In a groundbreaking discovery, Chinese astronomers have found compelling evidence supporting the existence of intermediate-mass black holes (IMBHs), bridging a critical gap in our understanding of black hole evolution.
The team, led by researchers from the Chinese Academy of Sciences' National Astronomical Observatories (NAOC), identified a runaway star named J0731+3717 ejected from the M15 globular cluster. Traveling at nearly 550 kilometers per second, this star's extreme velocity offers the strongest evidence yet for IMBHs.
IMBHs, with masses between stellar-mass black holes and supermassive black holes, have long been theorized but remain elusive. Their discovery is pivotal for understanding how seed black holes grow into the supermassive giants that reside at the centers of galaxies.
The study utilized data from the European Space Agency's Gaia spacecraft and China's Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), revealing that J0731+3717 shares a nearly identical chemical composition and age with M15. This alignment points to a dramatic event around 20 million years ago, where the star was violently ejected from the cluster.
Previous observations suggested that M15 might harbor an IMBH weighing between 1,700 to 3,200 solar masses. However, distinguishing an IMBH from dense clusters of neutron stars was challenging. The high-speed ejection of J0731+3717, explained by the Hills mechanism, indicates a tight binary star interacting with an IMBH's powerful gravitational forces, effectively confirming the black hole's presence.
\"Such a high-speed ejection requires a tight binary star to pass within one astronomical unit of an IMBH,\" explained Huang Yang, associate professor at NAOC and co-lead author of the study. \"The black hole's tidal forces would rip the binary apart, capturing one star and hurling the other outward.\"
Looking ahead, researchers anticipate that ongoing data collection from Gaia and LAMOST will lead to the discovery of more stars like J0731+3717. These findings will significantly enhance our understanding of IMBHs and their role in the cosmic landscape.
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Chinese scientists find proof of intermediate-mass black holes
cgtn.com
