A group of scientists led by astronomer Ruth Agnes Daly, from the University of Pennsylvania, in the United States, has recently published a new study on ArXiv in which they have managed to estimate the Sagittarius spin speed A*, the supermassive black hole of the Milky Way. The results show that the gigantic black hole is rotating at its maximum speed, even exceeding the values ​​of other similar structures in the cosmos.

Everything revolves in the cosmos

Virtually all objects in the Universe develop some type of spin or rotation. Asteroids do it, planets and moons rotate on their axes and even black holes have a form of rotation. This spin has a maximum speed, a limit point at which the object can rotate: scientists are demonstrating that Sagittarius A*, the black hole in our galaxy, rotates at almost that maximum rotation speed.

It is worth remembering that on May 12, 2022, the Event Horizon Telescope Collaboration project published the first image of Sagittarius A*based on radio interferometer data: this record finally confirmed the presence of a supermassive black hole at the heart of the Milky Way, something astronomers had suggested for decades. It is located approximately 26,000 light years from Earth.

The supermassive black holes They are characterized by having a mass on the order of millions or tens of billions of solar masses: however, they can also rotate. According to a article published in Universe Today, the rotation of black holes is very different from that seen in planets and other bodies. Black holes are not objects with a physical surface, nor are they made of a material that can fly into pieces if the maximum rotation speed is exceeded.

At maximum rotation speed

Despite all this, they still have a maximum rotation speed. Black holes are defined by their tremendous gravity, which distorts the space and time around them. He event horizon The black hole marks the point of no return for nearby objects, that is, the limit beyond which they will be absorbed by the black hole and will not be able to leave, but said horizon does not constitute a physical surface.

Albert Einstein determined that there is an upper limit to this spin, due to the inherent properties of space and time. In his equations of general relativity, he estimated that the spin of a black hole is measured by a quantity known as a, where a has to be between 0 and 1. If a black hole has no spin, then a = 0, and if it is at its maximum rotation, then a = 1.

The results of the new research, obtained based on the observation of the intensity of light at various wavelengths, indicate that Sagittarius A* It is spinning at a value between 0.84 and 0.96, which means it is spinning incredibly fast, almost at the limit of his speed. As a point of comparison, the researchers indicated that the spin parameter of the black hole in the M87 galaxy is estimated between 0.89 and 0.91, being below the values ​​of Sagittarius A*.

This result will allow us to advance in the understanding of the characteristics of Sagittarius A*, something crucial considering that the central supermassive black holes They would be directly related to the dynamics inherent to galaxies and their development over time.

Reference

New Black Hole Spin Values ​​for Sagittarius A* Obtained with the Outflow Method. Ruth A. Daly et al. ArXiv (2023). DOI:https://doi.org/10.48550/arXiv.2310.12108