Leisa Townsley (1964–2022)

Ann Hornschemeier Cardiff, Sarah Gallagher, Eric Feigelson

With great sadness, we reflect on the passing of Dr. Leisa Townsley. She passed away peacefully in Colorado, after a battle with cancer, on Monday August 8th with her life-long partner Pat Broos at her side. She worked at Penn State for more than 28 years as a leader of—and subsequently the Penn State PI for—the Chandra ACIS instrument. She and Pat had relocated to Colorado in 2014 to work remotely for Penn State in anticipation of their retirement there.

Leisa had a rich and substantial character and demonstrated fundamental integrity as a person and a scientist. She was greatly respected and is deeply missed by the high-energy astrophysics community and others who knew her.

Her talents as a scientist were truly remarkable. She helped establish the importance of X-ray studies of massive star-forming regions using Chandra and other observatories. She published Chandra catalogs of tens of thousands of young stars in dozens of clusters and associations, and she discovered diffuse X-ray emission in all regions arising from colliding OB-star winds. This work required the careful and comprehensive removal of point sources, accomplished using the superb ACIS Extract software package that she and Pat Broos developed. Her research invalidated the century-old belief that HII regions are suffused with 104 K gas, finding they are instead filled with 107 K gas with Hα produced only at the cloud surface. Leisa’s work helped establish the birth of our understanding of the hot interstellar medium (ISM) that fills most of the Galactic disk, showing that the hot ISM from winds precedes the more spectacular supernova remnants.

An astronomical image showing reddish-purple clouds with thousands of individual points of light.

Figure 1: The 1.2 Ms Chandra view of the Carina Nebula, where over 14,000 stars were detected. Credit: NASA/CXC/PSU/L.Townsley et al.

Colleagues have remarked on conversations with Leisa after she completed analysis of these regions, showing spectacular and unique color images of diffuse Chandra X-rays filling the gaps between Spitzer molecular clouds. These were views of how star formation was operating that led to conversations that no one in the world had been able to have prior to her work. She was a pioneer forging in directions that were enabled by the combination of her fundamental understanding of high energy astrophysics and her deep knowledge of the ACIS instrument. But this work represents only part of her accomplishments: calibrating the ACIS instrument (she created the first model used to correct the charge-transfer inefficiency from the early CCD radiation damage), leadership of the 1.2 Ms mosaic of the Carina Nebula resulting in a book-length issue of the ApJ Supplement Series, constructively leading and participating in dozens of other Chandra studies, managing Chandra affairs at Penn State, and more. Her death is a great loss.

Leisa Townsley and Pat Broos smiling at the camera. Leisa has on a purple blazer and a nametag, while Pat wears a red polo with a lanyard around his neck.

Figure 2: Leisa and Pat at the 2009 "Chandra's First Decade" Symposium.

Aside from her professional excellence, Leisa and her partner Pat mentored a generation of Penn State graduate students and postdocs, in a manner that could be described as "aggressive welcome." She generously sat through many practice talks to give feedback, and through her dedication she improved the communication skills of a host of early career researchers. She made sure that new scientists appreciated the skill and effort required to characterize an instrument so that results could be trusted. She invited early career high-energy astrophysicists (and many others) into her home on a routine basis. Colleagues from outside Penn State would remark on having been invited to an informal pizza party at her house, only to arrive at her warm and welcoming abode, finding people wandering around in the yard, and with two very happy dogs co-hosting the party. In an era when we are working on improving the culture of our field, Leisa Townsley embodied the ultimate goal: to greet everyone warmly and to celebrate—and encourage—the scientific success of everyone. She acknowledged and respected the contributions of all team members, and she was a savvy leader who understood people well and brought out their best work. Upon hearing of Leisa’s passing, one of the Penn State graduates commented on having invited Leisa and Pat to an awards banquet some years after graduation, to which Leisa remarked she wasn’t that important, herself. But to a generation of early-career folk at Penn State, Leisa wasn’t merely important—she was the reason they made it through. Her legacy is not only her impactful contributions to our understanding of star-forming regions, but the people in the community who are here, contributing and leading, thanks to her support and her example.

There will be an award for graduate students established at Penn State to honor Leisa’s legacy, for which donations will be gratefully accepted. Details of this award will be forthcoming.


Portions of this article have appeared in the Women in Astronomy blog and were sent to the AAS HEAD mailing list.