Artist’s impression showing the bipolar jets of gas emanating from the supermassive black hole at the center of our galaxy. Credit: ESA/Hubble, L. Calçada (ESO)
The study revealed that galaxies have a regulatory mechanism similar to that of hearts and lungs that controls their growth by limiting the amount of gas they absorb.
This mechanism is a supermassive Black Hole and its jet emission keeps the galaxy from expanding too quickly, extending its lifespan and preventing it from prematurely aging into a “zombie” galaxy.
Galaxies avoid premature death because they have “hearts and lungs” that effectively regulate their “breathing” and prevent them from growing out of control, a new study suggests.
If they hadn’t done so, the universe would have aged much faster than it does now, and all we see today would be giant “zombie” galaxies full of dead and dying stars.
this is, Monthly Notices of the Royal Astronomical Society, One of the great mysteries of the universe is “why Galaxy It’s not as big as astronomers would expect.
Something appears to be holding back its enormous potential by limiting the amount of gas it can absorb to turn into a star. That is, instead of growing endlessly, something inside it is resisting the pull of gravity that was thought to be inevitable.
The video shows a supersonic jet receiving pulses from the “heart” of the black hole, “acting like a bellows”, expanding and contracting “like lungs filled with air”, “exhaling warm air” (pressure ripples). The axis of the graph is a dimensionless scale for distance. Credit: C Richards/MD Smith/University of Kent
Galactic heart and lung analogy
the current, University of Kent Now, they think they may have unlocked the secret: they suggest that galaxies can actually control their growth rate by the way they “breathe.”
The researchers used this analogy to describe supermassive Black Hole Its heart is located at the center of the galaxy, and it emits bihypersonic jets of gas and radiation that flow into airways that feed a pair of lungs.
Pulsations from the black hole, or “heart,” can cause the jet shock wave front to oscillate back and forth along both jet axes, much like the human thoracic diaphragm moves up and down within the chest cavity, inflating and deflating the lungs.
As a result, the jet energy could be widely transferred to the surrounding medium, slowing the accumulation and growth of gas in the galaxy, just as we expel warm air.
Two different simulations of one side of a symmetric bipolar jet, with pressure ripples spreading across the extragalactic medium. Here the pressure variations are shown using a red-temperature colour scale (dark = low pressure, light = high pressure). Each jet enters from the left and experiences a rapid drop in pressure as it is forced into the surrounding medium. The axis is a dimensionless distance scale. Credit: C Richards/MD Smith/University of Kent
Simulation insights into galactic dynamics
PhD student Carl Richards came up with the theory after creating new, never-before-tested simulations to explore the role that supersonic jets play in inhibiting galaxy growth.
These include making the black hole’s “heart” pulsate and putting the jet under high pressure — akin to a kind of high blood pressure in the human body.
This causes the jet to “act like a bellows, sending out sound waves like ripples on the surface of the pond,” he said.
This phenomenon is similar to the Earthly equivalent of the sound waves and shock waves produced when a bottle of champagne is opened, a car screeches, a rocket exhaust, or a pressurized vessel is punctured.
This artist’s rendering shows the sound waves (ripples) of hot gas that fill the Perseus cluster of galaxies. The ripples are thought to be generated by cavities blown out by jets from the supermassive black hole (a bright white dot) at the galaxy’s center. Credit: NASA/NASA/CXC/M.Weiss
“We realised there had to be some way for the jets to support the gas around the object, the galaxy, and that’s what we found in the computer simulations,” Richards said.
“When we analysed computer simulations of high pressure and pulsating hearts, unexpected behaviour was revealed.
“This sent a pulsating flow into the high-pressure jet, causing the front of the jet shock wave to vibrate like a bellows, changing the shape of the jet.”
The researchers said these high-pressure jets effectively expanded “like lungs filled with air.”
In doing so, they show that sound waves travel to the surrounding galaxy in the form of a series of pressure ripples, which inhibit the galaxy’s growth.
Conclusion and future prospects
There is some evidence of ripples in extragalactic material, such as those observed in the nearby Perseus cluster of galaxies, which are associated with giant bubbles of hot gas that are thought to be examples of sound waves.
These ripples were already thought to play a role in maintaining the environment around galaxies, but the mechanisms that generate them remained unknown.
So traditional cosmological simulations are unable to explain the flow of gas into galaxies – leading to one of the great mysteries of the universe – and so they rely on highly active black holes at the centres of galaxies to provide some resistance.
“But this is not easy to do and there are constraints regarding the type of pulsation, the size of the black hole and the quality of the lungs,” said co-author Professor Michael Smith.
“If we breathe too fast or too slow, we won’t produce the life-giving vibrations necessary to sustain the galactic medium while at the same time keeping the heart fueled.”
The researchers concluded that the lifespan of a galaxy can be extended with the help of its “heart and lungs”. The supermassive black hole engine at the center of the galaxy helps to restrain its growth by limiting the amount of gas that can collapse into stars from the early stages.
This, they say, helped form the galaxy we see today.
Without such a mechanism, galaxies would run out of fuel and disappear, some as “red dead” or “zombie” galaxies.
Reference: “Simulations of Pulsed Overpressure Jets: Bellows and Ripple Formation in Galactic Environments” by Carl Richards and Michael D. Smith, July 12, 2024, Monthly Bulletin of the Royal Astronomical Society.
DOI: 10.1093/mnras/stae1498
