Supernova Signatures on Life in the Local Bubble

Winds from a central massive hot star cause the expansion of interstellar material, blowing outwards to create the Bubble Nebula. Credit: NASA, ESA, Hubble Heritage Team; CC BY 4.0

As the solar system travels through the Milky Way, our planet and the life it harbors are exposed to a variety of environments. A recent study suggests that a nearby supernova may have played a role in the evolution of life on Earth

The Local Bubble

About 6 million years ago, the solar system wandered into a 1,000 light-year-wide void known as the Local Bubble. Winds from massive stars and ionizing radiation from an estimated 15 supernovae carved out this bubble over the last 15 million years. As the solar system traveled from the bubble’s edge to its current position in the center, at least nine of the bubble-sculpting supernovae exploded, showering the Earth with supernova byproducts and intense radiation.

Evidence of these past explosions is embedded within the Earth’s crust — radioactive isotopes formed only in supernovae have decayed over time in deep-sea sediments. Less conspicuous are the ways cosmic rays from supernovae may have impacted the Earth; high-energy charged particles rained into the solar system, exposing the planet and the life on it to powerful radiation. Studying the Local Bubble and tracing the history of supernova explosions within it will allow researchers to gauge how the local environment has impacted our planet and the life it harbors.

Map of the Local Bubble showing the locations of surrounding stellar associations. The solar system lies near the center of the Local Bubble, and the surrounding stellar associations hosted supernovae that blew up the bubble. Modified from Nojiri et al 2025

Modeling Nearby Supernovae and Cosmic Radiation

Starting with the decay rate of the deep-sea isotopes, scientists estimate peaks in radioactive iron deposits approximately 2–3 and 5–6 million years ago. Using this information and the recent mapping of stellar associations in the Local Bubble, Caitlyn Nojiri (University of California, Santa Cruz) and collaborators modeled the necessary supernova input to produce the level of radioactive material present on Earth. From their modeling, they estimate that the iron peak ~2.5 million years ago can be attributed to a single supernova explosion from either the Upper Centaurus Lupus or Tucana Horologium stellar associations. The iron peak 5–6 million years ago, the authors suggest, arises from the solar system passing through the enriched outer shell of the Local Bubble.

Given the amount of radioactive iron deposited on Earth, the authors predict a powerful supernova progenitor capable of releasing some of the highest-energy cosmic rays in the universe. Through knowing the approximate location of the supernova and modeling its energy output, the authors estimate the amount of cosmic radiation Earth was exposed to from the time the supernova exploded to now. In their model, cosmic-ray radiation varies over time as the supernova evolves, meaning the Earth received a much higher volume of cosmic rays for the first 100,000 years after the explosion.

Cosmic-ray spectra (top panel) and the amount of cosmic radiation received at various depths on Earth (bottom panel) for the modeled supernova in the Upper Centaurus Lupus stellar association. Modified from Nojiri et al 2025

Impacts on Life

What does this cosmic-ray exposure mean for life on Earth? Though the exact effects of this radiation are not certain, biological studies have shown that radiation exposure can cause DNA to break, which can accelerate the rate at which genetic mutations and evolutionary changes occur. The authors note a prior study that showed the rate of virus diversification in Lake Tanganyika in Africa accelerated 2–3 million years ago. Though this cannot be definitively attributed to the supernova, the overlapping timeframes are suggestive of cosmic radiation playing a role in the evolution of life on our planet.

This study underscores the importance of considering cosmic radiation when it comes to understanding the environmental factors that drove biological evolution on Earth. Further studies must be performed in order to constrain the threshold at which this radiation goes from driving species diversification to becoming detrimental to life and its evolution. The Local Bubble has left imprints on the solar system and on Earth in ways that astronomers and biologists will continue to uncover.

By Lexi Gault

Citation

“Life in the Bubble: How a Nearby Supernova Left Ephemeral Footprints on the Cosmic-Ray Spectrum and Indelible Imprints on Life,” Caitlyn Nojiri et al 2025 ApJL 979 L18. doi: 10.3847/2041-8213/ada27a

Source: American Astronomical Society/AAS-Nova

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NSF–DOE Rubin Observatory’s Unparalleled Vision Will Revolutionize Multi-Messenger Astronomy

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Artist’s Illustration of Multi-Messenger Event

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Night Light

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Vera C. Rubin Observatory will unite coordinated observations of cosmic phenomena using the four messengers of the Universe

Photons, neutrinos, cosmic rays and gravitational waves all carry information about the Universe. Multi-messenger astronomy brings together these four signals to investigate astronomical events from multiple cosmic perspectives. With its sensitive camera and suite of filters, NSF–DOE Vera C. Rubin Observatory will increase the population of known multi-messenger sources by obtaining crucial color information and localizing events for follow-up observations by other telescopes.

Astronomy has always relied on light to convey information about the Universe. But capturing photons is no longer the only technique scientists have for studying astronomical phenomena. Subatomic particles, such as neutrinos and those that are delivered in the form of cosmic rays, as well as gravitational waves — ripples in the fabric of space-time — are also messengers. Multi-messenger astronomy aims to combine the information from more than one of these signals to give researchers a deeper understanding of some of the most extreme events in the Universe. NSF–DOE Vera C. Rubin Observatory will soon contribute to this emerging field by using its powerful camera and wide field of view to find faint multi-messenger sources and point other telescopes in the right direction for follow-up observations.

Rubin Observatory is jointly funded by the U.S. National Science Foundation (NSF) and the U.S. Department of Energy, Office of Science (DOE/SC). It is a Program of NSF NOIRLab, which, along with SLAC National Accelerator Laboratory, will jointly operate Rubin.

Multi-messenger astronomy is an enhanced way of studying cosmic events that are predicted to emit more than one type of signal, such as stellar explosions, actively feeding black holes, and collisions between compact objects, to name just a few. Each messenger communicates unique information about the physical processes and energies involved. When a single source is observed using multiple signals the data can be combined to reach a deeper level of insight. “The result is more than the sum of its parts,” says Raffaella Margutti, associate professor at the University of California at Berkeley.

In addition to conducting a massive study of the southern sky called the Legacy Survey of Space and Time (LSST), Rubin will also perform ‘Target of Opportunity’ observations in quick response to alerts of potential multi-messenger sources. As the fastest-slewing large telescope in the world, Rubin can point to targets in as little as three minutes. Such observations will provide crucial information about an event’s optical — meaning wavelengths detectable by the human eye — properties, which in turn helps localize the event for follow-up by other telescopes.

However, in order to coordinate multiple telescopes capable of detecting the different types of messengers, scientists have to know where to look. Signals such as gravitational waves and neutrinos can point scientists in the general direction of a source, but in order to pinpoint its exact location you need light. This is where Rubin, equipped with the largest and most sensitive camera ever built for astronomy and astrophysics, will shine.

Margutti, whose studies focus specifically on finding the electromagnetic counterparts to gravitational wave events, explains, “Gravitational wave observatories can only tell you ‘look at this large area and search for something very faint.’ But you don't know exactly where to look.” Furthermore, the distance at which current observatories are capable of detecting gravitational waves can be far beyond the limit of what they can detect with photons, making it hard to observe an event with both messengers.

With its deep and wide capabilities, Rubin will help mitigate both of these challenges. “Rubin wins twice,” says Margutti. “Its strong light-collecting power and ability to scan large sections of sky mean it’s very sensitive to faint optical signals, like those we would be seeking from a gravitational wave source.”

So far only one multi-messenger gravitational wave event has been observed: a merger between two neutron stars that sent both space-time ripples and photons careening across the cosmos. Other events predicted to emit more than one messenger are black hole-neutron star and black hole-black hole mergers. “I would be super excited if we found photons coming from these types of mergers,” says Margutti. “Rubin is uniquely positioned to confirm or expand on the types of mergers that produce light.”

Rubin’s ability to detect faint sources will also be a game changer for studying neutrinos. Robert Stein, California Institute of Technology postdoctoral scholar, explains: “In neutrino science there are many different types of possible sources, but existing optical telescopes are only able to see the brightest, most unusual ones.” Based on the number of neutrinos arriving at detectors here on Earth, scientists believe there to be a vast population of neutrino sources at varying distances throughout the Universe. However, given the limits of existing telescopes, Stein estimates that only 5–10% of them are also detectable with photons. By bringing myriad faint sources to light for the very first time, Rubin could increase that to 50%.

“Neutrino science is in its infancy, so our list of possible sources is still emerging,” says Stein. “In ten or fifteen years we will likely discover that events we’ve already known about are also neutrino source populations.”

Margutti and Stein are both confident that the overarching power of Rubin in the era of multi-messenger astronomy will be in uncovering the unexpected. As it covers vast swaths of the southern hemisphere sky, there’s no telling what Rubin’s unparalleled vision is going to reveal. “The best use of Rubin is as a discovery machine,” says Margutti. Stein echoes a similar sentiment, saying, “I hope to learn what new types of sources we should investigate next. If Rubin could give us that clarity, and I believe it will, that would be amazing.”

Source: NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab)/News

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More information

The NSF–DOE Rubin Observatory is a joint initiative of the U.S. National Science Foundation (NSF) and the Department of Energy (DOE). Its primary mission is to carry out the Legacy Survey of Space and Time, providing an unprecedented data set for scientific research supported by both agencies. Rubin is operated jointly by NSF NOIRLab and SLAC National Accelerator Laboratory (SLAC). NOIRLab is managed for NSF by the Association of Universities for Research in Astronomy (AURA) and SLAC is operated for DOE by Stanford University. France provides key support to the construction and operations of Rubin Observatory through contributions from CNRS/IN2P3. Additional contributions from a number of international organizations and teams are acknowledged.

The U.S. National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 to promote the progress of science. NSF supports basic research and people to create knowledge that transforms the future.

NSF NOIRLab (U.S. National Science Foundation National Optical-Infrared Astronomy Research Laboratory), the U.S. center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O’odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.

SLAC National Accelerator Laboratory is a vibrant multiprogram laboratory that explores how the Universe works at the biggest, smallest, and fastest scales and invents powerful tools used by scientists around the globe. With research spanning particle physics, astrophysics and cosmology, materials, chemistry, bio- and energy sciences and scientific computing, SLAC helps solve real-world problems and advance the interests of the nation.

SLAC is operated by Stanford University for the U.S. Department of Energy’s Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time.

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Links

• Vera C. Rubin Observatory website
• Vera C. Rubin Observatory images
• More Rubin images
• Rubin videos
• Rubin multimedia resources

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Contacts

Raffaella Margutti
Associate Professor
University of California Berkeley
Email: rmargutti@berkeley.edu

Robert Stein
Postdoctoral Scholar
California Institute of Technology
Email: rdstein@caltech.edu

Bob Blum
Director for Operations
Vera C. Rubin Observatory / NSF NOIRLab
Tel: +1 520-318-8233
Email: bob.blum@noirlab.edu

Željko Ivezić
Director of Rubin Construction
Professor of Astronomy, University of Washington / AURA
Tel: +1-206-403-6132
Email: ivezic@uw.edu

Josie Fenske
Jr. Public Information Officer
NSF NOIRLab
Email: josie.fenske@noirlab.edu

Manuel Gnida
Head of External Communications
SLAC National Accelerator Laboratory
Tel: +1 650-926-2632 (office)
Cell: +1 415-308-7832 (cell)
Email: mgnida@slac.stanford.edu

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Probing Deeper into Origins of Cosmic Rays

Schematic representation of cosmic rays propagating through magnetic clouds
Credit: Salvatore Buonocore

WASHINGTON, May 25, 2021 — Cosmic rays are high-energy atomic particles continually bombarding Earth’s surface at nearly the speed of light. Our planet’s magnetic field shields the surface from most of the radiation generated by these particles. Still, cosmic rays can cause electronic malfunctions and are the leading concern in planning for space missions.

Researchers know cosmic rays originate from the multitude of stars in the Milky Way, including our sun, and other galaxies. The difficulty is tracing the particles to specific sources, because the turbulence of interstellar gas, plasma, and dust causes them to scatter and rescatter in different directions.

In AIP Advances, by AIP Publishing, University of Notre Dame researchers developed a simulation model to better understand these and other cosmic ray transport characteristics, with the goal of developing algorithms to enhance existing detection techniques.

Brownian motion theory is generally employed to study cosmic ray trajectories. Much like the random motion of pollen particles in a pond, collisions between cosmic rays within fluctuating magnetic fields cause the particles to propel in different directions.

But this classic diffusion approach does not adequately address the different propagation rates affected by diverse interstellar environments and long spells of cosmic voids. Particles can become trapped for a time in magnetic fields, which slow them down, while others are thrust into higher speeds through star explosions.

To address the complex nature of cosmic ray travel, the researchers use a stochastic scattering model, a collection of random variables that evolve over time. The model is based on geometric Brownian motion, a classic diffusion theory combined with a slight trajectory drift in one direction.

In their first experiment, they simulated cosmic rays moving through interstellar space and interacting with localized magnetized clouds, represented as tubes. The rays travel undisturbed over a long period of time. They are interrupted by chaotic interaction with the magnetized clouds, resulting in some rays reemitting in random directions and others remaining trapped.

Monte Carlo numerical analysis, based on repeated random sampling, revealed ranges of density and reemission strengths of the interstellar magnetic clouds, leading to skewed, or heavy-tailed, distributions of the propagating cosmic rays.

The analysis denotes marked superdiffusive behavior. The model’s predictions agree well with known transport properties in complex interstellar media.

“Our model provides valuable insights on the nature of complex environments crossed by cosmic rays and could help advance current detection techniques,” author Salvatore Buonocore said.

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Link to article: Anomalous diffusion of cosmic rays: A geometric approach
DOI: 10.1063/5.0049401

For more information:

Larry Frum
media@aip.org
301-209-3090

Article Title

Anomalous diffusion of cosmic rays: A geometric approach

Authors

Salvatore Buonocore and Mihir Sen

Author Affiliations

University of Notre Dame

Source: AIP Advances

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AIP Advances

AIP Advances is a fully open access, online-only, peer-reviewed journal. It covers all areas of applied physical sciences. With its advanced web 2.0 functionality, the journal puts relevant content and discussion tools in the hands of the community to shape the direction of the physical sciences.

http://aipadvances.aip.org

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