by The IS supermassive black hole in the middle of our The Milky Way Galaxy spinning so fast that it is spinning space-time into an oval shape reminiscent of an American football (or a rugby ball for any non-American readers!. The result comes from a careful study of radio and X-ray observations.
According to Albert Einsteinand general theory of relativity, when a massive object is spinning, it can drag spacetime around with it. It is called “draw frame,” and even our spinning World It is closely observed space-time in its vicinity. However, the effect is much more pronounced for extremely massive objects, namely supermassive black holes that are millions or even billions of times larger. bigger than our sun. And the faster such a massive object spins, the more the space-time expands around it, thus taking on that oval shape.
However, the spin rate of a black hole is 4.1 million solar masses of our galaxy, known as Sagittarius A* or Sgr A* in short, it was hard to pin down. Most estimates varied widely. A group of astronomers, led by Ruth Daly of Penn State University, has now applied a procedure known as the “outflow method” to measure the angular velocity of Sgr A* – that is, how many times it turns six per second.
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The outflow method is quite literally named – it measures how matter is flowing out of a black hole, which may seem counter-intuitive at first as black holes are more famous for their matter pull in However, an outflow from a black hole can enter. form a jet of magnetic colliding matter that emits massive radio waves. Meanwhile, there are hot clusters of plasma (ionized gas) produced in the disk of matter around a black hole, and which can flow there, they are hot enough to radiate in X-rays. These clumps, called plasmoids, form more efficiently when a black hole is spinning rapidly because the resulting frame drag increases the black hole’s magnetic field and tightens it like a belt closer to the edge of the black hole. In turn, this creates intense magnetic conditions conducive to plasmoid formation.
So, going back to archival observations of Sarcel A* made with the Karl G. Jansky Very large array the radio telescopes and NASA Chandra X-ray ObservatoryDaly’s team measured the angular velocity of Sgr A* as 60% of the maximum possible value, which is defined by the speed of light. In other words, Sr A* is spinning very fast, fast enough to compress spacetime into a flattened oval shape.
“Our work may help solve the question of how fast our galaxy’s supermassive black hole is spinning,” Daly said in a. statement. “Our results show that Sr A* is spinning very fast, which is interesting and has far-reaching implications.”
These implications relate to Sr A*’s past and possible future activity. The faster a black hole spins, the more powerful the colliding jets of radiation it emits as particles in the hot disk of matter swirling around the black hole are swept up and scattered outwards. Currently, Sr A* is hardly active, but the fall of an unfortunate gas cloud or star could refuel its jets. Evidence that this happened in the past comes from what is called the Fermi bubbles, which are two humungous structures of gamma-ray emitting material extending above and below the plane of our galaxy, spanning a total of 50,000 light-years and centered on Sgt A*. The Fermi Bubbles are believed to be the remnants of powerful jets that once erupted from the black hole, but such powerful jets could only arise if Sarcel A* is spinning rapidly.
Structures such as the Fermi Bubble are capable of excavating gas from a galaxy, plowing through star-forming material like a snowplow.
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“Jets powered and collided with a galaxy’s spinning central black hole can greatly affect the gas supply for an entire galaxy, affecting how quickly and even if stars can form,” said Megan Donahue of Michigan State University in the same press release. “The Fermi Bubbles seen in X-rays and gamma rays around our Milky Way’s black hole indicate that the black hole was active in the past. An important test of this situation is to measure the spin of our black hole.”
The results were published in the January 2024 issue of the journal Monthly Notices of the Royal Astronomical Society.
