The supermassive black hole at the centre of our galaxy looks like an American football, according to a new study.
Black hole Sagittarius A* (Sgr A*) is reported as spinning so quickly that it is warping spacetime – that is, time and the three dimensions of space – so that it can look more like a prolate spheroid shape.
The results, described in the Monthly Notices of the Royal Astronomical Society, were made with NASA’s Chandra X-ray Observatory and the National Science Foundation’s Karl G. Jansky Very Large Array (VLA).
A team of researchers applied a new method that uses X-ray and radio data to determine how quickly Sgr A* is spinning based on how material is flowing towards and away from the black hole.
A NASA statement explains: “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 scientists a great deal about any black hole and how it behaves.”
The researchers found Sgr A* is spinning with an angular velocity that is about 60% of the maximum possible value, and with an angular momentum of about 90% of the maximum possible value.
In the past, astronomers made several other estimates of Sgr A*’s rotation speed using different techniques, with results ranging from Sgr A* not spinning at all to it spinning at almost the maximum rate.
The new study suggests that Sgr A* is, in fact, spinning very rapidly, which causes the spacetime around it to be squashed down.
An illustration shows a cross-section of Sgr A* and material swirling around it in a disk. The black sphere in the centre represents the so-called event horizon of the black hole, the point of no return from which nothing, not even light, can escape.
NASA say: “Looking at the spinning black hole from the side, as depicted in this illustration, the surrounding spacetime is shaped like a football. The faster the spin the flatter the football.”
