We know that there are batteries in space but have you ever heard of “black hole” batteries? This term actually refers to the phenomenon that active galaxies or to be more specific, blazars, are extracting energy from black holes. In the past, scientists have always thought that the extraction of energy only happen one way. But at the same time, they also noticed that there seems to be two different models of blazars.
One blazar is the flat-spectrum radio quasar or FSRQ that is characterized by a strong emission from a very active accretion disk (a variety of materials that orbit a larger body in tandem), higher luminosities, lower particle acceleration in jet blasts and small mass black holes. The other is a BL Lac, that are dominated by jet emissions that reach a higher energy and leave the accretion disk emission weak or totally absent.
An article from NASA announced that recently, the Fermi Gamma-ray Space Telescope found evidence that these two blazar models may be powered differently by their black holes. In the past, it was difficult to know for sure because the distance of BL Lacs is difficult to measure so they do not have the complete set of data needed for both models.
Recent developments, following years of observation in observatories all over the world and massive effort from different groups of scientists have finally solved this problem. They now have the specific distances of 200 BL Lacs that will help them make comparisons with the FSRQs.
The scientists observed that FSRQs decline over time only to have BL Lacs increase. What they believe happened is that galaxies start out as FSRQs and store energy in the increasing mass and faster spinning black holes. When large galaxies collide or merge with small galaxies, it produces gas. This is the gas that is sucked into the black hole and the quantity of gas allowed the black hole to have an active accretion disk that is the model of an FSRQ.
Soon, these galaxy collisions and mergers lessened and this initiated the change in the energy extraction in blazars – thus turning them into BL Lacs. The accretion disk is lessened and the blazar now taps into the stored energy in the black hole – much like an battery powered electric car. Since the stored energy is there, the only thing that can be observed are the jet blasts – which is a characteristic of BL Lacs. Soon, the luminosity of BL Lacs also decreases over time as the black hole finally loses energy and the spinning stops.
The new observation led scientists to believe that the black hole batteries may be powering one blazar like a fuel powered car (FSRQ) and the other blazar is powered like an electric car (BL Lac). This discovery reveals that black hole batteries are in fact, hybrid in nature.
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