David Charbonneau, Professor in Search of Planets in Outer Space, Wins $1 Million Kavli Prize

Sometimes, searching for other worlds pays off.

Harvard Astrophysics professor David Charbonneau won the 2024 Kavli Prize in Astrophysics in June, sharing a $1 million prize with MIT professor Sara Seager for their discoveries of exoplanets — planets located outside Earth’s solar system.

The Kavli Prize, administered by the Norwegian Academy of Science and Letters, honors scientists for pioneering contributions in astrophysics, nanoscience, and neuroscience. Charbonneau traveled to Oslo, Norway earlier this month to receive the award.

Charbonneau and Seager both began their quest to find and study exoplanets as graduate students at the Harvard-Smithsonian Center for Astrophysics.

At the time, Charbonneau said in an interview, exoplanet research was still in its infancy. To determine if planets orbited other stars, Charbonneau and his colleagues developed the “transit method,” which detects an exoplanet by observing a small — but measurable — dip in light as it passes in front of its host star.

Initially, the method was met with skepticism, as some doubted the signals would be detectable.

Charbonneau recalled attending his first scientific conference, where a “really lovely” organizer interrupted his talk to say, “David, you will never, ever be able to detect any of this stuff!”

But on Sept. 9, 1999, using a four-inch telescope in a parking lot, Charbonneau observed a one percent change in light — a vindication of his research method.

That first discovery, Charbonneau said, cemented his lifelong fascination with exoplanets.

“I think what kept me going was just that I was profoundly and deeply interested in the question of, are there planets from other stars? Are there Earth-like planets, and can we develop methods to look for life on those planets?” Charbonneau said. “So it didn’t matter that other people thought it wouldn’t work out.”

“I always just had a sense of self confidence that, as far as I could tell, the numbers worked, that the signal should be detectable,” he added.

In the years that followed, Charbonneau pioneered the use of space telescopes — including the Hubble and James Webb telescopes — to study extrasolar planets.

Meanwhile, Seager led the theoretical study of exoplanet atmospheres, cataloguing the spectral fingerprints of atmospheric molecules and predicting the presence of alkali gasses detectable by transit spectroscopy.

The Seager group claims to have identified phosphine in Venus’s atmosphere, a chemical that could indicate the presence of life, though finding remains hotly debated among scientists in the field.

Astronomy professor Abraham “Avi” Loeb, who taught Charbonneau and later served on his tenure committee, recalled Charbonneau as one of his brightest students.

Loeb added that Charbonneau made a strategic decision to switch from the oversaturated field of cosmology to the emerging frontier of exoplanet research.

“He basically pioneered an important new aspect of the search for planets and made very important discoveries,” Loeb said. “It wouldn't have been easy for him to do the same in the study of cosmology that I was working on, because it was very crowded, and still is.”

Looking back, Charbonneau offers young students the same advice.

“Look for fields that are young and where a student can make a big impact, because a lot of the very basic questions simply haven’t been answered,” he said.

—Staff writer Jennifer Y. Song can be reached at jennifer.song@thecrimson.com.