Our galaxy hides a secret: about 85% of its mass is dark matter, invisible and elusive. For years, astronomers have been trying to figure out exactly how it is distributed: as clots or evenly.
Dr. Sukanya Chakrabarti’s team at the University of Alabama has proposed an innovative method: using pulsars to map dark matter.
Pulsars are key
Pulsars, neutron stars left over from supernova explosions, are the perfect “beacons” of the Universe. They spin at incredible speeds, emitting particles through powerful magnetic fields. This process slows their rotation (a phenomenon known as magnetic braking). However, pulsars have been found to be affected not only by their own physics, but also by the gravity of dark matter.
Galactic “swing”
The Milky Way is not static. Its disk wobbles like a baby learning to walk. This effect is caused by the gravitational influence of the Large Magellanic Cloud, a dwarf galaxy that orbits around our own. When a galaxy approaches, it “pulls” some of the Milky Way’s mass behind it, creating an asymmetry. It is this asymmetry that indicates an uneven distribution of dark matter that amplifies gravitational effects.
From binary to single pulsars
Previously, Chakrabarti and her team used binary pulsars orbiting other stars. Their orbits are independent of magnetic braking, which allows accurate measurements of accelerations caused by dark matter. But most pulsars are solitary. The challenge was to account for their deceleration.
The team’s new technique allows them to accurately calculate the effect of magnetic braking on individual pulsars. “It’s like separating noise from signal,” explains Tom Donlon, a member of the team, ”Now we can use all types of pulsars to measure tiny changes in their velocity caused by dark matter.”
Toward an accurate map
The accelerations that scientists measure are incredibly small – about 10 cm/s per decade is the speed of a snail. However, they are the ones that reflect the gravitational “fingerprint” of dark matter. The more data from pulsars is collected, the more detailed the map of its distribution will become.
“This is the first time we have an instrument to study dark matter on a galaxy-wide scale. This opens the door to understanding how dark matter forms the structure of the Milky Way and interacts with visible matter,” Chakrabarti emphasizes.
Dark matter is the foundation that keeps galaxies from falling apart. Its distribution affects star formation, the movement of gas clouds, and even the fate of the galaxy itself. New research techniques are not only revealing the Milky Way’s past, but also helping to predict its future.
Earlier we reported on how dark matter was found on Earth.
According to universetoday.com
