A recent study from the ARC Center of Excellence for Dark Matter Particle Physics suggests that neutron stars could play a crucial role in understanding dark matter. The study found that dark matter particles, when they collide with neutron stars, can quickly heat up the stars, potentially making them observable through future astronomical technologies. This rapid heating process, previously thought to take longer than the age of the universe, now appears to be achievable within days, providing a new method for studying the interactions of dark matter with ordinary matter.
Recent research suggests that neutron stars can quickly heat up due to dark matter collisions, offering a new way to detect and study dark matter.
Scientists may be one step closer to unraveling one of the universe’s greatest mysteries. Their recent calculations suggest that neutron stars could play a crucial role in shedding light on mysterious dark matter.
In an article published in Journal of Cosmology and Astroparticle PhysicsPhysicists at the University of Melbourne’s ARC Center of Excellence for Dark Matter Particle Physics have calculated that the energy transferred when dark matter particles collide and annihilate inside cold, dead neutron stars can heat the stars very quickly.
It was previously thought that this energy transfer could take a very long time, in some cases longer than the age of the universe itself, making this heating irrelevant.
Professor Nicole Bell of the University of Melbourne said the new calculations show for the first time that most of the energy will be stored within days.
“The search for dark matter is one of the greatest detective stories in science. Dark matter makes up 85 percent of the matter in our universe, yet we can’t see it. Dark matter does not interact with light – it does not absorb light, it does not reflect light, it does not emit light. This means that our telescopes cannot directly observe it, even though we know it exists. Instead, its gravitational pull on the objects we see tells us it must be there.
“It is one thing to predict dark matter theoretically, but another to observe it experimentally. Experiments on Earth are limited by the technical problems of producing sufficiently large detectors. However, neutron stars act as huge natural dark matter detectors, collecting dark matter over astronomically long periods of time, so they are a good place to focus our efforts,” Professor Bell said.
The role of neutron stars in the detection of dark matter
Neutron stars form when a supermassive star runs out of fuel and collapses. They have a similar mass to our Sun, compressed into a sphere only 20 km wide. If they were denser, they would become black holes.
“While dark matter is the dominant type of matter in the universe, it is very difficult to detect because its interactions with ordinary matter are very weak. So weak, in fact, that dark matter can pass right through the Earth or even the Sun.
“But neutron stars are different – they are so dense that dark matter particles are much more likely to interact with the star. If dark matter particles actually collide with neutrons in a star, they lose energy and become trapped. Over time this would lead to an accumulation of dark matter in the star,” Professor Bell said.
University of Melbourne PhD candidate Michael Virgato said this is expected to heat old, cold neutron stars to levels that may be within range of future observations, or even trigger the collapse of the star at Black hole.
“If the energy transfer happens fast enough, neutron star he would be warmed up. For this to happen, the dark matter in the star has to undergo many collisions, transferring more and more dark matter energy until eventually all the energy is stored in the star,” said Mr Virgato.
It was previously unknown how long this process would take, because as the energy of the dark matter particles gets smaller and smaller, it becomes less and less likely that they will interact again. As a result, it was assumed that it would take a very long time to transfer all the energy – sometimes longer than the age of the universe. Instead, the researchers calculated that 99% of the energy would be transferred within a few days.
“This is good news because it means that dark matter can heat neutron stars to a level that can potentially be detected.” As a result, observations of a cold neutron star would provide vital information about the interactions between dark matter and ordinary matter, shedding light on the nature of this elusive substance.
“If we are to understand dark matter – which is everywhere – it is important that we use all the techniques at our disposal to find out what the hidden matter of our universe really is,” Mr Virgato said.
Reference: “Dark Matter Thermalization and Annihilation in Neutron Stars” by Nicole F. Bell, Giorgio Busoni, Sandra Robles and Michael Virgato, 3 Apr 2024, Journal of Cosmology and Astroparticle Physics.
DOI: 10.1088/1475-7516/2024/04/006
This research was carried out by a team of international experts from the ARC Center of Excellence for Dark Matter Particle Physics, including Professor Nicole Bell and Michael Virgato from the University of Melbourne, Drs. Giorgio Busoni from Australian National University and Dr. Sandra Robles from Fermi National Accelerator Laboratory, USA.