When astronomers detected gravitational waves for the first time in 2016, and then in 2017 they observed both gravitational waves and electromagnetic radiation from a neutron star merger, they hailed it as the start of a new era for their field. “Multi-messenger” astronomy—the coordinated observation of electromagnetic, particle, and gravitational signals—had come into its own.

These discoveries have also captivated historians and philosophers of science, who are asking: What does it mean to observe the universe through multiple “messengers”? How did this approach emerge from earlier traditions of multi-wavelength astronomy, neutrino detection, and gravitational-wave research? And perhaps most intriguingly, is multi-messenger astronomy truly a revolutionary break from the past, or is it simply the latest iteration of practices that astronomers have employed for over a century?

In this historiographical boom, scholars are racing to document and interpret this rapidly evolving field before its early history fades from view. A new, open-access special issue of Centaurus, “Shaping a multi-messenger universe,” explores multi-messenger astronomy’s emergence, bringing together historians, philosophers, and scientists to examine both continuities and transformations in astronomical practices.

Edited by Luisa Bonolis, Roberto Lalli, and Adele La Rana, this collection tackles fundamental questions about what multi-messenger astronomy actually is—a surprisingly contested issue, even among practitioners—and how it relates to the constellation of disciplines it encompasses. The collection’s seven articles span from the dawn of telescopic astronomy to 21st-century black hole imaging, revealing how new observational windows have repeatedly reshaped astronomical work.

Correlation in astronomy

The first article following the editors’ introduction, David DeVorkin’s “New tools, new universes: Correlation in astronomy,” provides essential historical context by arguing that the fundamental practice underlying multi-messenger astronomy—correlating diverse signals to understand cosmic phenomena—extends back to astrophysics’ birth in the late 19th century.

When spectroscopy first allowed astronomers to analyze starlight’s composition, they immediately began correlating spectral features with other stellar properties: brightness, color, motion, and variability. DeVorkin traces how each subsequent expansion of astronomy’s toolkit, from photography to radio telescopes, followed this same pattern: new data streams were systematically correlated with existing measurements to extract physical meaning.

Crucially, DeVorkin shows that making these correlations meaningful required extensive standardization: agreed-upon measurement systems, classification schemes, and theoretical frameworks negotiated among observers, theorists, and experimentalists. From this perspective, multi-messenger astronomy represents not a rupture, but, as DeVorkin puts it, “an extension of the core of traditional astronomical science.”

Supernovae and networks of collaboration

The special issue’s centerpiece is a two-part study by Adele La Rana, Luisa Bonolis, and Roberto Lalli examining how multi-messenger astronomy emerged from converging research traditions. Part one, “Supernovae as epistemic laboratories,” focuses on how the study of stellar explosions catalyzed interdisciplinary collaboration throughout the 20th century.

Drawing on concepts from science studies—“boundary objects,” “trading zones,” “challenging objects,” and “borderline problems”—the authors show that supernovae served as focal points where different communities such as nuclear physicists, optical astronomers, relativistic astrophysicists, and particle physicists were compelled to interact despite maintaining distinct practices and standards of evidence.

From Baade and Zwicky’s 1930s coining of the term “super-novae” and speculation about neutron stars, through the 1957 nucleosynthesis paper linking stellar explosions to element production, supernovae repeatedly challenged single-discipline explanations, and indeed were essential in creating conditions for multi-messenger thinking.

Part two, “A socio-epistemic network analysis of scientific literature, 1997–2023,” employs quantitative methods to map the field’s recent evolution. Analyzing 1,732 scientific publications in which the term “multi-messenger” appears, the authors trace co-authorship networks, institutional collaborations, keyword patterns, and citation relationships.

Their analysis reveals three distinct phases: an exploratory period (1997–2008) when the term appeared sporadically, mainly in very-high-energy gamma-ray astronomy; an emergence phase (2009–2015) characterized by anticipation of gravitational-wave detection and the conceptual integration of different messenger communities; and a consolidation phase (2016–2023) following the first gravitational-wave detection, when the field rapidly expanded and coalesced.

Strikingly, the network analysis shows that institutional and conceptual foundations were laid years before gravitational waves were actually detected, with what the authors call “future-oriented imaginaries” profoundly shaping research practices and priorities.

The imperative of cooperation

Luca Guzzardi’s “Multi-messenger astrophysics and the epistemic reasons for cooperative behavior” tackles a deceptively simple question: Why do multi-messenger astronomers cooperate so extensively?

While social, economic, and political factors clearly matter in big science, Guzzardi argues that epistemic constraints make cooperation fundamentally necessary rather than merely advantageous. Examining theoretical models of transient events like supernovae and neutron star mergers, he shows that these models predict nearly simultaneous emission of different messengers, each governed by distinct physical processes and requiring specialized detection technologies.

No single instrument or institution can capture all relevant signals. The observational requirements themselves demand coordination across distributed, heterogeneous facilities. The field’s distinctive feature isn’t simply that many groups work together, but that the scientific questions being asked cannot be answered without integrating fundamentally different observational capabilities.

What does “direct” observation mean?

Emilie Skulberg and Jamee Elder’s “What is a ‘direct’ image of a shadow?” explores how the concept of “directness” functions in multi-messenger contexts, using black hole imaging as a case study. When the Event Horizon Telescope released the first image of a black hole’s shadow in 2019, press releases described it as “direct visual evidence.” But what makes an observation “direct”?

Through interviews with EHT collaboration members and analysis of gravitational-wave detection debates, Skulberg and Elder reveal that practitioners hold divergent notions of directness—some emphasizing minimal processing of raw data, others focusing on the physical proximity of detected signals to their source, and still others highlighting the unambiguous signatures that distinguish one interpretation from alternatives.

Comparing black hole imaging to LIGO’s gravitational-wave detections, they identify at least six different meanings of “direct” deployed across contexts: strict observation of the entity itself, transmission without interference, closer proximity to the source, shorter chains of inference, unambiguous signatures, and reliance on measurement rather than source modeling.

Importantly, they show that “directness” is often invoked contrastively—to claim epistemic superiority over “indirect” methods—yet these claims rarely acknowledge which notion of directness is being deployed. This philosophical analysis illuminates a practical challenge in multi-messenger astronomy: integrating observations from communities with different epistemic cultures and different standards for what constitutes compelling evidence.

Kepler’s geometric struggles

The issue concludes with a step back in time. Christián Carman’s “Kepler’s first attempts to demonstrate the bisection of the Earth’s orbit” offers a detailed reconstruction of Johannes Kepler’s early calculations in 1600, when he first accessed Tycho Brahe’s observations of Mars. Using manuscript evidence, Carman traces Kepler’s attempts to prove that Earth’s orbit was bisected: that its center lay midway between the “mean Sun” (the center of uniform motion) and the true Sun.

This seemingly technical problem was crucial for Kepler’s revolutionary work because accurate Earth–Sun distances were essential for triangulating Mars’s position. Carman shows that Kepler struggled through multiple failed attempts, hampered by calculation errors, geometric limitations, and insufficient observations.

What emerges is a picture of scientific discovery as messy, iterative, and contingent. Yet these struggles laid groundwork for his eventual laws of planetary motion, illustrating how using one celestial body (Mars) to correct another’s orbit (Earth’s) through triangulation anticipated key multi-messenger principles: using independent observational channels to constrain the same phenomenon.

A new kind of astronomy?

This special issue makes a compelling case that multi-messenger astronomy, while undoubtedly transformative in its current form, emerged from deep roots. The authors repeatedly show that multi-messenger astronomy represents less a sudden break than a culmination of technical capabilities to detect diverse signals, institutional frameworks to coordinate observations globally, and conceptual integration of once-separate physical domains.

This work also raises questions about how scientific fields are defined and delimited. As the editors note in their introduction, the term “multi-messenger” remains ambiguous even among practitioners. This definitional instability runs deeper than semantics, reflecting genuine uncertainty about boundaries, priorities, and epistemic claims in astronomy. By bringing historical and philosophical scrutiny to bear on a field still actively forming, this collection offers tools to both practitioners and scholars for thinking more carefully about what multi-messenger astronomy is, how it emerged, and what makes it distinctive.

Rebecca Charbonneau
American Institute of Physics
rcharbonneau@aip.org

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