Utilizing archival data from NASA’s NEOWISE mission alongside information from various space and ground-based observatories, astronomers have uncovered a remarkable observational record of a massive star’s transition into a black hole—a phenomenon previously theorized but seldom witnessed.

In their final stages, massive stars often undergo instability, expanding and exhibiting significant fluctuations in brightness that can be observed by humans.

Typically, these stars meet their end in spectacular supernova explosions, which are incredibly luminous and readily detectable.

However, it is theorized that not all massive stars culminate in such explosive deaths.

In some cases, a star’s core collapses, causing the outer materials to fall inward, leading to the creation of a black hole.

These failed supernovae are particularly challenging to identify due to their weak energy signatures, often appearing as stars that simply vanish from sight.

Columbia University astronomer Kisharai De and colleagues leveraged lengthy infrared observations from the NEOWISE mission to investigate variable stars within the Andromeda Galaxy, leading to the discovery of the rare supergiant star M31-2014-DS1.

During 2014, this star brightened in mid-infrared light; however, from 2017 to 2022, it dimmed by around 10,000 times in optical light (rendering it undetectable) and about tenfold in total light.

Subsequent observations using Hubble and large terrestrial telescopes revealed faint red remnants detectable in near-infrared light, indicating the star is now heavily obscured by dust, or a shadow of its former supergiant self from years past.

Researchers interpret these findings as evidence of a failed supernova explosion, resulting in the birth of a stellar-mass black hole.

“The star’s dramatic and sustained dimming is extremely unusual, indicating the core did not explode as a supernova but collapsed directly into a black hole,” stated Dr. De.

“It was long assumed that stars of this mass always explode as supernovae.”

Their observations challenge the belief that stars of equivalent mass either necessarily explode or fail to do so, likely influenced by chaotic interactions between gravity, gas pressure, and powerful shockwaves within a dying star.

Dr. De and his fellow scientists identified M31-2014-DS1, another giant star that may have met a similar fate as NGC 6946-BH1.

This study advances our understanding of the fate of the star’s outer layers post-supernova failure and collapse into a black hole.

Interaction among these elements, particularly convection influenced by temperature variances within a star, plays a crucial role.

The internal regions are extremely hot compared to the cooler outer areas, resulting in gas movement from hotter to cooler zones.

Even after a star’s core collapse, gases in the outer layers continue to move rapidly due to convection currents.

Theoretical models suggest that these currents prevent most outer layers from plunging directly into the core. Instead, the innermost layer orbits the black hole, allowing for the ejection of the outermost layers in the convective region.

As the ejected material cools while moving from the surrounding heat of the black hole, it forms dust as atoms and molecules condense.

This dust obscures the hot gas orbiting the black hole, warming it and creating brightness observable at infrared wavelengths.

This lingering red glow remains visible long after the star has vanished.

“The accretion rate is significantly slower than if the stars collided directly,” asserted Andrea Antoni from the Flatiron Institute.

“This convective material possesses angular momentum, causing it to rotate in a circular motion around the black hole.”

“Consequently, the process takes decades instead of months or years to unfold.”

“All these factors contribute to a brighter source than otherwise anticipated, leading to a prolonged delay in the dimming of the original star.”

For further insights, refer to this paper. The findings are published in this week’s edition of Science.

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Kisharai De et al. (2026). Massive stars in the Andromeda Galaxy vanish due to black hole formation. Science 391(6786): 689-693; doi: 10.1126/science.adt4853