A space telescope designed to catch the universe's most fleeting explosions may have just recorded something even rarer: a black hole of middling size ripping a white dwarf star to shreds. The flash was so bright and so strange that astronomers around the world immediately knew they were watching something that had never been seen before.
The event, designated EP250702a, was first spotted on July 2, 2025, by the China led Einstein Probe satellite during a routine sweep of the sky. The X-ray source flared and faded in a pattern that did not match any known type of cosmic blast. Within hours, telescopes on multiple continents turned their gaze toward the same patch of sky.
A flash that arrived in two acts
The Einstein Probe carries two X-ray instruments. Its Wide field X-ray Telescope caught a steady but faint X-ray glow coming from a single point in space about a day before the main explosion. Then, roughly 15 hours later, the source erupted in a series of violent X-ray flares. At its peak, the outburst reached a luminosity of about 3 times 10 to the 49 ergs per second, one of the brightest instantaneous flashes ever recorded.
NASA's Fermi Gamma ray Space Telescope also detected several gamma ray bursts from the same region around the same time. But the early X-ray signal set this event apart. Ordinary gamma ray bursts do not produce a precursor X-ray glow a full day in advance. That mismatch told researchers they were dealing with something fundamentally different.
A black hole of the missing kind
The data point to an intermediate mass black hole, a class of black hole that has long been predicted but rarely observed. These objects are larger than stellar mass black holes but smaller than the supermassive ones that sit at the centers of galaxies. Astronomers have struggled to find clear evidence of their existence.
If the interpretation holds, this would be the first direct observation of an intermediate mass black hole consuming a white dwarf, the dense leftover core of a star like our sun. The white dwarf would have been torn apart by the black hole's gravity before being swallowed. The unusual X ray pattern matches theoretical models of such an event.
The research was coordinated by the Einstein Probe Science Center at the National Astronomical Observatories of the Chinese Academy of Sciences. Scientists from the University of Hong Kong and other institutions in several countries contributed to the analysis. The findings were published as the cover article in the journal Science Bulletin.
Why local astronomers took notice
For the Chinese led team behind the Einstein Probe, this detection validates the mission's design. The telescope was built specifically to catch fast moving X ray transients that other observatories might miss. Its lobster eye optics give it an unusually wide field of view, allowing it to monitor large swaths of the sky continuously.
Astronomers in Hong Kong played a key role in interpreting the observations. The University of Hong Kong physics department is a core member of the Einstein Probe collaboration. For them, the event represents a payoff for years of work on a mission that launched with the explicit goal of finding the unexpected.
A window into an extreme feeding event
If confirmed, the discovery would give astronomers their first clear look at a black hole of intermediate mass in the act of feeding. It would also show that white dwarfs, stars that are usually stable and long lived, can be destroyed in a flash when they wander too close to the wrong kind of black hole. The event opens a new observational window into how black holes grow and how different types of stars meet their end.
