- New research may help answer the question of how quickly. milky waysuper huge Black Hole is turning.
- The black hole, known as Sagittarius A* (Sgr A*), contains about 4 million times the mass of the Sun.
- use NASAThis study by the Chandra X-ray Observatory and the NSF’s Very Large Array found that Sgr A* is rotating at extremely high speeds.
- This high rotation distorts space-time around Sgr A* so that it appears to be in the shape of an American football.
This artist’s illustration depicts the results of a new study of the supermassive black hole at the center of a galaxy called Sagittarius A* (Sgr A* for short). The results showed that Sgr A* is spinning so fast that his three dimensions of space-time, or time and space, are distorted, making it look like a football.
These results were obtained using NASA’s Chandra X-ray Observatory and NSF’s Karl G. Jansky Very Large Array (VLA). The team of researchers applied a new method: x-ray Radio data to determine how fast Sgr A* is spinning based on how matter moves toward or away from the black hole. They found that Sgr A* rotates with an angular velocity of about 60% of the maximum possible value and an angular momentum of about 90% of the maximum possible value.
Black holes have two fundamental properties: mass (weight) and spin (rotational speed). Determining either of these two values can tell scientists a lot about black holes and their behavior. In the past, astronomers have used a variety of techniques to make estimates of Sgr A*’s rotational speed, and the results have ranged from Sgr A* not rotating at all to rotating at near maximum speed. It covers a wide range of things.
New research suggests that Sgr A* is actually spinning so fast that it is crushing spacetime around it. This figure shows a cross-section of Sgr A* and a disk of material swirling around it. The black sphere in the center represents the black hole’s so-called event horizon, the point of no return from which not even light can escape.
As shown in this diagram, when you look at a rotating black hole from the side, the spacetime around it is shaped like a football. The faster the spin, the flatter the football.
The yellow-orange material on either side represents gas swirling around Sgr A*. This material inevitably hurtles towards the black hole, crossing the event horizon as it enters the shape of the football. Therefore, the area inside the football shape but outside the event horizon is depicted as a void. The blue blobs show jets ejecting from the rotating black hole’s poles. Looking down on a black hole, spacetime becomes circular along the barrel of the jet.
The spin of a black hole acts as an important source of energy. A rotating supermassive black hole produces parallel outflows, such as jets, when its spin energy is extracted. This requires there to be at least some matter near the black hole. Because of the limited fuel surrounding Sgr A*, the black hole has been relatively quiet for the last several thousand years, with a relatively weak jet stream. However, this study shows that this can change as the amount of material near Sgr A* increases.
To determine the spin of Sgr A*, the authors used an empirical method called the “outflow method.” In this method, the spin of the black hole and its mass, the properties of matter near the black hole, and the outflow properties. The parallel outflow produces radio waves, and the disk of gas surrounding the black hole is responsible for emitting X-rays. Using this method, the researchers combined data from Chandra and his VLA with independent estimates of the black hole’s mass from other telescopes to constrain the black hole’s rotation.
A paper describing these results led by Ruth Daly (Pennsylvania State University) Royal Astronomical Society Monthly Notices.
Reference: “New black hole spin values for Sagittarius A* obtained using the outflow method” Ruth A Daly, Megan Donahue, Christopher P O’Dea, Biny Sebastian, Daryl Haggard, and Anan Lu, October 2023 21st, Royal Astronomical Society Monthly Notices.
Other authors are Biny Sebastian (University of Manitoba, Canada), Megan Donahue (Michigan State University), Christopher O’Dea (University of Manitoba), Daryl Haggard (McGill University), and Anan Lu (McGill University).
NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center manages scientific operations from Cambridge, Massachusetts and flight operations from Burlington, Massachusetts.