Astronomers have witnessed a massive star in the nearby Andromeda Galaxy disappear, quietly collapsing into a black hole without the expected dramatic supernova explosion. This rare cosmic event, identified as M31-2014-DS1, provides the clearest evidence yet of a star directly transforming into a black hole. The discovery, detailed in the journal Science on February 12, challenges long-held theories about how some of the universe's most massive stars meet their end.^[1][2][3][4] ### A Cosmic Disappearing Act Unfolds The vanishing act of M31-2014-DS1 unfolded over several years, located about 2.5 million light-years from Earth in the Andromeda Galaxy. Scientists first noticed unusual activity in 2014 when the star brightened in mid-infrared light by approximately 50 percent over two years.^[1][5] However, this trend reversed, and by 2016, the star had dimmed below its original brightness. The decline continued, and by 2023, the star had effectively vanished in visible light.^[1][5] Optical surveys showed the star faded by a factor of about 10,000 between 2016 and 2019.^[1][4] Follow-up imaging in 2023 with the MMT Observatory could not detect it at all in optical wavelengths. Hubble Space Telescope data from 2022 found no sign of the star in one optical filter.^[1] Today, M31-2014-DS1 is only visible in mid-infrared light, glowing at roughly one-tenth of its former brightness.^[1] "This star used to be one of the most luminous stars in the Andromeda Galaxy, and now it was nowhere to be seen," said Kishalay De, lead author of the study from the Simons Foundation's Flatiron Institute and Columbia University. "Imagine if the star Betelgeuse suddenly disappeared. Everybody would lose their minds! The same kind of thing [was] happening with this star in the Andromeda Galaxy."^[1][4] ### Challenging Supernova Expectations For decades, astronomers believed that massive stars, typically those at least 10 times the mass of our Sun, would end their lives in spectacular supernova explosions. These brilliant events briefly outshine entire galaxies.^[1][6] However, the observation of M31-2014-DS1 presents a different scenario. Instead of exploding, the star's core gave way under its own gravity, directly collapsing inward to form a black hole.^[2][3][4][7] This process is often referred to as a "failed supernova."^[7][8] The direct collapse means that the star did not undergo the violent outward blast usually associated with a supernova. Instead, its outer layers were gradually pushed away as the core collapsed.^[2][3] This makes such events incredibly difficult to detect, as they lack the bright, energetic signatures of a typical supernova.^[6] "The dramatic and sustained fading of this star is very unusual, and suggests a supernova failed to occur, leading to the collapse of the star's core directly into a black hole," De explained.^[7][6] The findings reshape our understanding of how some of the universe's biggest stars meet their end.^[3] ### Decades of Data Reveal the Truth The groundbreaking discovery was made possible by combining new telescope data with more than ten years of archived observations.^[2] Researchers, led by Kishalay De, combed through data from NASA's NEOWISE mission, which collected observations from 2005 to 2023.^[1][4] NEOWISE, initially designed to search for asteroids and comets, inadvertently captured the early stages of this star's transformation.^[5][7] The team also utilized a long list of ground and space telescopes to track the star's fading, including the Hubble Space Telescope, MMT Observatory, the Infrared Telescope Facility, and the Keck telescopes.^[1][6] These observations allowed scientists to piece together a detailed physical explanation of how the event unfolded.^[2] "The evidence of the disappearance of the star was lying in public archival data and nobody noticed for years until we picked it out," De said.^[5] ### What This Means for Black Hole Birth This direct observation offers a rare look at how black holes are born and could help explain why some massive stars explode while others collapse quietly.^[2][7] Models suggest that in some collapsing stars, neutrinos may not trigger a supernova, leading instead to a direct collapse into a black hole.^[7] The energy emitted by gas falling into the newborn black hole would heat surrounding dust, causing it to radiate in the infrared, matching current observations of M31-2014-DS1.^[7] The debris surrounding the new black hole is expected to remain visible for decades in infrared light.^[2][4] Telescopes like the James Webb Space Telescope will be able to monitor its slow fading.^[2][4] Scientists hope this event will become a benchmark for understanding how stellar black holes form across the universe.^[2][4] The team also revisited another disappearing star, NGC 6946-BH1, which showed a similar pattern of an optical outburst followed by fading, further supporting the theory of core collapse without a successful supernova.^[1][6] This unprecedented observation provides crucial insight into the lifecycle of massive stars and the mysterious formation of black holes.

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