NASA estimates that there are about tens to billions of black holes in the Milky Way, most of which may exist in isolation. But astronomers using the Hubble Space Telescope recently announced that they had found something unexpected, not one, or two, but a swarm of black holes concentrated in the center of a gigantic cosmic structure almost as old as the universe itself.
Astronomers at the Astrophysical Institute in Paris have detected for the first time a cluster of black holes clustered in the core region of a dense globular cluster called NGC 6397. This globular cluster is a dense collection of ancient stars, and NGC 6397 is just one of more than 150 stars known to exist in the Milky Way. This massive cosmic structure contains about 400,000 stars, most of which are tightly bound together by gravity and clustered in a central position. Located only 7,800 light-years from Earth, it is one of the closest and easiest stars to study.
Astronomers working on NGC 6397 initially thought that lurked in the center of this massive cluster the elusive and long-sought after "intermediate-mass black hole." This type of black hole is thought to be the "missing link" between a known supermassive black hole and a smaller stellar black hole, which sits at the center of most large galaxies, while a smaller stellar black hole is the remnants of collapsing massive stars.
Despite the widespread debate about intermediate-mass black holes, a number of candidate black holes have been identified, and the center of NGC 6397 is considered an ideal target. But when astronomers searched for the elusive object, they were surprised to find that it wasn't one but more than 20 stellar black holes. Because black holes can't be observed directly, astronomers use the Hubble Space Telescope and the Gaia Space Observatory to look inside globular clusters and measure how stars move.
Because the more massive a location is, the faster the star will move around it. After several years of observing the fine motions of closely packed stars, astronomers were able to calculate the mass distribution within the center of the cluster. Contrary to expectations, they did not find a nodous mass distribution that affects surrounding stars, such as a single, isolated, intermediate-mass black hole, but a more random mass distribution. This suggests that stars near the center of NGC 6397 are being affected by the remnants of black holes, including white dwarfs and neutron stars, but mainly multiple stars.
The researchers concluded that the mysterious family, with at least 20 black holes, gradually sank to the center of globular clusters after interacting with neighboring small-mass stars. According to astronomers, the discovery of this family of black holes offers an exciting possibility that dense groups of black holes could one day merge, causing gravitational waves to form ripples in space-time.
Scientists may use the laser interferometer Gravitational Wave Observatory to detect the event, which is better known as LIGO. Like most scientific discoveries, more questions are asked than answers, and while the elusive intermediate-mass black hole has yet to be discovered, a cluster of stellar black holes at the center of a dense globular cluster is the first to be discovered, and I'm sure we'll learn more about this mysterious stellar graveyard as we explore further.
Related knowledge
The Laser Interferometer Gravitational Wave Observatory (LIGO) is a large-scale physical experiment and observatory designed to detect gravitational waves in the universe and develop gravitational wave observations into astronomical tools. (1) The United States built two large observation stations with the aim of detecting gravitational waves by laser measurements. Using mirrors four kilometers apart, these observatories are able to detect changes that are less than one-ten-thousandth the diameter of a proton charge. (2) The original LIGO Observatory was funded by the National Science Foundation (NSF) and designed, built, and operated by the California Institute of Technology and the Massachusetts Institute of Technology. (3) (4) They collected data from 2002 to 2010, but did not detect gravitational waves.
The Advanced LIGO Project to Enhance the Original LIGO Detector began in 2008 and continues and continues to be supported by the National Science Foundation (NSF) in the United States, with important contributions from the UK Council on Science and Technology Facilities, the Max Planck Society in Germany and the Australian Research Council. (5) (6) The modified detector began operation in 2015. In 2016, the LIGO Scientific Cooperation (LSC) and the Virgo Cooperative reported on the detection of gravitational waves, with scientists from several universities and research institutions participating in an international collaboration, participating in the project and the gravitational wave astronomical data analysis scientists organized by the LSC, which included more than 1,000 scientists (7) (8) (9) and 440,000 active scientists Einstein@Home users as of December 2016. （10）
LIGO is the largest and most ambitious project ever funded by the NSF. (11) (12) In 2017, the Nobel Prize in Physics awarded Rainer Weiss, Kip Thorne, and Barry C. Baeish "a decisive contribution to the LIGO probe and gravitational wave observations."
By: Volunteer, Bo Effort