Researchers have identified a newly found intermediate mass black hole designated NGC 6099 HLX-1, situated in a dense star cluster at the edge of the elliptical galaxy NGC 6099, nearly 40,000 light-years from the galaxy’s core.
X-ray and infrared imagery of NGC 6099 HLX-1. Image credits: NASA/CXC/Inst. Astronomy, Taiwan / YC Chang / ESA / STSCI / HST / J. Depasquale.
NGC 6099 is roughly 450 million light-years distant from the constellation Hercules.
Astronomers first detected an unusual X-ray source in a photo of the galaxy captured by NASA’s Chandra X-Ray Observatory in 2009.
This source has since been studied further with ESA’s XMM-Newton Space Observatory.
“X-ray sources exhibiting such high luminosity are uncommon outside a galaxy’s nucleus and can be significant indicators for locating elusive central black holes,” states Dr. Yi-chi Chang, an astronomer at the National Tsing Hua University.
“These objects bridge a critical gap in the understanding of black holes, linking stellar mass black holes and supermassive black holes.”
The X-ray emissions from NGC 6099 HLX-1 reach a temperature of 3 million degrees, which aligns with events of tidal disruption.
Utilizing the NASA/ESA Hubble Space Telescope, astronomers discovered signs of a small cluster of stars encircling the black hole.
This cluster feasts on matter as the stars are densely grouped, just a few months away (approximately 500 billion miles).
The intriguing intermediate mass black hole peaked in brightness in 2012, after which its luminosity steadily decreased until 2023.
However, the optical and X-ray observations across this timeframe do not align, complicating interpretation.
The black hole may have disrupted captured stars, creating a plasma disk that exhibits variability, or it might have birthed a disk that flickers as gas spirals inward.
“If an intermediate mass black hole is consuming a star, how long does it take to digest the gas?” questions Dr. Roberto Soria, an astronomer from the National Institute of Astrophysics in Italy.
“In 2009, HLX-1 was relatively bright. By 2012, it was approximately 100 times brighter, but then its brightness declined again.”
. “Now, we need to observe and see if it enters multiple cycles and identify any peaks in activity.
The researchers stress the importance of examining central mass black holes to reveal the origins of larger supermassive black holes.
Two alternative theories are suggested. One posits that large galaxies grow by merging with other substantial galaxies, positioning intermediate mass black holes as components that help formulate even larger black holes. Intermediate mass black holes in galactic centers also expand during these collisions.
Hubble’s observations indicated a correlation: the larger the galaxy, the larger the black holes residing within. One fresh insight from this discovery suggests that galaxies may host intermediate mass black holes, existing within the halos of galaxies without necessarily spiraling toward the center.
Another theory suggests that gas clouds in primordial dark matter halos might collapse directly into supermassive black holes without first forming stars.
Observations indicating Webb’s distant black holes often appear disproportionately large compared to their host galaxies lend support to this hypothesis.
However, since smaller sizes are elusive, there may exist an observational bias toward detecting very large black holes in the early universe.
In truth, there’s considerable diversity in the methods by which black holes are generated in our dynamic universe.
Ultra-massive black holes collapsing within dark matter may evolve distinctly from those within dwarf galaxies, where accretion could be the primary growth mechanism.
“If fortune favors you, you might spot a wandering black hole suddenly brightening in X-rays due to a tidal disruption event,” Dr. Soria remarked.
“Conducting statistical studies will elucidate the frequency of these intermediate mass black holes, how often they consume stars, and the mechanisms by which galaxies have expanded through the amalgamation of smaller galaxies.”
Survey findings were published in the Astrophysical Journal.
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Yi-chi Chang et al. 2025. Multi-wavelength studies of high-light X-ray sources near NGC6099: A powerful IMBH candidate. APJ 983, 109; doi:10.3847/1538-4357/adbbee
Source: www.sci.news
