A new study may shed light on just how fast the Milky Way’s supermassive black hole spins.
This illustration shows the results of a recent study of the supermassive black hole Sagittarius, located at the center of our galaxy. The researchers used data from NASA’s Chandra X-ray Observatory and NSF’s Carl G. Jansky Very Large Array (VLA) to determine what is spinning so fast that it warps space-time, causing it to resemble the flattened shape of a football.

The researchers used data from NASA’s Chandra X-ray Observatory and NSF’s Carl G. Jansky Very Large Array (VLA) to determine what is spinning so fast that it warps space-time, causing it to resemble the flattened shape of a football.

Using a new approach combining X-ray and radio data, scientists were able to determine the rotation rate based on the flow of matter to and from the black hole. Analysis showed that it rotates at approximately 60% of the maximum possible angular velocity, while the angular momentum is about 90% of the maximum value.

Black holes are characterized by two fundamental properties: mass and spin, which provide valuable information about their behavior. Previous estimates of the rotation have varied widely, but this study shows that it is indeed spinning very quickly, causing space-time to compress around it.

The accompanying illustration shows a cross section surrounded by swirled material forming a disk. The central black sphere represents the event horizon, beyond which nothing, including light, can escape. When viewed from the side, the distortion of space-time around a spinning black hole resembles the flattened shape of a football, with the degree of flattening corresponding to the speed of rotation.

The yellow-orange material surrounding the black hole depicts gas swirling around the black hole, eventually falling into the event horizon due to gravitational forces. The blue blobs illustrate the jets emanating from the poles of the black hole. When viewed from above, along the axis of the jet, space-time appears round.

Black hole rotation is a crucial factor in energy production, as rapidly spinning black holes create focused jet-like flows. The relatively weak activity in recent millennia is due to the limited availability of nearby material. However, if the surrounding material increases, it may result in increased reactivity.

The study used the “outflow method”, which establishes a correlation between the black hole’s rotation, mass, properties of surrounding matter and outflow characteristics. By combining data from Chandra and VLA with independent mass estimates from other telescopes, the researchers were able to determine the rotation.