Evidence Mounts for a Dark Matter Concentration Near Our Solar System
For decades,scientists have theorized that the Milky Way is surrounded by a vast halo of dark matter,and within it,numerous smaller concentrations called subhalos. These subhalos, predicted to number in the tens of thousands, represent pockets where dark matter is particularly dense. While evidence of dark matter halos exists in other galaxies, identifying these subhalos within our own galactic neighborhood has proven incredibly challenging due to the elusive nature of dark matter itself.
Now, a new study, detailed in an article titled ‘Detection of a dark matter sub-halo near the Sun from pulsar timing’ (available on arxiv.org), proposes a novel method for detecting these hidden structures: precisely measuring the orbital periods of binary pulsars.
Pulsars are rapidly rotating remnants of massive stars that emit beams of radiation as they spin. Astronomers utilize the incredibly consistent timing of these pulses – akin to “beacons in the dark” – to measure astronomical phenomena like gravitational waves and detect exoplanets.
A team led by Sukanya Chakrabarti of the University of Alabama has leveraged this precision by analyzing 27 gravitationally bound pairs of pulsars. They meticulously calculated the time each pair takes to orbit their common center of mass, searching for unexplained accelerations. The goal was to identify a force acting on these systems that couldn’t be attributed to the galaxy’s gravity or known nearby objects.
The researchers discovered a consistent discrepancy: the pulsar pairs where moving at a speed inconsistent with expected gravitational influences. This anomaly suggests the presence of a considerable structure – estimated at 10 million times the mass of our Sun – exerting a gravitational pull on the pulsars.Crucially, investigations ruled out conventional explanations like black holes, gas clouds, or massive stars. This leaves the possibility of a dark matter subhalo as the moast likely cause.
“we have reviewed all possible data sets. We do not know,but we tend to think that it is more likely to be a sub halo,” Chakrabarti stated in Science magazine. This research represents one of the first attempts to use pulsars to detect a dark matter subhalo within the Milky Way.
Further observations of a larger number of pulsar pairs, tracked over extended periods, will be necessary to refine the method and confirm the existence of this potential dark matter concentration. The authors emphasize that continued, precise measurements will provide stronger constraints on the distribution of dark matter within our galaxy, offering new insights into its basic nature and the formation of galaxies themselves.
