Sagittarius A*, the 4.3-million-solar-mass black hole that resides at the center of the Milky Way Galaxy, is spinning so quickly it is warping the spacetime surrounding it into a shape that can look like a football, according to an analysis of data gathered by NASA’s Chandra X-ray Observatory and NSF’s Karl G. Jansky Very Large Array.
Black holes have two fundamental properties: their mass (how much they weigh) and their spin (how quickly they rotate).
Determining either of these two values tells astrophysicists a great deal about any black hole and how it behaves.
Penn State University’s Dr. Ruth Daly and colleagues applied a new method that uses X-ray and radio data to determine how quickly Sagittarius A* is spinning based on how material is flowing towards and away from the black hole.
They found that Sagittarius A* is spinning with an angular velocity (number of revolutions per second) that is about 60% of the maximum possible value, a limit set by material not being able to travel faster than the speed of light.
In the past, different astronomers made several other estimates of Sagittarius A*’s rotation speed using different techniques, with results ranging from Sagittarius A* not spinning at all to it spinning at almost the maximum rate.
“Our work may help settle the question of how fast our Galaxy’s supermassive black hole is spinning,” Dr. Daly said.
“Our results indicate that Sagittarius A* is spinning very rapidly, which is interesting and has far reaching implications.”
A rotating black hole pulls spacetime and nearby matter around as it spins. Spacetime around the spinning black hole is also squashed down.
Looking down on a black hole from the top, along the barrel of any jet it produces, spacetime is a circular shape.
Looking at the spinning black hole from the side, however, the spacetime is shaped like a football. The faster the spin the flatter the football.
A black hole’s spin can act as an important source of energy….
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