This is a mosaic image, one of the largest ever taken by NASA’s Hubble Space Telescope, of the Crab Nebula, a six-light-year-wide expanding remnant of a star’s supernova explosion.
NASA, ESA, J. Hester and A. Loll (Arizona State University).
News notice: Notes and Records, the Royal Society’s history of science journal, would like to notify historians that it is accepting submissions for its biennial Essay Award until February 28, 2026. The competition is open to researchers who have completed a postgraduate degree within the last five years. Submissions should be a previously unpublished essay of up to 8,000 words on any aspect of the history of science, technology, and medicine in any period. The winning entry will receive a cash prize of £500.
When we look back at the mid-20th century, it’s tempting to tell a tidy story about how modern astrophysics emerged: as new telescopes opened new wavelength “windows”—radio, x-ray, gamma-ray—astronomers gradually assembled a more complete picture of the cosmos. But as historians Luisa Bonolis and Stefano Furlan argue in a new two-part study titled “Unveiling the Violent Universe,” the transformation of astronomy in the 1950s and 1960s was not simply a matter of adding technologies, but a profound reorganization of scientific cultures, driven by discoveries of extreme astrophysical phenomena and unprecedented cross-fertilization between physics, astronomy, and cosmology.
Bonolis and Furlan’s work joins a growing historiography exploring how astronomy became entwined with physics. Previous studies have shown how astronomers first applied physical methods, such as measuring spectral lines, temperatures, and densities, to probe stellar composition. Bonolis and Furlan trace how the rise of radio astronomy, the advent of the Space Age, and the spread of computational tools developed in weapons laboratories drew astronomy together with physics describing phenomena under extreme conditions. The universe revealed by these approaches was a strikingly “violent” one of supernova shocks, relativistic jets, cosmic rays, and compact objects pushing the limits of physical understanding.
Drawing on archival sources and interviews, Bonolis and Furlan show how, by the early 1960s, scientists across the US and Soviet Union were beginning to treat the cosmos as a laboratory—one in which neutrinos, gamma rays, synchrotron radiation, and gravitational collapse became essential clues. These developments, they argue, were harbingers of what would eventually become particle astrophysics in the 1970s and 1980s and precursors to today’s multimessenger astronomy. Bonolis and Furlan trace how scientists from nuclear physics, particle physics, cosmology, and astronomy converged around a set of common problems in the decades after World War II.
The birth of a shared culture
Consider the case of synchrotron radiation, the mechanism by which ultra-relativistic electrons spiraling in magnetic fields produce electromagnetic radiation. In the early 1950s, when physicists such as Hannes Alfvén, Nicolai Herlofson, and Karl-Otto Kiepenheuer proposed synchrotron radiation as the mechanism behind puzzling radio sources, many astronomers remained wary. As Soviet physicist Vitaly Ginzburg later recalled, the mechanism seemed “mysterious and speculative.”
But physicists who understood particle accelerators immediately recognized the process. Their willingness to apply laboratory physics to cosmic environments reshaped how astronomers interpreted signals across the spectrum and helped seed the interdisciplinary “shared culture” that Bonolis and Furlan describe.
What makes this story particularly intriguing is how deeply it was embedded in the technological context of the Cold War. The same expertise that went into thermonuclear weapons research—understanding extreme temperatures, densities, and energies—turned out to be directly applicable to astrophysics. At the Livermore Laboratory, for instance, Stirling Colgate moved fluidly between modeling nuclear explosions and simulating supernova mechanisms, finding striking parallels between the two: Both involved massive releases of energy, shock waves, and the synthesis of heavy elements.
Meanwhile, the launch of Sputnik in 1957 transformed scientific possibilities almost overnight. As Bruno Rossi of MIT noted, cosmic-ray physicists were “in a privileged position” to take advantage of these new opportunities, and their expertise soon contributed to the discovery of the first cosmic x-ray sources, gamma-ray bursts, and other powerful emitters invisible from the ground. The Space Age provided not just new instruments, but new problem spaces—high-energy environments where physics and astronomy naturally met.
The case of Iosif Shklovsky
I. S. Shklovsky.
NRAO/NSF/AUI.
Bonolis and Furlan highlight a number of scientists working in this period, but Soviet astrophysicist Iosif Shklovsky stands out as particularly representative of the era’s interdisciplinary spirit.
His career trajectory illustrates how the boundaries between traditional astronomy and modern astrophysics were being redrawn. Trained as a physicist, he brought to astronomy a distinctive orientation toward physical mechanisms rather than the traditional focus on cataloging celestial objects. Shklovsky began by studying the physics of the solar corona in the late 1940s, correctly predicting the emission of x-rays from the Sun’s million-degree plasma. But what made him stand out was his ability to move seamlessly between the technical physics of high-energy phenomena and the broader questions that fascinated astronomers.
By the early 1950s, Shklovsky was grappling with the newly discovered radio sources in the sky. Initially skeptical of the synchrotron mechanism, he experienced what he called a “sudden illumination” while waiting for a tram in Moscow in 1953. As he later recalled, he realized that the optical spectrum of the Crab Nebula should be understood not as thermal radiation but as a continuation of its synchrotron radio spectrum. This insight opened the door to understanding the Crab and similar objects as sites of extreme particle acceleration.
Crucially, Shklovsky also served as an intellectual bridge. He could explain to astronomers why the identification of radio sources mattered for understanding cosmic ray origins, energy generation in galaxies, and the evolution of the universe. Conversely, he understood which observational questions needed answering to test theoretical predictions. As one colleague later put it, Shklovsky believed the fundamental question of astronomy was simply: “What is this?”
An unpublished 1963 letter from Shklovsky to Geoffrey Burbidge, discovered in John Wheeler’s archives, reveals his thinking at this crucial juncture. Writing about “radio stars” (a mid-century term for strong, point-like radio sources that appeared “stellar” in radio maps but whose true origins—often supernova remnants or active galaxies—were still unknown), Shklovsky argued that massive “super-stars” had undergone catastrophic explosions and collapses, leaving behind compact remnants whose gravitational fields could power the enormous energies observed in radio galaxies. He emphasized the role of the inverse Compton effect—high-energy electrons scattering thermal photons to higher energies—as a signature of these violent processes.
A new astronomy and “pragmatic unification”
What emerges from this historical analysis is that the key developments of the period—the discovery of quasars, pulsars, the cosmic microwave background, the first x-ray sources—fit into an increasingly integrated framework for understanding extreme energies and densities. The first Texas Symposium on Relativistic Astrophysics in 1963, conventionally seen as marking the birth of the field, was itself a response to the need for “overcoming the traditional segregation of specialists in their narrow cubbyholes.”
Scientists like Shklovsky, Yakov Zel’dovich, Geoffrey Burbidge, Fred Hoyle, and Philip Morrison shared a new willingness to think about connections between seemingly disparate areas—from elementary particles to the structure of galaxies. Shklovsky’s own career path from solar physics to radio astronomy to even the search for extraterrestrial intelligence (SETI) exemplified this expansive vision, while others’ work, like Geoffrey Burbidge’s on the energetics of radio galaxies and the synthesis of heavy elements, showed how astrophysical observations could be woven into broader questions about cosmic evolution and the physics of high-energy processes.
By the end of the 1960s, scientists were routinely thinking about connections between radio sources and synchrotron radiation from relativistic particles; quasars and supermassive black holes; supernovae and both neutron stars and cosmic rays; the early hot universe and elementary particle physics; gravitational collapse and x-ray emission. This represented both an accumulation of new data and a new way of doing astronomy.
Bonolis and Furlan also highlight their history as an example of “pragmatic unification,” that is, the gradual integration of different observational channels and theoretical frameworks through concrete problems. This unification offers a counterpoint to more speculative attempts in roughly the same period to arrive at grand theoretical synthesis. Progress came not from trying to unify everything at once from first principles, but from recognizing connections between phenomena, building instruments to test predictions, and allowing different communities to learn from each other.
“Clearing Up: Coast of Sicily” embodies the Sturm und Drang spirit, with stormy seas and towering cliffs illustrating nature’s drama and power.
Andreas Achenbach, 1847. Walters Art Museum.
The story also reminds us that major scientific advances often emerge from the intersection of different fields and approaches. The physicists who contributed most to the new astrophysics weren’t necessarily the most specialized experts, but those with broad training who could see analogies and connections others missed. Shklovsky, who once joked about astronomy’s “second revolution,” described the period as one of Sturm und Drang, referencing the late-18th-century German movement that rebelled against Enlightenment rationalism in favor of creative intensity.
Today’s multimessenger astronomy, which combines gravitational waves, neutrinos, and electromagnetic radiation to study cosmic events, represents the culmination of trends that Bonolis and Furlan trace back to the 1950s and 1960s. Understanding that deeper history helps us appreciate not just how we got here, but what made such an ambitious synthesis possible in the first place.
Rebecca Charbonneau
American Institute of Physics
rcharbonneau@aip.org
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