Unveiling the Secrets of Unusual Supernovae: Pioneering 3D Simulations Shed Light on Complex Explosive Phenomena

The groundbreaking three-dimensional simulations of unconventional supernovae disclose the chaotic configurations that arise during the ejection of matter in these explosions. Such turbulent formations have subsequent effects on the overall brightness and architecture of the supernova. Turbulence, originating from irregular flows of fluid, is instrumental in the complex mechanics of the supernova explosion. These chaotic formations meddle with and deform matter, impacting the emission and distribution of energy, and consequently altering the brightness and visual appearance of the supernova. The 3D simulations have allowed researchers to acquire a more profound comprehension of the physical mechanisms underpinning these unique types of supernovae. Credit: Ke-Jung Chen/ASIAA

An international consortium of astronomers employed advanced supercomputers at the Lawrence Berkeley National Laboratory in the United States and the National Astronomical Observatory of Japan. After dedicating years to rigorous research and utilizing over five million hours of supercomputing time, they have ultimately crafted the first-ever high-resolution 3D radiation hydrodynamics simulations for unconventional supernovae. These revelations will be published in an upcoming issue of The Astrophysical Journal.

Supernova eruptions represent the grand finale in the lifespans of massive stars, which culminate their existence through cataclysmic self-dismantlement, emitting brightness on a scale comparable to billions of suns and illuminating the cosmos. During this violent event, the star expels heavy elements, thus laying the groundwork for the genesis of new celestial bodies and potentially life itself. As a result, the study of supernovae has assumed a central role in contemporary astrophysics, encompassing myriad crucial questions in both theoretical and observational domains, and thereby holding substantial research importance.

For the past 50 years, scholars have attained a relatively thorough understanding of traditional supernovae. However, recently conducted large-scale surveys have begun to uncover abnormal stellar eruptions, termed exotic supernovae, which confound and disrupt previously understood principles of supernova physics.

Enigmas in Exotic Supernovae

Notably perplexing among exotic supernovae are superluminous supernovae and persistently luminous supernovae. Superluminous supernovae outshine standard supernovae by a factor of approximately 100 and maintain this brightness for a considerably shorter duration—weeks to two to three months. Conversely, the newly identified persistently luminous supernovae can sustain their brilliance for several years or even more.

Remarkably, certain exotic supernovae have been observed to display irregular and sporadic fluctuations in brightness, akin to intermittent eruptions. These distinctive supernovae could serve as crucial clues for comprehending the developmental pathways of the most colossal stars in the universe.

This visual representation depicts the concluding physical configurations of the exotic supernova, segmented into four distinct color quadrants that indicate different physical properties: I. temperature, II. velocity, III. radiative energy density, and IV. gaseous density. The white dashed circle delineates the position of the supernova’s photosphere. This illustration assists us in grasping the fundamental physics of exotic supernovae, offering a rationale for the observed features. Credit: Ke-Jung Chen/ASIAA

Origins and Structural Evolution

The progenitors of these exotic supernovae remain elusive, but they are suspected to emerge from atypically massive stars. For stars with masses ranging between 80 and 140 times that of our Sun, their cores engage in carbon fusion processes as they near the end of their lifespans. During these reactions, high-energy photons yield electron-positron pairs, instigating core pulsations and ensuing violent compressions.

These compressions liberate immense quantities of fusion energy, precipitating colossal stellar eruptions that can resemble standard supernova explosions. Additionally, when ejected materials from different eruptive phases collide, phenomena akin to superluminous supernovae can materialize.

Given the relatively infrequent occurrence of such massive stars, the rarity of exotic supernovae aligns well. Therefore, researchers conjecture that these stars are the likely progenitors of such unconventional supernovae. However, the erratic structural evolution of these stars poses significant challenges for computational modeling, which is predominantly limited to one-dimensional simulations.

Shortcomings of Prior Models

Previous one-dimensional models exhibited considerable inadequacies. Supernova detonations produce significant levels of turbulence, which is vital for both the explosive mechanism and brightness of the supernova. However, one-dimensional models cannot authentically simulate turbulence from fundamental principles. These limitations have hindered a thorough understanding of the physical processes governing exotic supernovae, remaining a significant obstacle in current theoretical astrophysics.

Advancements in Simulation Techniques

The high-resolution simulations posed substantial difficulties. As the scale of the simulations expanded, retaining high resolution became progressively challenging, raising both computational complexity and requirements while necessitating the incorporation of a multitude of physical variables. Ke-Jung Chen underscored that their simulation protocols held an edge over other international teams.

Earlier models were primarily constrained to one-dimensional and occasionally two-dimensional fluid simulations. In contrast, for exotic supernovae, multi-dimensional influences and radiation are pivotal, affecting both light emission and the overall explosion dynamics.

The Influence of Radiation Hydrodynamics Simulations

Radiation hydrodynamics simulations take into account both the propagation of radiation and its interactions with matter, thereby elevating the computational complexity and requirements substantially above fluid-only simulations. Nevertheless, leveraging their extensive expertise in modeling supernovae and conducting large-scale simulations, the research team succeeded in devising the world’s first 3D radiation hydrodynamics simulations for exotic supernovae.

Conclusions and Future Prospects

The team’s discoveries suggest that intermittent eruptions in massive stars can display characteristics similar to multiple, less luminous supernovae. When materials from distinct eruptive phases interact, roughly 20-30% of the kinetic energy of the gas may be converted into radiation, accounting for the phenomenon of superluminous supernovae.

Moreover, the radiation’s cooling effect causes the erupting gas to condense into a dense but irregular three-dimensional sheet structure, which then becomes the primary light emission source in the supernova. The simulation results effectively elucidate the observational characteristics of the aforementioned exotic supernovae.

Through advanced supercomputer simulations, this study marks a substantial leap in understanding the physics of exotic supernovae. As next-generation supernova surveys commence, it is anticipated that more exotic supernovae will be identified, further refining our grasp of the terminal phases of massive stars and their mechanisms of explosion.

Reference: “Multidimensional Radiation Hydrodynamics Simulations of Pulsational Pair-instability Supernovae” by Ke-Jung Chen, Daniel J. Whalen, S. E. Woosley, and Weiqun Zhang, 14 September 2023, The Astrophysical Journal.
DOI: 10.3847/1538-4357/ace968

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More about Exotic Supernovae 3D Simulations

• The Astrophysical Journal
• Lawrence Berkeley National Laboratory
• National Astronomical Observatory of Japan
• Overview of Supernova Research
• Introduction to Radiation Hydrodynamics
• Turbulence in Astrophysics