A burst of X-rays fired 8 billion years ago may be the first clear evidence that a white dwarf star was torn apart by a celestial body. black hole.
the study, Coordinated by Donyue Li and Wenda Zhang of the Chinese Academy of Sciences; I will explain the event as “unprecedented.” Analysis suggests that this sudden flare, one of the brightest X-ray bursts ever observed, is best explained by tidal disturbances of the white dwarf star by one of the most elusive objects in the universe. intermediate mass black hole.
“Our computational simulations show that the combination of the tidal forces of intermediate-mass black holes and the extreme density of white dwarfs can produce jet energies and evolutionary timescales that are highly consistent with observational data.” Co-lead author and astrophysicist Jinghong Chen said: PhD from the University of Hong Kong.
white dwarf It is the densest known object in the universe, surpassed only by neutron stars. black hole. They form when stars with up to about eight times the mass of the Sun reach the end of their lives and shed their outer layers, leaving behind a compact core. approximately the size of the earth However, it contains up to 1.4 times the mass of the Sun.
White dwarfs are so compact that only black holes within a narrow mass range can visibly tear them apart. tidal disruption phenomenon. Stellar-mass black holes are expected to produce short-lived and low-energy flares, but most black holes supermassive black hole It will swallow the white dwarf whole before it is destroyed.
Intermediate-mass black holes, with masses ranging from a few hundred to tens of thousands of solar masses, sit in a narrow sweet spot. However, no flares were recorded that allowed astronomers to confidently link an encounter between a white dwarf and an intermediate black hole.
That changed because einstein probe recorded a fiery X-ray flare from a distant galaxy in July 2025. The event, named EP250702a, reached a powerful peak before fading away as multiple instruments tracked its evolution. About a day after X-rays were discovered, NASA’s Fermi Gamma-ray Space Telescope recorded a gamma-ray burst.
“This early X-ray signal is very important.” Lee says.. “This shows that this was not a normal gamma-ray burst.”
Over about 20 days, the signal changed rapidly, decreasing by more than 100,000 from its peak brightness and changing from hard to soft X-rays. Moreover, it occurred on the outskirts of the galaxy, a region where older stars are common, rather than younger, more massive stars exploding as supernovae.
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By carefully studying data across the electromagnetic spectrum from EP250702a and comparing it to possible mechanisms, the researchers found that one explanation for what they observed stood out above the others.
“The white dwarf-intermediate-mass black hole model provides the most natural explanation for its rapid evolution and extreme energy output.” says astronomer Lixin Dai. PhD from the University of Hong Kong.
If confirmed, this flare could mark the first clear sighting of a white dwarf being torn apart in this way. Capturing the elusive intermediate-mass black hole In the act.
This research science bulletin.