2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Astrophysicists observed the process of destruction of a passing star by a supermassive black hole, which made it possible for the first time to obtain accurate data on the linear velocity of particles on the supposed event horizon of a supermassive black hole. The results of the work are presented in an article published in Science, the authors also made a presentation at the 233rd meeting of the American Astronomical Society in Seattle.
The speed of rotation of particles on the event horizon of a black hole has so far been difficult to measure. Previously, scientists were able to determine the speeds for some black holes in the Milky Way, belonging to the class of black holes of stellar mass (from 5 to 30 solar), by observing regular changes in their X-ray emission. For supermassive black holes, however, observations were limited to a few cycles of changes, which made it impossible to clearly deduce the values of the rotation rate.
In November 2014, using a network of telescopes collectively called ASASSN (All-sky Automated Survey for Supernovae), astronomers noticed a bright flash of light at a distance of about 290 million light-years from Earth. The event was named ASASSN14-li and was classified as the result of tidal destruction of stars (when one object is destroyed by another, much larger, using gravitational action). It happened in the immediate vicinity of the supermassive black hole, the center of the galaxy PGC 043234. Having discovered the outburst, the scientists involved in the study the X-ray-sensitive NASA observatories: Chandra and the Neil Gears Swift telescope, as well as the XMM-Newton telescope - the remnants of the star's material, twisting towards the center of a supermassive black hole, get very hot and produce huge amounts of X-rays. They form an extended accretion disk, which could not be accurately studied before the discovery of ASASSN14-li.
Observation of ASASSN14-li showed amazing stability and periodicity (rotation cycle is just over two minutes). It made it possible for the first time to accurately estimate the linear speed of rotation of particles on the supposed event horizon of a supermassive black hole: having fixed that the diameter of the event horizon is approximately 300 times larger than that of the Earth, astronomers calculated that the speed of rotation is enormous and is about half the speed of light in a vacuum (for comparison, the speed of rotation of the Sun is 150 thousand times less than the speed of light). Moreover, the accuracy of this measurement, according to astronomers, is very high, since the measurements were carried out for 300 thousand rotation cycles.
The absorption of companion stars by black holes has long been studied by astronomers, for example, in 2015, the INTEGRAL gamma observatory recorded a rare event - the absorption of a companion star by a black hole. But this discovery is likely to give a new impetus to the study of tidal destruction and may become the key to measuring the speed of rotation of particles on the event horizon of supermassive black holes from abrupt changes in the brightness of X-rays.