The discovery of highly unstable and explosive “axion stars” could help scientists finally shed light on the universe’s most mysterious substance: dark matter.
Although it makes up an estimated 85% of the mass of the universe, dark matter remains virtually invisible because it does not interact with light. This also means that it cannot be composed of particles like electrons and protons that make up the atoms that come together to form stars, planets, moons, and our bodies.
This has spurred scientists to look for elusive particles that might indeed explain dark matter. One of the leading suspects of dark matter are so-called “axions,” which are particles of light mass that were first theorized in 1977. New research suggests that axions can be found if scientists look for regions where particles may be clustered. Potentially, such clusters could have created pivot stars with explosive consequences.
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“Axions are one of the prime candidates for dark matter. We discovered that once assembled into dense clusters, they have the capacity to heat the universe, just like supernovae and ordinary stars,” said team member Malcolm Fairbairn, a professor at King’s College London. In a statement. “Armed with this information, we know with much more precision where to point our instruments in the field to find them.”
The mystery of dark matter could be revealed in a big explosion
Dark matter may not interact with photons of light, which are particles associated with the electromagnetic force, but it does interact with one of the four other fundamental forces of the universe: gravity.
In fact, dark matter was initially discovered when scientists realized that some galaxies were spinning so fast that the gravity associated with all the visible mass inside them was not enough to hold them together. It had to be something else. Additionally, in addition to discovering that dark matter prevents galaxies from falling apart, scientists now believe that most, if not all, large galaxies are surrounded by halos of dark matter that extend far beyond their visible disks and halos of stars, gas, and dust. .
This means that if dark matter consists of axions, these low-mass particles must be present in numbers large enough to account for the observed gravitational effects. This also means that there are areas where the axes are densely packed. In these regions, it is likely that the axes will begin to move in unison as a result of the laws of quantum physics. This can cause large groups of axons at the centers of galaxies to form axial stars.
However, the team says that these axis stars will not be as long-lived as the dark matter halos that surround galaxies.
Axion stars, if they existed, would become unstable once they reached a certain mass. This will cause stars to explode and release bursts of radiation.
The team thinks this radiation may have heated gas that once existed between galaxies, between the creation of the first atoms in the universe and the formation of the first stars, about 50 million to 500 million years after the Big Bang.
The binding of electrons to protons to form the first atoms during a period of the universe called the epoch of recombination also meant that free electrons were no longer endlessly scattering photons. So the universe suddenly became transparent to light, and this “first light” can now be seen in the form of radiation called the “cosmic microwave background” or “CMB,” a cosmic fossil that evenly fills the universe.
The team behind this research thinks that explosions of axial stars in the early universe may have left their mark on the CMB. So looking for this signature using radio waves, known as the 21 centimeter measurement, could confirm the axial nature of dark matter.
“Coherent axis stars, even relatively compact ones, have the potential to evolve into a halo of electromagnetism and light,” Fairbairn said. “Knowing what kinds of structures dark matter can form and its effect on the surrounding intergalactic gas could open new avenues for its detection.
“Being able to find the axis will likely help us solve one of science’s biggest questions, which has been studied for more than a century, and reveal the history of the early universe.”
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Calculating the number of axial stars in existence could ultimately reveal the full explosive potential of these unstable dark matter accumulations and help explain how these explosions might interact with intergalactic gas. This will give a clue as to the size of the signal stored in the CMB.
“The 21 cm measurement is widely seen as the future of cosmology, and the role it plays in the search for axes is a big reason why,” said King’s College London researcher David Marsh. “There’s a lot of axial research going on right now, including projects like Dark Matter Radio. It’s a very, very exciting time to be an astrophysicist right now.”
The research on Axion stars was published in a series of papers in the journal Physical Review D.