Scientists Finally Propose a Theory about the Formation of Dark Stars

Scientists Finally Propose a Theory about the Formation of Dark Stars

The existence of quantum stars may help explain dark matter which makes up 27% of the universe.

Recently, researchers discovered how quantum stars could form and be hidden throughout the universe. These strange star-like objects may theoretically act like single, giant atoms. Bright, fast bursts of cosmic radio waves that have confounded astronomers and fanned stories of alien civilizations may be attributed to so-called Axion Stars. These theorized stars do not shine and are made of hypothetical particles called Axions, a primary candidate for dark matter.

Axions are neutral, very light (but not massless) particles, that do not interact (or interact very weakly) with conventional matter. An axion resembles a ‘Strange Photon’, a theory which predicts that in the presence of electromagnetic fields an axion, if it exists, could transform into a photon (and vice-versa), making experimental axion detection possible. Different theories predict axions to have a wide range of masses, but overall, they’re expected to be extremely light — perhaps as tiny as 10^31 times lighter than a proton.

If axions exist, they would not interact with one another, unless gravity coaxes them together to form a dense sphere with exotic properties unlike those of any other kind of star. Quantum physics dictates that particles have discrete amounts of energy and all of them exist at particular energy levels. Bosons, a class of particles that includes photons, have multiple particles that can be at the same energy level simultaneously, unlike fermions, which include electrons and protons. In a boson/axion star, every axion would be at the lowest energy level, thus the entire star would have the same quantum behavior, like a single, giant particle.

Objects such as these are also known as a ‘Bose-Einstein Condensate’, a type of matter that physicists create in labs by cooling atoms to near Absolute Zero. It can form super-fluids which flow without friction. Dmitry Levkov, a Physicist at the Institute for Nuclear Research of the Russian Academy of Sciences, explained that some physicists have previously claimed that the gravity between the featherweight axions would be too weak to corral the particles into a star. However, new computer simulations suggest that axion stars could in fact readily form depending on the mass of the axion.

For a relatively heavy axion, dubbed a QCD axion, it might take 1 billion years to form an axion star. This makes it a favorite candidate for dark matter with some physicists as it could solve a mystery related to the strong force, which holds atomic nuclei together. Levkov described that for an extremely light axion — about 100 quadrillion times lighter than the QCD axion and dubbed “fuzzy dark matter” — it could take just 10 million years to build an axion star. Bhupal Dev, a Physicist at Washington University in St. Louis who wasn’t involved in the research, showed his excitement about the latest simulations by saying,

“It’s really interesting that just gravity can help you form Bose-Einstein condensates if given enough time — and that time is less than the age of the universe.”

Previously, simulations used to start with smaller chunks of axion Bose-Einstein Condensates, which then attracted one another via gravity to form axion stars. But in the new simulations, the researchers started with nothing but a gas of axions, and they found that a star formed all on its own. Over time, such a star could continue to accumulate axions and grow. Sebastian Baum, a Physicist at Stockholm University in Sweden who wasn’t a part of the study, expressed his views about the latest work in an interview and said,

“It’s nice work. It’s an important stepping stone in understanding the story of such objects and, in general, axion dark matter. If much of the dark matter is contained in these stars, then axions could be rarer elsewhere — and thus harder to find on Earth using detectors like the Axion Dark Matter Experiment at the University of Washington in Seattle.”

Detectable signals could be produced by axion stars themselves as axions can decay into photons, and a series of particle reactions from an axion star could produce detectable radiation. If an axion star slammed into a neutron star, the collision could generate powerful blasts of radio-frequency radiation and potentially explain the mysterious fast-radio bursts that have perplexed astronomers. Over the last decade, dozens of powerful cosmic radio signals of unknown origin have been detected by astronomers, prompting a plethora of explanations, including alien civilizations as a cause.

Computer Scientist by qualification who loves to read, write, eat, and travel

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