The Ernst Patzer Foundation is awarding up to three prizes each year for the best refereed publications by doctoral students and young postdocs at MPIA and ZAH. This year, Elisa Schösser (ZAH/ARI) is one of the three prize winners. She receives this prize for her paper on Extremely iron-poor O-type stars in the MagellanicBridge, 2025, Astronomy & Astrophysics 696, L3.
Together with Dr. Varsha Ramachandran, Dr. Andreas Sander and his research group at the Astronomisches Rechen-Institut, Elisa Schösser has identified the most iron-deficient massive stars known in our cosmic neighbourhood. These stars, discovered in the Magellanic Bridge - a stream of gas connecting the Large and Small Magellanic Clouds - provide insights into what the very first stars in the Universe might have been like. Using the Hubble Space Telescope’s Cosmic Origins Spectrograph, the team obtained high-resolution ultraviolet spectra of two O-type stars and used detailed atmosphere models to measure their iron abundances. The analysis revealed iron abundances as low as 3.6% of the Sun’s, making them the most iron-poor massive stars ever observed in such proximity. One of the stars exhibits an overabundance of alpha elements, a chemical signature characteristic of some of the earliest generation of stars. The study also challenges the common assumption that oxygen can serve as a reliable proxy for overall metallicity, showing no correlation between iron and oxygen abundances in these stars. These findings suggest a chemically diverse and poorly mixed interstellar medium in the Magellanic Bridge and provide new insight into the nature of massive stars in metal-poor environments that resemble the conditions of the early Universe.
Elisa Schösser began her Bachelor’s studies in Physics at the Technical University of Munich in 2016, with a particular interest in astrophysics from the very beginning. During her studies, she also joined two semesters at the University of Helsinki and completed both her Bachelor’s and Master’s theses at the Max Planck Institute for Extraterrestrial Physics in Garching, focusing on the study of gamma-ray bursts. In early 2023, she moved to Heidelberg to pursue her PhD studies in the research group of Andreas Sander at the Astronomisches Rechen-Institut of the University of Heidelberg.
"I applied for a PhD position through the central IMPRS system and through this, was invited to an interview with Andreas Sander and Varsha Ramachandran. During our conversation, they introduced me to the exciting field of massive stars which was a completely new topic for me at the time. Although I did not have a background in this area, I was immediately drawn to the new scientific challenges," she explained why she had joined Dr. Sander’s group. "Their enthusiasm, expertise, and the friendly, open atmosphere of the group convinced me right away. The opportunity to apply my knowledge of statistics to the group’s research was another key factor for me. I appreciate it a lot to work in such a supportive and inspiring team," Elisa Schösser adds.
Determining iron abundances from the countless UV lines in massive stars has long been a challenge in stellar spectroscopy, and it was also one of her major challenges of this project. To tackle this, Schösser developed a Bayesian statistical approach that provides a reliable estimate of the iron abundance and its uncertainties. "This method enabled the first robust measurement of iron abundances in massive stars within an environment comparable to distant metal-poor dwarf galaxies," the PhD researcher regards as one of the biggest challenges while working on the award-winning paper.
Her findings demonstrate that due to the discovery of extremely iron-poor massive stars in the Magellanic Bridge this area serves as a unique local analogue of the early, low-metallicity Universe. "Building on this finding, we have assembled a large set of high-resolution UV and optical spectra of OB-type stars covering the full extent of the Bridge. My goal is to use these observations to reconstruct their formation history and to derive empirical constraints for stellar winds, stellar evolution and population synthesis models at low metallicity," as Elisa Schösser further explains.
We congratulate Elisa Schösser most sincerely on this great success!
The award winners will be honored during the Patzer Colloquium on November 28th, 2025, at 15:00 in the MPIA Lecture Hall.
BACKGROUND INFORMATION
The Scientific Ernst Patzer Foundation was established in 2001 by the widow of the Philosopher Ernst Patzer. The goal of the foundation is to support young scientists in the field of astronomy, in particular at the Max Planck Institute for Astronomy in Heidelberg and ZAH. For more information see http://www.mpia.de/studfy-and-career/ernst-patzer-award.
LOCAL CONTACT
Elisa Schösser
Centre for Astronomy of Heidelberg University (ZAH)
Astronomisches Rechen-Institut (ARI)
elisa.schoesser@uni-heidelberg.de
