The location of SN 2023vbw (magenta circle) in the outskirts of its dwarf host galaxy (green circle). Credit: arXiv (2026). DOI: 10.48550/arxiv.2605.16487
Astronomers may have discovered one of the clearest examples yet of a rare "pair-instability" supernova. It is a catastrophic explosion thought to completely destroy some of the most massive stars in the universe, leaving behind no remnant. The paper outlining the properties of this rare explosion was posted to the arXiv preprint server on May 15.
The event, SN 2023vbw, was first detected by the Zwicky Transient Facility in October 2023 in the outskirts of a small, metal-poor dwarf galaxy about 1.3 billion light-years away. It was tentatively classified as a Type II supernova—the kind produced when a massive star exhausts its nuclear fuel, collapses under gravity, and explodes. But several of its properties refused to fit that picture.
An outlier
In a new study, astronomers conducted detailed observations and modeling of SN 2023vbw to pin down its true nature. The first clue that something unusual was happening came from its light curve—how its brightness changed over time. Rather than the plateau-like rise typical of a Type II supernova, after an initial cooling phase, SN 2023vbw rose steadily to a bright peak at around 190 days.
It also showed a rapid decline in its brightness from 190 days to 230 days. After the fade, the explosion curve settled into a slowly declining plateau called the "tail." The total energy it radiated, around 3 × 1050 ergs, is more than ten times greater than a normal Type II supernova.
During the rise, the explosion settled into a nearly constant temperature while its outer shell continued to expand. This behavior requires a large, continuous internal heating source, unlike typical supernova Type II.
As the supernova faded, forbidden emission lines began to emerge, and in the tail phase, the hydrogen lines developed a multicomponent profile with a redshifted component, indicating the ejecta interacting with a disk-like shell of material the star had shed before it died.
A 'blue' culprit
Modeling the light curve suggested that the explosion likely originated from an extraordinary blue supergiant star. The light curve morphology closely resembles that of SN 1987A, which is a Type II supernova that also came from a compact blue supergiant progenitor. But SN 2023vbw has a significantly higher luminosity and longer timescale, pointing to a far more massive progenitor.
Its ejecta mass is estimated at between 170 and 350 solar masses, and the kinetic energy of the explosion fell in the order that is 60 to 130 times greater than the maximum energy an ordinary iron core-collapse supernova can produce.
The low metallicity of the host environment—roughly one-tenth that of the sun—falls within theoretical predictions for pair-instability supernovae.
The team also suggests the blue supergiant star may have formed through a merger of two massive stars in a binary system. This formation channel would naturally explain the dense disk-like shell of material with which the ejecta interacted.
However, the team explains in their paper that significant uncertainties remain: it is still unclear whether very massive stars end their lives as red or blue supergiants, and when exactly during their lifetime such a merger would occur.
Self-destruction
Pair-instability supernovae occur in stars so massive that the extreme temperatures in their cores cause the production of electron-positron pairs. This removes the radiation pressure supporting the star against the inward gravitational pull, triggering a runaway thermonuclear explosion so violent that the entire star is consumed. As a result of this, no neutron star or black hole is expected to be left behind.
Stars with initial masses of roughly 140 to 260 solar masses and low metallicity are predicted to meet this fate, and the modeled properties of SN 2023vbw fall well within that regime.
Because it's at a close distance to us, "SN 2023vbw remains sufficiently bright for continued multiwavelength observations that will reveal its progenitor mass-loss history and explosive nucleosynthesis," the team writes.
The team notes that upcoming surveys with the Vera Rubin Observatory and the Nancy Grace Roman Space Telescope should find tens to hundreds of such events, finally highlighting the deaths and evolution of the universe's most massive stars.
Written for you by our author Shreejaya Karantha, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.
Publication details
Daichi Hiramatsu et al, The pair-instability origin of supernova 2023vbw, arXiv (2026). DOI: 10.48550/arxiv.2605.16487
Journal information: arXiv
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Shreejaya Karantha
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Sadie Harley
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Robert Egan
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