Persistent hiccups in a far-off galaxy draw astronomers to new black hole behavior

2 Apr 2024 Jennifer Chu Michal Zajaček Leoš Verner

Astronomers have found that a previously quiescent black hole, which sits at the center of a galaxy about 800 million light years away, has suddenly erupted, giving off plumes of gas every 8.5 days before settling back to its normal, quiet state. The periodic hiccups are a new behaviour that has not been observed in black holes until now.

The scientists from MIT, Italy, the Czech Republic, and elsewhere believe that the most likely explanation for the outbursts stems from a second, smaller black hole of intermediate mass that is orbiting around the central, supermassive black hole and pushing material out from the larger black hole’s disk of gas every 8.5 days. The existence of still unexplored intermediate-mass black holes in the Universe thus gains further support.

The findings of the international team, including the scientists form the Czech Republic Petra Suková a Vladimír Karas from the Astronomical Institute of the Academy of Sciences, Michal Zajaček from Masaryk University, Faculty of Science and Vojtěch Witzany from Charles University, were triggered by an automated detection of an optical flare by ASAS-SN (the All Sky Automated Survey for SuperNovae), a network of 20 robotic telescopes situated in various locations across the northern and southern hemispheres. The telescopes automatically survey the entire sky once a day for signs of supernovae and other transient phenomena. After the optical flash was detected, the galaxy was then intensively monitored by the X-ray telescope NICER (Neutron star Interior Composition Explorer), which is located on the International Space Station.

Animation of tiny black hole repeatedly punching through a larger black hole’s disk of gas new. Credit: Petra Suková, Astronomical Institute of the Czech Academy of Sciences.

The Czech team worked intensively with Dheeraj Pasham from MIT to compare the results of numerical simulations with observed data. What they found supports the theory: the observed dips in X-ray intensity were probably the footprint of a second, smaller black hole that orbits the central supermassive black hole and regularly pierces its disk. "The passage of the smaller black hole through the accretion disk well describes the observed periodic drops in X-ray intensity. Based on more detailed calculations, we found that for the ejected gas clumps to be large enough to cause the observed absorption, the smaller black hole must have a mass of at least 100 solar masses," says co-author Michal Zajaček from Masaryk University.

The results of the collaboration enrich the traditional idea of accretion disks of black holes, which until now have been assumed by scientists to be relatively smooth gaseous formations that rotate around a central supermassive black hole. The new results suggest that accretion disks may have a much more diverse structure and may interact with stars and even other black holes that collide with the accretion disk.

Video with a description of the mentioned phenomenon. Credit: AsU AV

The planned first Czech space telescope QUVIK, which is being developed by the Czech Aerospace Research Centre (VZLÚ) in cooperation with Masaryk University and other institutions, should contribute to the search for similar systems, in which a smaller black hole interacts with an accretion disk rotating around a central supermassive black hole.

This research was supported by the Grant Agency of the Czech Republic, the Academy of Sciences of the Czech Republic, Charles University and the American NASA.

Link to the original English version of the press release issued by MIT.