Black Hole Swift J1727.8–1613 Expels Half Its Consumed Matter, Study Finds

Astronomers used the Very Large Telescope in Chile to monitor the binary system Swift J1727.8–1613, located about 8,800 light-years from Earth. The system consists of a stellar-mass black hole and a companion star whose material forms an accretion disk before spiraling inward. In 2023 the system produced an exceptionally bright X-ray outburst that made it one of the sky’s most luminous X-ray sources. High-resolution optical records captured the entire feeding episode, allowing researchers to track how matter entered and later left the black hole’s vicinity.

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The research team, led by Noel Castro Segura of the University of Warwick, found that while a portion of the stripped stellar material was accreted, a substantial fraction was expelled as high-speed jets and slower “black-hole winds.” Co-author Kyle Solomons of the University of Cape Town noted that the outflows persisted even after the X-ray emission fell to a small fraction of its peak, indicating that the black hole continued to power massive gas ejections during the decline phase.

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Analysis of the VLT data suggests that at least 10 % of the transferred mass was expelled during the peak of the event, and the cumulative outflow may ultimately equal the mass that was actually consumed. The authors propose that roughly half of the stellar “meal” could be lost to space, a proportion far larger than previously assumed for such binary systems.

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These observations challenge the long-standing view of black holes as “bottomless pits.” Instead, the study, published in *Monthly Notices of the Royal Astronomical Society*, portrays black holes as dynamic digestive systems that can regurgitate a significant share of incoming matter. If such inefficiencies are common, they could alter models of binary-star evolution and the mass-growth histories of black holes across galaxies.

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