Scientists using NASA’s Chandra X-Ray Observatory have measured winds of 20 million MPH coming from a mysterious cosmic object known as a stellar-mass black hole within our galaxy.
Scientists from the University of Michigan have discovered the fastest winds ever measured from a stellar-mass black hole, a discovery with important implications in understanding the nature of this class of black holes. The winds were measured at 20 million MPH, and are emanating from a disk of gas that surrounds the black hole. The winds are many times faster than anything researchers have measured previously from a stellar-mass object, and equal some of the fastest known winds generated by much larger supermassive black holes, which are millions of times more massive.
The stellar-mass object is known as IGR J17091-3624, or IGR J17091. IGR J17091 is a binary system where a star is orbiting the black hole, and is located in the central part of our Milky Way Galaxy approximately 28,000 light years from Earth.
In a research paper in The Astrophysical Journal Letters, lead author Ashley King of the University of Michigan said that the winds were “…the cosmic equivalent of winds from a category five hurricane,” and that “We weren’t expecting to see such powerful winds from a black hole like this.”
The scientists were surprised that IGR J17091 was able to generate such enormous wind speeds. “It’s a surprise this small black hole is able to muster the wind speeds we typically only see in the giant black holes,” said co-author Jon M. Miller. “…this black hole is performing well above its weight class.” Typically these speeds are seen in black holes many millions or billions the mass of IGR J17091.
Stellar-mass black holes form when massive stars collapse at the end of their life cycles. Their masses generally range anywhere from three to several tens of solar masses, and the process is observed as either a supernova explosion or gamma ray burst. Stellar-mass black holes are one of three classes of black holes, which also include intermediate-mass black holes (found in globular clusters) and supermassive black holes, such as the one that exists at the center of our galaxy. It is believed that our Milky Way Galaxy may contain several of these stellar-mass black holes.
Besides producing incredible 20-million MPH winds, IGR J17091 is also displaying other unusual characteristics. One of the more unusual is that these extreme winds may be expelling more material into space than the black hole is capturing. According to King, “Contrary to the popular perception of black holes pulling in all of the material that gets close, we estimate up to 95% of the material in the disk around IGR J17091 is expelled by the wind.” Astronomers believe that IGR J17091’s gravity is pulling gas away from the star that orbits around it which then forms a gaseous disk around the black hole, driving winds away from the object.
Another unusual aspect of IGR J17091 is that its winds are blowing in various directions (unlike most winds in hurricanes on Earth), and that they differ from a black hole jet where twin outflows emerge in opposite directions from close to the disk.
The National Radio Astronomy Observatory’s Expanded Very Large Array observed that a jet was absent in IGR J17091 at the time when the 20 million MPH winds were measured. The jet was observed, however, at other times, indicating that these extreme winds may repress jets in black holes.
While science is coming to understand better the bigger picture and mechanics of the cosmos, it appears there is still much to learn about the nature and purpose of black holes. As the physicist who coined the term “black hole” stated, “[The black hole] teaches us that space can be crumpled like a piece of paper into an infinitesimal dot, that time can be extinguished like a blown-out flame, and that the laws of physics that we regard as ‘sacred,’ as immutable, are anything but.” – John A. Wheeler
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