Scientists discover ‘monster’ black hole in our galaxy
Up until now, the largest mass of a black hole ever recorded was only a mass of 15 to 20 times bigger than the sun
By ILANIT CHERNICKA simulated image of a black hole.(photo credit: Wikimedia Commons)
Scientists have discovered a stellar black hole in our galaxy with a mass 70 times greater than the sun.Sounds like something out of a science fiction film, doesn’t it?Up until now, the largest mass of a black hole ever recorded was only a mass of 15 to 20 times bigger than the sun. But this discovery by a team of international scientists led by the Chinese Academy of Sciences has imploded that discovery.Today, astronomers estimate that there are 100 million black holes in our galaxy known as the Milky Way. The Chinese Academy of Sciences define a black hole as “cosmic bodies formed by the collapse of massive stars and so dense even light can’t escape.”The discovery was published in a recent issue of Nature.For the scientists, this was a colossal surprise. “Black holes of such mass should not even exist in our Galaxy, according to most of the current models of stellar evolution,” explained lead author of the report Prof. Jifeng Liu.According to Liu, who is a professor at the National Astronomical Observatory of China, theorists will now “have to take up the challenge of explaining its formation.”“We thought that very massive stars with the chemical composition typical of our Galaxy must shed most of their gas in powerful stellar winds, as they approach the end of their life,” Liu said in a statement released by the Chinese Academy of Sciences. “Therefore, they should not leave behind such a massive remnant. [It’s] twice as massive as what we thought possible.”The University of Michigan’s Department of Astronomy explained the newly discovered “monster” black hole, as it’s being described, is located 15,000 light years from Earth and has been named LB-1 by the team.University of Michigan Astronomy professor Joel Bregman, one of the authors of the report, explained to The Jerusalem Post that the difference between black holes found in galaxies: there is a “supermassive black hole in the center of most galaxies” and then “there are many stellar mass black holes” throughout our galaxy.“Here we are talking about the latter ones,” he said. “The most massive black hole that had been known in the Milky Way” had a mass 16-times larger than the sun.He added that this new discovery is about four times larger.Bregman said that the gravity wave project, known as LIGO, has “detected the merging of... two black holes in a distant galaxy, about half of the mass of the one found here.“Because this is in the Milky Way, we can really study it, unlike black holes in distant galaxies,” he explained.Asked why this was an important discovery, Bregman said that it’s “because of the challenge in understanding how such a black hole is formed.”“A massive star loses most of its mass through its lifetime, leading to the lower mass black holes that we usually see in the Milky Way,” he continued. “The star that became a black hole either retained a remarkable amount of its original mass or it merged with another star before becoming a black hole.”He highlighted that it took a couple of years to find an interesting candidate to pursue and then to obtain the relevant data.“The lead author, Jifeng Liu, is still obtaining data and will publish a follow-up paper with some important infrared observations,” Bregman added.Michigan’s Astronomy Department also explained that until just a few years ago, black holes of stellar origin could only be discovered when they consumed “gas from a companion star.“This process creates powerful emissions of X-rays, detectable from Earth, which reveal the presence of the collapsed object,” it said. “However, the vast majority of black holes in our galaxy are not engaged in a cosmic banquet right now, and remain in complete darkness.”The scientists said that this is why only about “two dozen Galactic black holes out of 100 million have been well identified and measured.”However, the process to identify and measure new black holes is not simple. Bregman, together with the team of scientists have used a different technique to find new black holes.Using the LAMOST optical telescope, located in north-east China, they looked for stars that orbit around an invisible object, pulled by its gravity.“Only one star in a thousand may be going round a black hole: it is like trying to find a needle in a haystack,” the university explained. “Recent technological developments of telescopes and detectors have finally made this quest possible, more than 200 years after this technique was first proposed by the visionary English scientist John Michell.”Bregman went on to explain that “previously, such black holes were found only when they were eating a companion star, creating tremendously bright signals.“Here, we discover black hole binaries in more ordinary circumstances, by surveying massive stars to see if they are in orbit around a black hole,” he added.For LIGO director Prof. David Reitze of the University of Florida, this discovery “forces us to reexamine our models of how stellar-mass black holes form.“This remarkable result, along with the LIGO-Virgo detections of binary black hole collisions during the past four years, really points towards a renaissance in our understanding of black hole astrophysics,” he concluded in a statement.
