicist Martin Rees, and sculptor Antony Gormley. Her interests cross disciplinary boundaries, her science/art virtual reality installation with Gormley was on view at the Venice Biennale in 2019, and she is dedicated to demystifying science and the process of science for the public. For example, she writes about science for the New York Review of Books and has authored a book titled, “Mapping the Heavens: The Radical Scientific Ideas That Reveal the Cosmos.”

Natarajan’s career was not bereft of challenges, however. She says, “I think that for most women of color, there are ways big and small in which we are somehow invisible and marginalized, and over time there is an accumulation of disadvantages.” Natarajan has been putting in the work to do what she can to catalyze institutional change, including previously chairing the Women Faculty Forum (WFF) at Yale and active involvement in task-forces on diversity and inclusion.

Biases and their impact are things that Natarajan, like many, has personal experience of – in particular, how it plays out in grant proposal reviews and citations. “Most universities and our profession are hooked on these metrics, even though they are flawed and are even acknowledged to be so,” she says. To combat this problem, Natarajan is a supporter of dual anonymous proposal reviews, in which reviewers' and investigators’ identities are unknown from the start. These proposals cannot include information that identifies participants, including past records of grant receipt and work. Evaluations are driven solely by the intellectual case that is presented in the proposal.

Natarajan was involved in the implementation of the first dual anonymous proposal reviews as she chaired on the Hubble Space Telescope’s Time Allocation Committee (TAC). This was initially a controversial move and she admits, “it is not easy to put yourself in the crosshairs.” However, implementing this kind of proposal review “was too important,” she says. Natarajan says that this move is just "low-hanging fruit" in terms of mitigating bias and, although it will not solve the problem entirely, it is an important and easy first step. The institutional leadership that the Space Telescope Science Institute has led other agencies to follow suit.

Although the implementation of bias-mitigating efforts, such as dual anonymous proposal reviews, has its challenges, Natarajan has no regrets about her own experiences with science and academics so far. “For me, despite all the obstacles, the kind of joy that my work continues to give me is unparalleled,” she says. “Moments of excitement and joy always supersede the moments of frustration.”

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Alexandra Kirby Scammell