Neutron stars are dense adequate to capture dark matter. Dark matter connects only very weakly with ordinary matter. Extremely, nevertheless, neutron stars are so thick that they might be able to trap all dark matter particles that pass through them.
Theoretically, the dark matter particles would collide with neutrons in the star, lose energy, and end up being gravitationally caught. Over time, dark matter particles would collect in the core of the star.
Illustration revealing gamma-rays from a neutron star. Credit: NASA
Utilizing Neutron Stars To Detect Dark Matter
The look for dark matter might need a detector larger than we can develop on Earth, but it might be that a neutron star can do the job.
The mission to uncover the nature of dark matter is one of the best obstacles in science today, however the key to lastly understanding this strange compound might well lie in the stars.
Or to be precise, one specific type of star– the neutron star.
So far, researchers have actually been able to presume the existence of dark matter, but not directly observe it. Really spotting dark matter particles in experiments in the world is a powerful task, because the interactions of dark matter particles with routine matter are exceptionally rare.
Neutron stars are thick enough to record dark matter. Image: Animation of a spinning neutron star in space. Credit: NASAs Goddard Space Flight Center Conceptual Image Lab
To look for these incredibly uncommon signals, we need a large detector– perhaps so huge that it is impracticable to develop a detector large enough on Earth. Nature provides an alternative choice in the type of neutron stars– an entire neutron star can act as the supreme dark matter detector.
In research released in Physical Review Letters, we have figured out how to a lot more accurately utilize info gained from these special natural dark matter detectors.
Neutron stars are the densest stars known to exist and form when huge stars die in supernovae surges. Left behind is a collapsed core, in which gravity presses matter together so firmly that protons and electrons combine to make neutrons. With a mass equivalent to that of the Sun– compressed into a 10km radius– one teaspoon of neutron star product has a mass of about a billion loads!
These stars are cosmic laboratories, allowing us to study how dark matter acts under extreme conditions that can not be duplicated in the world.
Dark matter communicates only extremely weakly with normal matter. For instance, it can pass through a light-year of lead (about 10 trillion kilometers) without being stopped. Incredibly, however, neutron stars are so dense that they may have the ability to trap all dark matter particles that go through them.
While the presence of dark matter has been inferred, it has yet to be straight observed. Credit: NASA
In theory, the dark matter particles would clash with neutrons in the star, lose energy, and end up being gravitationally trapped. With time, dark matter particles would collect in the core of the star. This is expected to warm up old, cold, neutron stars to a level that may remain in reach of future observations. In severe cases, the accumulation of dark matter might trigger the collapse of the star to a black hole.
This suggests that neutron stars may enable us to penetrate particular types of dark matter that would be hard or difficult to observe in experiments on Earth.
In the world, dark matter experiments look for tiny nuclear-recoil signals, triggered by extremely unusual crashes of slow-moving dark matter particles. In comparison, the strong gravitational field of a neutron star speeds up dark matter to quasi-relativistic speeds, leading to much greater energy accidents.
Another problem for Earth-based detection is that nuclear-recoil experiments are most sensitive to dark matter particles that have a similar mass to atomic nuclei, making it more difficult to discover dark matter that may be much lighter or heavier.
Dark matter particles can theoretically be trapped in stars and worlds in considerable amounts, regardless of how light or heavy they are.
A critical difficulty in utilizing neutron stars to find dark matter is guaranteeing that the estimations scientists use, totally represent the special environment of the star. Although the capture of dark matter in neutron stars had actually been studied for years, existing calculations have actually missed out on crucial physical results.
The calculations used to detect dark matter in neutron stars need to totally account for the stars unique environment.
So, our team approached making essential improvements to the estimation of the dark matter capture rate– i.e., how fast the dark matter accumulates in neutron stars– which altered the answers significantly.
Our research study properly accounts for nucleon structure, instead of treating the neutrons as point particles, and consists of the effects of strong forces in between nucleons, instead of modeling the neutrons as a free gas of particles. This developed upon our earlier work in which we incorporated the composition of the star, relativistic results, quantum statistics, and gravitational focusing.
In other words, we demonstrated how to correctly think about dark matter crashes in the severe neutron star environment, which is so extremely various to dark matter detectors on Earth.
This brand-new research significantly increases the accuracy and toughness of our estimates of the dark matter capture rate. This leads the way for us to much better figure out the strength of dark matter interactions with common matter.
Eventually, evidence (or absence of evidence) of dark matter accumulation in stars would offer important hints about where to target experimental efforts on Earth, helping to open the secret of dark matter.
Referral: “Nucleon Structure and Strong Interactions in Dark Matter Capture in Neutron Stars” by Nicole F. Bell, Giorgio Busoni, Theo F. Motta, Sandra Robles, Anthony W. Thomas and Michael Virgato, 10 September 2021, Physical Review Letters.DOI: 10.1103/ PhysRevLett.127.111803.
The research study team involved scientists from the ARC Centre of Excellence for Dark Matter Particle Physics, consisting of Dr. Sandra Robles, Michael Virgato and Professor Nicole Bell from the University of Melbourne, Dr. Giorgio Busoni from limit Planck Institute for Nuclear Physics in Germany, and Theo Motta and Professor Anthony Thomas A/c from the University of Adelaide.
