The Hubble Space Telescope (HST) and James Webb Space Telescope (JWST) together offer an unprecedentedly detailed view of galaxies across cosmic time, from the first few hundred million years after the Big Bang through today. However, even these uniquely powerful telescopes struggle to resolve the small-scale building blocks of galaxies in the distant universe. Gravitational lensing provides an extra boost to the resolving power of HST and JWST, using massive galaxy clusters in the foreground as cosmic telescopes to magnify distant galaxies. In this talk, the speaker will discuss how the combination of HST, JWST, and gravitational lensing provides a window into the heart of distant galaxies, revealing compact star clusters and even individual massive stars that are key engines of evolution within galaxies. These measurements enable us to better understand how distant galaxies form stars, stop forming stars, and build up elements such as nitrogen, oxygen, and carbon that form the fundamental building blocks of life on Earth.
Brian Welch is an Astronomer and currently a Fellow at the International Space Science Institute. Brian holds a PhD from Johns Hopkins University (USA) , during which he explored the inner workings of distant galaxies, merging the power of the Hubble Space Telescope and gravitational lensing (when a very large celestial body bends the path of light around it, distorting and magnifying it, similar to what would happen with a lens). This was followed by post-doctoral work at NASA Goddard Space Flight Center, where he worked from 2022 until 2025. Since September 2025 he is a part of the ISSI Staff.
