Now scientists proved for the first time that the NGC 6240 galaxy have three supermassive black holes in its core. show the black holes close to each other in the core of the galaxy and merging of giant galaxies at the same time.
The study points to simultaneous merging processes during the formation of the largest galaxies in the universe.
Massive Galaxies like the Milky Way typically consist of hundreds of billions of stars and host a black hole with a mass of several million up to several 100 million solar masses at their centres.
The galaxy known as NGC 6240 is known as an irregular galaxy due to its particular shape. Until now, astronomers have assumed that it was formed by the collision of two smaller galaxies and therefore contains two black holes in its core.
These galactic ancestors moved towards each other at velocities of several 100 km/s and are still in the process of merging.
The galaxy system which is around 300 million light years away from us close by cosmic standards has been studied in detail at all wavelengths, and has so far been regarded as a prototype for the interaction of galaxies.
Each of the three heavyweights has a mass of more than 90 million Suns. They are located in a region of space less than 3000 light-years across, i.e. in less than one hundredth of the total size of the galaxy.
The discovery of this triple system is of fundamental importance for understanding the evolution of galaxies over time.
Until now it has not been possible to explain how the largest and most massive galaxies, which we know from our cosmic environment in the present time, were formed just by normal galaxy interaction and merging processes over the course of the previous 14 billion years approximately, ie the age of our universe.
For the unique high-precision observations of the galaxy NGC 6240 using the 8 metre VLT, a telescope operated by the European Southern Observatory in Chile, the 3D MUSE spectrograph was used in spatial high-resolution mode together with four artificially generated laser stars and an adaptive optics system.
The scientists assume that the observed, imminent merging of the supermassive black holes in a few million years will also generate very strong gravitational waves.
In the foreseeable future, signals of similar objects can be measured with the planned satellite based gravitational wave detector LISA and further merging systems can be discovered.