Free Astronomy Magazine May-June 2026

4 ASTRO PUBLISHING about 2.5 million light-years from Earth in the Andromeda galaxy. When it formed, the star was roughly 13 times the mass of the Sun. Over its lifetime, powerful stel- lar winds stripped away much of that mass, leaving it with about five times the mass of the Sun at the end of its life. Archival observations from NASA’s NEOWISE mission re- vealed that the star gradually brightened in infrared light over several years before fading dramat- ically and disappearing from view. Unlike a typical supernova, the event showed no evidence of a powerful outward explosion. In- stead, it left behind a shell of dust and a faint infrared glow. “The dramatic and sustained fading of this star is very unusual, and sug- gests a supernova failed to occur, leading to the collapse of the star’s core directly into a black hole,” De said. To better constrain the nature of the event, the team conducted follow-up observations using the Near-Infrared Echellette Spectro- graph (NIRES) on the Keck II Tele- scope, with observing time awarded via the NASA-Keck partnership. Prior to the Keck observations, there were no ground-based infra- red spectra of the source at suffi- cient sensitivity to test whether the star had truly faded at infrared wavelengths. NIRES is optimized for studying extremely faint infrared sources and is particularly well MAY-JUNE 2026 A stronomers using W. M. Keck Observatory on Maunakea, Hawai ‘ i Island contributed key observations to the identifica- tion of a rare stellar death in which a massive star appears to have col- lapsed directly into a black hole without first exploding as a super- nova. The event occurred in the Andromeda galaxy and provides strong observational support for a long-theorized but rarely confirmed route to black hole formation. The study, led by researchers at Co- lumbia University, combines archival space-based data with targeted ground-based follow-up observa- tions from multiple observatories. “This has probably been the most surprising discovery of my life,” said Kishalay De, professor of astronomy at Columbia University and lead au- thor of the study. “The evidence of the disappearance of the star was lying in public archival data, and no- body noticed it for years until we picked it out.” The object, designated M31-2014- DS1, was a supergiant star located Compelling evidence of a star collapsing directly into a black hole by Keck Observatory