There are four huge 'bubbles' in the hot gas at the center of the galaxy cluster RBS 797, located about 3.9 billion light years from us: discovered thanks to observations from NASA's Chandra orbital telescope, they could have been generated by the action of two supermassive black holes joined in a close orbit.
This is indicated by the study published in The Astrophysical Journal Letters by a research group led by the University of Bologna and the National Institute of Astrophysics (Inaf).
Cavities or bubbles have already been observed in other galaxy clusters and are thought to be generated by eruptions that arise near a supermassive black hole. In fact, in its active phase, the black hole devours the surrounding material and releases a large amount of energy, sometimes in the form of very high-speed jets of matter that create cavities in opposite directions within the intergalactic gas. In the case of RBS 797, however, the observed cavities are four: two pairs perpendicular to each other, one in an east-west direction and one in a north-south direction.
A possible explanation of this phenomenon, never observed before, is the presence inside the cluster of two supermassive black holes which, almost simultaneously, have ejected jets of matter in directions perpendicular to each other.
Some radio observations made by the European VLBI Network (EVN), a consortium formed by the major European radio astronomy institutes, had already identified in the past in the RBS 797 cluster two radio sources separated by about 250 light years.
If both of these sources were supermassive black holes, they would be one of the closest pairs of black holes ever detected.
But there is also another possible explanation for the two pairs of 'bubbles' observed in the RBS 797 cluster: a single supermassive black hole whose jets of matter change direction rather quickly.
