An international team of astronomers managed to identify and measure the mass of the black hole most distant sleeper ever observed, located in the heart of a galaxy called MRG-M0138more than 10,000 million light years from Earth. The discovery, published in the magazine Scienceexceeds the previous distance record for this type of object by 15 times and opens an unprecedented window into the early universe.
The black hole has a mass equivalent to about 6 billion times that of the Sun. It is observed at a time when the universe was only about 3 billion years old, that is, approximately a quarter of its current age. This age makes the object a key piece to understand how black holes formed and grew in the early stages of the cosmos, explained the University College London (UCL) in a statement.
What makes its detection especially difficult is that it is a sleeping black hole: It has no gaseous material falling towards it, so it emits no detectable radiation. Unlike quasars—active black holes that are among the most luminous objects in the universe—their presence can only be inferred indirectly.
To find it, the team turned to a technique known as stellar dynamicswhich consists of tracking the collective movement of the stars orbiting the black hole. The speed of these stars and the differences between those closest to the center and those furthest away allow us to accurately calculate the mass of the invisible object that attracts them.
It is the same method that was used to measure the black hole at the center of the Milky Waybut it has never before been applied to such large cosmological distances. The most distant galaxy studied with this technique so far was only 700 million light years away.
Cosmic lenses and the James Webb telescope
The biggest technical obstacle was that, at such a distance, the movement of the stars is normally impossible to observe. The team solved it through a natural phenomenon called gravitational lens: Another galaxy located between MRG-M0138 and Earth bends the background light with its gravity, acting as a cosmic magnifying glass and magnifying the image of the distant galaxy about 30 times. That allowed the team to reconstruct the internal details of the galaxy at a much higher resolution than would otherwise be possible.
The data came from James Webb Space Telescope from NASA, whose sensitivity was decisive in capturing the signals of stellar movement at that distance. The principal investigator of the study, Dr. Andrew Newman of Carnegie Science in Pasadena, California, explained the scope of the combination of tools.
«By combining JWST data with gravitational lensing, we were able to peer inside the black hole’s sphere of influence, where its gravity increases the stars’ velocities. This is one of the best techniques we have for weighing a black hole, so we were excited to extend it to a much earlier period in cosmic history,» he said.
The senior author of the work, Professor Richard Ellis from the Department of Physics and Astronomy at University College London, highlighted the methodological value of the achievement: «Determining how stars move collectively in the core of this distant galaxy allowed us to measure the mass of its otherwise undetectable supermassive black hole.»
«By demonstrating the feasibility of this technique for galaxies in the early universe, we can now carry out a more complete census of how black holes develop over time and infer their role in the evolution of galaxies,» he said.
The discovery also revealed that the galaxy surrounding the black hole is similarly dormant: it has stopped forming new stars. The researchers estimate that MRG-M0138 It probably once housed a luminous quasar. The hypothesis is that when the black hole formed and grew rapidly, the energy it released expelled or consumed the free gas circulating through the galaxy, the same gas that is essential for the birth of new stars.
This link between black hole activity and the cessation of star formation is one of the mechanisms that astronomers study to understand the coevolution between black holes and galaxies. Nearby galaxies show a close relationship between their total mass and that of their central black hole, but data from earlier periods of the universe are still lacking to fully understand these dynamics.
The team anticipates that new observations from the James Webb and other space telescopes will identify many more dormant black holes in the early universe. That could provide information about how they slow down star formation and also about how these objects can reactivate when large amounts of matter fall back toward them.
