Signs of a pair of supermassive black holes found at the center of Mrk 501 — ScienceDaily

An international group of astronomers has detected observational evidence of a system of two supermassive black holes at the center of the galaxy Mrk 501. The researchers suggest that the objects orbit one another with a period of about 121 days and, depending on their actual mass, may merge in roughly 100 years. ScienceDaily reports.

A second jet

The team led by Silke Britzen of the Max Planck Institute for Radio Astronomy in Bonn analyzed multi-frequency radio observations collected over approximately 23 years. In addition to the long-known bright jet—a stream of particles moving at nearly the speed of light—the scientists tracked the motion of a second jet.

The previously known jet is directed toward Earth, making it easier to observe. The new jet has a different direction. Over several weeks of observations, its position changed noticeably: according to the researchers' description, it emerged from behind the larger black hole and moved around it counterclockwise. The authors of the study believe that this behavior may be explained by the orbital motion of a system of two black holes.

More current news is available on the UA.News Telegram channel Telegram.

Possible approach

The estimated distance between the objects is between 250 and 540 times the distance between Earth and the Sun. For black holes with masses ranging from 100 million to one billion solar masses, this is a very tight orbit. In June 2022, astronomers also recorded a ring-shaped radiation structure resembling an Einstein ring. One possible explanation is gravitational lensing of light from the second jet by a black hole located in front of it.

The black holes in Mrk 501 are too close together in the sky for current instruments, including the Event Horizon Telescope, to distinguish them separately. If such a pair really exists at the center of the galaxy, it should generate ultra-low-frequency gravitational waves that could potentially be detected by pulsar timing arrays. This could help track the evolution of the orbit and determine whether the pair is approaching a merger.