NTHU Uncovers Rare Star-Eating Black Hole, Highlighted by NASA
HSINCHU, Taiwan, Oct. 07, 2025 – An international research team, led by Professor Albert Kong at National Tsing Hua University (NTHU) in Taiwan’s Institute of Astronomy, has identified NGC 6099 HLX-1 as a compelling candidate for an intermediate-mass black hole. This discovery represents a significant step towards understanding an important missing link in the black hole family.
The team initially observed the object following a sudden flare-up, a rare occurrence indicative of a tidal disruption event.
Rare Intermediate-Mass Black Holes
Intermediate-mass black holes (IMBHs) are uncommon cosmic entities, possessing masses hundreds to tens of thousands of times greater than our Sun.
In contrast to supermassive black holes, which become luminous as they consume gas and stars, these more elusive black holes generally remain undetectable, only manifesting during tidal disruption events.
Key Evidence Supporting the Study
NGC 6099 HLX-1, a strong candidate for an intermediate-mass black hole, exhibited a flare in 2012, emitting X-rays heated to approximately 3 million degrees Celsius, consistent with a tidal disruption event.
High-resolution images from the Hubble Space Telescope subsequently unveiled a compact star cluster surrounding the black hole, suggesting a potential fuel source. HLX-1 was initially detected through X-ray observations, accompanied by a distinct point-like optical counterpart.
Both simulations and observations suggest that the relatively blue emission originated from X-ray reprocessing within the accretion material, while the red emission likely stemmed from the surrounding stellar population.
Leveraging multi-wavelength observations, the team performed a comprehensive survey to characterize the black hole’s environment, ultimately identifying NGC 6099 HLX-1 as a candidate for an intermediate-mass black hole.
An Unexpected Discovery
“The finding was truly unexpected,” stated Professor Kong. “This X-ray source had been known for years, yet its unique characteristics were overlooked.”
HLX-1 was initially detected in 2009 by the Chandra X-ray Observatory within the halo of the elliptical galaxy NGC 6099, approximately 450 million light-years distant. A dramatic hundredfold increase in its brightness in 2012 captured the team’s attention, leading to subsequent observations that solidified its candidacy as an intermediate-mass black hole.
First author Yi-Chi Chang further explained, “Supermassive black holes are often observed as bright galactic centers when they feed on surrounding gas and matter, whereas intermediate-mass black holes typically lack sufficient material to generate powerful radiation.”
She highlighted that extremely bright X-ray sources are uncommon but pivotal in identifying these elusive black holes, proving crucial for uncovering the missing link between stellar-mass and supermassive black holes.
Looking Ahead
These discoveries represent a significant milestone in black hole research. The team plans to continue monitoring HLX-1 using X-ray and optical/UV telescopes, while also actively searching for new candidates to expand the elusive family of intermediate-mass black holes.
The forthcoming Vera C. Rubin Observatory in Chile, with its extensive all-sky survey capabilities, is expected to facilitate the detection of optical light transients, including tidal disruption events, by tracking variations in their brightness.
Upcoming X-ray observations will provide insights into HLX-1’s gas consumption, complementing optical and UV observations designed to map its surrounding stars and environment.
International Collaboration
The research, led by Professor Albert Kong of NTHU, involved an international collaboration with teams from the Italian National Institute for Astrophysics (Italy), Swinburne University of Technology (Australia), Université Paris Cité (France), and the Center for Astrophysics—Harvard-Smithsonian (USA). Their findings were published in The Astrophysical Journal and subsequently featured on NASA’s official website.
For video resources from NASA related to this discovery, visit
Contact:
Yi-Yeh Chen
NTHU
(886)3-5162006
yiyeh@mx.nthu.edu.tw
Professor Albert Kong and PhD student Yi-Chi Chang of the National Tsing Hua University (NTHU) Institute of Astronomy presented evidence concerning an intermediate-mass black hole candidate. Their research was published in *The Astrophysical Journal* and highlighted on NASA’s official website.
(Photo: National Tsing Hua University)
