“Modeling the first dataset from JWST taught me how science can rapidly transform our understanding of things. In a month, we can learn more than we have for years or even decades.”

Sagnick Mukherjee

Planets between the size of Neptune and Earth, called sub-Neptunes, are the most plentiful type in the galaxy, yet they are missing from our own solar system. Sagnick Mukherjee wants to know why. Until JWST began releasing precise data across a wide array of spectral wavelengths, only large planets similar to Jupiter or Saturn, which are much rarer than sub-Neptunes, could be characterized in detail with confidence.

When the first JWST observations became available in 2022, Mr. Mukherjee was part of a community of exoplanet scientists from around the world who convened at the University of California, Santa Cruz, to analyze this information for a large Saturn-like exoplanet. Mr. Mukherjee was astonished as findings from this effort reached his father in India through a local Bengali newspaper.

Buoyed by the power and reach of scientific discovery, Mr. Mukherjee soon fixed his curiosity on sub-Neptunes, which pose a host of intriguing questions—including why and how they form, what they are composed of, and whether they can sustain life.

As JWST provides increasingly sensitive observations of sub-Neptunes, it reveals discrepancies with most models currently describing these planets. As a planetary theorist and devoted open-source modeler, Mr. Mukherjee is eager to provide a more inclusive framework on which others can build. His development of open-source software, as well as mentorship of students from underrepresented backgrounds, reflects Mr. Mukherjee’s commitment to making the scientific community more accessible.

During his fellowship, he will develop and test a multi-part model that, unlike its predecessors, accounts for the chemical composition and cloud cover of sub-Neptunes, as well as interactions between their atmospheres and interiors, where gases spewed from possible magma oceans on these planets can dramatically alter their observable chemistry.

Between hundreds of hours of JWST data focused on sub-Neptunes and a new generation of Extremely Large Telescopes coming online, Mr. Mukherjee’s contributions are timely. With his model, he expects to reduce the uncertainties that cloud today’s understanding of sub-Neptunes—and reveal the compositions and origin stories of these abundant, compelling planets.

Mr. Mukherjee will receive his Ph.D. in astronomy and astrophysics from the University of California, Santa Cruz, in Spring 2025.