Recent research reveals how galaxies manage to avoid premature death thanks to a system that resembles human organs – the heart and lungs. This mechanism allows galaxies to regulate their own growth, preventing uncontrolled expansion.

Without this process, the universe would age much faster, and today we would witness massive "zombie" galaxies filled with dead and dying stars.

The study, published in the Monthly Notices of the Royal Astronomical Society, investigates why galaxies are not as large as astronomers expected. It seems that something is preventing their potential growth by limiting the amount of gas they absorb to form stars.

Astrophysicists from the University of Kent believe they have discovered the secret. They propose that galaxies control their growth through "breathing." They compared the supermassive black hole at the center of a galaxy to its heart, while bipolar supersonic jets of gas and radiation are depicted as airways feeding the lungs.

Pulsing from the black hole can cause oscillations in the jets, similar to how the diaphragm in the human body moves the lungs. This pulsing transmits energy into the surrounding space, similar to exhaling warm air, which slows down the growth of the galaxy.

Doctoral student Carl Richards developed this theory using new simulations that explore the role of supersonic jets in inhibiting galaxy growth. His simulations allow the black hole to pulse and the jets to be under high pressure, similar to hypertension in the human body.

Richards explained that the jets act like bellows, spreading sound waves through the galaxy. This phenomenon is reminiscent of sound and shock waves generated by opening a champagne bottle, screeching car brakes, or rocket exhausts.

Researchers found that these sound waves help maintain the galaxy's environment, as shown by computer simulations. Pulsing from the black hole caused changes in the shape of the jets, spreading sound waves that suppressed the growth of the galaxy.

Two simulations depict the spread of pressure waves through the extra-galactic medium. Variations in pressure are shown using a temperature color scale, where lighter shades indicate higher pressure. The jets enter from the left and quickly lose pressure as they penetrate the surrounding space.

Sound waves in the Perseus cluster are believed to be the results of cavities created by jets from the supermassive black hole at the center of the galaxy. These waves maintain the surrounding galaxy environment, although the mechanism for their generation has been unknown until now.

Conventional cosmological simulations cannot explain the flow of gas in galaxies, which represents a major mystery of the universe. Researchers believe that a highly active black hole provides the resistance needed to maintain the galaxy.

Professor Michael Smith
emphasized that regulating the pulsing rate of the black hole and the quality of the jets is crucial for maintaining the galaxy. Breathing too fast or too slow will not provide the necessary shakes to sustain the galaxy and supply the black hole with fuel.

The conclusion of the research is that the lifespan of a galaxy can be extended thanks to "the heart and lungs." The supermassive black hole at the center of the galaxy helps inhibit growth by limiting the amount of gas that collapses into stars from an early stage.

Without this mechanism, galaxies would have already consumed their fuel and extinguished, becoming "red and dead" or "zombie" galaxies.

Source: The Royal Astronomical Society