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Dr. Alex Tetarenko, Credit: EAO<\/p><\/div>\n
Published today in the journal Science, the research shows that the system known as Cygnus X-1, contains the most massive stellar-mass black hole ever detected without the use of gravitational waves. \u201cOur new observations have shown us that Cygnus X-1 is further away from Earth than previously thought, which in turn tells us this black hole is much larger than previous estimates, weighing in at more than 20 times the mass of our own Sun\u201d says Dr. Tetarenko.<\/p>\n
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The Cygnus X-1 binary system consists of a stellar-mass black hole that is pulling material off of a \u2018donor star\u2019. \u201cOur new observations have shown us that Cygnus X-1 is further away from Earth than previously thought, which in turn tells us the black hole is much larger than previous estimates, weighing in at more than 20 times the mass of our own Sun.\u201d Artist: Pete Wheeler (COMET) Credit: International Centre for Radio Astronomy Research.<\/p><\/div>\n
Cygnus X-1 is one of the closest black holes to Earth. It was discovered in 1964 when a pair of Geiger counters were carried on board a sub-orbital rocket launched from New Mexico. This object was famously the focus of a scientific wager between physicists Stephen Hawking and Kip Thorne, with Hawking betting in 1974 that it was not a black hole and eventually conceding the bet in 1990.<\/p>\n
In this latest work, astronomers observed a full orbit of the black hole over a six day period using the Very Long Baseline Array \u2014 a continent-sized radio telescope made up of 10 dishes spread across the United States \u2014 together with a clever technique to measure distances in space. \u201cOne of the telescopes in the Very Long Baseline Array is located in Hawai\u02bbi on the slopes of Maunakea, and this antenna plays a critical role in making it possible to do this kind of science\u201d explains Dr. Tetarenko.<\/p>\n
Lead researcher, Professor James-Miller Jones from Curtin University and the International Centre for Radio Astronomy Research (ICRAR) outlines the clever technique used by this team of researchers. \u201cIf we can view the same object from different locations, we can calculate its distance away from us by measuring how far the object appears to move relative to the background. If you hold your finger out in front of your eyes and view it with one eye at a time, you\u2019ll notice your finger appears to jump from one spot to another. It\u2019s exactly the same principle.\u201d<\/p>\n
\u201cThe domino effect of our new observations has led to fascinating new insights about how stars evolve and how black holes form\u201d says co-author Dr. Arash Bahramian, who is also at Curtin University and ICRAR. Tetarenko and Bahramian are longtime colleagues, having both completed their PhDs at the University of Alberta in Canada.<\/p>\n
In fact, this study has sparked two more companion papers. Co-author Professor Ilya Mandel from Monash University and the ARC Centre of Excellence in Gravitational Wave Discovery (OzGrav) further explains the wide reaching implications of this work.<\/p>\n
\u201cCygnus X-1 in particular began life as a star approximately 60 times the mass of the Sun and collapsed tens of thousands of years ago. During their lifetime stars lose mass to their surrounding environment through stellar winds that blow away from their surface. But to make a black hole as heavy as Cygnus X-1, we need to dial down the amount of mass that bright stars lose during their lifetimes\u201d.<\/p>\n
The new measurements of distance and mass also tell us that the black hole in Cygnus X-1 is spinning incredibly quickly (very close to the speed of light), as shown in a second companion paper led by PhD candidate, Xueshan Zhao, at the Chinese Academy of Sciences.<\/p>\n