When it comes to physics and astrophysics, understanding dark matter has proven to be a challenge, but scientists at the Max Planck Institute for Radio Astronomy suggest that studying super-dense stars may be one key to figuring out how dark matter interacts with ordinary matter.
As far as the measurement of matter contained in our universe, scientists believe that 80 percent of it is dark matter. In the past, our knowledge of dark matter has come strictly through carefully examining things like the rotation of galaxies, gravitational lenses and observing galaxy clusters, as Phys.org report. It is highly likely, according to physicists, that sub-atomic particles that have not yet been discovered may make up this dark matter.
Physicists also question whether there is a fifth force at play that may be working alongside dark matter besides electromagnetic and weak interaction, strong interaction and gravity. Because of this, up until recently nobody has worked to test the idea of a fifth force in conjunction with an object like a neutron star, as Max Planck’s Lijing Shao explained.
“There are two reasons that binary pulsars open up a completely new way of testing for such a fifth force between normal matter and dark matter. First, a neutron star consists of matter which cannot be constructed in a laboratory, many times denser than an atomic nucleus and consisting nearly entirely of neutrons. Moreover, the enormous gravitational fields inside a neutron star, billion times stronger than that of the Sun, could in principle greatly enhance the interaction with dark matter.”
— Phys.org (@physorg_com) June 15, 2018
In the new study, researchers sought to examine free fall heading towards dark matter by studying PSR J1713+0747, which is a binary pulsar that can be found approximately 3,800 light years away from Earth. It was particularly helpful that this pulsar orbits a white dwarf over a period of 68 days.
With a wide orbit, it was determined to be much more reactive toward any possible violation of free fall. As such, if it were to feel a slide toward dark matter that would be different from that of the white dwarf star, in theory, there should be a change in its binary orbit which could be spotted, according to Max Planck’s Norbert Wex.
“More than 20 years of regular high precision timing with Effelsberg and other radio telescopes of the European Pulsar Timing Array and the North American NANOGrav pulsar timing projects showed with high precision that there is no change in the eccentricity of the orbit. This means that to a high degree the neutron star feels the same kind of attraction towards dark matter as towards other forms of standard matter.”
Michael Kramer, who runs the Fundamental Physics in Radio Astronomy group, noted that with the use of the Square Kilometer Array, further tests like these will be even more precise.
“To make these tests even better, we are busily searching for suitable pulsars near large amounts of expected dark matter. The ideal place is the galactic center where we use Effelsberg and other telescopes in the world to have a look as part of our Black Hole Cam project. Once we will have the Square Kilometer Array, we can make those tests super-precise.”
The new study on using neutron stars to better understand dark matter can be found in Physical Review Letters.