Chandra images of hot gas in the centers of the nine galaxies evaluated by the researchers (Image: NASA / CXC / Stanford U./S.Allen et al)
Reading aloud Black holes are the most fuel-efficient engines in the universe: they can convert matter into energy with incredibly high efficiency, surpassing nuclear power plants by more than 20 times. This has been proven by an American-British astronomer team using the X-ray telescope Chandra. The photographs of nine supermassive black holes in the centers of so-called elliptical galaxies enabled the scientists for the first time to directly determine the ratio of available matter and expelled energy. Were it a car engine with the same efficiency, he could cover more than 410 million kilometers with a liter of gasoline, reported study director Steve Allen from Stanford University on a teleconference of the US Space Agency Nasa. Unlike previous research, Allen and his colleagues did not limit themselves to a single black hole. Rather, the researchers evaluated the data from nine of these giants, which are 55 to 440 million light-years away from the Milky Way and whose masses are between 200 million and 3 billion solar masses. These very old black holes were actually considered boring by astronomers, as they emit very little radiation in contrast to the more active quasars. But apparently they have been underestimated so far: "When the black holes become calmer, they do not seem to lose their efficiency, but convert matter into a different kind of energy, " said co-author Chris Reynolds of the University of Maryland.

The black holes investigated by the researchers are surrounded by hot gas that moves toward the center of the galaxy due to the enormous gravity. Exactly this matter is the fuel that keeps the machine running, the researchers said. Just outside the so-called event horizon? that is, the area from which neither matter nor radiation can escape the black hole? Namely, the energy of a part of this gas is released and thrown in the form of extremely high-energy particle beams into the universe. "These jets can reach speeds in excess of 95 percent of the speed of light, " Reynolds reported.

The researchers were able to calculate how much energy these jets contain from the traces they leave as they travel through the hot gas surrounding the black hole: they create huge bubbles in the glowing matter that are clearly visible on the Chandra images were. From this value and the total amount of matter in the galaxy centers, astronomers were finally able to determine the energy efficiency of their study objects. The results showed that, through their effective energy production, the black holes regulated, among other things, star formation in their immediate environment, the researchers said. However, a whole series of new questions emerged, which could only be clarified by further investigations.

Steve Allen et al .: Monthly Notices of the Royal Astronomical Society, in Press ddp / science.de? Ilka Lehnen-Beyel advertisement

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