Cornell Department of Astronomy & Space Sciences Fall 2026 Colloquium Series

The Yervant Terzian Lecture Series

On the occasion of Yervant Terzian's 70th birthday, the University established the Yervant Terzian Lectureship in Astronomy to bring outstanding scientists to Cornell for brief visits. The Lectureship was endowed by a generous gift from Friend of Astronomy Charles Mund, Jr.

Title: Beyond Temperature: Explaining the Diversity of Cold Worlds in the era of JWST

Short Abstract: The James Webb Space Telescope is revealing the complex chemistry of worlds formed beyond our own Solar System with unprecedented detail. Brown dwarfs—objects that bridge the divide between stars and planets—have become critical laboratories for understanding the atmospheric physics and chemistry of giant exoplanets. In this talk, I will present a growing library of JWST observations of brown dwarfs spanning temperatures from ~700 K down to just 250 K—only about 100 degrees warmer than Jupiter. Their spectra reveal a rich inventory of molecules and provide a remarkable view into the chemistry of cold worlds beyond our own.

For decades, we expected temperature to be the primary driver of how brown dwarf atmospheres look and evolve. JWST is revealing a far more complex landscape. Objects with similar temperatures can have strikingly different spectra, pointing to the important roles of age, metallicity, gravity, and other secondary parameters in shaping their atmospheres. I will show how this emerging diversity is changing our understanding of brown dwarfs and providing a new framework for interpreting the atmospheres of giant exoplanets.