Black hole shreds massive star in rare cosmic event; mysterious fast-moving helium suggests survival

On a night in 2024, astronomers watching the sky through the Zwicky Transient Facility at Palomar Observatory in California caught something extraordinary: a star being torn to pieces by a black hole. The event, formally catalogued as AT2024wpp but nicknamed "the Whippet" by those who studied it, would become one of the most violent cosmic encounters ever recorded. For a brief window, the energy pouring out of this destruction reached roughly 400 billion times what our Sun produces in the same span of time—a figure that dwarfs even the most powerful supernovae astronomers have ever documented.

Anna Ho, an assistant professor of astronomy at Cornell University, was among the first to identify the object as it brightened across Earth's telescopes. Within hours, observations from the Liverpool Telescope in the Canary Islands and NASA's Swift satellite confirmed what researchers suspected: they were witnessing a Luminous Fast Blue Optical Transient, or LFBOT, a rare and poorly understood phenomenon in which a star is consumed by a black hole in a tidal disruption event. The object appeared intensely blue and was flooding space with X-rays. Distance measurements from colleagues at UCLA and Caltech revealed the energy output far exceeded anything a collapsing star alone could produce. Daniel Perley, an associate professor of astrophysics at Liverpool John Moores University and lead author of the paper published in the Monthly Notices of the Royal Astronomical Society, described the moment of realization: the black hole was merging with a massive companion star, shredding it into a disk that fed the black hole's hunger.

What made the Whippet so exceptional was not just its raw power but its scale. Tidal disruption events—instances where black holes consume stars—had been observed before, but never on this magnitude. The destruction generated a shock wave that raced outward through the dense gas surrounding the black hole at one-fifth the speed of light, a velocity that speaks to the violence of the encounter. Material torn from the star spiraled inward, heating to extreme temperatures and producing not only X-rays but also a powerful wind of gas that collided with material the star had ejected in earlier epochs. This collision created the brilliant blue and ultraviolet light that first caught astronomers' attention, along with radio and millimeter signals that continued to arrive at Earth's observatories.

But around six months after the initial explosion, something unexpected happened. The shock wave that had been racing outward suddenly seemed to lose its momentum, "fizzling out" as it reached the outer boundary of a bubble of gas the doomed star had expelled long before its destruction. The event was fading, and with it came a puzzle that would occupy researchers' attention in the months that followed. Observations from the Keck Observatory, the Magellan Observatory, and the Very Large Telescope showed no clear chemical signatures in the first month after the explosion. Then, as the brightness dimmed, weak traces of hydrogen and helium began to appear in the light reaching Earth.

The helium signal proved most intriguing. It was moving at more than 6,000 kilometers per second along the line of sight toward Earth—a speed that suggested something dense and bound had survived the black hole's initial assault and was now hurtling through space. Researchers offered two explanations. The first: a stream of material released from the star's core as the black hole's gravity tore it apart, still moving at tremendous velocity. The second, more speculative: a third object in the system, perhaps a companion to the star itself, being blasted by the intense wind and radiation pouring from the feeding black hole. Either way, the detection of this fast-moving helium raised a new question about what survives when a black hole destroys a star, and what that survival might teach us about how black holes form, grow, and interact with the stars around them.