Leveraging archival datasets from NASA’s NEOWISE observatory, augmented by observations from a constellation of other space-based and terrestrial telescopes, astrophysicists have documented the most definitive evidence to date of a colossal star’s demise and subsequent disappearance into a black hole—a phenomenon previously posited by theory but seldom witnessed.
Location and disappearance of M31-2014-DS1. Image credit: De et al., doi: 10.1126/science.adt4853.
As immense celestial bodies approach the twilight of their existence, they can enter states of instability, undergoing significant volumetric expansion and exhibiting pronounced fluctuations in luminosity within observable temporal frames.
Frequently, these stellar entities meet their end in spectacular supernova events, characterized by prodigious luminosity and ease of detection.
Nonetheless, not all stellar deaths culminate in explosive supernovae. Theoretical frameworks postulate that certain massive stars may not achieve a successful explosive expulsion.
Conversely, upon the gravitational collapse of the star’s nucleus, its external mass may recede inward, precipitating the formation of a black hole.
However, such “failed” supernovae prove challenging to detect due to their faint energetic emissions, predominantly manifesting as stars that simply recede from our field of view.
In their pursuit of variable celestial objects within the proximate Andromeda galaxy, astronomer Kishalay De of Columbia University and his research associates meticulously analyzed longitudinal infrared observational records compiled by the NEOWISE mission. This endeavor led to the identification of an anomalous supergiant star designated M31-2014-DS1.
This star experienced a surge in brightness in the mid-infrared spectrum during 2014. Subsequently, between 2017 and 2022, it experienced a dramatic dimming, diminishing by approximately 10,000-fold in optical wavelengths (rendering it imperceptible) and by a factor of about 10 in overall luminosity.
Subsequent observational campaigns employing the Hubble Space Telescope and substantial ground-based observatories revealed only a faint, reddish remnant detectable in the near-infrared region. This finding implicates that the star is now heavily enshrouded in particulate matter, a mere vestige of the radiant supergiant it was merely years prior.
The research cadre interpreted these gathered data as compelling evidence for a failed supernova event that heralded the genesis of a stellar-mass black hole.
“The pronounced and sustained attenuation in luminosity exhibited by this star is exceedingly rare, strongly suggesting a failed supernova leading to the direct gravitational collapse of the star’s core into a black hole,” stated Dr. De.
“For an extended period, it has been presupposed that stars of comparable mass inevitably undergo supernova explosions.”
“The observation that this did not occur implies that stars possessing the same mass may or may not experience a successful explosive event, potentially contingent upon the intricate interplay of gravitational forces, gas pressure dynamics, and potent shockwaves within the dying star.”
Dr. De and his collaborators pinpointed another massive star, NGC 6946-BH1, which may have undergone a similar evolutionary trajectory to that of M31-2014-DS1.
This discovery facilitated a significant advancement in comprehending the fate of the stellar envelope material following its failure to detonate as a supernova and subsequent collapse into a black hole.
A critical, previously unacknowledged factor is convection, a phenomenon arising from the substantial temperature gradients within the star.
The stellar interior, proximate to its core, possesses extremely elevated temperatures, whereas its outer strata are considerably cooler. This disparity induces the movement of gaseous constituents within the star from regions of higher thermal energy to those of lower thermal energy.
When the star’s core undergoes collapse, the gaseous matter in its outer shells continues to exhibit rapid motion due to this convective process.
Theoretical simulations indicate that this continuous motion impedes a significant portion of the outer layers from accreting directly onto the nascent black hole. Instead, the innermost strata establish orbital paths external to the black hole, thereby facilitating the expulsion of the outermost layers of the convective zone.
The ejected material undergoes cooling as it propagates away from the intensely hot material enveloping the black hole. This cooled matter readily coalesces into dust as atoms and molecules aggregate.
The generated dust effectively obscures the high-temperature gas orbiting the black hole, leading to the warming of the dust and the emission of a detectable radiative surge in infrared wavelengths.
This persistent ruddy luminescence remains observable for decades after the star itself has ceased to be visible.
“The rate of accretion is considerably diminished compared to a scenario where the star implodes instantaneously,” remarked Andrea Antoni of the Flatiron Institute.
“This convective material possesses angular momentum, causing it to adopt a circular trajectory around the black hole.”
“Rather than succumbing to accretion within months or a year, this process extends over decades.”
“Consequently, due to these factors, it evolves into a more luminous source than it would otherwise be, and we observe a protracted delay in the dimming of the original stellar entity.”
A scholarly article detailing these discoveries was disseminated this week in the esteemed journal Science.
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Kishalay De et al. 2026. Disappearance of a massive star in the Andromeda Galaxy due to formation of a black hole. Science 391 (6786): 689-693; doi: 10.1126/science.adt4853
