A significant discovery indicates the presence of a gigantic dark matter cloud adjacent to our solar system. These clouds, previously unidentified in the Milky Way, have been detected thanks to precise cosmic clocks known as pulsars.

Current cosmological models propose that galaxies are enveloped in diffuse clouds of dark matter called halos, with smaller subhaloes scattered throughout. However, the elusive nature of dark matter, which neither emits, absorbs, nor reflects light, complicates the detection of these halos and subhalos.

To quantify this dark matter phenomenon, Sukanya Chakrabarti and her research team at the University of Alabama in Huntsville leveraged pairs of rapidly spinning neutron stars known as pulsars. These cosmic clocks emit beams of light at consistent intervals, allowing researchers to measure variations in their trajectories when influenced by large nearby mass.

Given that dark matter interacts with ordinary matter solely through gravity, an adjacent dark matter subhalo would alter the orbit of neighboring pulsars. This is precisely what Chakrabarti and her collaborators identified approximately 3,000 light years from our solar system. “Our observations detected a pair of pulsars whose motions indicate an unexpected gravitational pull from an unseen object,” comments Philip Chan from the University of Wisconsin-Milwaukee.

The research revealed that this gravitational influence originated from an object approximately 60 million times more massive than the Sun and spanning hundreds of light years. After mapping the location against stellar data, no correlations with known celestial bodies were found. If validated, this object could be a unique example of dark matter.

This potential dark matter subhalo could be the only instance of such size in our local galactic vicinity. “There may only be one or two of these large features nearby, depending on dark matter models,” suggests Alice Quillen at the University of Rochester in New York. “Different dark matter theories propose varying distributions of these structures.”

This pursuit is what catalyzed Chakrabarti’s interest in subhalo research. “Our objective is to map as many subhaloes as we can throughout the galaxy, and we’re just beginning to achieve that. Ultimately, we aim to elucidate the nature of dark matter,” she asserts.

However, pulsar binaries are scarce; only 27 instances provide sufficient accuracy for measuring gravitational acceleration. This scarcity explains why this subhalo remained undetected until now. “Given the finite number of pulsars, we are exploring alternative methods to monitor them using a broader array of objects,” states Zhang. If successful, this could be a breakthrough in understanding the true nature of dark matter.