
Summer Program
Cosmic Change Agents: Massive Stars in the Early Universe
July 6–27, 2025
Organizers:
Vicky (Vassiliki) Kalogera, Northwestern University
*Allison Strom, Northwestern University
Grace Telford, Princeton University
*represents the organizer in charge of promoting diversity
Massive stars have a profound impact on both galaxy evolution and the evolution of the Universe as a whole. Despite their key role in many areas of astrophysics, crucial aspects of massive-star physics remain uncertain. This is particularly true in the early Universe, where JWST has revealed evidence for extreme massive stellar populations in low-metallicity galaxies that cannot be explained by our existing models. Several major efforts are now underway to obtain detailed observations of metal-poor massive stars in nearby galaxies with the aim of informing a new generation of stellar models suitable for early galaxies. Still, these local environments are only approximate analogs to the star-formation conditions and chemistry in young, distant galaxies. To make progress, we must leverage observations of low-metallicity stars and clusters in nearby galaxies together with observations of unresolved stellar populations of galaxies in the early Universe. This workshop will bring together theorists and observers with complementary expertise in star-forming galaxies at high redshift and in massive stars. The major goals will be to find ways that observations and models of massive stars in nearby galaxies can inform interpretation of early galaxy observations and vice versa; to identify gaps in the community’s current set of analysis tools and techniques; and to facilitate long-format discussions to inspire new collaborations across these different disciplines.
Summer Workshops
The summer program, running for 16 weeks from late-May to mid-September, emphasizes exciting open problems at the cutting edge. Two or three concurrent workshops, each with a specific focus selected for timeliness and the potential for breakthroughs and of two to five weeks in length, establish the main themes of each week, with twelve or thirteen different workshops each summer, balanced across fields including particle physics, string theory, astrophysics and hard and soft condensed matter physics, as well as emerging areas including biological physics, ultra-cold atom physics, quantum information, and physical mathematics. Additional researchers participate in small working groups or as individual researchers. This framework is designed to maximize informal interactions and free discussion within each area and to promote cross-fertilization between different areas via the common language of theoretical physics. Participation in the summer program of the Aspen Center for Physics is by application and subsequent invitation only. View past workshops.
