Radiolab Episode Summary: "Galaxy Quenching"

Host and Guest Introduction Radiolab, hosted by Lulu Miller from WNYC Studios, delves deep into the intricate processes of the universe, blending scientific inquiry with personal storytelling. In the episode titled "Galaxy Quenching," released on August 1, 2025, host Lulu Miller engages in a profound conversation with astrophysicist Charity Woodrum. The episode intertwines the scientific exploration of how galaxies "die" with Charity's personal journey through tragedy and resilience.

Understanding Galaxy Quenching The episode begins with Lulu Miller posing a fundamental question to Charity Woodrum: "I wonder if you can tell me about all the different ways a galaxy can die." ([01:27]). Charity explains that galaxy quenching refers to the cessation of star formation within a galaxy. For stars to form, galaxies require cold, dense gas—primarily hydrogen—as fuel. Various mechanisms can prevent this fuel from being available:

• Supermassive Black Holes: These immense entities at the centers of galaxies can either heat the surrounding gas or eject it entirely through powerful jets, effectively starving the galaxy of the necessary material for new star formation.
• Starvation and Strangulation: These terms describe scenarios where the inflow of cold gas from the cosmic web is halted, preventing new gas from replenishing the galaxy's fuel reserves.

Charity elaborates, "So it's like it could get pushed out from the inside or it just stops coming in." ([03:10])

Charity's Personal Journey The narrative shifts to Charity's upbringing in rural Canyonville, Oregon. Growing up under dark night skies fostered her fascination with the cosmos, serving as a refuge from a turbulent home life where both parents struggled with addiction and chaos. Despite excelling academically—becoming her high school's valedictorian—Charity faced skepticism about her aspirations in science, especially from teachers who doubted the feasibility of a career in astronomy for someone from her background.

Determined to escape poverty, Charity became a registered nurse. However, the emotional toll of witnessing daily human suffering led her to seek solace in books, particularly those by Carl Sagan and Stephen Hawking. Inspired by the Hubble Deep Field image, which revealed thousands of galaxies in what was thought to be an empty patch of sky, she found a renewed purpose: "Each of those galaxies has billions of stars, and each of those stars, we think, has at least one planet." ([09:24])

This epiphany motivated her to pursue physics, despite initial resistance and challenges, including balancing academics with motherhood.

Academic Pursuits and the Cosmic Wolf Pack Charity joined Dr. Scott Fisher's research group, affectionately named the "Cosmic Wolf Pack," alongside three other undergraduates. Together, they honed their skills in observing and analyzing galaxies, often conducting night sky tours at Pine Mountain Observatory. These experiences not only deepened Charity's scientific expertise but also provided a rare sense of normalcy and joy amidst personal upheavals.

Tragedy Strikes: January 15, 2017 A pivotal moment in the episode recounts the harrowing events of January 15, 2017. Charity, along with her husband Jason and son Woody, embarked on a mini-vacation to the Oregon coast. On this day, a "sneaker wave"—a sudden, unexpected large wave—swept Jason and Woody out to sea. Charity's recollection is both vivid and fragmented: "I eventually found myself in an ambulance and my eyes were closed and I felt a banging on my head." ([18:20])

Believing her family was lost, Charity experienced a mental breakdown, leading to her hospitalization and a brief stay in a psych ward. The incident was widely publicized, intensifying her grief and sense of loss.

Discovery of Rejuvenation in Galaxies Amidst her personal struggles, Charity continued her astronomical research. In her second to third year of graduate school, she made a groundbreaking discovery: some quiescent galaxies still harbored cold gas reservoirs, suggesting the possibility of "rejuvenation"—a resurgence of star formation within galaxies previously thought to be dead. This finding challenged existing theories and opened new avenues for understanding galaxy evolution: "There was this significant amount of what we called secondary star formation episodes, or rejuvenation." ([27:23])

Charity proposes that interactions between galaxies, such as collisions or flybys, can trigger these rejuvenation episodes by funneling gas back into quiescent galaxies, reigniting star formation.

Parallel Between Cosmic Phenomena and Personal Healing Charity draws a poignant parallel between the rejuvenation of galaxies and her own journey through grief: "Just like with the physical processes that can make a galaxy quench, there's physical processes that can make a galaxy rejuvenate as well." ([28:23])

Her recovery was bolstered by the support of friends, family, and even strangers, mirroring the inflows of gas that can revitalize a galaxy. This support system became her "cosmic wolf pack," providing the necessary environment for her to heal and find purpose again.

Achieving Her Dream at NASA Charity's perseverance led her to a postdoctoral fellowship at NASA, working with the James Webb Space Telescope. This role represents a full-circle moment, as she is now studying galaxies in the same region observed in the Hubble Deep Field—"...a perfect full circle moment for me." ([33:23])

Her work focuses on the stardust in early galaxies, symbolizing the cycles of destruction and creation that define both the cosmos and her personal narrative.

Emotional Dedication and Reflection In a deeply moving moment, Charity shares a dedication from her PhD dissertation: "For Woody and Jason Thomas, from the local universe to the first galaxies, the brightest moments in space and time occurred during our brief epoch together. That light is unquenchable." ([37:50])

This tribute encapsulates the intertwining of her scientific pursuits with her enduring love and memory of her family.

Conclusion: Light, Resilience, and Legacy The episode concludes with Charity reflecting on the cyclical nature of the universe and life: "I'm studying these clouds of gas and dust that are from exploding stars. And so eventually we'll be part of the same cloud of gas and dust again, and maybe we'll forge inside the same star again." ([37:24])

Her story is a testament to resilience, illustrating how the same forces that govern galaxies can also influence personal healing and growth. Charity's journey from tragedy to triumph serves as a beacon of hope, much like the stars she so passionately studies.

Notable Quotes:

• "So it's like it could get pushed out from the inside or it just stops coming in." — Charity Woodrum ([03:10])
• "Each of those galaxies has billions of stars, and each of those stars, we think, has at least one planet." — Charity Woodrum ([09:24])
• "There was this significant amount of what we called secondary star formation episodes, or rejuvenation." — Charity Woodrum ([27:23])
• "For Woody and Jason Thomas, from the local universe to the first galaxies, the brightest moments in space and time occurred during our brief epoch together. That light is unquenchable." — Charity Woodrum ([37:50])

Final Thoughts "Galaxy Quenching" is more than an exploration of astrophysics; it's a narrative of love, loss, and the relentless pursuit of knowledge. Charity Woodrum's story embodies the essence of Radiolab's mission to blend scientific curiosity with human experience, offering listeners both enlightenment and emotional resonance.